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SubjectRe: [PATCH] perf: make perf.data more self-descriptive (v4)
From
David,

Something I don't quite understand with your issues with endianess.

How does endianess change anything to a int32 (aka int) vs. uint32?

The byte swapping you need to do is regardless of the sign of
the data or am I missing something here?


On Thu, Sep 8, 2011 at 5:27 PM, David Ahern <dsahern@gmail.com> wrote:
>
>
> On 09/07/2011 01:10 PM, Stephane Eranian wrote:
> >
> > The goal of this patch is to include more information
> > about the host environment into the perf.data so it is
> > more self-descriptive. Overtime, profiles are captured
> > on various machines and it becomes hard to track what
> > was recorded, on what machine and when.
> >
> > This patch provides a way to solve this by extending
> > the perf.data file with basic information about the
> > host machine. To add those extensions, we leverage
> > the feature bits capabilities of the perf.data format.
> > The change is backward compatible with existing perf.data
> > files.
> >
> > We define the following useful new extensions:
> >  - HEADER_HOSTNAME: the hostname
> >  - HEADER_OSRELEASE: the kernel release number
> >  - HEADER_ARCH: the hw architecture
> >  - HEADER_CPUID: the cpu model description
> >  - HEADER_NRCPUS: number of online/avail cpus
> >  - HEADER_CMDLINE: perf command line
> >  - HEADER_VERSION: perf version
> >  - HEADER_TOPOLOGY: cpu topology
> >  - HEADER_EVENT_DESC: full event description (attrs)
> >
> > The small granularity for the entries is to make it easier
> > to extend without breaking backward compatiblity. All entries
> > are provided as ASCII strings, easy to parse, except for the
> > event description.
> >
> > In the second version, we dropped the -I option for the
> > perf record command. The extra information is systematically
> > captured. But it's still displayed optionally by perf report.
> > There are also a couple of cleanups of function prototypes
> > and global variables.
> >
> > In the third version, we:
> > - fixed missing MIPS support for CPUID
> > - used u32 instead of int when writing integers to file
> > - fixed couple of bswap() bugs
> > - refactorize all write/print functions using function pointers
> > - improved write_cmdline() to include actual path to perf binary
> >
> > In the fourth version, we:
> > - fixed a couple of int vs. u32 issues
> > - factorized HEADER_BUILD_ID, HEADER_TRACE_INFO
> > - added -I option to perf script report
> > - reverted change to evsel.c (unrelated to meta-data)
> > - modified write_*() to always write despite errors (adds_feature bit present)
> > - added HEADER_TOTAL_MEM: total memory installed on this system
> > - added HEADER_NUMA_TOPOLOGY: shows NUMA nodes and for each memory, cpu list
> > - renamed HEADER_TOPOLOGY to HEADER_CPU_TOPOLOGY
>
> Still some endianness problems; cross-endian analysis is causing perf to
> abort. I need some time to investigate. I can send you a ppc data file
> if you have the time.
>
> David
>
> >
> >
> > $ perf record -ecycles,instructions noploop 1
> > noploop for 1 seconds
> > [ perf record: Woken up 1 times to write data ]
> > [ perf record: Captured and wrote 0.098 MB perf.data (~4260 samples) ]
> > $ perf report -I --stdio
> > #
> > # captured on: Wed Sep  7 21:00:10 2011
> > # hostname : quad
> > # os release : 3.1.0-rc4-tip
> > # arch : x86_64
> > # cpuid : Intel(R) Core(TM)2 Quad CPU Q6600 @ 2.40GHz
> > # nrcpus online : 4
> > # nrcpus avail : 4
> > # event = cycles, type = 0, config = 0x0, config1 = 0x0, config2 = 0x0, excl_usr = 0, excl_kern = 0, id = { 536, 537, 538, 539 }
> > # event = instructions, type = 0, config = 0x1, config1 = 0x0, config2 = 0x0, excl_usr = 0, excl_kern = 0, id = { 540, 541, 542,
> > # cmdline : /home/eranian/perfmon/official/tip/build/tools/perf/perf record -ecycles,instructions noploop 1
> > # perf version : 3.1.0-rc4
> > # CPU0   sibling cores  : 0-3
> > # CPU0   sibling threads: 0
> > # CPU1   sibling cores  : 0-3
> > # CPU1   sibling threads: 1
> > # CPU2   sibling cores  : 0-3
> > # CPU2   sibling threads: 2
> > # CPU3   sibling cores  : 0-3
> > # CPU3   sibling threads: 3
> > # total memory: 8105344 kB
> > # node0   meminfo : 8320608 kB
> > # node0   cpu list: 0-3
> > #
> > # Events: 995  cycles
> > #
> > # Overhead  Command      Shared Object                Symbol
> > # ........  .......  .................  ....................
> > #
> >     99.90%  noploop  noploop            [.] noploop
> >      0.10%  noploop  [kernel.kallsyms]  [k] trace_hardirqs_on
> >      0.00%  noploop  [kernel.kallsyms]  [k] lock_release
> >      0.00%  noploop  [kernel.kallsyms]  [k] intel_pmu_enable_all
> > ...
> >
> >
> > Signed-off-by: Stephane Eranian <eranian@google.com>
> > ---
> >
> > diff --git a/tools/perf/Documentation/perf-report.txt b/tools/perf/Documentation/perf-report.txt
> > index 04253c0..191e10e 100644
> > --- a/tools/perf/Documentation/perf-report.txt
> > +++ b/tools/perf/Documentation/perf-report.txt
> > @@ -134,6 +134,11 @@ OPTIONS
> >       CPUs are specified with -: 0-2. Default is to report samples on all
> >       CPUs.
> >
> > +-I::
> > +--show-info::
> > +     Display information about the perf.data file, incl. hostname,
> > +     os release, perf version, machine desc.
> > +
> >  SEE ALSO
> >  --------
> >  linkperf:perf-stat[1]
> > diff --git a/tools/perf/Documentation/perf-script.txt b/tools/perf/Documentation/perf-script.txt
> > index db01786..ebf8a23 100644
> > --- a/tools/perf/Documentation/perf-script.txt
> > +++ b/tools/perf/Documentation/perf-script.txt
> > @@ -188,6 +188,13 @@ OPTIONS
> >       CPUs are specified with -: 0-2. Default is to report samples on all
> >       CPUs.
> >
> > +-I::
> > +--show-info::
> > +     Display information about the perf.data file, incl. hostname,
> > +     os release, perf version, machine desc. It can only be used with the
> > +     perf script report mode and it must be specified after the script name
> > +     like for instance: perf script report syscall-counts -I.
> > +
> >  SEE ALSO
> >  --------
> >  linkperf:perf-record[1], linkperf:perf-script-perl[1],
> > diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
> > index 6b0519f..524ebbf 100644
> > --- a/tools/perf/builtin-record.c
> > +++ b/tools/perf/builtin-record.c
> > @@ -513,6 +513,18 @@ static int __cmd_record(int argc, const char **argv)
> >       if (have_tracepoints(&evsel_list->entries))
> >               perf_header__set_feat(&session->header, HEADER_TRACE_INFO);
> >
> > +     perf_header__set_feat(&session->header, HEADER_HOSTNAME);
> > +     perf_header__set_feat(&session->header, HEADER_OSRELEASE);
> > +     perf_header__set_feat(&session->header, HEADER_ARCH);
> > +     perf_header__set_feat(&session->header, HEADER_CPUID);
> > +     perf_header__set_feat(&session->header, HEADER_NRCPUS);
> > +     perf_header__set_feat(&session->header, HEADER_EVENT_DESC);
> > +     perf_header__set_feat(&session->header, HEADER_CMDLINE);
> > +     perf_header__set_feat(&session->header, HEADER_VERSION);
> > +     perf_header__set_feat(&session->header, HEADER_CPU_TOPOLOGY);
> > +     perf_header__set_feat(&session->header, HEADER_TOTAL_MEM);
> > +     perf_header__set_feat(&session->header, HEADER_NUMA_TOPOLOGY);
> > +
> >       /* 512 kiB: default amount of unprivileged mlocked memory */
> >       if (mmap_pages == UINT_MAX)
> >               mmap_pages = (512 * 1024) / page_size;
> > @@ -782,6 +794,8 @@ int cmd_record(int argc, const char **argv, const char *prefix __used)
> >       int err = -ENOMEM;
> >       struct perf_evsel *pos;
> >
> > +     perf_header__set_cmdline(argc, argv);
> > +
> >       evsel_list = perf_evlist__new(NULL, NULL);
> >       if (evsel_list == NULL)
> >               return -ENOMEM;
> > diff --git a/tools/perf/builtin-report.c b/tools/perf/builtin-report.c
> > index d7ff277..7721030 100644
> > --- a/tools/perf/builtin-report.c
> > +++ b/tools/perf/builtin-report.c
> > @@ -40,6 +40,7 @@ static char         const *input_name = "perf.data";
> >  static bool          force, use_tui, use_stdio;
> >  static bool          hide_unresolved;
> >  static bool          dont_use_callchains;
> > +static bool          show_info;
> >
> >  static bool          show_threads;
> >  static struct perf_read_values       show_threads_values;
> > @@ -276,6 +277,9 @@ static int __cmd_report(void)
> >                       goto out_delete;
> >       }
> >
> > +     if (show_info)
> > +             perf_session__fprintf_info(session, stdout);
> > +
> >       if (show_threads)
> >               perf_read_values_init(&show_threads_values);
> >
> > @@ -487,6 +491,8 @@ static const struct option options[] = {
> >       OPT_STRING(0, "symfs", &symbol_conf.symfs, "directory",
> >                   "Look for files with symbols relative to this directory"),
> >       OPT_STRING('c', "cpu", &cpu_list, "cpu", "list of cpus to profile"),
> > +     OPT_BOOLEAN('I', "show-info", &show_info,
> > +                     "display information about perf.data file"),
> >       OPT_END()
> >  };
> >
> > diff --git a/tools/perf/builtin-script.c b/tools/perf/builtin-script.c
> > index 09024ec..dac86ab 100644
> > --- a/tools/perf/builtin-script.c
> > +++ b/tools/perf/builtin-script.c
> > @@ -22,6 +22,7 @@ static u64                  last_timestamp;
> >  static u64                   nr_unordered;
> >  extern const struct option   record_options[];
> >  static bool                  no_callchain;
> > +static bool                  show_info = false;
> >  static const char            *cpu_list;
> >  static DECLARE_BITMAP(cpu_bitmap, MAX_NR_CPUS);
> >
> > @@ -1083,7 +1084,8 @@ static const struct option options[] = {
> >                    "comma separated output fields prepend with 'type:'. Valid types: hw,sw,trace,raw. Fields: comm,tid,pid,time,cpu,event,trace,ip,sym,dso,addr",
> >                    parse_output_fields),
> >       OPT_STRING('c', "cpu", &cpu_list, "cpu", "list of cpus to profile"),
> > -
> > +     OPT_BOOLEAN('I', "show-info", &show_info,
> > +                     "display host information from perf.data file"),
> >       OPT_END()
> >  };
> >
> > @@ -1268,6 +1270,9 @@ int cmd_script(int argc, const char **argv, const char *prefix __used)
> >                       return -1;
> >       }
> >
> > +     if (show_info)
> > +             perf_session__fprintf_info(session, stdout);
> > +
> >       if (!no_callchain)
> >               symbol_conf.use_callchain = true;
> >       else
> > diff --git a/tools/perf/builtin.h b/tools/perf/builtin.h
> > index 4702e24..b382bd5 100644
> > --- a/tools/perf/builtin.h
> > +++ b/tools/perf/builtin.h
> > @@ -4,7 +4,6 @@
> >  #include "util/util.h"
> >  #include "util/strbuf.h"
> >
> > -extern const char perf_version_string[];
> >  extern const char perf_usage_string[];
> >  extern const char perf_more_info_string[];
> >
> > diff --git a/tools/perf/perf.h b/tools/perf/perf.h
> > index a5fc660..08b0b5e 100644
> > --- a/tools/perf/perf.h
> > +++ b/tools/perf/perf.h
> > @@ -9,18 +9,21 @@ void get_term_dimensions(struct winsize *ws);
> >  #include "../../arch/x86/include/asm/unistd.h"
> >  #define rmb()                asm volatile("lock; addl $0,0(%%esp)" ::: "memory")
> >  #define cpu_relax()  asm volatile("rep; nop" ::: "memory");
> > +#define CPUINFO_PROC "model name"
> >  #endif
> >
> >  #if defined(__x86_64__)
> >  #include "../../arch/x86/include/asm/unistd.h"
> >  #define rmb()                asm volatile("lfence" ::: "memory")
> >  #define cpu_relax()  asm volatile("rep; nop" ::: "memory");
> > +#define CPUINFO_PROC "model name"
> >  #endif
> >
> >  #ifdef __powerpc__
> >  #include "../../arch/powerpc/include/asm/unistd.h"
> >  #define rmb()                asm volatile ("sync" ::: "memory")
> >  #define cpu_relax()  asm volatile ("" ::: "memory");
> > +#define CPUINFO_PROC "cpu"
> >  #endif
> >
> >  #ifdef __s390__
> > @@ -37,30 +40,35 @@ void get_term_dimensions(struct winsize *ws);
> >  # define rmb()               asm volatile("" ::: "memory")
> >  #endif
> >  #define cpu_relax()  asm volatile("" ::: "memory")
> > +#define CPUINFO_PROC "cpu type"
> >  #endif
> >
> >  #ifdef __hppa__
> >  #include "../../arch/parisc/include/asm/unistd.h"
> >  #define rmb()                asm volatile("" ::: "memory")
> >  #define cpu_relax()  asm volatile("" ::: "memory");
> > +#define CPUINFO_PROC "cpu"
> >  #endif
> >
> >  #ifdef __sparc__
> >  #include "../../arch/sparc/include/asm/unistd.h"
> >  #define rmb()                asm volatile("":::"memory")
> >  #define cpu_relax()  asm volatile("":::"memory")
> > +#define CPUINFO_PROC "cpu"
> >  #endif
> >
> >  #ifdef __alpha__
> >  #include "../../arch/alpha/include/asm/unistd.h"
> >  #define rmb()                asm volatile("mb" ::: "memory")
> >  #define cpu_relax()  asm volatile("" ::: "memory")
> > +#define CPUINFO_PROC "cpu model"
> >  #endif
> >
> >  #ifdef __ia64__
> >  #include "../../arch/ia64/include/asm/unistd.h"
> >  #define rmb()                asm volatile ("mf" ::: "memory")
> >  #define cpu_relax()  asm volatile ("hint @pause" ::: "memory")
> > +#define CPUINFO_PROC "model name"
> >  #endif
> >
> >  #ifdef __arm__
> > @@ -71,6 +79,7 @@ void get_term_dimensions(struct winsize *ws);
> >   */
> >  #define rmb()                ((void(*)(void))0xffff0fa0)()
> >  #define cpu_relax()  asm volatile("":::"memory")
> > +#define CPUINFO_PROC "Processor"
> >  #endif
> >
> >  #ifdef __mips__
> > @@ -83,6 +92,7 @@ void get_term_dimensions(struct winsize *ws);
> >                               : /* no input */                        \
> >                               : "memory")
> >  #define cpu_relax()  asm volatile("" ::: "memory")
> > +#define CPUINFO_PROC "cpu model"
> >  #endif
> >
> >  #include <time.h>
> > @@ -171,5 +181,6 @@ struct ip_callchain {
> >  };
> >
> >  extern bool perf_host, perf_guest;
> > +extern const char perf_version_string[];
> >
> >  #endif
> > diff --git a/tools/perf/util/header.c b/tools/perf/util/header.c
> > index b6c1ad1..73fa59e 100644
> > --- a/tools/perf/util/header.c
> > +++ b/tools/perf/util/header.c
> > @@ -7,6 +7,7 @@
> >  #include <stdlib.h>
> >  #include <linux/list.h>
> >  #include <linux/kernel.h>
> > +#include <sys/utsname.h>
> >
> >  #include "evlist.h"
> >  #include "evsel.h"
> > @@ -17,12 +18,19 @@
> >  #include "session.h"
> >  #include "symbol.h"
> >  #include "debug.h"
> > +#include "cpumap.h"
> >
> >  static bool no_buildid_cache = false;
> >
> >  static int event_count;
> >  static struct perf_trace_event_type *events;
> >
> > +static u32 header_argc;
> > +static const char **header_argv;
> > +
> > +static int dsos__write_buildid_table(struct perf_header *header, int fd);
> > +static int perf_session__cache_build_ids(struct perf_session *session);
> > +
> >  int perf_header__push_event(u64 id, const char *name)
> >  {
> >       if (strlen(name) > MAX_EVENT_NAME)
> > @@ -110,6 +118,843 @@ static int write_padded(int fd, const void *bf, size_t count,
> >       return err;
> >  }
> >
> > +static int do_write_string(int fd, const char *str)
> > +{
> > +     u32 len, olen;
> > +     int ret;
> > +
> > +     olen = strlen(str) + 1;
> > +     len = ALIGN(olen, NAME_ALIGN);
> > +
> > +     /* write len, incl. \0 */
> > +     ret = do_write(fd, &len, sizeof(len));
> > +     if (ret < 0)
> > +             return ret;
> > +
> > +     return write_padded(fd, str, olen, len);
> > +}
> > +
> > +static char *do_read_string(int fd, struct perf_header *ph)
> > +{
> > +     ssize_t sz, ret;
> > +     u32 len;
> > +     char *buf;
> > +
> > +     sz = read(fd, &len, sizeof(len));
> > +     if (sz < (ssize_t)sizeof(len))
> > +             return NULL;
> > +
> > +     if (ph->needs_swap)
> > +             len = bswap_32(len);
> > +
> > +     buf = malloc(len);
> > +     if (!buf)
> > +             return NULL;
> > +
> > +     ret = read(fd, buf, len);
> > +     if (ret == (ssize_t)len) {
> > +             /*
> > +              * strings are padded by zeroes
> > +              * thus the actual strlen of buf
> > +              * may be less than len
> > +              */
> > +             return buf;
> > +     }
> > +
> > +     free(buf);
> > +     return NULL;
> > +}
> > +
> > +int
> > +perf_header__set_cmdline(int argc, const char **argv)
> > +{
> > +     int i;
> > +
> > +     header_argc = (u32)argc;
> > +
> > +     /* do not include NULL termination */
> > +     header_argv = calloc(argc, sizeof(char *));
> > +     if (!header_argv)
> > +             return -ENOMEM;
> > +
> > +     /*
> > +      * must copy argv contents because it gets moved
> > +      * around during option parsing
> > +      */
> > +     for (i = 0; i < argc ; i++)
> > +             header_argv[i] = argv[i];
> > +
> > +     return 0;
> > +}
> > +
> > +static int write_trace_info(int fd, struct perf_header *h __used,
> > +                         struct perf_evlist *evlist)
> > +{
> > +     return read_tracing_data(fd, &evlist->entries);
> > +}
> > +
> > +
> > +static int write_build_id(int fd, struct perf_header *h,
> > +                       struct perf_evlist *evlist __used)
> > +{
> > +     struct perf_session *session;
> > +     int err;
> > +
> > +     session = container_of(h, struct perf_session, header);
> > +
> > +     err = dsos__write_buildid_table(h, fd);
> > +     if (err < 0) {
> > +             pr_debug("failed to write buildid table\n");
> > +             return err;
> > +     }
> > +     if (!no_buildid_cache)
> > +             perf_session__cache_build_ids(session);
> > +
> > +     return 0;
> > +}
> > +
> > +static int write_hostname(int fd, struct perf_header *h __used,
> > +                       struct perf_evlist *evlist __used)
> > +{
> > +     struct utsname uts;
> > +     int ret;
> > +
> > +     ret = uname(&uts);
> > +     if (ret < 0)
> > +             return -1;
> > +
> > +     return do_write_string(fd, uts.nodename);
> > +}
> > +
> > +static int write_osrelease(int fd, struct perf_header *h __used,
> > +                        struct perf_evlist *evlist __used)
> > +{
> > +     struct utsname uts;
> > +     int ret;
> > +
> > +     ret = uname(&uts);
> > +     if (ret < 0)
> > +             return -1;
> > +
> > +     return do_write_string(fd, uts.release);
> > +}
> > +
> > +static int write_arch(int fd, struct perf_header *h __used,
> > +                   struct perf_evlist *evlist __used)
> > +{
> > +     struct utsname uts;
> > +     int ret;
> > +
> > +     ret = uname(&uts);
> > +     if (ret < 0)
> > +             return -1;
> > +
> > +     return do_write_string(fd, uts.machine);
> > +}
> > +
> > +static int write_version(int fd, struct perf_header *h __used,
> > +                      struct perf_evlist *evlist __used)
> > +{
> > +     return do_write_string(fd, perf_version_string);
> > +}
> > +
> > +static int write_cpuid(int fd, struct perf_header *h __used,
> > +                    struct perf_evlist *evlist __used)
> > +{
> > +#ifndef CPUINFO_PROC
> > +#define CPUINFO_PROC NULL
> > +#endif
> > +     FILE *file;
> > +     char buf[256];
> > +     char *s, *p;
> > +     const char *search = CPUINFO_PROC;
> > +
> > +     file = fopen("/proc/cpuinfo", "r");
> > +     if (!file)
> > +             return -1;
> > +
> > +     if (search) {
> > +             while (fgets(buf, sizeof(buf), file)) {
> > +                     if (strstr(buf, search))
> > +                             goto found;
> > +             }
> > +     }
> > +     strcpy(buf, "unknown type");
> > +found:
> > +     fclose(file);
> > +
> > +     s = buf;
> > +
> > +     p = strchr(buf, ':');
> > +     if (p && *(p+1) == ' ' && *(p+2))
> > +             s = p + 2;
> > +     p = strchr(s, '\n');
> > +     if (p)
> > +             *p = '\0';
> > +
> > +     /* squash extra space characters (branding string) */
> > +     p = s;
> > +     while (*p) {
> > +             if (isspace(*p)) {
> > +                     char *r = p + 1;
> > +                     char *q = r;
> > +                     *p = ' ';
> > +                     while (*q && isspace(*q))
> > +                             q++;
> > +                     if (q != (p+1))
> > +                             while ((*r++ = *q++));
> > +             }
> > +             p++;
> > +     }
> > +     return do_write_string(fd, s);
> > +}
> > +
> > +static int write_nrcpus(int fd, struct perf_header *h __used,
> > +                     struct perf_evlist *evlist __used)
> > +{
> > +     long nr;
> > +     u32 nrc, nra;
> > +     int ret;
> > +
> > +     nr = sysconf(_SC_NPROCESSORS_CONF);
> > +     if (nr < 0)
> > +             return -1;
> > +
> > +     nrc = (u32)(nr & UINT_MAX);
> > +
> > +     ret = sysconf(_SC_NPROCESSORS_ONLN);
> > +     if (ret < 0)
> > +             return -1;
> > +
> > +     nra = (u32)(nr & UINT_MAX);
> > +
> > +     ret = do_write(fd, &nrc, sizeof(nrc));
> > +     if (ret < 0)
> > +             return ret;
> > +
> > +     return do_write(fd, &nra, sizeof(nra));
> > +}
> > +
> > +static int write_event_desc(int fd, struct perf_header *h __used,
> > +                         struct perf_evlist *evlist)
> > +{
> > +     struct perf_evsel *attr;
> > +     u32 nre = 0, nri, sz;
> > +     int ret;
> > +
> > +     list_for_each_entry(attr, &evlist->entries, node)
> > +             nre++;
> > +
> > +     /*
> > +      * write number of events
> > +      */
> > +     ret = do_write(fd, &nre, sizeof(nre));
> > +     if (ret < 0)
> > +             return ret;
> > +
> > +     /*
> > +      * size of perf_event_attr struct
> > +      */
> > +     sz = (u32)sizeof(attr->attr);
> > +     ret = do_write(fd, &sz, sizeof(sz));
> > +     if (ret < 0)
> > +             return ret;
> > +
> > +     list_for_each_entry(attr, &evlist->entries, node) {
> > +
> > +             ret = do_write(fd, &attr->attr, sz);
> > +             if (ret < 0)
> > +                     return ret;
> > +             /*
> > +              * write number of unique id per event
> > +              * there is one id per instance of an event
> > +              *
> > +              * copy into an nri to be independent of the
> > +              * type of ids,
> > +              */
> > +             nri = attr->ids;
> > +             ret = do_write(fd, &nri, sizeof(nri));
> > +             if (ret < 0)
> > +                     return ret;
> > +
> > +             /*
> > +              * write event string as passed on cmdline
> > +              */
> > +             ret = do_write_string(fd, attr->name);
> > +             if (ret < 0)
> > +                     return ret;
> > +             /*
> > +              * write unique ids for this event
> > +              */
> > +             ret = do_write(fd, attr->id, attr->ids * sizeof(u64));
> > +             if (ret < 0)
> > +                     return ret;
> > +     }
> > +     return 0;
> > +}
> > +
> > +static int write_cmdline(int fd, struct perf_header *h __used,
> > +                      struct perf_evlist *evlist __used)
> > +{
> > +     char buf[MAXPATHLEN];
> > +     char proc[32];
> > +     u32 i, n;
> > +     int ret;
> > +
> > +     /*
> > +      * actual atual path to perf binary
> > +      */
> > +     sprintf(proc, "/proc/%d/exe", getpid());
> > +     ret = readlink(proc, buf, sizeof(buf));
> > +     if (ret <= 0)
> > +             return -1;
> > +
> > +     /* readlink() does not add null termination */
> > +     buf[ret] = '\0';
> > +
> > +     /* account for binary path */
> > +     n = header_argc + 1;
> > +
> > +     ret = do_write(fd, &n, sizeof(n));
> > +     if (ret < 0)
> > +             return ret;
> > +
> > +     ret = do_write_string(fd, buf);
> > +     if (ret < 0)
> > +             return ret;
> > +
> > +     for (i = 0 ; i < header_argc; i++) {
> > +             ret = do_write_string(fd, header_argv[i]);
> > +             if (ret < 0)
> > +                     return ret;
> > +     }
> > +     return 0;
> > +}
> > +
> > +static const char *topo_fmt[] = {
> > +     "/sys/devices/system/cpu/cpu%d/topology/core_siblings_list",
> > +     "/sys/devices/system/cpu/cpu%d/topology/thread_siblings_list",
> > +     NULL
> > +};
> > +
> > +static int write_topo_cpu(int fd, int cpu)
> > +{
> > +     FILE *fp;
> > +     char filename[MAXPATHLEN];
> > +     char buf[MAXPATHLEN], *p, *c;
> > +     const char **q = topo_fmt;
> > +     int ret;
> > +
> > +     while (*q) {
> > +
> > +             sprintf(filename, *q, cpu);
> > +
> > +             fp = fopen(filename, "r");
> > +             if (!fp)
> > +                     return -1;
> > +
> > +             c = fgets(buf, sizeof(buf), fp);
> > +             if (!c) {
> > +                     fclose(fp);
> > +                     return -1;
> > +             }
> > +
> > +             p = strchr(buf, '\n');
> > +             if (p)
> > +                     *p = '\0';
> > +
> > +             fclose(fp);
> > +
> > +             ret = do_write_string(fd, c);
> > +             if (ret < 0)
> > +                     return ret;
> > +             q++;
> > +     }
> > +     return 0;
> > +}
> > +
> > +static int write_cpu_topology(int fd, struct perf_header *h __used,
> > +                       struct perf_evlist *evlist __used)
> > +{
> > +     u32 nr, i;
> > +     long ncpus;
> > +     int ret;
> > +
> > +     ncpus = sysconf(_SC_NPROCESSORS_CONF);
> > +     if (ncpus < 0)
> > +             return -1;
> > +
> > +     /* hopefully, this will keep compilers happy about the cast */
> > +     nr = (u32)(ncpus & UINT_MAX);
> > +
> > +     ret = do_write(fd, &nr, sizeof(nr));
> > +     if (ret < 0)
> > +             return -1;
> > +
> > +     for (i = 0; i < nr; i++) {
> > +             ret = do_write(fd, &i, sizeof(i));
> > +             if (ret < 0)
> > +                     return ret;
> > +
> > +             ret = write_topo_cpu(fd, i);
> > +             if (ret < 0)
> > +                     return ret;
> > +     }
> > +     return 0;
> > +}
> > +
> > +static int write_total_mem(int fd, struct perf_header *h __used,
> > +                       struct perf_evlist *evlist __used)
> > +{
> > +     char buf[MAXPATHLEN], *c;
> > +     FILE *fp;
> > +     int ret = -1, n;
> > +     uint64_t mem;
> > +
> > +     fp = fopen("/proc/meminfo", "r");
> > +     if (!fp)
> > +             return -1;
> > +
> > +     while ((c = fgets(buf, sizeof(buf), fp))) {
> > +             c = strstr(buf, "MemTotal:");
> > +             if (c)
> > +                     break;
> > +     }
> > +     fclose(fp);
> > +
> > +     n = sscanf(buf, "%*s %"PRIu64, &mem);
> > +     if (n == 1)
> > +             ret = do_write(fd, &mem, sizeof(mem));
> > +
> > +     return ret;
> > +}
> > +
> > +static int write_topo_node(int fd, int node)
> > +{
> > +     char filename[MAXPATHLEN];
> > +     char buf[MAXPATHLEN], *p, *c;
> > +     FILE *fp;
> > +     uint64_t mem;
> > +     int ret;
> > +
> > +     sprintf(filename, "/sys/devices/system/node/node%d/meminfo", node);
> > +     fp = fopen(filename, "r");
> > +     if (!fp)
> > +             return -1;
> > +
> > +     while ((c = fgets(buf, sizeof(buf), fp))) {
> > +             c = strstr(buf, "MemTotal:");
> > +             if (c)
> > +                     break;
> > +     }
> > +     fclose(fp);
> > +     if (!c)
> > +             return -1;
> > +     ret = sscanf(buf, "%*s %*d %*s %"PRIu64, &mem);
> > +     if (ret != 1)
> > +             return -1;
> > +
> > +     ret = do_write(fd, &mem, sizeof(mem));
> > +     if (ret < 0)
> > +             return -1;
> > +
> > +     sprintf(filename, "/sys/devices/system/node/node%d/cpulist", node);
> > +     fp = fopen(filename, "r");
> > +     if (!fp)
> > +             return -1;
> > +
> > +     c = fgets(buf, sizeof(buf), fp);
> > +     fclose(fp);
> > +     if (!c)
> > +             return -1;
> > +
> > +     p = strchr(buf, '\n');
> > +     if (p)
> > +             *p = '\0';
> > +
> > +     return do_write_string(fd, c);
> > +}
> > +
> > +static int write_numa_topology(int fd, struct perf_header *h __used,
> > +                       struct perf_evlist *evlist __used)
> > +{
> > +     char buf[MAXPATHLEN];
> > +     FILE *fp;
> > +     struct cpu_map *node_map;
> > +     char *c;
> > +     u32 nr, i, j;
> > +     int ret;
> > +
> > +     fp = fopen("/sys/devices/system/node/online", "r");
> > +     if (!fp)
> > +             return -1;
> > +
> > +     c = fgets(buf, sizeof(buf), fp);
> > +     fclose(fp);
> > +     if (!c)
> > +             return -1;
> > +
> > +     c = strchr(buf, '\n');
> > +     if (c)
> > +             *c = '\0';
> > +
> > +     node_map = cpu_map__new(buf);
> > +     if (!node_map)
> > +             return -1;
> > +
> > +     nr = (u32)node_map->nr;
> > +     ret = do_write(fd, &nr, sizeof(nr));
> > +     if (ret < 0)
> > +             return -1;
> > +
> > +     for (i = 0; i < nr; i++) {
> > +             j = (u32)node_map->map[i];
> > +             ret = do_write(fd, &j, sizeof(j));
> > +             if (ret < 0)
> > +                     goto error;
> > +
> > +             ret = write_topo_node(fd, i);
> > +             if (ret < 0)
> > +                     goto error;
> > +     }
> > +     ret = 0;
> > +error:
> > +     free(node_map);
> > +     return ret;
> > +}
> > +
> > +static void print_hostname(struct perf_header *ph, int fd, FILE *fp)
> > +{
> > +     char *str = do_read_string(fd, ph);
> > +     fprintf(fp, "# hostname : %s\n", str);
> > +     free(str);
> > +}
> > +
> > +static void print_osrelease(struct perf_header *ph, int fd, FILE *fp)
> > +{
> > +     char *str = do_read_string(fd, ph);
> > +     fprintf(fp, "# os release : %s\n", str);
> > +     free(str);
> > +}
> > +
> > +static void print_arch(struct perf_header *ph, int fd, FILE *fp)
> > +{
> > +     char *str = do_read_string(fd, ph);
> > +     fprintf(fp, "# arch : %s\n", str);
> > +     free(str);
> > +}
> > +
> > +static void print_cpuid(struct perf_header *ph, int fd, FILE *fp)
> > +{
> > +     char *str = do_read_string(fd, ph);
> > +     fprintf(fp, "# cpuid : %s\n", str);
> > +     free(str);
> > +}
> > +
> > +static void print_nrcpus(struct perf_header *ph, int fd, FILE *fp)
> > +{
> > +     ssize_t ret;
> > +     u32 nr;
> > +
> > +     ret = read(fd, &nr, sizeof(nr));
> > +     if (ret != (ssize_t)sizeof(nr))
> > +             nr = -1; /* interpreted as error */
> > +
> > +     if (ph->needs_swap)
> > +             nr = bswap_32(nr);
> > +
> > +     fprintf(fp, "# nrcpus online : %u\n", nr);
> > +
> > +     ret = read(fd, &nr, sizeof(nr));
> > +     if (ret != (ssize_t)sizeof(nr))
> > +             nr = -1; /* interpreted as error */
> > +
> > +     if (ph->needs_swap)
> > +             nr = bswap_32(nr);
> > +
> > +     fprintf(fp, "# nrcpus avail : %u\n", nr);
> > +}
> > +
> > +static void print_version(struct perf_header *ph, int fd, FILE *fp)
> > +{
> > +     char *str = do_read_string(fd, ph);
> > +     fprintf(fp, "# perf version : %s\n", str);
> > +     free(str);
> > +}
> > +
> > +static void print_cmdline(struct perf_header *ph, int fd, FILE *fp)
> > +{
> > +     ssize_t ret;
> > +     char *str;
> > +     u32 nr, i;
> > +
> > +     ret = read(fd, &nr, sizeof(nr));
> > +     if (ret != (ssize_t)sizeof(nr)) {
> > +             fprintf(fp, "# cmdline : unknown\n");
> > +             return;
> > +     }
> > +
> > +     if (ph->needs_swap)
> > +             nr = bswap_32(nr);
> > +
> > +     fprintf(fp, "# cmdline : ");
> > +
> > +     for (i = 0; i < nr; i++) {
> > +             str = do_read_string(fd, ph);
> > +             fprintf(fp, "%s ", str);
> > +             free(str);
> > +     }
> > +     fputc('\n', fp);
> > +}
> > +
> > +static void print_cpu_topology(struct perf_header *ph, int fd, FILE *fp)
> > +{
> > +     ssize_t ret;
> > +     u32 nr, c, i;
> > +     char *str;
> > +
> > +     ret = read(fd, &nr, sizeof(nr));
> > +     if (ret != (ssize_t)sizeof(nr)) {
> > +             fprintf(fp, "# cpu topology  : not available\n");
> > +             return;
> > +     }
> > +
> > +     if (ph->needs_swap)
> > +             nr = bswap_32(nr);
> > +
> > +     for (i = 0; i < nr; i++) {
> > +
> > +             ret = read(fd, &c, sizeof(c));
> > +             if (ret != (ssize_t)sizeof(c))
> > +                     c = -1; /* interpreted as error */
> > +
> > +             if (ph->needs_swap)
> > +                     c = bswap_32(c);
> > +
> > +             str = do_read_string(fd, ph);
> > +             fprintf(fp, "# CPU%u sibling cores  : %s\n", c, str);
> > +             free(str);
> > +
> > +             str = do_read_string(fd, ph);
> > +             fprintf(fp, "# CPU%u sibling threads: %s\n", c, str);
> > +             free(str);
> > +     }
> > +}
> > +
> > +static void print_event_desc(struct perf_header *ph, int fd, FILE *fp)
> > +{
> > +     struct perf_event_attr attr;
> > +     uint64_t id;
> > +     void *buf = NULL;
> > +     char *str;
> > +     u32 nre, sz, nr, i, j, msz;
> > +     int ret;
> > +
> > +     /* number of events */
> > +     ret = read(fd, &nre, sizeof(nre));
> > +     if (ret != (ssize_t)sizeof(nre))
> > +             goto error;
> > +
> > +     if (ph->needs_swap)
> > +             nre = bswap_32(nre);
> > +
> > +     ret = read(fd, &sz, sizeof(sz));
> > +     if (ret != (ssize_t)sizeof(sz))
> > +             goto error;
> > +
> > +     if (ph->needs_swap)
> > +             sz = bswap_32(sz);
> > +
> > +     /*
> > +      * ensure it is at least to our ABI rev
> > +      */
> > +     if (sz < (u32)sizeof(attr))
> > +             goto error;
> > +
> > +     memset(&attr, 0, sizeof(attr));
> > +
> > +     /* read entire region to sync up to next field */
> > +     buf = malloc(sz);
> > +     if (!buf)
> > +             goto error;
> > +
> > +     msz = sizeof(attr);
> > +     if (sz < msz)
> > +             msz = sz;
> > +
> > +     for (i = 0 ; i < nre; i++) {
> > +
> > +             ret = read(fd, buf, sz);
> > +             if (ret != (ssize_t)sz)
> > +                     goto error;
> > +
> > +             if (ph->needs_swap)
> > +                     perf_event__attr_swap(buf);
> > +
> > +             memcpy(&attr, buf, msz);
> > +
> > +             ret = read(fd, &nr, sizeof(nr));
> > +             if (ret != (ssize_t)sizeof(nr))
> > +                     goto error;
> > +
> > +             if (ph->needs_swap)
> > +                     nr = bswap_32(nr);
> > +
> > +             str = do_read_string(fd, ph);
> > +             fprintf(fp, "# event = %s, ", str);
> > +             free(str);
> > +
> > +             fprintf(fp, "type = %d, config = 0x%"PRIx64
> > +                         ", config1 = 0x%"PRIx64", config2 = 0x%"PRIx64,
> > +                             attr.type,
> > +                             (u64)attr.config,
> > +                             (u64)attr.config1,
> > +                             (u64)attr.config2);
> > +
> > +             fprintf(fp, ", excl_usr = %d, excl_kern = %d",
> > +                             attr.exclude_user,
> > +                             attr.exclude_kernel);
> > +
> > +             if (nr)
> > +                     fprintf(fp, ", id = {");
> > +
> > +             for (j = 0 ; j < nr; j++) {
> > +                     ret = read(fd, &id, sizeof(id));
> > +                     if (ret != (ssize_t)sizeof(id))
> > +                             goto error;
> > +
> > +                     if (ph->needs_swap)
> > +                             id = bswap_64(id);
> > +
> > +                     if (j)
> > +                             fputc(',', fp);
> > +
> > +                     fprintf(fp, " %"PRIu64, id);
> > +             }
> > +             if (nr && j == nr)
> > +                     fprintf(fp, " }");
> > +             fputc('\n', fp);
> > +     }
> > +     free(buf);
> > +     return;
> > +error:
> > +     fprintf(fp, "# event desc: not available or unable to read\n");
> > +}
> > +
> > +static void print_total_mem(struct perf_header *h __used, int fd, FILE *fp)
> > +{
> > +     uint64_t mem;
> > +     ssize_t ret;
> > +
> > +     ret = read(fd, &mem, sizeof(mem));
> > +     if (ret != sizeof(mem))
> > +             goto error;
> > +
> > +     if (h->needs_swap)
> > +             mem = bswap_64(mem);
> > +
> > +     fprintf(fp, "# total memory: %"PRIu64" kB\n", mem);
> > +     return;
> > +error:
> > +     fprintf(fp, "# total memory: unknown\n");
> > +}
> > +
> > +static void print_numa_topology(struct perf_header *h __used, int fd, FILE *fp)
> > +{
> > +     ssize_t ret;
> > +     u32 nr, c, i;
> > +     char *str;
> > +     uint64_t mem;
> > +
> > +     /* nr nodes */
> > +     ret = read(fd, &nr, sizeof(nr));
> > +     if (ret != (ssize_t)sizeof(nr))
> > +             goto error;
> > +
> > +     if (h->needs_swap)
> > +             nr = bswap_32(nr);
> > +
> > +     for (i = 0; i < nr; i++) {
> > +
> > +             /* node number */
> > +             ret = read(fd, &c, sizeof(c));
> > +             if (ret != (ssize_t)sizeof(c))
> > +                     goto error;
> > +
> > +             if (h->needs_swap)
> > +                     c = bswap_32(c);
> > +
> > +             ret = read(fd, &mem, sizeof(mem));
> > +             if (ret != sizeof(mem))
> > +                     goto error;
> > +
> > +             if (h->needs_swap)
> > +                     mem = bswap_64(mem);
> > +
> > +             fprintf(fp, "# node%u meminfo : %"PRIu64" kB\n", c, mem);
> > +
> > +             str = do_read_string(fd, h);
> > +             fprintf(fp, "# node%u cpu list: %s\n", c, str);
> > +             free(str);
> > +     }
> > +     return;
> > +error:
> > +     fprintf(fp, "# numa topology : not available\n");
> > +}
> > +
> > +struct feature_ops {
> > +     int (*write)(int fd, struct perf_header *h, struct perf_evlist *evlist);
> > +     void (*print)(struct perf_header *h, int fd, FILE *fp);
> > +};
> > +
> > +#define FEAT_OP(n, w, p) [n] = { .write = w, .print = p }
> > +
> > +static struct feature_ops feat_ops[HEADER_LAST_FEATURE] = {
> > +     FEAT_OP(HEADER_TRACE_INFO, write_trace_info, NULL),
> > +     FEAT_OP(HEADER_BUILD_ID, write_build_id, NULL),
> > +     FEAT_OP(HEADER_HOSTNAME, write_hostname, print_hostname),
> > +     FEAT_OP(HEADER_OSRELEASE, write_osrelease, print_osrelease),
> > +     FEAT_OP(HEADER_ARCH, write_arch, print_arch),
> > +     FEAT_OP(HEADER_CPUID, write_cpuid, print_cpuid),
> > +     FEAT_OP(HEADER_NRCPUS, write_nrcpus, print_nrcpus),
> > +     FEAT_OP(HEADER_EVENT_DESC, write_event_desc, print_event_desc),
> > +     FEAT_OP(HEADER_CMDLINE, write_cmdline, print_cmdline),
> > +     FEAT_OP(HEADER_VERSION, write_version, print_version),
> > +     FEAT_OP(HEADER_CPU_TOPOLOGY, write_cpu_topology, print_cpu_topology),
> > +     FEAT_OP(HEADER_TOTAL_MEM, write_total_mem, print_total_mem),
> > +     FEAT_OP(HEADER_NUMA_TOPOLOGY, write_numa_topology, print_numa_topology),
> > +};
> > +
> > +static int perf_header_fprintf_info(struct perf_file_section *section,
> > +                                 struct perf_header *ph,
> > +                                 int feat, int fd, void *data)
> > +{
> > +     FILE *fp = data;
> > +
> > +     if (lseek(fd, section->offset, SEEK_SET) == (off_t)-1) {
> > +             pr_debug("Failed to lseek to %" PRIu64 " offset for feature "
> > +                             "%d, continuing...\n", section->offset, feat);
> > +             return 0;
> > +     }
> > +     if (feat < HEADER_TRACE_INFO || feat >= HEADER_LAST_FEATURE) {
> > +             pr_warning("unknown feature %d\n", feat);
> > +             return -1;
> > +     }
> > +
> > +     if (feat_ops[feat].print)
> > +             feat_ops[feat].print(ph, fd, fp);
> > +
> > +     return 0;
> > +}
> > +
> > +int perf_header__fprintf_info(struct perf_session *session, FILE *fp __used)
> > +{
> > +     int fd = session->fd;
> > +     struct perf_header *header = &session->header;
> > +     perf_header__process_sections(header, fd, fp, perf_header_fprintf_info);
> > +     return 0;
> > +}
> > +
> >  #define dsos__for_each_with_build_id(pos, head)      \
> >       list_for_each_entry(pos, head, node)    \
> >               if (!pos->has_build_id)         \
> > @@ -356,15 +1201,41 @@ static bool perf_session__read_build_ids(struct perf_session *session, bool with
> >       return ret;
> >  }
> >
> > +static int do_write_feat(int fd, struct perf_header *h, int type,
> > +                      struct perf_file_section **p,
> > +                      struct perf_evlist *evlist)
> > +{
> > +     int err;
> > +     int ret = 0;
> > +
> > +     if (perf_header__has_feat(h, type)) {
> > +
> > +             (*p)->offset = lseek(fd, 0, SEEK_CUR);
> > +
> > +             err = feat_ops[type].write(fd, h, evlist);
> > +             if (err < 0) {
> > +                     pr_debug("failed to write feature %d\n", type);
> > +
> > +                     /* undo anything written */
> > +                     lseek(fd, (*p)->offset, SEEK_SET);
> > +
> > +                     return -1;
> > +             }
> > +             (*p)->size = lseek(fd, 0, SEEK_CUR) - (*p)->offset;
> > +             (*p)++;
> > +     }
> > +     return ret;
> > +}
> > +
> >  static int perf_header__adds_write(struct perf_header *header,
> >                                  struct perf_evlist *evlist, int fd)
> >  {
> >       int nr_sections;
> >       struct perf_session *session;
> > -     struct perf_file_section *feat_sec;
> > +     struct perf_file_section *feat_sec, *p;
> >       int sec_size;
> >       u64 sec_start;
> > -     int idx = 0, err;
> > +     int err;
> >
> >       session = container_of(header, struct perf_session, header);
> >
> > @@ -376,7 +1247,7 @@ static int perf_header__adds_write(struct perf_header *header,
> >       if (!nr_sections)
> >               return 0;
> >
> > -     feat_sec = calloc(sizeof(*feat_sec), nr_sections);
> > +     feat_sec = p = calloc(sizeof(*feat_sec), nr_sections);
> >       if (feat_sec == NULL)
> >               return -ENOMEM;
> >
> > @@ -385,36 +1256,65 @@ static int perf_header__adds_write(struct perf_header *header,
> >       sec_start = header->data_offset + header->data_size;
> >       lseek(fd, sec_start + sec_size, SEEK_SET);
> >
> > -     if (perf_header__has_feat(header, HEADER_TRACE_INFO)) {
> > -             struct perf_file_section *trace_sec;
> > -
> > -             trace_sec = &feat_sec[idx++];
> > +     err = do_write_feat(fd, header, HEADER_TRACE_INFO, &p, evlist);
> > +     if (err)
> > +             goto out_free;
> >
> > -             /* Write trace info */
> > -             trace_sec->offset = lseek(fd, 0, SEEK_CUR);
> > -             read_tracing_data(fd, &evlist->entries);
> > -             trace_sec->size = lseek(fd, 0, SEEK_CUR) - trace_sec->offset;
> > +     err = do_write_feat(fd, header, HEADER_BUILD_ID, &p, evlist);
> > +     if (err) {
> > +             perf_header__clear_feat(header, HEADER_BUILD_ID);
> > +             goto out_free;
> >       }
> >
> > -     if (perf_header__has_feat(header, HEADER_BUILD_ID)) {
> > -             struct perf_file_section *buildid_sec;
> > +     err = do_write_feat(fd, header, HEADER_HOSTNAME, &p, evlist);
> > +     if (err)
> > +             perf_header__clear_feat(header, HEADER_HOSTNAME);
> >
> > -             buildid_sec = &feat_sec[idx++];
> > +     err = do_write_feat(fd, header, HEADER_OSRELEASE, &p, evlist);
> > +     if (err)
> > +             perf_header__clear_feat(header, HEADER_OSRELEASE);
> >
> > -             /* Write build-ids */
> > -             buildid_sec->offset = lseek(fd, 0, SEEK_CUR);
> > -             err = dsos__write_buildid_table(header, fd);
> > -             if (err < 0) {
> > -                     pr_debug("failed to write buildid table\n");
> > -                     goto out_free;
> > -             }
> > -             buildid_sec->size = lseek(fd, 0, SEEK_CUR) -
> > -                                       buildid_sec->offset;
> > -             if (!no_buildid_cache)
> > -                     perf_session__cache_build_ids(session);
> > -     }
> > +     err = do_write_feat(fd, header, HEADER_ARCH, &p, evlist);
> > +     if (err)
> > +             perf_header__clear_feat(header, HEADER_ARCH);
> > +
> > +     err = do_write_feat(fd, header, HEADER_CPUID, &p, evlist);
> > +     if (err)
> > +             perf_header__clear_feat(header, HEADER_CPUID);
> > +
> > +     err = do_write_feat(fd, header, HEADER_NRCPUS, &p, evlist);
> > +     if (err)
> > +             perf_header__clear_feat(header, HEADER_NRCPUS);
> > +
> > +     err = do_write_feat(fd, header, HEADER_EVENT_DESC, &p, evlist);
> > +     if (err)
> > +             perf_header__clear_feat(header, HEADER_EVENT_DESC);
> > +
> > +     err = do_write_feat(fd, header, HEADER_CMDLINE, &p, evlist);
> > +     if (err)
> > +             perf_header__clear_feat(header, HEADER_CMDLINE);
> > +
> > +     err = do_write_feat(fd, header, HEADER_VERSION, &p, evlist);
> > +     if (err)
> > +             perf_header__clear_feat(header, HEADER_VERSION);
> > +
> > +     err = do_write_feat(fd, header, HEADER_CPU_TOPOLOGY, &p, evlist);
> > +     if (err)
> > +             perf_header__clear_feat(header, HEADER_CPU_TOPOLOGY);
> > +
> > +     err = do_write_feat(fd, header, HEADER_TOTAL_MEM, &p, evlist);
> > +     if (err)
> > +             perf_header__clear_feat(header, HEADER_TOTAL_MEM);
> > +
> > +     err = do_write_feat(fd, header, HEADER_NUMA_TOPOLOGY, &p, evlist);
> > +     if (err)
> > +             perf_header__clear_feat(header, HEADER_NUMA_TOPOLOGY);
> >
> >       lseek(fd, sec_start, SEEK_SET);
> > +     /*
> > +      * may write more than needed due to dropped feature, but
> > +      * this is okay, reader will skip the mising entries
> > +      */
> >       err = do_write(fd, feat_sec, sec_size);
> >       if (err < 0)
> >               pr_debug("failed to write feature section\n");
> > @@ -554,9 +1454,10 @@ static int perf_header__getbuffer64(struct perf_header *header,
> >  }
> >
> >  int perf_header__process_sections(struct perf_header *header, int fd,
> > +                               void *data,
> >                                 int (*process)(struct perf_file_section *section,
> > -                                              struct perf_header *ph,
> > -                                              int feat, int fd))
> > +                               struct perf_header *ph,
> > +                               int feat, int fd, void *data))
> >  {
> >       struct perf_file_section *feat_sec;
> >       int nr_sections;
> > @@ -584,7 +1485,7 @@ int perf_header__process_sections(struct perf_header *header, int fd,
> >               if (perf_header__has_feat(header, feat)) {
> >                       struct perf_file_section *sec = &feat_sec[idx++];
> >
> > -                     err = process(sec, header, feat, fd);
> > +                     err = process(sec, header, feat, fd, data);
> >                       if (err < 0)
> >                               break;
> >               }
> > @@ -796,7 +1697,7 @@ out:
> >
> >  static int perf_file_section__process(struct perf_file_section *section,
> >                                     struct perf_header *ph,
> > -                                   int feat, int fd)
> > +                                   int feat, int fd, void *data __used)
> >  {
> >       if (lseek(fd, section->offset, SEEK_SET) == (off_t)-1) {
> >               pr_debug("Failed to lseek to %" PRIu64 " offset for feature "
> > @@ -935,7 +1836,8 @@ int perf_session__read_header(struct perf_session *session, int fd)
> >               event_count =  f_header.event_types.size / sizeof(struct perf_trace_event_type);
> >       }
> >
> > -     perf_header__process_sections(header, fd, perf_file_section__process);
> > +     perf_header__process_sections(header, fd, NULL,
> > +                                   perf_file_section__process);
> >
> >       lseek(fd, header->data_offset, SEEK_SET);
> >
> > diff --git a/tools/perf/util/header.h b/tools/perf/util/header.h
> > index 1886256..455480b 100644
> > --- a/tools/perf/util/header.h
> > +++ b/tools/perf/util/header.h
> > @@ -12,6 +12,19 @@
> >  enum {
> >       HEADER_TRACE_INFO = 1,
> >       HEADER_BUILD_ID,
> > +
> > +     HEADER_HOSTNAME,
> > +     HEADER_OSRELEASE,
> > +     HEADER_ARCH,
> > +     HEADER_CPUID,
> > +     HEADER_NRCPUS,
> > +     HEADER_EVENT_DESC,
> > +     HEADER_CMDLINE,
> > +     HEADER_VERSION,
> > +     HEADER_CPU_TOPOLOGY,
> > +     HEADER_TOTAL_MEM,
> > +     HEADER_NUMA_TOPOLOGY,
> > +
> >       HEADER_LAST_FEATURE,
> >  };
> >
> > @@ -68,10 +81,15 @@ void perf_header__set_feat(struct perf_header *header, int feat);
> >  void perf_header__clear_feat(struct perf_header *header, int feat);
> >  bool perf_header__has_feat(const struct perf_header *header, int feat);
> >
> > +int perf_header__set_cmdline(int argc, const char **argv);
> > +
> >  int perf_header__process_sections(struct perf_header *header, int fd,
> > +                               void *data,
> >                                 int (*process)(struct perf_file_section *section,
> > -                                              struct perf_header *ph,
> > -                                              int feat, int fd));
> > +                               struct perf_header *ph,
> > +                               int feat, int fd, void *data));
> > +
> > +int perf_header__fprintf_info(struct perf_session *session, FILE *fp);
> >
> >  int build_id_cache__add_s(const char *sbuild_id, const char *debugdir,
> >                         const char *name, bool is_kallsyms);
> > diff --git a/tools/perf/util/session.c b/tools/perf/util/session.c
> > index 72458d9..54613a2 100644
> > --- a/tools/perf/util/session.c
> > +++ b/tools/perf/util/session.c
> > @@ -1326,3 +1326,21 @@ int perf_session__cpu_bitmap(struct perf_session *session,
> >
> >       return 0;
> >  }
> > +
> > +void perf_session__fprintf_info(struct perf_session *session, FILE *fp)
> > +{
> > +     struct stat st;
> > +     int ret;
> > +
> > +     if (session == NULL || fp == NULL)
> > +             return;
> > +
> > +     ret = fstat(session->fd, &st);
> > +     if (ret == -1)
> > +             return;
> > +
> > +     fprintf(fp, "#\n# captured on: %s", ctime(&st.st_ctime));
> > +     ret = perf_header__fprintf_info(session, fp);
> > +     if (ret == 0)
> > +             fprintf(fp, "#\n");
> > +}
> > diff --git a/tools/perf/util/session.h b/tools/perf/util/session.h
> > index 170601e..33a3a46 100644
> > --- a/tools/perf/util/session.h
> > +++ b/tools/perf/util/session.h
> > @@ -176,4 +176,5 @@ void perf_session__print_ip(union perf_event *event,
> >  int perf_session__cpu_bitmap(struct perf_session *session,
> >                            const char *cpu_list, unsigned long *cpu_bitmap);
> >
> > +void perf_session__fprintf_info(struct perf_session *session, FILE *fp);
> >  #endif /* __PERF_SESSION_H */
--
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