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SubjectRe: I.1 - System calls - ioctl
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On Mon, 2009-06-22 at 08:58 -0400, Christoph Hellwig wrote:
> But talking about syscalls the sys_perf_counter_open prototype is
> really ugly - it uses either the pid or cpu argument which is a pretty
> clear indicator it should actually be two sys calls.

Would something like the below be any better?

It would allow us to later add something like PERF_TARGET_SOCKET and
things like that.

(utterly untested)

---
include/linux/perf_counter.h | 12 ++++++++++++
include/linux/syscalls.h | 3 ++-
kernel/perf_counter.c | 24 +++++++++++++++++++++++-
tools/perf/builtin-record.c | 11 ++++++++++-
tools/perf/builtin-stat.c | 12 ++++++++++--
tools/perf/builtin-top.c | 11 ++++++++++-
tools/perf/perf.h | 7 +++----
7 files changed, 70 insertions(+), 10 deletions(-)

diff --git a/include/linux/perf_counter.h b/include/linux/perf_counter.h
index 5e970c7..f7dd22e 100644
--- a/include/linux/perf_counter.h
+++ b/include/linux/perf_counter.h
@@ -189,6 +189,18 @@ struct perf_counter_attr {
__u64 __reserved_3;
};

+enum perf_counter_target_ids {
+ PERF_TARGET_PID = 0,
+ PERF_TARGET_CPU = 1,
+
+ PERF_TARGET_MAX /* non-ABI */
+};
+
+struct perf_counter_target {
+ __u32 id;
+ __u64 val;
+};
+
/*
* Ioctls that can be done on a perf counter fd:
*/
diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
index 80de700..670edad 100644
--- a/include/linux/syscalls.h
+++ b/include/linux/syscalls.h
@@ -760,5 +760,6 @@ int kernel_execve(const char *filename, char *const argv[], char *const envp[]);

asmlinkage long sys_perf_counter_open(
struct perf_counter_attr __user *attr_uptr,
- pid_t pid, int cpu, int group_fd, unsigned long flags);
+ struct perf_counter_target __user *target,
+ int group_fd, unsigned long flags);
#endif
diff --git a/kernel/perf_counter.c b/kernel/perf_counter.c
index fa20a9d..205f0b6 100644
--- a/kernel/perf_counter.c
+++ b/kernel/perf_counter.c
@@ -3969,15 +3969,18 @@ err_size:
*/
SYSCALL_DEFINE5(perf_counter_open,
struct perf_counter_attr __user *, attr_uptr,
- pid_t, pid, int, cpu, int, group_fd, unsigned long, flags)
+ struct perf_counter_target __user *, target_uptr,
+ int, group_fd, unsigned long, flags)
{
struct perf_counter *counter, *group_leader;
struct perf_counter_attr attr;
+ struct perf_counter_target target;
struct perf_counter_context *ctx;
struct file *counter_file = NULL;
struct file *group_file = NULL;
int fput_needed = 0;
int fput_needed2 = 0;
+ int pid, cpu;
int ret;

/* for future expandability... */
@@ -3998,6 +4001,25 @@ SYSCALL_DEFINE5(perf_counter_open,
return -EINVAL;
}

+ ret = copy_from_user(&target, target_uptr, sizeof(target));
+ if (ret)
+ return ret;
+
+ switch (target.id) {
+ case PERF_TARGET_PID:
+ pid = target.val;
+ cpu = -1;
+ break;
+
+ case PERF_TARGET_CPU:
+ cpu = target.val;
+ pid = -1;
+ break;
+
+ default:
+ return -EINVAL;
+ }
+
/*
* Get the target context (task or percpu):
*/
diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
index 4ef78a5..b172d30 100644
--- a/tools/perf/builtin-record.c
+++ b/tools/perf/builtin-record.c
@@ -374,6 +374,7 @@ static struct perf_header_attr *get_header_attr(struct perf_counter_attr *a, int
static void create_counter(int counter, int cpu, pid_t pid)
{
struct perf_counter_attr *attr = attrs + counter;
+ struct perf_counter_target target;
struct perf_header_attr *h_attr;
int track = !counter; /* only the first counter needs these */
struct {
@@ -409,8 +410,16 @@ static void create_counter(int counter, int cpu, pid_t pid)
attr->inherit = (cpu < 0) && inherit;
attr->disabled = 1;

+ if (cpu < 0) {
+ target.id = PERF_TARGET_PID;
+ target.val = pid;
+ } else {
+ target.id = PERF_TARGET_CPU;
+ target.val = cpu;
+ }
+
try_again:
- fd[nr_cpu][counter] = sys_perf_counter_open(attr, pid, cpu, group_fd, 0);
+ fd[nr_cpu][counter] = sys_perf_counter_open(attr, &target, group_fd, 0);

if (fd[nr_cpu][counter] < 0) {
int err = errno;
diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c
index 27921a8..342e642 100644
--- a/tools/perf/builtin-stat.c
+++ b/tools/perf/builtin-stat.c
@@ -106,6 +106,7 @@ static u64 runtime_cycles_noise;
static void create_perf_stat_counter(int counter, int pid)
{
struct perf_counter_attr *attr = attrs + counter;
+ struct perf_counter_target target;

if (scale)
attr->read_format = PERF_FORMAT_TOTAL_TIME_ENABLED |
@@ -114,8 +115,12 @@ static void create_perf_stat_counter(int counter, int pid)
if (system_wide) {
unsigned int cpu;

+ target.id = PERF_TARGET_CPU;
+
for (cpu = 0; cpu < nr_cpus; cpu++) {
- fd[cpu][counter] = sys_perf_counter_open(attr, -1, cpu, -1, 0);
+ target.val = cpu;
+
+ fd[cpu][counter] = sys_perf_counter_open(attr, &target, -1, 0);
if (fd[cpu][counter] < 0 && verbose)
fprintf(stderr, ERR_PERF_OPEN, counter,
fd[cpu][counter], strerror(errno));
@@ -125,7 +130,10 @@ static void create_perf_stat_counter(int counter, int pid)
attr->disabled = 1;
attr->enable_on_exec = 1;

- fd[0][counter] = sys_perf_counter_open(attr, pid, -1, -1, 0);
+ target.id = PERF_TARGET_PID;
+ target.val = pid;
+
+ fd[0][counter] = sys_perf_counter_open(attr, &target, -1, 0);
if (fd[0][counter] < 0 && verbose)
fprintf(stderr, ERR_PERF_OPEN, counter,
fd[0][counter], strerror(errno));
diff --git a/tools/perf/builtin-top.c b/tools/perf/builtin-top.c
index 95d5c0a..facc870 100644
--- a/tools/perf/builtin-top.c
+++ b/tools/perf/builtin-top.c
@@ -548,6 +548,7 @@ int group_fd;

static void start_counter(int i, int counter)
{
+ struct perf_counter_target target;
struct perf_counter_attr *attr;
unsigned int cpu;

@@ -560,8 +561,16 @@ static void start_counter(int i, int counter)
attr->sample_type = PERF_SAMPLE_IP | PERF_SAMPLE_TID;
attr->freq = freq;

+ if (cpu < 0) {
+ target.id = PERF_TARGET_PID;
+ target.val = target_pid;
+ } else {
+ target.id = PERF_TARGET_CPU;
+ target.val = cpu;
+ }
+
try_again:
- fd[i][counter] = sys_perf_counter_open(attr, target_pid, cpu, group_fd, 0);
+ fd[i][counter] = sys_perf_counter_open(attr, &target, group_fd, 0);

if (fd[i][counter] < 0) {
int err = errno;
diff --git a/tools/perf/perf.h b/tools/perf/perf.h
index e5148e2..3d663d7 100644
--- a/tools/perf/perf.h
+++ b/tools/perf/perf.h
@@ -85,12 +85,11 @@ static inline unsigned long long rdclock(void)

static inline int
sys_perf_counter_open(struct perf_counter_attr *attr,
- pid_t pid, int cpu, int group_fd,
- unsigned long flags)
+ struct perf_counter_target *target,
+ int group_fd, unsigned long flags)
{
attr->size = sizeof(*attr);
- return syscall(__NR_perf_counter_open, attr, pid, cpu,
- group_fd, flags);
+ return syscall(__NR_perf_counter_open, attr, target, group_fd, flags);
}

#define MAX_COUNTERS 256



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