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Subject[RFC PATCH 2/2] powerpc/perf: Implement get_cpu_str()

[RFC PATCH 2/2] powerpc/perf: Implement get_cpu_str()

get_cpu_str() returns a string identifying the CPU type on the system.
This string is then used to locate a cached JSON file which defines
the list of PMU events supported by the CPU.

Eg: if get_cpu_str() returns "power8", the perf tool would refer to the
PMU events defined in ~/.cache/pmu-events/power8.json.

Signed-off-by: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
---
tools/perf/arch/powerpc/util/header.c | 69 +++++++++++++++++++++++++++++++++
tools/perf/perf.c | 11 ++++++
tools/perf/perf.h | 2 +
3 files changed, 82 insertions(+)

diff --git a/tools/perf/arch/powerpc/util/header.c b/tools/perf/arch/powerpc/util/header.c
index 6c1b8a7..4d82593 100644
--- a/tools/perf/arch/powerpc/util/header.c
+++ b/tools/perf/arch/powerpc/util/header.c
@@ -3,9 +3,12 @@
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
+#include <elf.h>
+#include <link.h>

#include "../../util/header.h"
#include "../../util/util.h"
+#include "../../util/jevents.h"

#define mfspr(rn) ({unsigned long rval; \
asm volatile("mfspr %0," __stringify(rn) \
@@ -15,6 +18,8 @@
#define PVR_VER(pvr) (((pvr) >> 16) & 0xFFFF) /* Version field */
#define PVR_REV(pvr) (((pvr) >> 0) & 0xFFFF) /* Revison field */

+static char *cached_cpu_str;
+
int
get_cpuid(char *buffer, size_t sz)
{
@@ -32,3 +37,67 @@ get_cpuid(char *buffer, size_t sz)
}
return -1;
}
+
+static void dup_platform(char *platform)
+{
+ char *bp;
+
+ bp = cached_cpu_str = malloc(128);
+ if (!bp)
+ return;
+
+ /*
+ * Platform could be POWER8 or POWER8E. Exclude any suffixes
+ * after the digit(s)
+ */
+ while (isalpha(*platform))
+ *bp++ = tolower(*platform++);
+
+ while (isdigit(*platform))
+ *bp++ = *platform++;
+ *bp = '\0';
+}
+
+static void *find_auxv(void)
+{
+ char **envp;
+
+ /*
+ * Exec() copies the AUX Variables after the environment variables.
+ */
+ envp = environ;
+ while (*envp)
+ envp++;
+ envp++;
+
+ return envp;
+}
+
+void cache_cpu_str(void)
+{
+ ElfW(auxv_t) * auxv;
+
+ auxv = (ElfW(auxv_t)*)find_auxv();
+
+ while (auxv->a_type != AT_NULL) {
+ if (auxv->a_type == AT_BASE_PLATFORM) {
+ dup_platform((char *)auxv->a_un.a_val);
+ return;
+ }
+ auxv++;
+ }
+}
+
+/*
+ * Return an identier string for the CPU on this system.
+ *
+ * On Non-NULL return, assume that the caller will free the
+ * returned string buffer.
+ */
+char *get_cpu_str(void)
+{
+ if (cached_cpu_str)
+ return strdup(cached_cpu_str);
+
+ return NULL;
+}
diff --git a/tools/perf/perf.c b/tools/perf/perf.c
index 95c58fc..fb9beb0 100644
--- a/tools/perf/perf.c
+++ b/tools/perf/perf.c
@@ -452,6 +452,10 @@ void pthread__unblock_sigwinch(void)
pthread_sigmask(SIG_UNBLOCK, &set, NULL);
}

+__attribute__((weak)) void cache_cpu_str(void)
+{
+}
+
int main(int argc, const char **argv)
{
const char *cmd;
@@ -460,6 +464,13 @@ int main(int argc, const char **argv)
page_size = sysconf(_SC_PAGE_SIZE);
cacheline_size = sysconf(_SC_LEVEL1_DCACHE_LINESIZE);

+ /*
+ * Architectures that rely on AUXV variables to determine
+ * CPU type must cache the cpu type before setenv() calls
+ * So do that early.
+ */
+ cache_cpu_str();
+
cmd = perf_extract_argv0_path(argv[0]);
if (!cmd)
cmd = "perf-help";
diff --git a/tools/perf/perf.h b/tools/perf/perf.h
index 510c65f..406fd5c 100644
--- a/tools/perf/perf.h
+++ b/tools/perf/perf.h
@@ -65,4 +65,6 @@ struct record_opts {
unsigned initial_delay;
};

+extern void cache_cpu_str(void);
+
#endif
--
1.7.9.5


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