[PATCH v3 08/15] btrace: identify cpu

Markus Metzger
2015-01-29T16:28:44Z

Add a struct for identifying a processor and use it in linux-btrace.c when
identifying the processor we're running on.

We will need this feature for the new btrace format.

2015-01-29 Markus Metzger <markus.t.metzger@intel.com>

gdb/
* common/btrace-common.h (btrace_cpu_vendor, btrace_cpu): New.
* nat/linux-btrace.c: Include x86-cpuid.h.
(btrace_this_cpu): New.
(cpu_supports_bts): Call btrace_this_cpu.
(intel_supports_bts): Add cpu parameter.
---
gdb/common/btrace-common.h | 28 +++++++++++++++++++
gdb/nat/linux-btrace.c | 70 +++++++++++++++++++++++++++++++---------------
2 files changed, 76 insertions(+), 22 deletions(-)

diff --git a/gdb/common/btrace-common.h b/gdb/common/btrace-common.h
index 69e223c..5e67e52 100644
--- a/gdb/common/btrace-common.h
+++ b/gdb/common/btrace-common.h
@@ -61,6 +61,34 @@ enum btrace_format
BTRACE_FORMAT_BTS
};

+/* An enumeration of cpu vendors. */
+
+enum btrace_cpu_vendor
+{
+ /* We do not know this vendor. */
+ CV_UNKNOWN,
+
+ /* Intel. */
+ CV_INTEL
+};
+
+/* A cpu identifier. */
+
+struct btrace_cpu
+{
+ /* The processor vendor. */
+ enum btrace_cpu_vendor vendor;
+
+ /* The cpu family. */
+ unsigned short family;
+
+ /* The cpu model. */
+ unsigned char model;
+
+ /* The cpu stepping. */
+ unsigned char stepping;
+};
+
/* A BTS configuration. */

struct btrace_config_bts
diff --git a/gdb/nat/linux-btrace.c b/gdb/nat/linux-btrace.c
index c7db313..3376a0f 100644
--- a/gdb/nat/linux-btrace.c
+++ b/gdb/nat/linux-btrace.c
@@ -59,6 +59,41 @@ struct perf_event_sample
struct perf_event_bts bts;
};

+/* Identify the cpu we're running on. */
+static struct btrace_cpu
+btrace_this_cpu (void)
+{
+ struct btrace_cpu cpu;
+ unsigned int eax, ebx, ecx, edx;
+ int ok;
+
+ memset (&cpu, 0, sizeof (cpu));
+
+ ok = x86_cpuid (0, &eax, &ebx, &ecx, &edx);
+ if (ok != 0)
+ {
+ if (ebx == signature_INTEL_ebx && ecx == signature_INTEL_ecx
+ && edx == signature_INTEL_edx)
+ {
+ unsigned int cpuid, ignore;
+
+ ok = x86_cpuid (1, &cpuid, &ignore, &ignore, &ignore);
+ if (ok != 0)
+ {
+ cpu.vendor = CV_INTEL;
+
+ cpu.family = (cpuid >> 8) & 0xf;
+ cpu.model = (cpuid >> 4) & 0xf;
+
+ if (cpu.family == 0x6)
+ cpu.model += (cpuid >> 12) & 0xf0;
+ }
+ }
+ }
+
+ return cpu;
+}
+
/* Return non-zero if there is new data in PEVENT; zero otherwise. */

static int
@@ -302,22 +337,12 @@ kernel_supports_bts (void)
/* Check whether an Intel cpu supports BTS. */

static int
-intel_supports_bts (void)
+intel_supports_bts (const struct btrace_cpu *cpu)
{
- unsigned int cpuid, model, family;
-
- if (!x86_cpuid (1, &cpuid, NULL, NULL, NULL))
- return 0;
-
- family = (cpuid >> 8) & 0xf;
- model = (cpuid >> 4) & 0xf;
-
- switch (family)
+ switch (cpu->family)
{
case 0x6:
- model += (cpuid >> 12) & 0xf0;
-
- switch (model)
+ switch (cpu->model)
{
case 0x1a: /* Nehalem */
case 0x1f:
@@ -345,17 +370,18 @@ intel_supports_bts (void)
static int
cpu_supports_bts (void)
{
- unsigned int ebx, ecx, edx;
+ struct btrace_cpu cpu;

- if (!x86_cpuid (0, NULL, &ebx, &ecx, &edx))
- return 0;
-
- if (ebx == signature_INTEL_ebx && ecx == signature_INTEL_ecx
- && edx == signature_INTEL_edx)
- return intel_supports_bts ();
+ cpu = btrace_this_cpu ();
+ switch (cpu.vendor)
+ {
+ default:
+ /* Don't know about others. Let's assume they do. */
+ return 1;

- /* Don't know about others. Let's assume they do. */
- return 1;
+ case CV_INTEL:
+ return intel_supports_bts (&cpu);
+ }
}

/* Check whether the linux target supports BTS. */
--
1.8.3.1