[PATCH V3 01/10] perf: Add irq and exception return branch types

[Anshuman Khandual]

This expands generic branch type classification by adding two more entries
there in i.e irq and exception return. Also updates the x86 implementation
to process X86_BR_IRET and X86_BR_IRQ records as appropriate. This changes
branch types reported to user space on x86 platform but it should not be a
problem. The possible scenarios and impacts are enumerated here.

--------------------------------------------------------------------------
| kernel | perf tool |                     Impact                        |
--------------------------------------------------------------------------
|   old  |    old    |  Works as before                                  |
--------------------------------------------------------------------------
|   old  |    new    |  PERF_BR_UNKNOWN is processed                     |
--------------------------------------------------------------------------
|   new  |    old    |  PERF_BR_ERET/IRQ are blocked via old PERF_BR_MAX |
--------------------------------------------------------------------------
|   new  |    new    |  PERF_BR_ERET/IRQ are recognized                  |
--------------------------------------------------------------------------

When PERF_BR_ERET/IRQ are blocked via old PERF_BR_MAX (new kernel with old
perf tool) the user space might throw up an warning complaining about some
unrecognized branch types being reported, but it is expected. PERF_BR_ERET
and PERF_BR_IRQ branch types will be used for BRBE implementation on arm64
platform.

Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
Cc: Mark Rutland <mark.rutland@xxxxxxx>
Cc: Alexander Shishkin <alexander.shishkin@xxxxxxxxxxxxxxx>
Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Will Deacon <will@xxxxxxxxxx>
Cc: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx
Cc: linux-perf-users@xxxxxxxxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx
Reviewed-by: James Clark <james.clark@xxxxxxx>
Signed-off-by: Anshuman Khandual <anshuman.khandual@xxxxxxx>
---
 arch/x86/events/intel/lbr.c     | 4 ++--
 include/uapi/linux/perf_event.h | 2 ++
 2 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/arch/x86/events/intel/lbr.c b/arch/x86/events/intel/lbr.c
index 669c2be14784..fe1742c4ca49 100644
--- a/arch/x86/events/intel/lbr.c
+++ b/arch/x86/events/intel/lbr.c
@@ -1329,10 +1329,10 @@ static int branch_map[X86_BR_TYPE_MAP_MAX] = {
 	PERF_BR_SYSCALL,	/* X86_BR_SYSCALL */
 	PERF_BR_SYSRET,		/* X86_BR_SYSRET */
 	PERF_BR_UNKNOWN,	/* X86_BR_INT */
-	PERF_BR_UNKNOWN,	/* X86_BR_IRET */
+	PERF_BR_ERET,		/* X86_BR_IRET */
 	PERF_BR_COND,		/* X86_BR_JCC */
 	PERF_BR_UNCOND,		/* X86_BR_JMP */
-	PERF_BR_UNKNOWN,	/* X86_BR_IRQ */
+	PERF_BR_IRQ,		/* X86_BR_IRQ */
 	PERF_BR_IND_CALL,	/* X86_BR_IND_CALL */
 	PERF_BR_UNKNOWN,	/* X86_BR_ABORT */
 	PERF_BR_UNKNOWN,	/* X86_BR_IN_TX */
diff --git a/include/uapi/linux/perf_event.h b/include/uapi/linux/perf_event.h
index 82858b697c05..d37629dbad72 100644
--- a/include/uapi/linux/perf_event.h
+++ b/include/uapi/linux/perf_event.h
@@ -251,6 +251,8 @@ enum {
 	PERF_BR_SYSRET		= 8,	/* syscall return */
 	PERF_BR_COND_CALL	= 9,	/* conditional function call */
 	PERF_BR_COND_RET	= 10,	/* conditional function return */
+	PERF_BR_ERET		= 11,	/* exception return */
+	PERF_BR_IRQ		= 12,	/* irq */
 	PERF_BR_MAX,
 };
 
-- 
2.25.1