linux-kernel - [PATCH] arm64: perf: Report arm pc registers for compat perf

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Date:   Tue, 12 Nov 2019 10:01:41 +0900
From:   Seung-Woo Kim <sw0312.kim@...sung.com>
To:     linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        will@...nel.org, mark.rutland@....com, catalin.marinas@....com
Cc:     sw0312.kim@...sung.com, sungguk.na@...sung.com
Subject: [PATCH] arm64: perf: Report arm pc registers for compat perf

If perf is built as arm 32-bit, it only reads 15 registers as arm
32-bit register map and this breaks dwarf call-chain in compat
perf because pc register information is not filled.
Report arm pc registers for 32-bit compat perf.

Without this, arm 32-bit perf dwarf call-graph shows below
verbose message:
  unwind: reg 15, val 0
  unwind: reg 13, val ffbc6360
  unwind: no map for 0

Signed-off-by: Seung-Woo Kim <sw0312.kim@...sung.com>
---
 arch/arm64/kernel/perf_regs.c |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)

diff --git a/arch/arm64/kernel/perf_regs.c b/arch/arm64/kernel/perf_regs.c
index 0bbac61..d4172e7 100644
--- a/arch/arm64/kernel/perf_regs.c
+++ b/arch/arm64/kernel/perf_regs.c
@@ -24,6 +24,8 @@ u64 perf_reg_value(struct pt_regs *regs, int idx)
 			return regs->compat_sp;
 		if ((u32)idx == PERF_REG_ARM64_LR)
 			return regs->compat_lr;
+		if ((u32)idx == 15) /* PERF_REG_ARM_PC */
+			return regs->pc;
 	}
 
 	if ((u32)idx == PERF_REG_ARM64_SP)
-- 
1.7.4.1