Re: [PATCH] perf: perf can not parser the backtrace of app in the 32bit system and 64bit kernel.

[Jiping Ma]

Hi, Will

Please help to review the patch.

Thanks,
Jiping

On 04/29/2020 12:51 PM, Jiping Ma wrote:

We test it as the following steps.
# gcc -g -mthumb -gdwarf -o test test.c
# export CALLGRAPH=dwarf
#(./perftest ./test profiling 1; cd ./profiling/; perf script)

Thanks,
Jiping

On 04/29/2020 12:01 PM, Jiping Ma wrote:

Record PC value from regs[15], it should be regs[32], which cause perf
parser the backtrace failed.

Signed-off-by: Jiping Ma <jiping....@windriver.com>
---
  arch/arm64/kernel/perf_regs.c | 4 ++++
  1 file changed, 4 insertions(+)

diff --git a/arch/arm64/kernel/perf_regs.c b/arch/arm64/kernel/perf_regs.c

index 0bbac61..04088e6 100644
--- a/arch/arm64/kernel/perf_regs.c
+++ b/arch/arm64/kernel/perf_regs.c
@@ -32,6 +32,10 @@ u64 perf_reg_value(struct pt_regs *regs, int idx)
      if ((u32)idx == PERF_REG_ARM64_PC)
          return regs->pc;
  +    if (perf_reg_abi(current) == PERF_SAMPLE_REGS_ABI_32
+        && idx == 15)
+        return regs->regs[PERF_REG_ARM64_PC];
+
      return regs->regs[idx];
  }