Re: [PATCH] perf riscv: Add perf_regs_load and enable the dwarf unwind test

[Chen Pei <cp0613@linux.alibaba.com>]

Both items checked. Neither needs a v2 of this patch.

> Does this file need to explicitly include <stdlib.h>? Since musl libc
> enforces strict POSIX header inclusions, missing the declaration for
> malloc could lead to a build failure regression on musl libc systems.

It is not missing. "perf_regs.h" three lines above resolves to
arch/riscv/include/perf_regs.h, which has #include <stdlib.h> and is
also where PERF_REGS_MAX comes from, so this file cannot be built
without it. arm64 relies on the same transitive include. Checked with
riscv64 gcc 15.3, where an implicit declaration is a hard error:
including only that header is enough to call malloc() and calloc().

> Can perf_sample__user_regs() return NULL here?

It can, but that is not introduced here and cannot be fixed from this
file. arch/x86, arch/arm, arch/arm64 and arch/powerpc all dereference
it the same way, and tests/dwarf-unwind.c:118 does
zfree(&sample.user_regs->regs) unconditionally, so an early return here
would still crash in the caller. A fix has to cover the whole "Test
dwarf unwind" path, or the contract of perf_sample__user_regs() itself.
Either is a separate series, which I can send if wanted.

Best regards,
Pei