From: sashiko-bot@kernel.org
To: "Matt Turner" <mattst88@gmail.com>
Cc: linux-perf-users@vger.kernel.org
Subject: Re: [PATCH 4/4] alpha: add HAVE_PERF_REGS and HAVE_PERF_USER_STACK_DUMP support
Date: Sun, 11 Oct 2026 20:25:00 +0000 [thread overview]
Message-ID: <sashiko-outbox-167449@kernel.org> (raw)
In-Reply-To: <20261011-alpha-perf-regs-v3-v1-4-eaa625a39712@gmail.com>
> Let perf sample registers and dump the user stack, which is what the
> perf tool needs for --call-graph dwarf.
>
> The register indices follow the hardware numbering, so r0-r30 map
> directly to DWARF register numbers, with pc after them. r9-r15
> are callee-saved and live in switch_stack rather than pt_regs, so they
> cannot be sampled. Without r15 an unwinder cannot recover the CFA of a
> first frame that uses $15 as its frame pointer.
>
> sp is not in pt_regs either: for user frames it comes from
> user_stack_pointer(), and for kernel frames (PERF_SAMPLE_REGS_INTR) it
> is the end of the trap frame, as in stacktrace.c.
>
> Assisted-by: Claude:claude-opus-5-5
> Signed-off-by: Matt Turner <mattst88@gmail.com>
Sashiko has reviewed this patch and found no issues. It looks great!
--
Sashiko AI review · https://sashiko.dev/#/patchset/20261011-alpha-perf-regs-v3-v1-0-eaa625a39712@gmail.com?part=4
next prev parent reply other threads:[~2026-10-11 20:25 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-10-11 20:16 [PATCH 0/4] alpha: perf register sampling and user stack dumps Matt Turner
2026-10-11 20:16 ` [PATCH 1/4] alpha: fix stale user_stack_pointer() Matt Turner
2026-10-11 20:32 ` sashiko-bot
2026-10-12 16:18 ` Magnus Lindholm
2026-10-11 20:16 ` [PATCH 2/4] alpha: stop storing the user stack pointer in pt_regs Matt Turner
2026-10-11 20:30 ` sashiko-bot
2026-10-12 16:20 ` Magnus Lindholm
2026-10-11 20:16 ` [PATCH 3/4] alpha: use user_stack_pointer() in KSTK_ESP() and dump_elf_thread() Matt Turner
2026-10-11 20:31 ` sashiko-bot
2026-10-12 17:12 ` Magnus Lindholm
2026-10-11 20:16 ` [PATCH 4/4] alpha: add HAVE_PERF_REGS and HAVE_PERF_USER_STACK_DUMP support Matt Turner
2026-10-11 20:25 ` sashiko-bot [this message]
2026-10-12 17:34 ` Magnus Lindholm
2026-10-11 21:47 ` [PATCH 0/4] alpha: perf register sampling and user stack dumps Ian Rogers
2026-10-12 15:51 ` Magnus Lindholm
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