From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 77BD3397935 for ; Sun, 18 Oct 2026 14:36:15 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1792334176; cv=none; b=OyRKHtE2P19w+TCkEpLfYOLWGBp5qmzRQYmKmeIWhNcEHQQU0xNwDuQJdlHoIUKdVdhqQ6huIMzJcMznf9zUwcAWQrlzxIOLRnJEbXzt+645LYcJ3a7I0LrKXqC+5BN6xnnWO6HpIu/fvqMpNdgHFABSYgYUjTiUjk/Z9xhntbY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1792334176; c=relaxed/simple; bh=fUAYll5gdguY3OwgaTGy2Q4lTTAI4gJB2GOYkJY/4XA=; h=Message-ID:From:Subject:To:Cc:In-Reply-To:References:Content-Type: Date; b=PGbhMS/1ybXhy2/iOItSKbdSSkXoavoRnn560q/wSDCIEdL2j9KHGbluEYPDbBWo+BEzFcycMRTUYxWKcjm7bS3jeKzL9/oyhHA4iJmCVb2fj4hsnLzJoknpcBKI6QnkkoSO5RISww1lCkgFe8a4kGMNFF4SUhfYD7XLeNwoTM4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=elG4dPfZ; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="elG4dPfZ" Received: by smtp.kernel.org (Postfix) with ESMTPSA id C87A71F000C4; Sun, 18 Oct 2026 14:36:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1792334174; bh=fUAYll5gdguY3OwgaTGy2Q4lTTAI4gJB2GOYkJY/4XA=; h=From:Subject:Reply-To:To:Cc:In-Reply-To:References:Date; b=elG4dPfZHOMIaOIYCmo4qfjg7VHMWl/X9nX/s2lhTwkwpTcEfF/gnvlTSyb1f2WRQ ipL0wEgKAwo4mGsUn+Jm39zXxYunPiX3uZ5kfoVHP5wrL/vsfWj1GdImq5Byp0f2A7 xciZ5AM2hZ7cNh5eC5qVVY/T6OPPibonEIrqSEjGK0aWKKl+eVRaWeS8RfSNk2L05S U9MRXFVzRakans0u6ZYC13qtrcft6TCApMaU9EHsUZKLvi/JJmge8IAOdcuzxDTxbm ZI/z45gjOEOoGmDSWUFVSAUnjoI96YieITcHYdBA4UqJ4Cm+7YwDZ4CRh+vjjl/TgU ihT9wbTJIX1XA== Message-ID: From: sashiko-bot@kernel.org Subject: Re: [PATCH v3 4/5] alpha: add HAVE_PERF_REGS and HAVE_PERF_USER_STACK_DUMP support Reply-To: sashiko-reviews@lists.linux.dev To: "Matt Turner" Cc: linux-perf-users@vger.kernel.org In-Reply-To: <20261018-alpha-perf-regs-v3-v3-4-52be85332c57@gmail.com> References: <20261018-alpha-perf-regs-v3-v3-0-52be85332c57@gmail.com> <20261018-alpha-perf-regs-v3-v3-4-52be85332c57@gmail.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Date: Sun, 18 Oct 2026 14:36:14 +0000 Precedence: bulk X-Mailing-List: linux-perf-users@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: > Let perf sample registers and dump the user stack, which is what the > perf tool needs for --call-graph dwarf. >=20 > 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. >=20 > 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. >=20 > Software events such as context switches and tracepoints hand perf a > per-CPU pt_regs filled in by perf_fetch_caller_regs() instead of a > trap frame. It is not on the stack and has no room for sp, so report > sp as 0 there rather than the address of the per-CPU buffer. >=20 > Assisted-by: Claude:claude-opus-5-5 > Acked-by: Ian Rogers > Tested-by: Magnus Lindholm > Reviewed-by: Magnus Lindholm > Signed-off-by: Matt Turner Sashiko has reviewed this patch and found no issues. --=20 Sashiko AI review =C2=B7 https://sashiko.dev/#/patchset/20261018-alpha-perf= -regs-v3-v3-0-52be85332c57@gmail.com?part=3D4