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[108.93.236.139]) by smtp.gmail.com with ESMTPSA id 00721157ae682-8b0e590b586sm15829807b3.31.2026.10.16.18.55.51 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 16 Oct 2026 18:55:53 -0700 (PDT) From: Matt Turner Subject: [PATCH v2 0/5] alpha: perf register sampling and user stack dumps Date: Fri, 16 Oct 2026 21:55:46 -0400 Message-Id: <20261016-alpha-perf-regs-v3-v2-0-17654742226a@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit X-B4-Tracking: v=1; b=H4sIAAAAAAAC/22NywrCQAxFf0WyNjJJaauu/A/pIoxpG+iLGRmU0 n93LC5dngP33BWiBtMI18MKQZNFm6cMfDyA72XqFO2RGdhxRc4RyrD0gouGFoN2EVOBtXJRurM nLwx5uARt7bVH703m3uJzDu/9I9HX/nL0N5cIHapIxaUUl5r41o1iw8nPIzTbtn0A3qXslrQAA AA= X-Change-ID: 20261001-alpha-perf-regs-v3-7e23508c1ca2 To: Richard Henderson , Magnus Lindholm Cc: linux-alpha@vger.kernel.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-perf-users@vger.kernel.org, Ian Rogers , Matt Turner X-Mailer: b4 0.14.3 X-Developer-Signature: v=1; a=openpgp-sha256; l=2600; i=mattst88@gmail.com; h=from:subject:message-id; bh=amj26N7GBgNkKSic738dtOdhoZO7SxmjDL8PSryCbBM=; b=owGbwMvMwCW25rVmCc8sv+mMp9WSGLIuXV10VlF/39zcEnabm29+TT3kMS/kx1KnuxE/ue+/q VO/dvaiRMdHFgYxLoaZYooscesVWWa17Vjqc1r6F8wcViaQIdIiDQxAwMLAl5uYV2qkY6Rnqm2o Zwhk6BjFQ+T0GDQyi4tLU4t00wqKHPLySxJLMvPzivXyC1LzCtIL9NIy00oyMvKLilOBRujlpZa Yujq6GRkamFg6Wpg5WTiamjg7Oxk6uTk6Ors6GVmamxg4WzqauFqaM3BxCsBc8+sII8OBrdfP7X Eqff9YNU3ZSX5F71HXXXLHn+imX3ir3Lk8a7cSw/+I9/9t113QsWAvmjDz/+8rwXUP++dvXz5n2 /tNtxWXsuczAwA= X-Developer-Key: i=mattst88@gmail.com; a=openpgp; fpr=3BB639E56F861FA2E86505690FDD682D974CA72A This lets perf sample registers and dump the user stack on alpha, which perf record --call-graph dwarf needs to unwind user space. r9-r15 are not in pt_regs, so they cannot be sampled. An unwinder therefore cannot get past a first frame that uses $15 as its frame pointer (-O0 code or alloca). The perf tool side is a separate patch for perf-tools-next: https://lore.kernel.org/r/20261011-alpha-perf-tools-regs-v1-1-2a5940e22548@gmail.com libdw also needs alpha unwinding support, which I sent to elfutils-devel: https://inbox.sourceware.org/elfutils-devel/20261012-alpha-v1-0-46760216dfb7@gmail.com/ --- Changes in v2: - Patch 4: report sp as 0 for software event samples, whose pt_regs is a per-CPU buffer rather than a trap frame (Magnus). - New patch 5: fill in pc for those samples via perf_arch_fetch_caller_regs() (Magnus). - Collect trailers. Magnus's Tested-by on patch 4 dropped until he retests the change. - Link the perf and elfutils postings. - Link to v1: https://lore.kernel.org/r/20261011-alpha-perf-regs-v3-v1-0-eaa625a39712@gmail.com --- Matt Turner (5): alpha: fix stale user_stack_pointer() alpha: stop storing the user stack pointer in pt_regs alpha: use user_stack_pointer() in KSTK_ESP() and dump_elf_thread() alpha: add HAVE_PERF_REGS and HAVE_PERF_USER_STACK_DUMP support alpha: fill in pc for software event samples .../features/perf/perf-regs/arch-support.txt | 2 +- .../features/perf/perf-stackdump/arch-support.txt | 2 +- arch/alpha/Kconfig | 2 + arch/alpha/include/asm/perf_event.h | 7 +++ arch/alpha/include/asm/processor.h | 3 +- arch/alpha/include/asm/ptrace.h | 7 +-- arch/alpha/include/uapi/asm/perf_regs.h | 45 +++++++++++++++ arch/alpha/include/uapi/asm/ptrace.h | 2 +- arch/alpha/kernel/Makefile | 1 + arch/alpha/kernel/asm-offsets.c | 1 - arch/alpha/kernel/entry.S | 5 -- arch/alpha/kernel/perf_regs.c | 64 ++++++++++++++++++++++ arch/alpha/kernel/process.c | 2 +- arch/alpha/kernel/ptrace.c | 12 ++++ arch/alpha/kernel/traps.c | 8 --- 15 files changed, 137 insertions(+), 26 deletions(-) --- base-commit: 8f5dbfb93440d1aba216a1a34369a65654b94be9 change-id: 20261001-alpha-perf-regs-v3-7e23508c1ca2 Best regards, -- Matt Turner