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 E99EB2D8795 for ; Mon, 3 Aug 2026 21:03:59 +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=1785791041; cv=none; b=NxUfWMPlqx2gkDT7k0NEsITtWSi070osC8J6BFWSHkReEBgKmmDsOlRxp//xU+vAIRpr3dauGtM6SJm3ztQ9qzLYsM56AZ2S9P8RYu/jHH5j6Bo8OlfBKZFW4Dpeo+9f0oFgpcBruR9WhPowXbzW+uZlFcUqjoUcJ96SFe0lvoM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785791041; c=relaxed/simple; bh=W2cGqnusXD2LFqDYrdLnj0cewoGr0NYqM2L+7sGk158=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=olVif98TSv8hHy0UIIhEkzH/q6ltfWSElEeB3/gXSD62JZL1Fg8D2Ya0CcOUm4KspkO3toBXi66+nOQ5GeYZfJJArZocJxgySEe78qsGAl0VdUrMMF8+nUnW/lOsjI30u1Tez6dkJ6iIVr+xG2fpWF7Ei+2MfXHIN5z08D/mtQg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=GpqCRGvs; 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="GpqCRGvs" Received: by smtp.kernel.org (Postfix) with ESMTPSA id BEC8A1F000E9; Mon, 3 Aug 2026 21:03:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1785791039; bh=+SX8NxUbZeYfjH43erTRUuQb/35jvvrPydgzwfAAIdc=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=GpqCRGvsJfOOSg0f+NSxU/pqTBvU++6BwvXjiD8rDtGWpw5iPfBjizLrzE4JUMNNr q0XZadVxARxSI6pS8u+UBtShp+C4m5GldZkLCKuhTjs+E5Of5L8qYq5GXbveaVfFIP W3O8LkQjdXhMg3RoKpSeqpXzSd5MnYuFoCY9eUgGbUxitYajo0GjCVIW3P9KCiogdw hzrkEKWPUD2vL0hO0La7uR32Xc3mR0XizKENoa8C87KkSp6R0ZPQ6lcA/y+uNIFTO7 yv5kvieoEDGNyAQIROvEMrzez+ovxOBfyZyQXU13U7EjdLWbulEOl71TE1haybQR0U /1nHyzXW5VGJQ== From: Jiri Olsa To: Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko Cc: bpf@vger.kernel.org, Martin KaFai Lau , Eduard Zingerman , Song Liu , Yonghong Song , Quentin Monnet , Tao Chen , STAR Labs SG , Arnaud Lecomte Subject: [PATCHv3 bpf-next 12/12] bpf: Avoid changing callchain in bpf_get_stackid_pe Date: Mon, 3 Aug 2026 23:01:49 +0200 Message-ID: <20260803210149.296496-13-jolsa@kernel.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260803210149.296496-1-jolsa@kernel.org> References: <20260803210149.296496-1-jolsa@kernel.org> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit There's no need to modify the trace object bpf_get_stackid_pe, we just need to pass the needed callchain length in separate argument. This way we can have callchain pointers const and remove the trace->nr modification and restoration. Assisted-by: Codex:GPT-5.5 Signed-off-by: Jiri Olsa --- kernel/bpf/stackmap.c | 39 +++++++++++++++++---------------------- 1 file changed, 17 insertions(+), 22 deletions(-) diff --git a/kernel/bpf/stackmap.c b/kernel/bpf/stackmap.c index 19858e1562ce..da72efc8b774 100644 --- a/kernel/bpf/stackmap.c +++ b/kernel/bpf/stackmap.c @@ -506,7 +506,7 @@ get_callchain_entry_for_task(struct task_struct *task, u32 max_depth) struct stackid { struct stack_map_bucket *bucket; - u64 *ips; + const u64 *ips; u32 nr; u32 len; u32 hash; @@ -515,21 +515,21 @@ struct stackid { }; static int stackid_init(struct stackid *stackid, struct bpf_map *map, - struct perf_callchain_entry *trace, u64 flags) + const struct perf_callchain_entry *trace, u32 trace_nr, u64 flags) { struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map); u32 skip = flags & BPF_F_SKIP_FIELD_MASK; u32 max_depth; - if (trace->nr <= skip) + if (trace_nr <= skip) /* skipping more than usable stack trace */ return -EFAULT; max_depth = stack_map_calculate_max_depth(map->value_size, stack_map_data_size(map), flags); - stackid->nr = min_t(u32, trace->nr - skip, max_depth - skip); + stackid->nr = min_t(u32, trace_nr - skip, max_depth - skip); stackid->len = stackid->nr * sizeof(u64); stackid->ips = trace->ip + skip; - stackid->hash = jhash2((u32 *)stackid->ips, stackid->len / sizeof(u32), 0); + stackid->hash = jhash2((const u32 *)stackid->ips, stackid->len / sizeof(u32), 0); stackid->id = stackid->hash & (smap->n_buckets - 1); stackid->bucket = READ_ONCE(smap->buckets[stackid->id]); stackid->hash_matches = stackid->bucket && stackid->bucket->hash == stackid->hash; @@ -537,11 +537,12 @@ static int stackid_init(struct stackid *stackid, struct bpf_map *map, } static int stackid_fastpath(struct stackid *stackid, struct bpf_map *map, - struct perf_callchain_entry *trace, u64 flags) + const struct perf_callchain_entry *trace, u32 trace_nr, + u64 flags) { int err; - err = stackid_init(stackid, map, trace, flags); + err = stackid_init(stackid, map, trace, trace_nr, flags); if (err) return err; @@ -640,7 +641,7 @@ BPF_CALL_3(bpf_get_stackid, struct pt_regs *, regs, struct bpf_map *, map, /* couldn't fetch the stack trace */ return -EFAULT; - err = stackid_fastpath(&stackid, map, trace, flags); + err = stackid_fastpath(&stackid, map, trace, trace->nr, flags); if (err != -ENOENT) return err; @@ -676,12 +677,13 @@ static __u64 count_kernel_ip(const struct perf_callchain_entry *trace) BPF_CALL_3(bpf_get_stackid_pe, struct bpf_perf_event_data_kern *, ctx, struct bpf_map *, map, u64, flags) { + const struct perf_callchain_entry *trace; struct perf_event *event = ctx->event; struct stack_map_bucket *new_bucket; - struct perf_callchain_entry *trace; struct stackid stackid; bool kernel, user; __u64 nr_kernel; + u32 trace_nr; int ret; /* perf_sample_data doesn't have callchain, use bpf_get_stackid */ @@ -701,13 +703,13 @@ BPF_CALL_3(bpf_get_stackid_pe, struct bpf_perf_event_data_kern *, ctx, return -EFAULT; nr_kernel = count_kernel_ip(trace); - __u64 nr = trace->nr; /* save original */ if (kernel) { - trace->nr = nr_kernel; + trace_nr = nr_kernel; } else { /* user */ u64 skip = flags & BPF_F_SKIP_FIELD_MASK; + trace_nr = trace->nr; skip += nr_kernel; if (skip > BPF_F_SKIP_FIELD_MASK) return -EFAULT; @@ -715,21 +717,14 @@ BPF_CALL_3(bpf_get_stackid_pe, struct bpf_perf_event_data_kern *, ctx, flags = (flags & ~BPF_F_SKIP_FIELD_MASK) | skip; } - ret = stackid_fastpath(&stackid, map, trace, flags); + ret = stackid_fastpath(&stackid, map, trace, trace_nr, flags); if (ret != -ENOENT) - goto out; + return ret; new_bucket = stackid_new_bucket(&stackid, map); - if (new_bucket) { - trace->nr = nr; + if (new_bucket) return stackid_install(&stackid, map, new_bucket, flags); - } - ret = -ENOMEM; - -out: - /* restore nr */ - trace->nr = nr; - return ret; + return -ENOMEM; } const struct bpf_func_proto bpf_get_stackid_proto_pe = { -- 2.54.0