Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 58731C433EF for ; Fri, 17 Dec 2021 15:45:56 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238064AbhLQPpz (ORCPT ); Fri, 17 Dec 2021 10:45:55 -0500 Received: from foss.arm.com ([217.140.110.172]:59354 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235790AbhLQPpw (ORCPT ); Fri, 17 Dec 2021 10:45:52 -0500 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 676171042; Fri, 17 Dec 2021 07:45:52 -0800 (PST) Received: from ip-10-252-15-108.eu-west-1.compute.internal (unknown [10.252.15.108]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id 370663F774; Fri, 17 Dec 2021 07:45:50 -0800 (PST) From: German Gomez To: linux-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org, acme@kernel.org Cc: Alexandre Truong , German Gomez , John Garry , Will Deacon , Mathieu Poirier , Leo Yan , Mark Rutland , Alexander Shishkin , Jiri Olsa , Namhyung Kim , linux-arm-kernel@lists.infradead.org Subject: [PATCH v5 6/6] perf arm64: inject missing frames if perf-record used "--call-graph=fp" Date: Fri, 17 Dec 2021 15:45:20 +0000 Message-Id: <20211217154521.80603-7-german.gomez@arm.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20211217154521.80603-1-german.gomez@arm.com> References: <20211217154521.80603-1-german.gomez@arm.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Alexandre Truong When unwinding using frame pointers on ARM64, the return address of the current function may not have been pushed into the stack when a function was interrupted, which makes perf show an incorrect call graph to the user. Consider the following example program: void leaf() { /* long computation */ } void parent() { // (1) leaf(); // (2) } ... could be compiled into (using gcc -fno-inline -fno-omit-frame-pointer): leaf: /* long computation */ nop ret parent: // (1) stp x29, x30, [sp, -16]! mov x29, sp bl parent nop ldp x29, x30, [sp], 16 // (2) ret If the program is interrupted at (1), (2), or any point in "leaf:", the call graph will skip the callers of the current function. We can unwind using the dwarf info and check if the return addr is the same as the LR register, and inject the missing frame into the call graph. Before this patch, the above example shows the following call-graph when recording using "--call-graph fp" mode in ARM64: # Children Self Command Shared Object Symbol # ........ ........ ........ ................ ...................... # 99.86% 99.86% program3 program3 [.] leaf | ---_start __libc_start_main main leaf As can be seen, the "parent" function is missing. This is specially problematic in "leaf" because for leaf functions the compiler may always omit pushing the return addr into the stack. After this patch, it shows the correct graph: # Children Self Command Shared Object Symbol # ........ ........ ........ ................ ...................... # 99.86% 99.86% program3 program3 [.] leaf | ---_start __libc_start_main main parent leaf Signed-off-by: Alexandre Truong Signed-off-by: German Gomez --- tools/perf/util/Build | 1 + .../util/arm64-frame-pointer-unwind-support.c | 63 +++++++++++++++++++ .../util/arm64-frame-pointer-unwind-support.h | 10 +++ tools/perf/util/machine.c | 19 ++++-- tools/perf/util/machine.h | 1 + 5 files changed, 89 insertions(+), 5 deletions(-) create mode 100644 tools/perf/util/arm64-frame-pointer-unwind-support.c create mode 100644 tools/perf/util/arm64-frame-pointer-unwind-support.h diff --git a/tools/perf/util/Build b/tools/perf/util/Build index 2e5bfbb69960..03d4c647bd86 100644 --- a/tools/perf/util/Build +++ b/tools/perf/util/Build @@ -1,3 +1,4 @@ +perf-y += arm64-frame-pointer-unwind-support.o perf-y += annotate.o perf-y += block-info.o perf-y += block-range.o diff --git a/tools/perf/util/arm64-frame-pointer-unwind-support.c b/tools/perf/util/arm64-frame-pointer-unwind-support.c new file mode 100644 index 000000000000..4f5ecf51ed38 --- /dev/null +++ b/tools/perf/util/arm64-frame-pointer-unwind-support.c @@ -0,0 +1,63 @@ +// SPDX-License-Identifier: GPL-2.0 +#include "arm64-frame-pointer-unwind-support.h" +#include "callchain.h" +#include "event.h" +#include "perf_regs.h" // SMPL_REG_MASK +#include "unwind.h" + +#define perf_event_arm_regs perf_event_arm64_regs +#include "../arch/arm64/include/uapi/asm/perf_regs.h" +#undef perf_event_arm_regs + +struct entries { + u64 stack[2]; + size_t length; +}; + +static bool get_leaf_frame_caller_enabled(struct perf_sample *sample) +{ + return callchain_param.record_mode == CALLCHAIN_FP && sample->user_regs.regs + && sample->user_regs.mask & SMPL_REG_MASK(PERF_REG_ARM64_LR); +} + +static int add_entry(struct unwind_entry *entry, void *arg) +{ + struct entries *entries = arg; + + entries->stack[entries->length++] = entry->ip; + return 0; +} + +u64 get_leaf_frame_caller_aarch64(struct perf_sample *sample, struct thread *thread, int usr_idx) +{ + int ret; + struct entries entries = {}; + struct regs_dump old_regs = sample->user_regs; + + if (!get_leaf_frame_caller_enabled(sample)) + return 0; + + /* + * If PC and SP are not recorded, get the value of PC from the stack + * and set its mask. SP is not used when doing the unwinding but it + * still needs to be set to prevent failures. + */ + + if (!(sample->user_regs.mask & SMPL_REG_MASK(PERF_REG_ARM64_PC))) { + sample->user_regs.cache_mask |= SMPL_REG_MASK(PERF_REG_ARM64_PC); + sample->user_regs.cache_regs[PERF_REG_ARM64_PC] = sample->callchain->ips[usr_idx+1]; + } + + if (!(sample->user_regs.mask & SMPL_REG_MASK(PERF_REG_ARM64_SP))) { + sample->user_regs.cache_mask |= SMPL_REG_MASK(PERF_REG_ARM64_SP); + sample->user_regs.cache_regs[PERF_REG_ARM64_SP] = 0; + } + + ret = unwind__get_entries(add_entry, &entries, thread, sample, 2); + sample->user_regs = old_regs; + + if (ret || entries.length != 2) + return ret; + + return callchain_param.order == ORDER_CALLER ? entries.stack[0] : entries.stack[1]; +} diff --git a/tools/perf/util/arm64-frame-pointer-unwind-support.h b/tools/perf/util/arm64-frame-pointer-unwind-support.h new file mode 100644 index 000000000000..32af9ce94398 --- /dev/null +++ b/tools/perf/util/arm64-frame-pointer-unwind-support.h @@ -0,0 +1,10 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef __PERF_ARM_FRAME_POINTER_UNWIND_SUPPORT_H +#define __PERF_ARM_FRAME_POINTER_UNWIND_SUPPORT_H + +#include "event.h" +#include "thread.h" + +u64 get_leaf_frame_caller_aarch64(struct perf_sample *sample, struct thread *thread, int user_idx); + +#endif /* __PERF_ARM_FRAME_POINTER_UNWIND_SUPPORT_H */ diff --git a/tools/perf/util/machine.c b/tools/perf/util/machine.c index 3eddad009f78..a00fd6796b35 100644 --- a/tools/perf/util/machine.c +++ b/tools/perf/util/machine.c @@ -34,6 +34,7 @@ #include "bpf-event.h" #include // page_size #include "cgroup.h" +#include "arm64-frame-pointer-unwind-support.h" #include #include @@ -2710,10 +2711,13 @@ static int find_prev_cpumode(struct ip_callchain *chain, struct thread *thread, return err; } -static u64 get_leaf_frame_caller(struct perf_sample *sample __maybe_unused, - struct thread *thread __maybe_unused, int usr_idx __maybe_unused) +static u64 get_leaf_frame_caller(struct perf_sample *sample, + struct thread *thread, int usr_idx) { - return 0; + if (machine__normalize_is(thread->maps->machine, "arm64")) + return get_leaf_frame_caller_aarch64(sample, thread, usr_idx); + else + return 0; } static int thread__resolve_callchain_sample(struct thread *thread, @@ -3114,14 +3118,19 @@ int machine__set_current_tid(struct machine *machine, int cpu, pid_t pid, } /* - * Compares the raw arch string. N.B. see instead perf_env__arch() if a - * normalized arch is needed. + * Compares the raw arch string. N.B. see instead perf_env__arch() or + * machine__normalize_is() if a normalized arch is needed. */ bool machine__is(struct machine *machine, const char *arch) { return machine && !strcmp(perf_env__raw_arch(machine->env), arch); } +bool machine__normalize_is(struct machine *machine, const char *arch) +{ + return machine && !strcmp(perf_env__arch(machine->env), arch); +} + int machine__nr_cpus_avail(struct machine *machine) { return machine ? perf_env__nr_cpus_avail(machine->env) : 0; diff --git a/tools/perf/util/machine.h b/tools/perf/util/machine.h index a143087eeb47..665535153411 100644 --- a/tools/perf/util/machine.h +++ b/tools/perf/util/machine.h @@ -208,6 +208,7 @@ static inline bool machine__is_host(struct machine *machine) } bool machine__is(struct machine *machine, const char *arch); +bool machine__normalize_is(struct machine *machine, const char *arch); int machine__nr_cpus_avail(struct machine *machine); struct thread *__machine__findnew_thread(struct machine *machine, pid_t pid, pid_t tid); -- 2.25.1