From: "Madhavan T. Venkataraman" <madvenka@linux.microsoft.com> To: Mark Rutland <mark.rutland@arm.com> Cc: broonie@kernel.org, jpoimboe@redhat.com, ardb@kernel.org, nobuta.keiya@fujitsu.com, sjitindarsingh@gmail.com, catalin.marinas@arm.com, will@kernel.org, jmorris@namei.org, linux-arm-kernel@lists.infradead.org, live-patching@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v11 1/5] arm64: Call stack_backtrace() only from within walk_stackframe() Date: Tue, 30 Nov 2021 11:13:28 -0600 [thread overview] Message-ID: <f2dfa6cd-7a23-e1b7-09d5-737d4a95b90c@linux.microsoft.com> (raw) In-Reply-To: <YaY9zLNumYZ1lLkc@FVFF77S0Q05N> On 11/30/21 9:05 AM, Mark Rutland wrote: > On Tue, Nov 23, 2021 at 01:37:19PM -0600, madvenka@linux.microsoft.com wrote: >> From: "Madhavan T. Venkataraman" <madvenka@linux.microsoft.com> >> >> Currently, arch_stack_walk() calls start_backtrace() and walk_stackframe() >> separately. There is no need to do that. Instead, call start_backtrace() >> from within walk_stackframe(). In other words, walk_stackframe() is the only >> unwind function a consumer needs to call. >> >> Currently, the only consumer is arch_stack_walk(). In the future, >> arch_stack_walk_reliable() will be another consumer. >> >> Currently, there is a check for a NULL task in unwind_frame(). It is not >> needed since all current consumers pass a non-NULL task. > > Can you split the NULL check change into a preparatory patch? That change is > fine in isolation (and easier to review/ack), and it's nicer for future > bisection to not group that with unrelated changes. > Will do this in the next version. >> Use struct stackframe only within the unwind functions. >> >> Signed-off-by: Madhavan T. Venkataraman <madvenka@linux.microsoft.com> >> --- >> arch/arm64/kernel/stacktrace.c | 41 ++++++++++++++++++---------------- >> 1 file changed, 22 insertions(+), 19 deletions(-) >> >> diff --git a/arch/arm64/kernel/stacktrace.c b/arch/arm64/kernel/stacktrace.c >> index 0fb58fed54cb..7217c4f63ef7 100644 >> --- a/arch/arm64/kernel/stacktrace.c >> +++ b/arch/arm64/kernel/stacktrace.c >> @@ -69,9 +69,6 @@ static int notrace unwind_frame(struct task_struct *tsk, >> unsigned long fp = frame->fp; >> struct stack_info info; >> >> - if (!tsk) >> - tsk = current; >> - >> /* Final frame; nothing to unwind */ >> if (fp == (unsigned long)task_pt_regs(tsk)->stackframe) >> return -ENOENT; >> @@ -143,15 +140,19 @@ static int notrace unwind_frame(struct task_struct *tsk, >> NOKPROBE_SYMBOL(unwind_frame); >> >> static void notrace walk_stackframe(struct task_struct *tsk, >> - struct stackframe *frame, >> + unsigned long fp, unsigned long pc, >> bool (*fn)(void *, unsigned long), void *data) >> { >> + struct stackframe frame; >> + >> + start_backtrace(&frame, fp, pc); >> + >> while (1) { >> int ret; >> >> - if (!fn(data, frame->pc)) >> + if (!fn(data, frame.pc)) >> break; >> - ret = unwind_frame(tsk, frame); >> + ret = unwind_frame(tsk, &frame); >> if (ret < 0) >> break; >> } >> @@ -195,17 +196,19 @@ noinline notrace void arch_stack_walk(stack_trace_consume_fn consume_entry, >> void *cookie, struct task_struct *task, >> struct pt_regs *regs) >> { >> - struct stackframe frame; >> - >> - if (regs) >> - start_backtrace(&frame, regs->regs[29], regs->pc); >> - else if (task == current) >> - start_backtrace(&frame, >> - (unsigned long)__builtin_frame_address(1), >> - (unsigned long)__builtin_return_address(0)); >> - else >> - start_backtrace(&frame, thread_saved_fp(task), >> - thread_saved_pc(task)); >> - >> - walk_stackframe(task, &frame, consume_entry, cookie); >> + unsigned long fp, pc; >> + >> + if (regs) { >> + fp = regs->regs[29]; >> + pc = regs->pc; >> + } else if (task == current) { >> + /* Skip arch_stack_walk() in the stack trace. */ >> + fp = (unsigned long)__builtin_frame_address(1); >> + pc = (unsigned long)__builtin_return_address(0); >> + } else { >> + /* Caller guarantees that the task is not running. */ >> + fp = thread_saved_fp(task); >> + pc = thread_saved_pc(task); >> + } >> + walk_stackframe(task, fp, pc, consume_entry, cookie); > > I'd prefer to leave this as-is. The new and old structure are largely > equivalent, so we haven't made this any simpler, but we have added more > arguments to walk_stackframe(). > This is just to simplify things when we eventually add arch_stack_walk_reliable(). That is all. All of the unwinding is done by a single unwinding function and there are two consumers of that unwinding function - arch_stack_walk() and arch_stack_walk_reliable(). > One thing I *would* like to do is move tsk into strcut stackframe, so we only > need to pass that around, which'll make it easier to refactor the core unwind > logic. > Will do this in the next version. Thanks, Madhavan
WARNING: multiple messages have this Message-ID (diff)
From: "Madhavan T. Venkataraman" <madvenka@linux.microsoft.com> To: Mark Rutland <mark.rutland@arm.com> Cc: broonie@kernel.org, jpoimboe@redhat.com, ardb@kernel.org, nobuta.keiya@fujitsu.com, sjitindarsingh@gmail.com, catalin.marinas@arm.com, will@kernel.org, jmorris@namei.org, linux-arm-kernel@lists.infradead.org, live-patching@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v11 1/5] arm64: Call stack_backtrace() only from within walk_stackframe() Date: Tue, 30 Nov 2021 11:13:28 -0600 [thread overview] Message-ID: <f2dfa6cd-7a23-e1b7-09d5-737d4a95b90c@linux.microsoft.com> (raw) In-Reply-To: <YaY9zLNumYZ1lLkc@FVFF77S0Q05N> On 11/30/21 9:05 AM, Mark Rutland wrote: > On Tue, Nov 23, 2021 at 01:37:19PM -0600, madvenka@linux.microsoft.com wrote: >> From: "Madhavan T. Venkataraman" <madvenka@linux.microsoft.com> >> >> Currently, arch_stack_walk() calls start_backtrace() and walk_stackframe() >> separately. There is no need to do that. Instead, call start_backtrace() >> from within walk_stackframe(). In other words, walk_stackframe() is the only >> unwind function a consumer needs to call. >> >> Currently, the only consumer is arch_stack_walk(). In the future, >> arch_stack_walk_reliable() will be another consumer. >> >> Currently, there is a check for a NULL task in unwind_frame(). It is not >> needed since all current consumers pass a non-NULL task. > > Can you split the NULL check change into a preparatory patch? That change is > fine in isolation (and easier to review/ack), and it's nicer for future > bisection to not group that with unrelated changes. > Will do this in the next version. >> Use struct stackframe only within the unwind functions. >> >> Signed-off-by: Madhavan T. Venkataraman <madvenka@linux.microsoft.com> >> --- >> arch/arm64/kernel/stacktrace.c | 41 ++++++++++++++++++---------------- >> 1 file changed, 22 insertions(+), 19 deletions(-) >> >> diff --git a/arch/arm64/kernel/stacktrace.c b/arch/arm64/kernel/stacktrace.c >> index 0fb58fed54cb..7217c4f63ef7 100644 >> --- a/arch/arm64/kernel/stacktrace.c >> +++ b/arch/arm64/kernel/stacktrace.c >> @@ -69,9 +69,6 @@ static int notrace unwind_frame(struct task_struct *tsk, >> unsigned long fp = frame->fp; >> struct stack_info info; >> >> - if (!tsk) >> - tsk = current; >> - >> /* Final frame; nothing to unwind */ >> if (fp == (unsigned long)task_pt_regs(tsk)->stackframe) >> return -ENOENT; >> @@ -143,15 +140,19 @@ static int notrace unwind_frame(struct task_struct *tsk, >> NOKPROBE_SYMBOL(unwind_frame); >> >> static void notrace walk_stackframe(struct task_struct *tsk, >> - struct stackframe *frame, >> + unsigned long fp, unsigned long pc, >> bool (*fn)(void *, unsigned long), void *data) >> { >> + struct stackframe frame; >> + >> + start_backtrace(&frame, fp, pc); >> + >> while (1) { >> int ret; >> >> - if (!fn(data, frame->pc)) >> + if (!fn(data, frame.pc)) >> break; >> - ret = unwind_frame(tsk, frame); >> + ret = unwind_frame(tsk, &frame); >> if (ret < 0) >> break; >> } >> @@ -195,17 +196,19 @@ noinline notrace void arch_stack_walk(stack_trace_consume_fn consume_entry, >> void *cookie, struct task_struct *task, >> struct pt_regs *regs) >> { >> - struct stackframe frame; >> - >> - if (regs) >> - start_backtrace(&frame, regs->regs[29], regs->pc); >> - else if (task == current) >> - start_backtrace(&frame, >> - (unsigned long)__builtin_frame_address(1), >> - (unsigned long)__builtin_return_address(0)); >> - else >> - start_backtrace(&frame, thread_saved_fp(task), >> - thread_saved_pc(task)); >> - >> - walk_stackframe(task, &frame, consume_entry, cookie); >> + unsigned long fp, pc; >> + >> + if (regs) { >> + fp = regs->regs[29]; >> + pc = regs->pc; >> + } else if (task == current) { >> + /* Skip arch_stack_walk() in the stack trace. */ >> + fp = (unsigned long)__builtin_frame_address(1); >> + pc = (unsigned long)__builtin_return_address(0); >> + } else { >> + /* Caller guarantees that the task is not running. */ >> + fp = thread_saved_fp(task); >> + pc = thread_saved_pc(task); >> + } >> + walk_stackframe(task, fp, pc, consume_entry, cookie); > > I'd prefer to leave this as-is. The new and old structure are largely > equivalent, so we haven't made this any simpler, but we have added more > arguments to walk_stackframe(). > This is just to simplify things when we eventually add arch_stack_walk_reliable(). That is all. All of the unwinding is done by a single unwinding function and there are two consumers of that unwinding function - arch_stack_walk() and arch_stack_walk_reliable(). > One thing I *would* like to do is move tsk into strcut stackframe, so we only > need to pass that around, which'll make it easier to refactor the core unwind > logic. > Will do this in the next version. Thanks, Madhavan _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next prev parent reply other threads:[~2021-11-30 17:13 UTC|newest] Thread overview: 42+ messages / expand[flat|nested] mbox.gz Atom feed top [not found] <8b861784d85a21a9bf08598938c11aff1b1249b9> 2021-11-23 19:37 ` [PATCH v11 0/5] arm64: Reorganize the unwinder and implement stack trace reliability checks madvenka 2021-11-23 19:37 ` madvenka 2021-11-23 19:37 ` [PATCH v11 1/5] arm64: Call stack_backtrace() only from within walk_stackframe() madvenka 2021-11-23 19:37 ` madvenka 2021-11-25 13:48 ` Mark Brown 2021-11-25 13:48 ` Mark Brown 2021-11-30 15:05 ` Mark Rutland 2021-11-30 15:05 ` Mark Rutland 2021-11-30 17:13 ` Madhavan T. Venkataraman [this message] 2021-11-30 17:13 ` Madhavan T. Venkataraman 2021-11-30 18:29 ` Mark Rutland 2021-11-30 18:29 ` Mark Rutland 2021-11-30 20:29 ` Madhavan T. Venkataraman 2021-11-30 20:29 ` Madhavan T. Venkataraman 2021-12-10 4:13 ` Madhavan T. Venkataraman 2021-12-10 4:13 ` Madhavan T. Venkataraman 2021-11-23 19:37 ` [PATCH v11 2/5] arm64: Rename unwinder functions madvenka 2021-11-23 19:37 ` madvenka 2021-11-24 17:10 ` Mark Brown 2021-11-24 17:10 ` Mark Brown 2021-11-30 15:08 ` Mark Rutland 2021-11-30 15:08 ` Mark Rutland 2021-11-30 17:15 ` Madhavan T. Venkataraman 2021-11-30 17:15 ` Madhavan T. Venkataraman 2021-11-23 19:37 ` [PATCH v11 3/5] arm64: Make the unwind loop in unwind() similar to other architectures madvenka 2021-11-23 19:37 ` madvenka 2021-11-25 14:30 ` Mark Brown 2021-11-25 14:30 ` Mark Brown 2021-11-23 19:37 ` [PATCH v11 4/5] arm64: Introduce stack trace reliability checks in the unwinder madvenka 2021-11-23 19:37 ` madvenka 2021-11-25 14:56 ` Mark Brown 2021-11-25 14:56 ` Mark Brown 2021-11-25 16:59 ` Madhavan T. Venkataraman 2021-11-25 16:59 ` Madhavan T. Venkataraman 2021-11-26 13:29 ` Mark Brown 2021-11-26 13:29 ` Mark Brown 2021-11-26 17:23 ` Madhavan T. Venkataraman 2021-11-26 17:23 ` Madhavan T. Venkataraman 2021-11-23 19:37 ` [PATCH v11 5/5] arm64: Create a list of SYM_CODE functions, check return PC against list madvenka 2021-11-23 19:37 ` madvenka 2021-11-25 15:05 ` Mark Brown 2021-11-25 15:05 ` Mark Brown
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