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Date: Thu, 30 Sep 2021 10:29:33 +0200 From: Peter Zijlstra <peterz@...radead.org> To: Kees Cook <keescook@...omium.org> Cc: Ingo Molnar <mingo@...hat.com>, Juri Lelli <juri.lelli@...hat.com>, Vincent Guittot <vincent.guittot@...aro.org>, Dietmar Eggemann <dietmar.eggemann@....com>, Steven Rostedt <rostedt@...dmis.org>, Ben Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>, Daniel Bristot de Oliveira <bristot@...hat.com>, kernel test robot <oliver.sang@...el.com>, Vito Caputo <vcaputo@...garu.com>, Jann Horn <jannh@...gle.com>, Andrew Morton <akpm@...ux-foundation.org>, Christian Brauner <christian.brauner@...ntu.com>, Anand K Mistry <amistry@...gle.com>, "Kenta.Tada@...y.com" <Kenta.Tada@...y.com>, Alexey Gladkov <legion@...nel.org>, Michael Weiß <michael.weiss@...ec.fraunhofer.de>, Michal Hocko <mhocko@...e.com>, Helge Deller <deller@....de>, Qi Zheng <zhengqi.arch@...edance.com>, "Tobin C. Harding" <me@...in.cc>, Tycho Andersen <tycho@...ho.pizza>, Thomas Gleixner <tglx@...utronix.de>, Borislav Petkov <bp@...en8.de>, "H. Peter Anvin" <hpa@...or.com>, Mark Rutland <mark.rutland@....com>, Jens Axboe <axboe@...nel.dk>, Stefan Metzmacher <metze@...ba.org>, Lai Jiangshan <laijs@...ux.alibaba.com>, Andy Lutomirski <luto@...nel.org>, Dave Hansen <dave.hansen@...ux.intel.com>, "Eric W. Biederman" <ebiederm@...ssion.com>, Ohhoon Kwon <ohoono.kwon@...sung.com>, Kalesh Singh <kaleshsingh@...gle.com>, YiFei Zhu <yifeifz2@...inois.edu>, Josh Poimboeuf <jpoimboe@...hat.com>, linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org, linux-hardening@...r.kernel.org, x86@...nel.org Subject: Re: [PATCH v2 2/6] sched: Add wrapper for get_wchan() to keep task blocked On Thu, Sep 30, 2021 at 10:28:37AM +0200, Peter Zijlstra wrote: > On Thu, Sep 30, 2021 at 10:27:07AM +0200, Peter Zijlstra wrote: > > On Wed, Sep 29, 2021 at 03:02:14PM -0700, Kees Cook wrote: > > > Having a stable wchan means the process must be blocked and for it to > > > stay that way while performing stack unwinding. > > > > How's this instead? > > > On top of which we can do.. But that then leads to.. --- Subject: arch: Fix STACKTRACE_SUPPORT From: Peter Zijlstra <peterz@...radead.org> Date: Thu Sep 30 10:21:15 CEST 2021 A few archs got save_stack_trace_tsk() vs in_sched_functions() wrong. Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org> --- arch/csky/kernel/stacktrace.c | 7 ++++++- arch/mips/kernel/stacktrace.c | 27 ++++++++++++++++----------- arch/nds32/kernel/stacktrace.c | 20 +++++++++++--------- 3 files changed, 33 insertions(+), 21 deletions(-) --- a/arch/csky/kernel/stacktrace.c +++ b/arch/csky/kernel/stacktrace.c @@ -132,12 +132,17 @@ static bool save_trace(unsigned long pc, return __save_trace(pc, arg, false); } +static bool save_trace_nosched(unsigned long pc, void *arg) +{ + return __save_trace(pc, arg, true); +} + /* * Save stack-backtrace addresses into a stack_trace buffer. */ void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace) { - walk_stackframe(tsk, NULL, save_trace, trace); + walk_stackframe(tsk, NULL, save_trace_nosched, trace); } EXPORT_SYMBOL_GPL(save_stack_trace_tsk); --- a/arch/mips/kernel/stacktrace.c +++ b/arch/mips/kernel/stacktrace.c @@ -66,16 +66,7 @@ static void save_context_stack(struct st #endif } -/* - * Save stack-backtrace addresses into a stack_trace buffer. - */ -void save_stack_trace(struct stack_trace *trace) -{ - save_stack_trace_tsk(current, trace); -} -EXPORT_SYMBOL_GPL(save_stack_trace); - -void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace) +void __save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace, bool savesched) { struct pt_regs dummyregs; struct pt_regs *regs = &dummyregs; @@ -88,6 +79,20 @@ void save_stack_trace_tsk(struct task_st regs->cp0_epc = tsk->thread.reg31; } else prepare_frametrace(regs); - save_context_stack(trace, tsk, regs, tsk == current); + save_context_stack(trace, tsk, regs, savesched); +} + +/* + * Save stack-backtrace addresses into a stack_trace buffer. + */ +void save_stack_trace(struct stack_trace *trace) +{ + __save_stack_trace_tsk(current, trace, true); +} +EXPORT_SYMBOL_GPL(save_stack_trace); + +void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace) +{ + __save_stack_trace_tsk(tsk, trace, false); } EXPORT_SYMBOL_GPL(save_stack_trace_tsk); --- a/arch/nds32/kernel/stacktrace.c +++ b/arch/nds32/kernel/stacktrace.c @@ -6,13 +6,7 @@ #include <linux/stacktrace.h> #include <linux/ftrace.h> -void save_stack_trace(struct stack_trace *trace) -{ - save_stack_trace_tsk(current, trace); -} -EXPORT_SYMBOL_GPL(save_stack_trace); - -void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace) +static void __save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace, bool savesched) { unsigned long *fpn; int skip = trace->skip; @@ -21,10 +15,8 @@ void save_stack_trace_tsk(struct task_st if (tsk == current) { __asm__ __volatile__("\tori\t%0, $fp, #0\n":"=r"(fpn)); - savesched = 1; } else { fpn = (unsigned long *)thread_saved_fp(tsk); - savesched = 0; } while (!kstack_end(fpn) && !((unsigned long)fpn & 0x3) @@ -50,4 +42,14 @@ void save_stack_trace_tsk(struct task_st fpn = (unsigned long *)fpp; } } +void save_stack_trace(struct stack_trace *trace) +{ + __save_stack_trace_tsk(current, trace, true); +} +EXPORT_SYMBOL_GPL(save_stack_trace); + +void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace) +{ + __save_stack_trace_tsk(tsk, trace, false); +} EXPORT_SYMBOL_GPL(save_stack_trace_tsk);
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