From: Guo Ren <guoren@kernel.org> To: Alexandre Ghiti <alex@ghiti.fr> Cc: arnd@arndb.de, palmer@rivosinc.com, tglx@linutronix.de, peterz@infradead.org, luto@kernel.org, conor.dooley@microchip.com, heiko@sntech.de, jszhang@kernel.org, lazyparser@gmail.com, falcon@tinylab.org, chenhuacai@kernel.org, apatel@ventanamicro.com, atishp@atishpatra.org, mark.rutland@arm.com, ben@decadent.org.uk, bjorn@kernel.org, linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org, linux-riscv@lists.infradead.org, "Guo Ren" <guoren@linux.alibaba.com>, "Björn Töpel" <bjorn@rivosinc.com> Subject: Re: [PATCH -next V12 3/7] riscv: entry: Add noinstr to prevent instrumentation inserted Date: Wed, 4 Jan 2023 09:40:38 +0800 [thread overview] Message-ID: <CAJF2gTTSretKkJGNV7Y6iJboPuAWUQ=to=RPA8_-Nz8dnufGAg@mail.gmail.com> (raw) In-Reply-To: <36314eb6-e41d-30b9-9ac4-12b88a108b7b@ghiti.fr> On Tue, Jan 3, 2023 at 5:12 PM Alexandre Ghiti <alex@ghiti.fr> wrote: > > Hi Guo, > > On 1/3/23 04:35, guoren@kernel.org wrote: > > From: Guo Ren <guoren@linux.alibaba.com> > > > > Without noinstr the compiler is free to insert instrumentation (think > > all the k*SAN, KCov, GCov, ftrace etc..) which can call code we're not > > yet ready to run this early in the entry path, for instance it could > > rely on RCU which isn't on yet, or expect lockdep state. (by peterz) > > > > Link: https://lore.kernel.org/linux-riscv/YxcQ6NoPf3AH0EXe@hirez.programming.kicks-ass.net/ > > Reviewed-by: Björn Töpel <bjorn@rivosinc.com> > > Suggested-by: Peter Zijlstra <peterz@infradead.org> > > Tested-by: Jisheng Zhang <jszhang@kernel.org> > > Signed-off-by: Guo Ren <guoren@linux.alibaba.com> > > Signed-off-by: Guo Ren <guoren@kernel.org> > > --- > > arch/riscv/kernel/traps.c | 4 ++-- > > arch/riscv/mm/fault.c | 2 +- > > 2 files changed, 3 insertions(+), 3 deletions(-) > > > > diff --git a/arch/riscv/kernel/traps.c b/arch/riscv/kernel/traps.c > > index 549bde5c970a..96ec76c54ff2 100644 > > --- a/arch/riscv/kernel/traps.c > > +++ b/arch/riscv/kernel/traps.c > > @@ -95,9 +95,9 @@ static void do_trap_error(struct pt_regs *regs, int signo, int code, > > } > > > > #if defined(CONFIG_XIP_KERNEL) && defined(CONFIG_RISCV_ALTERNATIVE) > > -#define __trap_section __section(".xip.traps") > > +#define __trap_section __noinstr_section(".xip.traps") > > #else > > -#define __trap_section > > +#define __trap_section noinstr > > #endif > > #define DO_ERROR_INFO(name, signo, code, str) \ > > asmlinkage __visible __trap_section void name(struct pt_regs *regs) \ > > diff --git a/arch/riscv/mm/fault.c b/arch/riscv/mm/fault.c > > index d86f7cebd4a7..b26f68eac61c 100644 > > --- a/arch/riscv/mm/fault.c > > +++ b/arch/riscv/mm/fault.c > > @@ -204,7 +204,7 @@ static inline bool access_error(unsigned long cause, struct vm_area_struct *vma) > > * This routine handles page faults. It determines the address and the > > * problem, and then passes it off to one of the appropriate routines. > > */ > > -asmlinkage void do_page_fault(struct pt_regs *regs) > > +asmlinkage void noinstr do_page_fault(struct pt_regs *regs) > > > (I dug the archive but can't find the series before v4, so sorry if it > was already answered) > > I think we should not disable the instrumentation of those trap handlers > as at least profiling them with ftrace would provide valuable > information (and gcov would be nice too): why do we need to do that? A > trap very early in the boot process is not recoverable anyway. Everything that calls irqentry_enter() should be noinstr, and this patch prepares for the next generic_entry convert. eg: asmlinkage void noinstr do_page_fault(struct pt_regs *regs) { irqentry_state_t state = irqentry_enter(regs); __do_page_fault(regs); local_irq_disable(); irqentry_exit(regs, state); } NOKPROBE_SYMBOL(do_page_fault); You still could profile __do_page_fault. > > And I took a look at other architectures, none of them disables the > instrumentation on do_page_fault. That's not true, have a look at power & arm64. All of them have some limitations at the entry of page_fault. > > > > { > > struct task_struct *tsk; > > struct vm_area_struct *vma; -- Best Regards Guo Ren
WARNING: multiple messages have this Message-ID (diff)
From: Guo Ren <guoren@kernel.org> To: Alexandre Ghiti <alex@ghiti.fr> Cc: arnd@arndb.de, palmer@rivosinc.com, tglx@linutronix.de, peterz@infradead.org, luto@kernel.org, conor.dooley@microchip.com, heiko@sntech.de, jszhang@kernel.org, lazyparser@gmail.com, falcon@tinylab.org, chenhuacai@kernel.org, apatel@ventanamicro.com, atishp@atishpatra.org, mark.rutland@arm.com, ben@decadent.org.uk, bjorn@kernel.org, linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org, linux-riscv@lists.infradead.org, "Guo Ren" <guoren@linux.alibaba.com>, "Björn Töpel" <bjorn@rivosinc.com> Subject: Re: [PATCH -next V12 3/7] riscv: entry: Add noinstr to prevent instrumentation inserted Date: Wed, 4 Jan 2023 09:40:38 +0800 [thread overview] Message-ID: <CAJF2gTTSretKkJGNV7Y6iJboPuAWUQ=to=RPA8_-Nz8dnufGAg@mail.gmail.com> (raw) In-Reply-To: <36314eb6-e41d-30b9-9ac4-12b88a108b7b@ghiti.fr> On Tue, Jan 3, 2023 at 5:12 PM Alexandre Ghiti <alex@ghiti.fr> wrote: > > Hi Guo, > > On 1/3/23 04:35, guoren@kernel.org wrote: > > From: Guo Ren <guoren@linux.alibaba.com> > > > > Without noinstr the compiler is free to insert instrumentation (think > > all the k*SAN, KCov, GCov, ftrace etc..) which can call code we're not > > yet ready to run this early in the entry path, for instance it could > > rely on RCU which isn't on yet, or expect lockdep state. (by peterz) > > > > Link: https://lore.kernel.org/linux-riscv/YxcQ6NoPf3AH0EXe@hirez.programming.kicks-ass.net/ > > Reviewed-by: Björn Töpel <bjorn@rivosinc.com> > > Suggested-by: Peter Zijlstra <peterz@infradead.org> > > Tested-by: Jisheng Zhang <jszhang@kernel.org> > > Signed-off-by: Guo Ren <guoren@linux.alibaba.com> > > Signed-off-by: Guo Ren <guoren@kernel.org> > > --- > > arch/riscv/kernel/traps.c | 4 ++-- > > arch/riscv/mm/fault.c | 2 +- > > 2 files changed, 3 insertions(+), 3 deletions(-) > > > > diff --git a/arch/riscv/kernel/traps.c b/arch/riscv/kernel/traps.c > > index 549bde5c970a..96ec76c54ff2 100644 > > --- a/arch/riscv/kernel/traps.c > > +++ b/arch/riscv/kernel/traps.c > > @@ -95,9 +95,9 @@ static void do_trap_error(struct pt_regs *regs, int signo, int code, > > } > > > > #if defined(CONFIG_XIP_KERNEL) && defined(CONFIG_RISCV_ALTERNATIVE) > > -#define __trap_section __section(".xip.traps") > > +#define __trap_section __noinstr_section(".xip.traps") > > #else > > -#define __trap_section > > +#define __trap_section noinstr > > #endif > > #define DO_ERROR_INFO(name, signo, code, str) \ > > asmlinkage __visible __trap_section void name(struct pt_regs *regs) \ > > diff --git a/arch/riscv/mm/fault.c b/arch/riscv/mm/fault.c > > index d86f7cebd4a7..b26f68eac61c 100644 > > --- a/arch/riscv/mm/fault.c > > +++ b/arch/riscv/mm/fault.c > > @@ -204,7 +204,7 @@ static inline bool access_error(unsigned long cause, struct vm_area_struct *vma) > > * This routine handles page faults. It determines the address and the > > * problem, and then passes it off to one of the appropriate routines. > > */ > > -asmlinkage void do_page_fault(struct pt_regs *regs) > > +asmlinkage void noinstr do_page_fault(struct pt_regs *regs) > > > (I dug the archive but can't find the series before v4, so sorry if it > was already answered) > > I think we should not disable the instrumentation of those trap handlers > as at least profiling them with ftrace would provide valuable > information (and gcov would be nice too): why do we need to do that? A > trap very early in the boot process is not recoverable anyway. Everything that calls irqentry_enter() should be noinstr, and this patch prepares for the next generic_entry convert. eg: asmlinkage void noinstr do_page_fault(struct pt_regs *regs) { irqentry_state_t state = irqentry_enter(regs); __do_page_fault(regs); local_irq_disable(); irqentry_exit(regs, state); } NOKPROBE_SYMBOL(do_page_fault); You still could profile __do_page_fault. > > And I took a look at other architectures, none of them disables the > instrumentation on do_page_fault. That's not true, have a look at power & arm64. All of them have some limitations at the entry of page_fault. > > > > { > > struct task_struct *tsk; > > struct vm_area_struct *vma; -- Best Regards Guo Ren _______________________________________________ linux-riscv mailing list linux-riscv@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-riscv
next prev parent reply other threads:[~2023-01-04 1:41 UTC|newest] Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top 2023-01-03 3:35 [PATCH -next V12 0/7] riscv: Add GENERIC_ENTRY support guoren 2023-01-03 3:35 ` guoren 2023-01-03 3:35 ` [PATCH -next V12 1/7] compiler_types.h: Add __noinstr_section() for noinstr guoren 2023-01-03 3:35 ` guoren 2023-01-03 3:35 ` [PATCH -next V12 2/7] riscv: ptrace: Remove duplicate operation guoren 2023-01-03 3:35 ` guoren 2023-01-03 3:35 ` [PATCH -next V12 3/7] riscv: entry: Add noinstr to prevent instrumentation inserted guoren 2023-01-03 3:35 ` guoren 2023-01-03 9:11 ` Alexandre Ghiti 2023-01-03 9:11 ` Alexandre Ghiti 2023-01-04 1:40 ` Guo Ren [this message] 2023-01-04 1:40 ` Guo Ren 2023-01-04 12:03 ` Mark Rutland 2023-01-04 12:03 ` Mark Rutland 2023-01-07 11:48 ` Guo Ren 2023-01-07 11:48 ` Guo Ren 2023-01-04 11:55 ` Mark Rutland 2023-01-04 11:55 ` Mark Rutland 2023-01-07 11:49 ` Guo Ren 2023-01-07 11:49 ` Guo Ren 2023-01-03 3:35 ` [PATCH -next V12 4/7] riscv: entry: Convert to generic entry guoren 2023-01-03 3:35 ` guoren 2023-01-03 3:35 ` [PATCH -next V12 5/7] riscv: entry: Remove extra level wrappers of trace_hardirqs_{on,off} guoren 2023-01-03 3:35 ` guoren 2023-01-03 3:35 ` [PATCH -next V12 6/7] riscv: entry: Consolidate ret_from_kernel_thread into ret_from_fork guoren 2023-01-03 3:35 ` guoren 2023-01-03 3:35 ` [PATCH -next V12 7/7] riscv: entry: Consolidate general regs saving/restoring guoren 2023-01-03 3:35 ` guoren
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