Re: [PATCH V4 4/8] riscv: traps: Add noinstr to prevent instrumentation inserted

Peter Zijlstra
2022-09-08T07:34:23Z

On Wed, Sep 07, 2022 at 10:25:02PM -0400, 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/raw
> Suggested-by: Peter Zijlstra <peterz@infradead.org>
> Signed-off-by: Guo Ren <guoren@linux.alibaba.com>
> Signed-off-by: Guo Ren <guoren@kernel.org>
> ---
> arch/riscv/kernel/traps.c | 8 ++++----
> arch/riscv/mm/fault.c | 2 +-
> 2 files changed, 5 insertions(+), 5 deletions(-)
>
> diff --git a/arch/riscv/kernel/traps.c b/arch/riscv/kernel/traps.c
> index 635e6ec26938..3ed3dbec250d 100644
> --- a/arch/riscv/kernel/traps.c
> +++ b/arch/riscv/kernel/traps.c
> @@ -97,7 +97,7 @@ static void do_trap_error(struct pt_regs *regs, int signo, int code,
> #define __trap_section
> #endif
> #define DO_ERROR_INFO(name, signo, code, str) \
> -asmlinkage __visible __trap_section void name(struct pt_regs *regs) \
> +asmlinkage __visible __trap_section void noinstr name(struct pt_regs *regs) \

But now you have __trap_section and noinstr both adding a section
attribute.