Re: [PATCH] arm64: ftrace: Fix to enable syscall events on arm64

[Steven Rostedt]

On Wed, 28 Nov 2018 01:29:45 +0900
Masami Hiramatsu <mhiramat@xxxxxxxxxx> wrote:

> Since commit 4378a7d4be30 ("arm64: implement syscall wrappers")
> introduced "__arm64_" prefix to all syscall wrapper symbols in
> sys_call_table, syscall tracer can not find corresponding
> metadata from syscall name. In the result, we have no syscall
> ftrace events on arm64 kernel, and some bpf testcases are failed
> on arm64.
> 
> To fix this issue, this introduces custom
> arch_syscall_match_sym_name() which skips first 8 bytes when
> comparing the syscall and symbol names.
> 

Acked-by: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx>

-- Steve

> Fixes: 4378a7d4be30 ("arm64: implement syscall wrappers")
> Reported-by: Naresh Kamboju <naresh.kamboju@xxxxxxxxxx>
> Signed-off-by: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx
> ---
>  arch/arm64/include/asm/ftrace.h |    9 +++++++++
>  1 file changed, 9 insertions(+)
> 
> diff --git a/arch/arm64/include/asm/ftrace.h b/arch/arm64/include/asm/ftrace.h
> index caa955f10e19..a710f79db442 100644
> --- a/arch/arm64/include/asm/ftrace.h
> +++ b/arch/arm64/include/asm/ftrace.h
> @@ -56,6 +56,15 @@ static inline bool arch_trace_is_compat_syscall(struct pt_regs *regs)
>  {
>  	return is_compat_task();
>  }
> +
> +#define ARCH_HAS_SYSCALL_MATCH_SYM_NAME
> +
> +static inline bool arch_syscall_match_sym_name(const char *sym,
> +					       const char *name)
> +{
> +	/* Since all syscall functions have __arm64_ prefix, we must skip it */
> +	return !strcmp(sym + 8, name);
> +}
>  #endif /* ifndef __ASSEMBLY__ */
>  
>  #endif /* __ASM_FTRACE_H */