Re: [PATCH 4.16 188/279] powerpc/trace/syscalls: Update syscall name matching logic

[Naveen N. Rao]

Greg Kroah-Hartman wrote:
> 4.16-stable review patch.  If anyone has any objections, please let me know.

Please drop this and the next patch since these depend on commit 
e145242ea0df6, which is not in v4.16.

- Naveen


> ------------------
>
> From: "Naveen N. Rao" <naveen.n.rao@xxxxxxxxxxxxxxxxxx>
>
> [ Upstream commit 0b7758aaf6543b9a10c8671db559e9d374a3fd95 ]
>
> On powerpc64 ABIv1, we are enabling syscall tracing for only ~20
> syscalls. This is due to commit e145242ea0df6 ("syscalls/core,
> syscalls/x86: Clean up syscall stub naming convention") which has
> changed the syscall entry wrapper prefix from "SyS" to "__se_sys".
>
> Update the logic for ABIv1 to not just skip the initial dot, but also
> the "__se_sys" prefix.
>
> Fixes: commit e145242ea0df6 ("syscalls/core, syscalls/x86: Clean up syscall stub naming convention")
> Reported-by: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
> Signed-off-by: Naveen N. Rao <naveen.n.rao@xxxxxxxxxxxxxxxxxx>
> Signed-off-by: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
> Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxxxx>
> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
> ---
>  arch/powerpc/include/asm/ftrace.h |   10 +++-------
>  1 file changed, 3 insertions(+), 7 deletions(-)
>
> --- a/arch/powerpc/include/asm/ftrace.h
> +++ b/arch/powerpc/include/asm/ftrace.h
> @@ -73,13 +73,9 @@ struct dyn_arch_ftrace {
>  #define ARCH_HAS_SYSCALL_MATCH_SYM_NAME
>  static inline bool arch_syscall_match_sym_name(const char *sym, const char *name)
>  {
> -	/*
> -	 * Compare the symbol name with the system call name. Skip the .sys or .SyS
> -	 * prefix from the symbol name and the sys prefix from the system call name and
> -	 * just match the rest. This is only needed on ppc64 since symbol names on
> -	 * 32bit do not start with a period so the generic function will work.
> -	 */
> -	return !strcmp(sym + 4, name + 3);
> +	/* We need to skip past the initial dot, and the __se_sys alias */
> +	return !strcmp(sym + 1, name) ||
> +		(!strncmp(sym, ".__se_sys", 9) && !strcmp(sym + 6, name));
>  }
>  #endif
>  #endif /* CONFIG_FTRACE_SYSCALLS && !__ASSEMBLY__ */