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SubjectRe: [PATCH] tracing/x86: Update syscall trace events to handle new x86 syscall func names
On Tue, 17 Apr 2018 18:10:29 +0200
Dominik Brodowski <linux@dominikbrodowski.net> wrote:


> > Because the x86 system calls had "__x86_" appended to the "sys" for the
>
> __x64 actually.

Heh, I constantly make that mistake.

Hmm, OK, I need to look at this a bit more. If this is x64, then
there's probably syscalls (on 32 bit), that don't have that. It should
probably include more checks. Something like:

return !strcmp(sym + 9, name + 3) || !strcmp(sym + 3, name + 3);


>
> > names, they do not match the default compare algorithm. As this was a
> > problem for power pc, the algorithm can be overwritten by the architecture.
> > The solution is to have x86 have its own algorithm to do the compare and
> > this brings back the system call trace events.
>
> this lets me wonder *which* syscall "function" should be included in this
> directory. Is it really the stub (__x64_sys_waitid, for example), or better
> the sign-extending C function (__se_sys_waitid) which then calls an
> internal helper (__do_sys_waitid). An additional advantage:
> __se_sys_waitid would be available on x86 and, AFAICS, on all other archs.

It should include anything that uses the "SYSCALL_DEFINE#()" macros.

>
> > Reported-by: Arnaldo Carvalho de Melo <acme@redhat.com>
> > Fixes: d5a00528b58c ("syscalls/core, syscalls/x86: Rename struct pt_regs-based sys_*() to __x64_sys_*()")
> > Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
> > ---
> > arch/x86/include/asm/ftrace.h | 10 ++++++++++
> > 1 file changed, 10 insertions(+)
> >
> > diff --git a/arch/x86/include/asm/ftrace.h b/arch/x86/include/asm/ftrace.h
> > index 09ad88572746..c30b3fac20ae 100644
> > --- a/arch/x86/include/asm/ftrace.h
> > +++ b/arch/x86/include/asm/ftrace.h
> > @@ -31,6 +31,16 @@ static inline unsigned long ftrace_call_adjust(unsigned long addr)
> > return addr;
> > }
> >
> > +#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
> > + * "__x64_sys" prefix.
> > + */
> > + return !strcmp(sym + 9, name + 3);
> > +}
>
> What are the first three chars you skip for *name?

"sys_"

-- Steve

>
> Thanks,
> Dominik

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