Steven,
On Tue, Apr 17, 2018 at 11:54:40AM -0400, Steven Rostedt wrote:
> From: "Steven Rostedt (VMware)" <rost...@goodmis.org>
>
> Arnaldo noticed that the latest kernel is missing the syscall event system
> directory in x86. I bisected it down to d5a00528b58c ("syscalls/core,
> syscalls/x86: Rename struct pt_regs-based sys_*() to __x64_sys_*()").
>
> The system call trace events are special, as there is only one trace event
> for all system calls (the raw_syscalls). But a macro that wraps the system
> calls creates meta data for them that copies the name to find the system
> call that maps to the system call table (the number). At boot up, it does a
> kallsyms lookup for this mapping. If it does not find a function, then that
> system call is ignored.
>
> Because the x86 system calls had "__x86_" appended to the "sys" for the
__x64 actually.
> 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.
> Reported-by: Arnaldo Carvalho de Melo <a...@redhat.com>
> Fixes: d5a00528b58c ("syscalls/core, syscalls/x86: Rename struct
> pt_regs-based sys_*() to __x64_sys_*()")
> Signed-off-by: Steven Rostedt (VMware) <rost...@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?
Thanks,
Dominik
