Messages in this thread | | | Date | Tue, 17 Apr 2018 18:10:29 +0200 | From | Dominik Brodowski <> | Subject | Re: [PATCH] tracing/x86: Update syscall trace events to handle new x86 syscall func names |
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Steven,
On Tue, Apr 17, 2018 at 11:54:40AM -0400, Steven Rostedt wrote: > From: "Steven Rostedt (VMware)" <rostedt@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 <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?
Thanks, Dominik
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