Messages in this thread Patch in this message | | | Subject | Re: [PATCH 4/6] ftrace syscalls: Allow arch specific syscall symbol matching | From | Steven Rostedt <> | Date | Wed, 02 Feb 2011 09:04:44 -0500 |
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On Wed, 2011-02-02 at 18:11 +1100, Ian Munsie wrote:
I'll answer your question here.
> diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h > index dcd6a7c..0d0e109 100644 > --- a/include/linux/ftrace.h > +++ b/include/linux/ftrace.h > @@ -527,6 +527,15 @@ extern enum ftrace_dump_mode ftrace_dump_on_oops; > #ifdef CONFIG_FTRACE_SYSCALLS > > unsigned long arch_syscall_addr(int nr); > +#ifndef arch_syscall_match_sym_name > +/* > + * Only compare after the "sys" prefix. Archs that use > + * syscall wrappers may have syscalls symbols aliases prefixed > + * with "SyS" instead of "sys", leading to an unwanted > + * mismatch. > + */ > +#define arch_syscall_match_sym_name(sym, name) !strcmp(sym + 3, name + 3)
Instead, you could have:
#ifndef ARCH_HAS_SYSCALL_MATCH_SYM_NAME
static inline arch_syscall_match_sym_name(const char *sym, const char *name) { return strcmp(sym + 3, name + 3) != 0; }
If an arch needs to make its own, then it can simply override it by creating its own version and defining:
#define ARCH_HAS_SYSCALL_MATCH_SYM_NAME
Just like they do when an arch has its own strcmp.
This just keeps things cleaner. I like to avoid macros as they can have nasty side effects (never would have guess that if you look at what I've done in trace/ftrace.h ;-)
For example, if we use your call as:
arch_syscall_match_sym_name(str = sym[5], name);
That str would end up being something unexpected. I'm not condoning such side-effect code, but it is something to think about when using macros.
-- Steve
> +#endif > > #endif /* CONFIG_FTRACE_SYSCALLS */ > > diff --git a/kernel/trace/trace_syscalls.c b/kernel/trace/trace_syscalls.c > index 33360b9..76bffba 100644 > --- a/kernel/trace/trace_syscalls.c > +++ b/kernel/trace/trace_syscalls.c > @@ -72,13 +72,7 @@ static struct syscall_metadata *find_syscall_meta(unsigned long syscall) > kallsyms_lookup(syscall, NULL, NULL, NULL, str); > > for ( ; start < stop; start++) { > - /* > - * Only compare after the "sys" prefix. Archs that use > - * syscall wrappers may have syscalls symbols aliases prefixed > - * with "SyS" instead of "sys", leading to an unwanted > - * mismatch. > - */ > - if (start->name && !strcmp(start->name + 3, str + 3)) > + if (start->name && arch_syscall_match_sym_name(str, start->name)) > return start; > } > return NULL;
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