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From: Benjamin Herrenschmidt on 13 May 2010 20:10
On Thu, 2010-05-13 at 17:43 +1000, Ian Munsie wrote:
> From: Ian Munsie <imunsie(a)au1.ibm.com>
>
> Some architectures have unusual symbol names and the generic code to
> match the symbol name with the function name for the syscall metadata
> will fail. For example, symbols on PPC64 start with a period and the
> generic code will fail to match them.
>
> This patch splits out the match logic into a standalone weak function
> that can be overridden on archs with unusual symbol names.
>
> Signed-off-by: Ian Munsie <imunsie(a)au1.ibm.com>
> ---

Acked-by: Benjamin Herrenschmidt <benh(a)kernel.crashing.org>
---

Ian, I assume you will implement the support for the "special" ppc_*
syscalls via a subsequent patch and not a respin of this one right ?

Cheers,
Ben.

> Documentation/trace/ftrace-design.txt | 3 +++
> include/linux/ftrace.h | 1 +
> kernel/trace/trace_syscalls.c | 19 ++++++++++++-------
> 3 files changed, 16 insertions(+), 7 deletions(-)
>
> diff --git a/Documentation/trace/ftrace-design.txt b/Documentation/trace/ftrace-design.txt
> index 8369a1c..3936d5f 100644
> --- a/Documentation/trace/ftrace-design.txt
> +++ b/Documentation/trace/ftrace-design.txt
> @@ -247,6 +247,9 @@ You need very few things to get the syscalls tracing in an arch.
> - If the system call table on this arch is more complicated than a simple array
> of addresses of the system calls, implement an arch_syscall_addr to return
> the address of a given system call.
> +- If the symbol names of the system calls do not match the function names on
> + this arch, implement an arch_syscall_match_sym_name with the appropriate
> + logic to return true if the function name corresponds with the symbol name.
> - Tag this arch as HAVE_SYSCALL_TRACEPOINTS.
>
>
> diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
> index e0ae83b..26ad1f5 100644
> --- a/include/linux/ftrace.h
> +++ b/include/linux/ftrace.h
> @@ -534,6 +534,7 @@ static inline void trace_hw_branch_oops(void) {}
> #ifdef CONFIG_FTRACE_SYSCALLS
>
> unsigned long arch_syscall_addr(int nr);
> +bool arch_syscall_match_sym_name(const char *sym, const char *name);
>
> #endif /* CONFIG_FTRACE_SYSCALLS */
>
> diff --git a/kernel/trace/trace_syscalls.c b/kernel/trace/trace_syscalls.c
> index 1c231d0..ebbc74d 100644
> --- a/kernel/trace/trace_syscalls.c
> +++ b/kernel/trace/trace_syscalls.c
> @@ -32,13 +32,7 @@ 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;
> @@ -408,6 +402,17 @@ unsigned long __init __weak arch_syscall_addr(int nr)
> return (unsigned long)sys_call_table[nr];
> }
>
> +bool __weak arch_syscall_match_sym_name(const char *sym, const char *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.
> + */
> + return (!strcmp(sym + 3, name + 3));
> +}
> +
> int __init init_ftrace_syscalls(void)
> {
> struct syscall_metadata *meta;


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