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Date: Wed, 12 Oct 2016 19:50:39 +1100
From: Michael Ellerman <mpe@...erman.id.au>
To: Marcin Nowakowski <marcin.nowakowski@...tec.com>,
linux-kernel@...r.kernel.org
Cc: linux-api@...r.kernel.org, luto@...capital.net,
rostedt@...dmis.org,
Marcin Nowakowski <marcin.nowakowski@...tec.com>,
Ingo Molnar <mingo@...hat.com>,
Benjamin Herrenschmidt <benh@...nel.crashing.org>,
Paul Mackerras <paulus@...ba.org>,
linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH v3 03/11] tracing/syscalls: add compat syscall metadata
Marcin Nowakowski <marcin.nowakowski@...tec.com> writes:
> Now that compat syscalls are properly distinguished from native calls,
> we can add metadata for compat syscalls as well.
> All the macros used to generate the metadata are the same as for
> standard syscalls, but with a compat_ prefix to distinguish them easily.
>
> Signed-off-by: Marcin Nowakowski <marcin.nowakowski@...tec.com>
> Cc: Steven Rostedt <rostedt@...dmis.org>
> Cc: Ingo Molnar <mingo@...hat.com>
> Cc: Benjamin Herrenschmidt <benh@...nel.crashing.org>
> Cc: Paul Mackerras <paulus@...ba.org>
> Cc: Michael Ellerman <mpe@...erman.id.au>
> Cc: linuxppc-dev@...ts.ozlabs.org
> ---
> arch/powerpc/include/asm/ftrace.h | 15 +++++---
> include/linux/compat.h | 74 +++++++++++++++++++++++++++++++++++++++
> kernel/trace/trace_syscalls.c | 8 +++--
> 3 files changed, 90 insertions(+), 7 deletions(-)
>
> diff --git a/arch/powerpc/include/asm/ftrace.h b/arch/powerpc/include/asm/ftrace.h
> index 686c5f7..9697a73 100644
> --- a/arch/powerpc/include/asm/ftrace.h
> +++ b/arch/powerpc/include/asm/ftrace.h
> @@ -73,12 +73,17 @@ struct dyn_arch_ftrace {
> 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 .sys or .SyS
> - * prefix from the symbol name and the sys prefix from the system call name and
> - * just match the rest. This is only needed on ppc64 since symbol names on
> - * 32bit do not start with a period so the generic function will work.
> + * Compare the symbol name with the system call name. Skip the .sys,
> + * .SyS or .compat_sys prefix from the symbol name and the sys prefix
> + * from the system call name and just match the rest. This is only
> + * needed on ppc64 since symbol names on 32bit do not start with a
> + * period so the generic function will work.
> */
> - return !strcmp(sym + 4, name + 3);
> + int prefix_len = 3;
> +
> + if (!strncasecmp(name, "compat_", 7))
> + prefix_len = 10;
> + return !strcmp(sym + prefix_len + 1, name + prefix_len);
> }
It's annoying that we have to duplicate all that just to do a + 1.
How about this as a precursor?
cheers
diff --git a/Documentation/trace/ftrace-design.txt b/Documentation/trace/ftrace-design.txt
index dd5f916b351d..bd65f2adeb09 100644
--- a/Documentation/trace/ftrace-design.txt
+++ b/Documentation/trace/ftrace-design.txt
@@ -226,10 +226,6 @@ 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, define ARCH_HAS_SYSCALL_MATCH_SYM_NAME in asm/ftrace.h and
- implement 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/arch/powerpc/include/asm/ftrace.h b/arch/powerpc/include/asm/ftrace.h
index 686c5f70eb84..dc48f5b2878d 100644
--- a/arch/powerpc/include/asm/ftrace.h
+++ b/arch/powerpc/include/asm/ftrace.h
@@ -60,6 +60,12 @@ struct dyn_arch_ftrace {
struct module *mod;
};
#endif /* CONFIG_DYNAMIC_FTRACE */
+
+#ifdef PPC64_ELF_ABI_v1
+/* On ppc64 ABIv1 (BE) we have to skip the leading '.' in the symbol name */
+#define ARCH_SYM_NAME_SKIP_CHARS 1
+#endif
+
#endif /* __ASSEMBLY__ */
#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
@@ -67,20 +73,4 @@ struct dyn_arch_ftrace {
#endif
#endif
-#if defined(CONFIG_FTRACE_SYSCALLS) && !defined(__ASSEMBLY__)
-#ifdef PPC64_ELF_ABI_v1
-#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 .sys or .SyS
- * prefix from the symbol name and the sys prefix from the system call name and
- * just match the rest. This is only needed on ppc64 since symbol names on
- * 32bit do not start with a period so the generic function will work.
- */
- return !strcmp(sym + 4, name + 3);
-}
-#endif
-#endif /* CONFIG_FTRACE_SYSCALLS && !__ASSEMBLY__ */
-
#endif /* _ASM_POWERPC_FTRACE */
diff --git a/kernel/trace/trace_syscalls.c b/kernel/trace/trace_syscalls.c
index b2b6efc083a4..91a7315dbe43 100644
--- a/kernel/trace/trace_syscalls.c
+++ b/kernel/trace/trace_syscalls.c
@@ -31,8 +31,11 @@ extern struct syscall_metadata *__stop_syscalls_metadata[];
static struct syscall_metadata **syscalls_metadata;
-#ifndef ARCH_HAS_SYSCALL_MATCH_SYM_NAME
-static inline bool arch_syscall_match_sym_name(const char *sym, const char *name)
+#ifndef ARCH_SYM_NAME_SKIP_CHARS
+#define ARCH_SYM_NAME_SKIP_CHARS 0
+#endif
+
+static inline bool syscall_match_sym_name(const char *sym, const char *name)
{
/*
* Only compare after the "sys" prefix. Archs that use
@@ -40,9 +43,8 @@ static inline bool arch_syscall_match_sym_name(const char *sym, const char *name
* with ".SyS" or ".sys" instead of "sys", leading to an unwanted
* mismatch.
*/
- return !strcmp(sym + 3, name + 3);
+ return !strcmp(sym + 3 + ARCH_SYM_NAME_SKIP_CHARS, name + 3);
}
-#endif
#ifdef ARCH_TRACE_IGNORE_COMPAT_SYSCALLS
/*
@@ -88,11 +90,11 @@ find_syscall_meta(unsigned long syscall)
stop = __stop_syscalls_metadata;
kallsyms_lookup(syscall, NULL, NULL, NULL, str);
- if (arch_syscall_match_sym_name(str, "sys_ni_syscall"))
+ if (syscall_match_sym_name(str, "sys_ni_syscall"))
return NULL;
for ( ; start < stop; start++) {
- if ((*start)->name && arch_syscall_match_sym_name(str, (*start)->name))
+ if ((*start)->name && syscall_match_sym_name(str, (*start)->name))
return *start;
}
return NULL;
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