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Subject[PATCH 3/5] ftrace: enable mcount recording for modules
This patch enables the loading of the __mcount_section of modules and
changing all the callers of mcount into nops.

The modification is done before the init_module function is called, so
again, we do not need to use kstop_machine to make these changes.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
---
include/linux/ftrace.h | 3 +++
kernel/module.c | 11 +++++++++++
kernel/trace/ftrace.c | 5 +++++
3 files changed, 19 insertions(+)

Index: linux-tip.git/include/linux/ftrace.h
===================================================================
--- linux-tip.git.orig/include/linux/ftrace.h 2008-08-07 13:09:25.000000000 -0400
+++ linux-tip.git/include/linux/ftrace.h 2008-08-07 13:09:31.000000000 -0400
@@ -143,8 +143,11 @@ ftrace_special(unsigned long arg1, unsig

#ifdef CONFIG_FTRACE_MCOUNT_RECORD
extern void ftrace_init(void);
+extern void ftrace_init_module(unsigned long *start, unsigned long *end);
#else
static inline void ftrace_init(void) { }
+static inline void
+ftrace_init_module(unsigned long *start, unsigned long *end) { }
#endif

#endif /* _LINUX_FTRACE_H */
Index: linux-tip.git/kernel/module.c
===================================================================
--- linux-tip.git.orig/kernel/module.c 2008-08-07 13:09:17.000000000 -0400
+++ linux-tip.git/kernel/module.c 2008-08-07 13:33:58.000000000 -0400
@@ -48,6 +48,7 @@
#include <linux/license.h>
#include <asm/sections.h>
#include <linux/tracepoint.h>
+#include <linux/ftrace.h>

#if 0
#define DEBUGP printk
@@ -1835,6 +1836,7 @@ static struct module *load_module(void _
unsigned int markersstringsindex;
unsigned int tracepointsindex;
unsigned int tracepointsstringsindex;
+ unsigned int mcountindex;
struct module *mod;
long err = 0;
void *percpu = NULL, *ptr = NULL; /* Stops spurious gcc warning */
@@ -2125,6 +2127,9 @@ static struct module *load_module(void _
tracepointsstringsindex = find_sec(hdr, sechdrs, secstrings,
"__tracepoints_strings");

+ mcountindex = find_sec(hdr, sechdrs, secstrings,
+ "__mcount_loc");
+
/* Now do relocations. */
for (i = 1; i < hdr->e_shnum; i++) {
const char *strtab = (char *)sechdrs[strindex].sh_addr;
@@ -2185,6 +2190,12 @@ static struct module *load_module(void _
mod->tracepoints + mod->num_tracepoints);
#endif
}
+
+ if (mcountindex) {
+ void *mseg = (void *)sechdrs[mcountindex].sh_addr;
+ ftrace_init_module(mseg, mseg + sechdrs[mcountindex].sh_size);
+ }
+
err = module_finalize(hdr, sechdrs, mod);
if (err < 0)
goto cleanup;
Index: linux-tip.git/kernel/trace/ftrace.c
===================================================================
--- linux-tip.git.orig/kernel/trace/ftrace.c 2008-08-07 13:09:25.000000000 -0400
+++ linux-tip.git/kernel/trace/ftrace.c 2008-08-07 13:09:31.000000000 -0400
@@ -1548,6 +1548,11 @@ static int ftrace_convert_nops(unsigned
return 0;
}

+void ftrace_init_module(unsigned long *start, unsigned long *end)
+{
+ ftrace_convert_nops(start, end);
+}
+
extern unsigned long __start_mcount_loc[];
extern unsigned long __stop_mcount_loc[];

--


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