ftrace: Allow for function tracing to record init functions on boot up

Adding a hook into free_reserve_area() that informs ftrace that boot up init
text is being free, lets ftrace safely remove those init functions from its
records, which keeps ftrace from trying to modify text that no longer
exists.

Note, this still does not allow for tracing .init text of modules, as
modules require different work for freeing its init code.

Link: http://lkml.kernel.org/r/1488502497.7212.24.camel@linux.intel.com
Cc: linux-mm@kvack.org
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Peter Zijlstra <peterz@infradead.org>
Requested-by: Todd Brandt <todd.e.brandt@linux.intel.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
index 569db55..0276a2c 100644 (file)
--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -146,6 +146,10 @@ struct ftrace_ops_hash {
        struct ftrace_hash              *filter_hash;
        struct mutex                    regex_lock;
 };
+
+void ftrace_free_mem(void *start, void *end);
+#else
+static inline void ftrace_free_mem(void *start, void *end) { }
 #endif
 
 /*
@@ -262,6 +266,7 @@ static inline int ftrace_nr_registered_ops(void)
 }
 static inline void clear_ftrace_function(void) { }
 static inline void ftrace_kill(void) { }
+static inline void ftrace_free_mem(void *start, void *end) { }
 #endif /* CONFIG_FUNCTION_TRACER */
 
 #ifdef CONFIG_STACK_TRACER

diff --git a/include/linux/init.h b/include/linux/init.h
index 79af096..94769d6 100644 (file)
--- a/include/linux/init.h
+++ b/include/linux/init.h
@@ -39,7 +39,7 @@
 
 /* These are for everybody (although not all archs will actually
    discard it in modules) */
-#define __init         __section(.init.text) __cold notrace __latent_entropy
+#define __init         __section(.init.text) __cold __inittrace __latent_entropy
 #define __initdata     __section(.init.data)
 #define __initconst    __section(.init.rodata)
 #define __exitdata     __section(.exit.data)
@@ -68,8 +68,10 @@
 
 #ifdef MODULE
 #define __exitused
+#define __inittrace notrace
 #else
 #define __exitused  __used
+#define __inittrace
 #endif
 
 #define __exit          __section(.exit.text) __exitused __cold notrace

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index b9691ee..0556a20 100644 (file)
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -5262,6 +5262,50 @@ void ftrace_module_init(struct module *mod)
 }
 #endif /* CONFIG_MODULES */
 
+void ftrace_free_mem(void *start_ptr, void *end_ptr)
+{
+       unsigned long start = (unsigned long)start_ptr;
+       unsigned long end = (unsigned long)end_ptr;
+       struct ftrace_page **last_pg = &ftrace_pages_start;
+       struct ftrace_page *pg;
+       struct dyn_ftrace *rec;
+       struct dyn_ftrace key;
+       int order;
+
+       key.ip = start;
+       key.flags = end;        /* overload flags, as it is unsigned long */
+
+       mutex_lock(&ftrace_lock);
+
+       for (pg = ftrace_pages_start; pg; last_pg = &pg->next, pg = *last_pg) {
+               if (end < pg->records[0].ip ||
+                   start >= (pg->records[pg->index - 1].ip + MCOUNT_INSN_SIZE))
+                       continue;
+ again:
+               rec = bsearch(&key, pg->records, pg->index,
+                             sizeof(struct dyn_ftrace),
+                             ftrace_cmp_recs);
+               if (!rec)
+                       continue;
+               pg->index--;
+               if (!pg->index) {
+                       *last_pg = pg->next;
+                       order = get_count_order(pg->size / ENTRIES_PER_PAGE);
+                       free_pages((unsigned long)pg->records, order);
+                       kfree(pg);
+                       pg = container_of(last_pg, struct ftrace_page, next);
+                       if (!(*last_pg))
+                               ftrace_pages = pg;
+                       continue;
+               }
+               memmove(rec, rec + 1,
+                       (pg->index - (rec - pg->records)) * sizeof(*rec));
+               /* More than one function may be in this block */
+               goto again;
+       }
+       mutex_unlock(&ftrace_lock);
+}
+
 void __init ftrace_init(void)
 {
        extern unsigned long __start_mcount_loc[];

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 6cbde31..eee82bf 100644 (file)
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -65,6 +65,7 @@
 #include <linux/page_owner.h>
 #include <linux/kthread.h>
 #include <linux/memcontrol.h>
+#include <linux/ftrace.h>
 
 #include <asm/sections.h>
 #include <asm/tlbflush.h>
@@ -6605,6 +6606,9 @@ unsigned long free_reserved_area(void *start, void *end, int poison, char *s)
        void *pos;
        unsigned long pages = 0;
 
+       /* This may be .init text, inform ftrace to remove it */
+       ftrace_free_mem(start, end);
+
        start = (void *)PAGE_ALIGN((unsigned long)start);
        end = (void *)((unsigned long)end & PAGE_MASK);
        for (pos = start; pos < end; pos += PAGE_SIZE, pages++) {

diff --git a/scripts/recordmcount.c b/scripts/recordmcount.c
index aeb3422..16e086d 100644 (file)
--- a/scripts/recordmcount.c
+++ b/scripts/recordmcount.c
@@ -412,6 +412,7 @@ static int
 is_mcounted_section_name(char const *const txtname)
 {
        return strcmp(".text",           txtname) == 0 ||
+               strcmp(".init.text",     txtname) == 0 ||
                strcmp(".ref.text",      txtname) == 0 ||
                strcmp(".sched.text",    txtname) == 0 ||
                strcmp(".spinlock.text", txtname) == 0 ||

diff --git a/scripts/recordmcount.pl b/scripts/recordmcount.pl
index 0b6002b..1633c3e 100755 (executable)
--- a/scripts/recordmcount.pl
+++ b/scripts/recordmcount.pl
@@ -130,6 +130,7 @@ if ($inputfile =~ m,kernel/trace/ftrace\.o$,) {
 # Acceptable sections to record.
 my %text_sections = (
      ".text" => 1,
+     ".init.text" => 1,
      ".ref.text" => 1,
      ".sched.text" => 1,
      ".spinlock.text" => 1,