lkml.org 
[lkml]   [2017]   [Aug]   [19]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH v3 5/5] kernel: tracepoints: add support for relative references
Date
To avoid the need for relocating absolute references to tracepoint
structures at boot time when running relocatable kernels (which may
take a disproportionate amount of space), add the option to emit
these tables as relative references instead.

Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Ingo Molnar <mingo@redhat.com>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
---
include/linux/tracepoint.h | 19 +++++++++++++++----
kernel/tracepoint.c | 17 +++++++++++++----
2 files changed, 28 insertions(+), 8 deletions(-)

diff --git a/include/linux/tracepoint.h b/include/linux/tracepoint.h
index a26ffbe09e71..d02bf1a695e8 100644
--- a/include/linux/tracepoint.h
+++ b/include/linux/tracepoint.h
@@ -228,6 +228,19 @@ extern void syscall_unregfunc(void);
return static_key_false(&__tracepoint_##name.key); \
}

+#ifdef CONFIG_HAVE_ARCH_PREL32_RELOCATIONS
+#define __TRACEPOINT_ENTRY(name) \
+ asm(" .section \"__tracepoints_ptrs\", \"a\" \n" \
+ " .balign 4 \n" \
+ " .long " VMLINUX_SYMBOL_STR(__tracepoint_##name) " - .\n" \
+ " .previous \n")
+#else
+#define __TRACEPOINT_ENTRY(name) \
+ static struct tracepoint * const __tracepoint_ptr_##name __used \
+ __attribute__((section("__tracepoints_ptrs"))) = \
+ &__tracepoint_##name
+#endif
+
/*
* We have no guarantee that gcc and the linker won't up-align the tracepoint
* structures, so we create an array of pointers that will be used for iteration
@@ -237,11 +250,9 @@ extern void syscall_unregfunc(void);
static const char __tpstrtab_##name[] \
__attribute__((section("__tracepoints_strings"))) = #name; \
struct tracepoint __tracepoint_##name \
- __attribute__((section("__tracepoints"))) = \
+ __attribute__((section("__tracepoints"), used)) = \
{ __tpstrtab_##name, STATIC_KEY_INIT_FALSE, reg, unreg, NULL };\
- static struct tracepoint * const __tracepoint_ptr_##name __used \
- __attribute__((section("__tracepoints_ptrs"))) = \
- &__tracepoint_##name;
+ __TRACEPOINT_ENTRY(name);

#define DEFINE_TRACE(name) \
DEFINE_TRACE_FN(name, NULL, NULL);
diff --git a/kernel/tracepoint.c b/kernel/tracepoint.c
index 685c50ae6300..68b0218ef66b 100644
--- a/kernel/tracepoint.c
+++ b/kernel/tracepoint.c
@@ -508,12 +508,21 @@ static void for_each_tracepoint_range(struct tracepoint * const *begin,
void (*fct)(struct tracepoint *tp, void *priv),
void *priv)
{
- struct tracepoint * const *iter;
-
if (!begin)
return;
- for (iter = begin; iter < end; iter++)
- fct(*iter, priv);
+
+ if (IS_ENABLED(CONFIG_HAVE_ARCH_PREL32_RELOCATIONS)) {
+ const int *iter;
+
+ for (iter = (const int *)begin; iter < (const int *)end; iter++)
+ fct((struct tracepoint *)((unsigned long)iter + *iter),
+ priv);
+ } else {
+ struct tracepoint * const *iter;
+
+ for (iter = begin; iter < end; iter++)
+ fct(*iter, priv);
+ }
}

/**
--
2.11.0
\
 
 \ /
  Last update: 2017-08-19 20:12    [W:0.165 / U:0.156 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site