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Subject[PATCH 02/12] firmware: declare {__start,__end}_builtin_fw as external array
Date
The test in this loop:

for (b_fw = __start_builtin_fw; b_fw != __end_builtin_fw; b_fw++) {

was getting completely compiled out by my gcc, 7.0.0 20160520. The result
was that the loop was going beyond the end of the builtin_fw array and
giving me a page fault when trying to dereference b_fw->name inside
strcmp().

By using the new external array helper macros we get the expected
behaviour.

Reported-by: Jiri Slaby <jslaby@suse.cz>
Cc: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: stable@vger.kernel.org
Signed-off-by: Vegard Nossum <vegard.nossum@oracle.com>
---
arch/x86/kernel/cpu/microcode/core.c | 5 ++---
drivers/base/firmware_class.c | 9 +++++----
include/asm-generic/vmlinux.lds.h | 2 +-
3 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/arch/x86/kernel/cpu/microcode/core.c b/arch/x86/kernel/cpu/microcode/core.c
index 5ce5155..6669746 100644
--- a/arch/x86/kernel/cpu/microcode/core.c
+++ b/arch/x86/kernel/cpu/microcode/core.c
@@ -91,15 +91,14 @@ static bool __init check_loader_disabled_bsp(void)
return *res;
}

-extern struct builtin_fw __start_builtin_fw[];
-extern struct builtin_fw __end_builtin_fw[];
+DECLARE_EXTARRAY(struct builtin_fw, builtin_fw);

bool get_builtin_firmware(struct cpio_data *cd, const char *name)
{
#ifdef CONFIG_FW_LOADER
struct builtin_fw *b_fw;

- for (b_fw = __start_builtin_fw; b_fw != __end_builtin_fw; b_fw++) {
+ ext_for_each(b_fw, builtin_fw) {
if (!strcmp(name, b_fw->name)) {
cd->size = b_fw->size;
cd->data = b_fw->data;
diff --git a/drivers/base/firmware_class.c b/drivers/base/firmware_class.c
index 22d1760..b85d943e6 100644
--- a/drivers/base/firmware_class.c
+++ b/drivers/base/firmware_class.c
@@ -9,6 +9,7 @@

#include <linux/capability.h>
#include <linux/device.h>
+#include <linux/extarray.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/timer.h>
@@ -43,15 +44,14 @@ MODULE_LICENSE("GPL");

#ifdef CONFIG_FW_LOADER

-extern struct builtin_fw __start_builtin_fw[];
-extern struct builtin_fw __end_builtin_fw[];
+DECLARE_EXTARRAY(struct builtin_fw, builtin_fw)

static bool fw_get_builtin_firmware(struct firmware *fw, const char *name,
void *buf, size_t size)
{
struct builtin_fw *b_fw;

- for (b_fw = __start_builtin_fw; b_fw != __end_builtin_fw; b_fw++) {
+ ext_for_each(b_fw, builtin_fw) {
if (strcmp(name, b_fw->name) == 0) {
fw->size = b_fw->size;
fw->data = b_fw->data;
@@ -69,9 +69,10 @@ static bool fw_is_builtin_firmware(const struct firmware *fw)
{
struct builtin_fw *b_fw;

- for (b_fw = __start_builtin_fw; b_fw != __end_builtin_fw; b_fw++)
+ ext_for_each(b_fw, builtin_fw) {
if (fw->data == b_fw->data)
return true;
+ }

return false;
}
diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index 3074796..d6121ac 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -317,7 +317,7 @@
.builtin_fw : AT(ADDR(.builtin_fw) - LOAD_OFFSET) { \
VMLINUX_SYMBOL(__start_builtin_fw) = .; \
*(.builtin_fw) \
- VMLINUX_SYMBOL(__end_builtin_fw) = .; \
+ VMLINUX_SYMBOL(__stop_builtin_fw) = .; \
} \
\
TRACEDATA \
--
2.10.0.479.g221bd91
\
 
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