This patch fixes a bug that the last symbol in the .symtab section of
kernel modules is not displayed with /proc/kallsyms. This happens
because the first symbol is processed twice before and inside the loop
without incrementing "src".
This bug exists since the following commit was introduced.
module: reduce symbol table for loaded modules (v2)
commit: 4a4962263f07d14660849ec134ee42b63e95ea9a
This patch is tested on 3.7-rc2 kernel with the simple test module by the
below steps, to check if all the core symbols appear in /proc/kallsyms.
[Test steps]
1. Compile the test module, like below.
(My compiler tends to put a function named with 18 charactors,
like zzzzzzzzzzzzzzzzzz, at the end of .symtab section.
I don't know why, though.)
# cat tp.c
#include <linux/module.h>
#include <linux/kernel.h>
void zzzzzzzzzzzzzzzzzz(void) {}
static int init_tp(void)
{
return 0;
}
static void exit_tp(void) {}
module_init(init_tp);
module_exit(exit_tp);
MODULE_LICENSE("GPL");
# cat Makefile
KERNEL_RELEASE=$(shell uname -r)
BUILDDIR := /lib/modules/$(KERNEL_RELEASE)/source
obj-m := tp.o
all:
$(MAKE) -C $(BUILDDIR) M=$(PWD) V=1 modules
clean:
$(MAKE) -C $(BUILDDIR) M=$(PWD) V=1 clean
# make
2. Check if the target symbol, zzzzzzzzzzzzzzzzzz in this case,
is located at the last entry.
# readelf -s tp.ko | tail
18: 0000000000000020 11 FUNC LOCAL DEFAULT 2 exit_tp
19: 0000000000000000 12 OBJECT LOCAL DEFAULT 4 __mod_license15
20: 0000000000000000 0 FILE LOCAL DEFAULT ABS tp.mod.c
21: 000000000000000c 9 OBJECT LOCAL DEFAULT 4 __module_depends
22: 0000000000000015 45 OBJECT LOCAL DEFAULT 4 __mod_vermagic5
23: 0000000000000000 600 OBJECT GLOBAL DEFAULT 8 __this_module
24: 0000000000000020 11 FUNC GLOBAL DEFAULT 2 cleanup_module
25: 0000000000000010 13 FUNC GLOBAL DEFAULT 2 init_module
26: 0000000000000000 0 NOTYPE GLOBAL DEFAULT UND mcount
27: 0000000000000000 11 FUNC GLOBAL DEFAULT 2 zzzzzzzzzzzzzzzzzz
3. Load the module.
# insmod tp.ko
4. Check if all the core symbols are shown /proc/kallsyms properly.
[Before my patch applied]
# grep "\[tp\]" /proc/kallsyms
ffffffffa0135010 t init_tp [tp]
ffffffffa0135020 t exit_tp [tp]
ffffffffa0137000 d __this_module [tp]
ffffffffa0135020 t cleanup_module [tp]
ffffffffa0135010 t init_module [tp]
(The last entry, or zzzzzzzzzzzzzzzzzz, is not shown.)
[After my patch applied]
# grep "\[tp\]" /proc/kallsyms
ffffffffa0135010 t init_tp [tp]
ffffffffa0135020 t exit_tp [tp]
ffffffffa0137000 d __this_module [tp]
ffffffffa0135020 t cleanup_module [tp]
ffffffffa0135010 t init_module [tp]
ffffffffa0135000 t zzzzzzzzzzzzzzzzzz [tp]
(The last entry, or zzzzzzzzzzzzzzzzzz, is shown properly.)
Signed-off-by: Masaki Kimura <masaki.kimura...@hitachi.com>
---
kernel/module.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)
diff --git a/kernel/module.c b/kernel/module.c
index 6085f5e..1a48ffe 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -2293,7 +2293,11 @@ static void layout_symtab(struct module *mod, struct
load_info *info)
src = (void *)info->hdr + symsect->sh_offset;
nsrc = symsect->sh_size / sizeof(*src);
- /* Compute total space required for the core symbols' strtab. */
+ /*
+ * Compute total space required for the core symbols' strtab.
+ * We start searching core symbols from the second entry.
+ */
+ src++;
for (ndst = i = strtab_size = 1; i < nsrc; ++i, ++src)
if (is_core_symbol(src, info->sechdrs, info->hdr->e_shnum)) {
strtab_size += strlen(&info->strtab[src->st_name]) + 1;
@@ -2334,6 +2338,8 @@ static void add_kallsyms(struct module *mod, const struct
load_info *info)
src = mod->symtab;
*dst = *src;
*s++ = 0;
+ /* We start searching core symbols from the second entry. */
+ src++;
for (ndst = i = 1; i < mod->num_symtab; ++i, ++src) {
if (!is_core_symbol(src, info->sechdrs, info->hdr->e_shnum))
continue;
--
1.7.10.1
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