Commit ca4787b7 authored by Tim Abbott's avatar Tim Abbott Committed by Rusty Russell

kernel/module.c: compare symbol values when marking symbols as exported in /proc/kallsyms.

When there are two symbols in a module with the same name, one of which is
exported, both will be marked as exported in /proc/kallsyms.  There aren't
any instances of this in the current kernel, but it is easy to construct a
simple module with two compilation units that exhibits the problem.

$ objdump -j .text -t testmod.ko | grep foo
00000000 l     F .text	00000032 foo
00000080 g     F .text	00000001 foo
$ sudo insmod testmod.ko
$ grep "T foo" /proc/kallsyms
c28e8000 T foo	[testmod]
c28e8080 T foo	[testmod]

Fix this by comparing the symbol values once we've found the exported
symbol table entry matching the symbol name.  Tested using Ksplice:

$ ksplice-create --patch=this_commit.patch --id=bar .
$ sudo ksplice-apply ksplice-bar.tar.gz
Done!
$ grep "T foo" /proc/kallsyms
c28e8080 T foo	[testmod]
Signed-off-by: default avatarTim Abbott <tabbott@mit.edu>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarRusty Russell <rusty@rustcorp.com.au>
parent a327ca2c
......@@ -1725,15 +1725,15 @@ static const struct kernel_symbol *lookup_symbol(const char *name,
return NULL;
}
static int is_exported(const char *name, const struct module *mod)
static int is_exported(const char *name, unsigned long value,
const struct module *mod)
{
if (!mod && lookup_symbol(name, __start___ksymtab, __stop___ksymtab))
return 1;
const struct kernel_symbol *ks;
if (!mod)
ks = lookup_symbol(name, __start___ksymtab, __stop___ksymtab);
else
if (mod && lookup_symbol(name, mod->syms, mod->syms + mod->num_syms))
return 1;
else
return 0;
ks = lookup_symbol(name, mod->syms, mod->syms + mod->num_syms);
return ks != NULL && ks->value == value;
}
/* As per nm */
......@@ -2504,7 +2504,7 @@ int module_get_kallsym(unsigned int symnum, unsigned long *value, char *type,
strlcpy(name, mod->strtab + mod->symtab[symnum].st_name,
KSYM_NAME_LEN);
strlcpy(module_name, mod->name, MODULE_NAME_LEN);
*exported = is_exported(name, mod);
*exported = is_exported(name, *value, mod);
preempt_enable();
return 0;
}
......
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