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

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

kernel/module.c

+8 −8
Original line number Diff line number Diff line
@@ -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;

	else

		if (mod && lookup_symbol(name, mod->syms, mod->syms + mod->num_syms))

			return 1;

	const struct kernel_symbol *ks;

	if (!mod)

		ks = lookup_symbol(name, __start___ksymtab, __stop___ksymtab);

	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;

		}