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Date: Wed, 11 Nov 2015 10:29:00 -0600
From: Chris J Arges <chris.j.arges@...onical.com>
To: live-patching@...r.kernel.org
Cc: jeyu@...hat.com, Chris J Arges <chris.j.arges@...onical.com>,
Josh Poimboeuf <jpoimboe@...hat.com>,
Seth Jennings <sjenning@...hat.com>,
Jiri Kosina <jikos@...nel.org>,
Vojtech Pavlik <vojtech@...e.com>, linux-kernel@...r.kernel.org
Subject: [PATCH 2/3 v4] livepatch: add old_sympos as disambiguator field to klp_reloc
In cases of duplicate symbols, sympos will be used to disambiguate instead
of val. By default old_sympos will be 0, and patching will only succeed if
the symbol is unique. Specifying a positive value will ensure that
occurrence of the symbol will be used for patching if it is valid.
Signed-off-by: Chris J Arges <chris.j.arges@...onical.com>
---
include/linux/livepatch.h | 5 ++--
kernel/livepatch/core.c | 74 ++++++++++-------------------------------------
2 files changed, 18 insertions(+), 61 deletions(-)
diff --git a/include/linux/livepatch.h b/include/linux/livepatch.h
index df7b752..fb968a2 100644
--- a/include/linux/livepatch.h
+++ b/include/linux/livepatch.h
@@ -68,8 +68,8 @@ struct klp_func {
/**
* struct klp_reloc - relocation structure for live patching
* @loc: address where the relocation will be written
- * @val: address of the referenced symbol (optional,
- * vmlinux patches only)
+ * @val: address of the referenced symbol
+ * @sympos: position in kallsyms to disambiguate symbols (optional)
* @type: ELF relocation type
* @name: name of the referenced symbol (for lookup/verification)
* @addend: offset from the referenced symbol
@@ -78,6 +78,7 @@ struct klp_func {
struct klp_reloc {
unsigned long loc;
unsigned long val;
+ unsigned long sympos;
unsigned long type;
const char *name;
int addend;
diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c
index 26f9778..4eb8691 100644
--- a/kernel/livepatch/core.c
+++ b/kernel/livepatch/core.c
@@ -207,45 +207,6 @@ static int klp_find_object_symbol(const char *objname, const char *name,
return -EINVAL;
}
-struct klp_verify_args {
- const char *name;
- const unsigned long addr;
-};
-
-static int klp_verify_callback(void *data, const char *name,
- struct module *mod, unsigned long addr)
-{
- struct klp_verify_args *args = data;
-
- if (!mod &&
- !strcmp(args->name, name) &&
- args->addr == addr)
- return 1;
-
- return 0;
-}
-
-static int klp_verify_vmlinux_symbol(const char *name, unsigned long addr)
-{
- struct klp_verify_args args = {
- .name = name,
- .addr = addr,
- };
- int ret;
-
- mutex_lock(&module_mutex);
- ret = kallsyms_on_each_symbol(klp_verify_callback, &args);
- mutex_unlock(&module_mutex);
-
- if (!ret) {
- pr_err("symbol '%s' not found at specified address 0x%016lx, kernel mismatch?\n",
- name, addr);
- return -EINVAL;
- }
-
- return 0;
-}
-
static int klp_find_verify_func_addr(struct klp_object *obj,
struct klp_func *func)
{
@@ -261,7 +222,7 @@ static int klp_find_verify_func_addr(struct klp_object *obj,
* object is either vmlinux or the kmod being patched).
*/
static int klp_find_external_symbol(struct module *pmod, const char *name,
- unsigned long *addr)
+ unsigned long *addr, unsigned long sympos)
{
const struct kernel_symbol *sym;
@@ -276,7 +237,7 @@ static int klp_find_external_symbol(struct module *pmod, const char *name,
preempt_enable();
/* otherwise check if it's in another .o within the patch module */
- return klp_find_object_symbol(pmod->name, name, addr, 0);
+ return klp_find_object_symbol(pmod->name, name, addr, sympos);
}
static int klp_write_object_relocations(struct module *pmod,
@@ -292,24 +253,19 @@ static int klp_write_object_relocations(struct module *pmod,
return -EINVAL;
for (reloc = obj->relocs; reloc->name; reloc++) {
- if (!klp_is_module(obj)) {
- ret = klp_verify_vmlinux_symbol(reloc->name,
- reloc->val);
- if (ret)
- return ret;
- } else {
- /* module, reloc->val needs to be discovered */
- if (reloc->external)
- ret = klp_find_external_symbol(pmod,
- reloc->name,
- &reloc->val);
- else
- ret = klp_find_object_symbol(obj->mod->name,
- reloc->name,
- &reloc->val, 0);
- if (ret)
- return ret;
- }
+ /* reloc->val needs to be discovered */
+ if (reloc->external)
+ ret = klp_find_external_symbol(pmod,
+ reloc->name,
+ &reloc->val,
+ reloc->sympos);
+ else
+ ret = klp_find_object_symbol(obj->mod->name,
+ reloc->name,
+ &reloc->val,
+ reloc->sympos);
+ if (ret)
+ return ret;
ret = klp_write_module_reloc(pmod, reloc->type, reloc->loc,
reloc->val + reloc->addend);
if (ret) {
--
1.9.1
--
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