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Date: Thu, 12 Nov 2015 10:59:52 -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 3/4 v5] livepatch: add sympos as disambiguator field to klp_reloc
In cases of duplicate symbols, sympos will be used to disambiguate instead
of val. By default 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 in kallsyms for the patched object will be used
for patching if it is valid.
Remove klp_verify_callback, klp_verify_args and klp_verify_vmlinux_symbol
as they are no longer used.
>From the klp_reloc structure remove val, as it can be refactored as a
local variable in klp_write_object_relocations.
Signed-off-by: Chris J Arges <chris.j.arges@...onical.com>
---
include/linux/livepatch.h | 5 ++-
kernel/livepatch/core.c | 81 +++++++++++++----------------------------------
2 files changed, 24 insertions(+), 62 deletions(-)
diff --git a/include/linux/livepatch.h b/include/linux/livepatch.h
index 9808dd4..9149de4 100644
--- a/include/linux/livepatch.h
+++ b/include/linux/livepatch.h
@@ -68,8 +68,7 @@ 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)
+ * @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
@@ -78,7 +77,7 @@ 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 4cd079c..071895f 100644
--- a/kernel/livepatch/core.c
+++ b/kernel/livepatch/core.c
@@ -202,45 +202,6 @@ 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;
-}
-
/*
* External symbols are exported symbols that are defined outside both
* the patched object and the patch.
@@ -266,6 +227,7 @@ static int klp_write_object_relocations(struct module *pmod,
struct klp_object *obj)
{
int ret;
+ unsigned long val;
struct klp_reloc *reloc;
if (WARN_ON(!klp_is_object_loaded(obj)))
@@ -275,29 +237,30 @@ 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;
- }
+ /* discover the address of the referenced symbol */
+ if (reloc->external) {
+ /*
+ * external symbols aren't specified by the user
+ * therefore sympos should not be used
+ */
+ if (reloc->sympos) {
+ pr_err("symbol '%s' is external and has sympos %lu\n",
+ reloc->name, reloc->sympos);
+ return -EINVAL;
+ }
+ ret = klp_find_external_symbol(pmod, reloc->name, &val);
+ } else
+ ret = klp_find_object_symbol(obj->mod->name,
+ reloc->name,
+ &val,
+ reloc->sympos);
+ if (ret)
+ return ret;
ret = klp_write_module_reloc(pmod, reloc->type, reloc->loc,
- reloc->val + reloc->addend);
+ val + reloc->addend);
if (ret) {
pr_err("relocation failed for symbol '%s' at 0x%016lx (%d)\n",
- reloc->name, reloc->val, ret);
+ reloc->name, val, ret);
return ret;
}
}
--
1.9.1
--
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