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authorChris J Arges <chris.j.arges@canonical.com>2015-12-02 05:40:54 +0300
committerJiri Kosina <jkosina@suse.cz>2015-12-04 01:01:26 +0300
commitb2b018ef48675a9a524fa9791ea7d67fdac405f7 (patch)
treee683d922f21f8b88b2ae502e4d076fcaac27d898 /include/linux/livepatch.h
parenta3d66b5a17f81ee84604f95b0e2c9ccf0434c6f0 (diff)
downloadlinux-b2b018ef48675a9a524fa9791ea7d67fdac405f7.tar.xz
livepatch: add old_sympos as disambiguator field to klp_func
Currently, patching objects with duplicate symbol names fail because the creation of the sysfs function directory collides with the previous attempt. Appending old_addr to the function name is problematic as it reveals the address of the function being patch to a normal user. Using the symbol's occurrence in kallsyms to postfix the function name in the sysfs directory solves the issue of having consistent unique names and ensuring that the address is not exposed to a normal user. In addition, using the symbol position as the user's method to disambiguate symbols instead of addr allows for disambiguating symbols in modules as well for both function addresses and for relocs. This also simplifies much of the code. Special handling for kASLR is no longer needed and can be removed. The klp_find_verify_func_addr function can be replaced by klp_find_object_symbol, and klp_verify_vmlinux_symbol and its callback can be removed completely. In cases of duplicate symbols, old_sympos will be used to disambiguate instead of old_addr. 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 in kallsyms for the patched object will be used for patching if it is valid. In addition, make old_addr an internal structure field not to be specified by the user. Finally, remove klp_find_verify_func_addr as it can be replaced by klp_find_object_symbol directly. Support for symbol position disambiguation for relocations is added in the next patch in this series. Signed-off-by: Chris J Arges <chris.j.arges@canonical.com> Reviewed-by: Petr Mladek <pmladek@suse.com> Acked-by: Josh Poimboeuf <jpoimboe@redhat.com> Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Diffstat (limited to 'include/linux/livepatch.h')
-rw-r--r--include/linux/livepatch.h19
1 files changed, 10 insertions, 9 deletions
diff --git a/include/linux/livepatch.h b/include/linux/livepatch.h
index 31db7a05dd36..b60e8abab0ab 100644
--- a/include/linux/livepatch.h
+++ b/include/linux/livepatch.h
@@ -37,8 +37,9 @@ enum klp_state {
* struct klp_func - function structure for live patching
* @old_name: name of the function to be patched
* @new_func: pointer to the patched function code
- * @old_addr: a hint conveying at what address the old function
- * can be found (optional, vmlinux patches only)
+ * @old_sympos: a hint indicating which symbol position the old function
+ * can be found (optional)
+ * @old_addr: the address of the function being patched
* @kobj: kobject for sysfs resources
* @state: tracks function-level patch application state
* @stack_node: list node for klp_ops func_stack list
@@ -48,16 +49,16 @@ struct klp_func {
const char *old_name;
void *new_func;
/*
- * The old_addr field is optional and can be used to resolve
- * duplicate symbol names in the vmlinux object. If this
- * information is not present, the symbol is located by name
- * with kallsyms. If the name is not unique and old_addr is
- * not provided, the patch application fails as there is no
- * way to resolve the ambiguity.
+ * The old_sympos field is optional and can be used to resolve
+ * duplicate symbol names in livepatch objects. If this field is zero,
+ * it is expected the symbol is unique, otherwise patching fails. If
+ * this value is greater than zero then that occurrence of the symbol
+ * in kallsyms for the given object is used.
*/
- unsigned long old_addr;
+ unsigned long old_sympos;
/* internal */
+ unsigned long old_addr;
struct kobject kobj;
enum klp_state state;
struct list_head stack_node;