[PATCH] livepatch: Improve the accuracy of symbol search

[luhao <lu.haoA@h3c.com>]

module_kallsyms_on_each_symbol, when the input parameter modname is not
 empty, only searches for symbols within the current module. When
patching a kernel object (ko), if the patched function calls
functions from vmlinux or other ko modules, symbol lookup may fail.

When patching a ko, the current approach first searches for symbols
within the module itself. If not found, it uses
kallsyms_on_each_match_symbol to search in vmlinux. If still not
found, it calls module_kallsyms_on_each_symbol with modname set to
NULL to search across all ko modules. The reason for not searching
across all ko modules from the start is to avoid issues with
duplicate symbol names.

Reviewed-by: zhangchun <zhang.chunA@h3c.com>
Reviewed-by: wangshijie <wang.shijie@h3c.com>
Signed-off-by: luhao <lu.haoA@h3c.com>
---
 kernel/livepatch/core.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c
index 28d15ba58a26..9c587cc4896b 100644
--- a/kernel/livepatch/core.c
+++ b/kernel/livepatch/core.c
@@ -167,9 +167,14 @@ static int klp_find_object_symbol(const char *objname, const char *name,
                .pos = sympos,
        };

-       if (objname)
+       if (objname) {
                module_kallsyms_on_each_symbol(objname, klp_find_callback, &args);
-       else
+
+               if (args.addr == 0)
+                       kallsyms_on_each_match_symbol(klp_match_callback, name, &args);
+               if (args.addr == 0)
+                       module_kallsyms_on_each_symbol(NULL, klp_find_callback, &args);
+       } else
                kallsyms_on_each_match_symbol(klp_match_callback, name, &args);

        /*
--
2.51.0

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