Messages in this thread Patch in this message | | | Date | Tue, 26 Jan 2021 15:25:16 +0100 | From | Jessica Yu <> | Subject | Re: [PATCH 04/13] livepatch: move klp_find_object_module to module.c |
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+++ Christoph Hellwig [21/01/21 08:49 +0100]: >To uncouple the livepatch code from module loader internals move a >slightly refactored version of klp_find_object_module to module.c >This allows to mark find_module static and removes one of the last >users of module_mutex outside of module.c. > >Signed-off-by: Christoph Hellwig <hch@lst.de> >--- > include/linux/module.h | 3 +-- > kernel/livepatch/core.c | 39 +++++++++++++-------------------------- > kernel/module.c | 17 ++++++++++++++++- > 3 files changed, 30 insertions(+), 29 deletions(-) > >diff --git a/include/linux/module.h b/include/linux/module.h >index b4654f8a408134..8588482bde4116 100644 >--- a/include/linux/module.h >+++ b/include/linux/module.h >@@ -586,8 +586,7 @@ static inline bool within_module(unsigned long addr, const struct module *mod) > return within_module_init(addr, mod) || within_module_core(addr, mod); > } > >-/* Search for module by name: must hold module_mutex. */ >-struct module *find_module(const char *name); >+struct module *find_klp_module(const char *name); > > /* Check if a module is loaded. */ > bool module_loaded(const char *name); >diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c >index a7f625dc24add3..878759baadd81c 100644 >--- a/kernel/livepatch/core.c >+++ b/kernel/livepatch/core.c >@@ -49,30 +49,6 @@ static bool klp_is_module(struct klp_object *obj) > return obj->name; > } > >-/* sets obj->mod if object is not vmlinux and module is found */ >-static void klp_find_object_module(struct klp_object *obj) >-{ >- struct module *mod; >- >- mutex_lock(&module_mutex); >- /* >- * We do not want to block removal of patched modules and therefore >- * we do not take a reference here. The patches are removed by >- * klp_module_going() instead. >- */ >- mod = find_module(obj->name); >- /* >- * Do not mess work of klp_module_coming() and klp_module_going(). >- * Note that the patch might still be needed before klp_module_going() >- * is called. Module functions can be called even in the GOING state >- * until mod->exit() finishes. This is especially important for >- * patches that modify semantic of the functions. >- */ >- if (mod && mod->klp_alive) >- obj->mod = mod; >- mutex_unlock(&module_mutex); >-}
Hmm, I am not a huge fan of moving more livepatch code into module.c, I wonder if we can keep them separate.
Why not have module_is_loaded() kill two birds with one stone? That is, just have it return a module pointer to signify that the module is loaded, NULL if not. Then we don't need an extra find_klp_module() function just to call find_module() and return a pointer, as module_is_loaded() can just do that for us.
As for the mod->klp_alive check, I believe this function (klp_find_object_module()) is called with klp_mutex held, and mod->klp_alive is only modified under klp_mutex. Also, if klp_alive is true, the module is at least COMING and cannot be GOING until it acquires the klp_mutex again in klp_module_going(). So does that hunk really need to be under module_mutex? It has been a long time since I've looked at livepatch code so it would be great if someone could double check.
Jessica
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