From 064c89df6247cd829a7880cc8a87b7ed2cdfccd8 Mon Sep 17 00:00:00 2001 From: Chris J Arges Date: Tue, 1 Dec 2015 20:40:55 -0600 Subject: [PATCH] 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. For external relocations sympos is not supported. 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 Reviewed-by: Petr Mladek Acked-by: Josh Poimboeuf Signed-off-by: Jiri Kosina --- include/linux/livepatch.h | 5 +-- kernel/livepatch/core.c | 84 +++++++++------------------------------ 2 files changed, 21 insertions(+), 68 deletions(-) diff --git a/include/linux/livepatch.h b/include/linux/livepatch.h index b60e8abab0ab..a8828652f794 100644 --- a/include/linux/livepatch.h +++ b/include/linux/livepatch.h @@ -67,8 +67,7 @@ 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 @@ -76,7 +75,7 @@ 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 e416f96e938d..e842534d3493 100644 --- a/kernel/livepatch/core.c +++ b/kernel/livepatch/core.c @@ -203,45 +203,6 @@ 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 located outside the parent object (where the parent * object is either vmlinux or the kmod being patched). @@ -272,6 +233,7 @@ 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))) @@ -281,35 +243,27 @@ static int klp_write_object_relocations(struct module *pmod, return -EINVAL; for (reloc = obj->relocs; reloc->name; reloc++) { - if (!klp_is_module(obj)) { - -#if defined(CONFIG_RANDOMIZE_BASE) - /* If KASLR has been enabled, adjust old value accordingly */ - if (kaslr_enabled()) - reloc->val += kaslr_offset(); -#endif - 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, - 0, &reloc->val); - if (ret) - return ret; - } + /* discover the address of the referenced symbol */ + if (reloc->external) { + if (reloc->sympos > 0) { + pr_err("non-zero sympos for external reloc symbol '%s' is not supported\n", + reloc->name); + return -EINVAL; + } + ret = klp_find_external_symbol(pmod, reloc->name, &val); + } else + ret = klp_find_object_symbol(obj->name, + reloc->name, + reloc->sympos, + &val); + 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; } } -- 2.20.1