The existing livepatch code assumes that a fentry call is inserted before a function prolog by -mfentry option of gcc. But the location of mcount() can be identified by using ftrace_lookup_mcount(), and which eventually allows arch's which don't support -mfentry option, like arm64, to support livepatch.
This patch modifies core and x86 code before adding livepatch support for arm64.
Signed-off-by: AKASHI Takahiro takahiro.akashi@linaro.org --- arch/x86/include/asm/livepatch.h | 5 +++++ include/linux/livepatch.h | 2 ++ kernel/livepatch/core.c | 16 ++++++++++++---- 3 files changed, 19 insertions(+), 4 deletions(-)
diff --git a/arch/x86/include/asm/livepatch.h b/arch/x86/include/asm/livepatch.h index a455a53..914954a 100644 --- a/arch/x86/include/asm/livepatch.h +++ b/arch/x86/include/asm/livepatch.h @@ -39,6 +39,11 @@ static inline void klp_arch_set_pc(struct pt_regs *regs, unsigned long ip) { regs->ip = ip; } + +static inline unsigned long klp_arch_lookup_mcount(unsigned long addr) +{ + return addr; +} #else #error Live patching support is disabled; check CONFIG_LIVEPATCH #endif diff --git a/include/linux/livepatch.h b/include/linux/livepatch.h index 95023fd..fec7800 100644 --- a/include/linux/livepatch.h +++ b/include/linux/livepatch.h @@ -47,6 +47,7 @@ struct klp_func { /* external */ const char *old_name; void *new_func; + unsigned long new_func_mcount; /* * The old_addr field is optional and can be used to resolve * duplicate symbol names in the vmlinux object. If this @@ -56,6 +57,7 @@ struct klp_func { * way to resolve the ambiguity. */ unsigned long old_addr; + unsigned long old_addr_mcount;
/* internal */ struct kobject kobj; diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c index 3f9f1d6..3c7c8070 100644 --- a/kernel/livepatch/core.c +++ b/kernel/livepatch/core.c @@ -245,6 +245,9 @@ static int klp_find_verify_func_addr(struct klp_object *obj, ret = klp_verify_vmlinux_symbol(func->old_name, func->old_addr);
+ if (func->old_addr && !ret) + func->old_addr_mcount = klp_arch_lookup_mcount(func->old_addr); + return ret; }
@@ -330,7 +333,7 @@ static void notrace klp_ftrace_handler(unsigned long ip, if (WARN_ON_ONCE(!func)) goto unlock;
- klp_arch_set_pc(regs, (unsigned long)func->new_func); + klp_arch_set_pc(regs, func->new_func_mcount); unlock: rcu_read_unlock(); } @@ -358,7 +361,8 @@ static int klp_disable_func(struct klp_func *func) return ret; }
- ret = ftrace_set_filter_ip(&ops->fops, func->old_addr, 1, 0); + ret = ftrace_set_filter_ip(&ops->fops, + func->old_addr_mcount, 1, 0); if (ret) pr_warn("function unregister succeeded but failed to clear the filter\n");
@@ -401,7 +405,8 @@ static int klp_enable_func(struct klp_func *func) INIT_LIST_HEAD(&ops->func_stack); list_add_rcu(&func->stack_node, &ops->func_stack);
- ret = ftrace_set_filter_ip(&ops->fops, func->old_addr, 0, 0); + ret = ftrace_set_filter_ip(&ops->fops, + func->old_addr_mcount, 0, 0); if (ret) { pr_err("failed to set ftrace filter for function '%s' (%d)\n", func->old_name, ret); @@ -412,7 +417,8 @@ static int klp_enable_func(struct klp_func *func) if (ret) { pr_err("failed to register ftrace handler for function '%s' (%d)\n", func->old_name, ret); - ftrace_set_filter_ip(&ops->fops, func->old_addr, 1, 0); + ftrace_set_filter_ip(&ops->fops, + func->old_addr_mcount, 1, 0); goto err; }
@@ -742,6 +748,8 @@ static int klp_init_func(struct klp_object *obj, struct klp_func *func) { INIT_LIST_HEAD(&func->stack_node); func->state = KLP_DISABLED; + func->new_func_mcount = + klp_arch_lookup_mcount((unsigned long)func->new_func);
return kobject_init_and_add(&func->kobj, &klp_ktype_func, obj->kobj, "%s", func->old_name);