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@xxxxxxxxxx>
---
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);
--
1.7.9.5
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