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livepatch: Use the default ftrace_ops instead of REGS when ARGS is available 

When CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS is available, the ftrace call
will be able to set the ip of the calling function. This will improve the
performance of live kernel patching where it does not need all the regs to
be stored just to change the instruction pointer.

If all archs that support live kernel patching also support
HAVE_DYNAMIC_FTRACE_WITH_ARGS, then the architecture specific function
klp_arch_set_pc() could be made generic.

It is possible that an arch can support HAVE_DYNAMIC_FTRACE_WITH_ARGS but
not HAVE_DYNAMIC_FTRACE_WITH_REGS and then have access to live patching.

Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Jiri Kosina <jikos@kernel.org>
Cc: live-patching@vger.kernel.org
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Miroslav Benes <mbenes@suse.cz>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
This commit is contained in:
Steven Rostedt (VMware) 2020-10-28 17:15:27 -04:00
parent 02a474ca26
commit 2860cd8a23
8 changed files with 29 additions and 9 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
arch/powerpc/include/asm/livepatch.h
View File

@ -12,8 +12,10 @@
#include <linux/sched/task_stack.h>
#ifdef CONFIG_LIVEPATCH
static inline void klp_arch_set_pc(struct pt_regs *regs, unsigned long ip)
static inline void klp_arch_set_pc(struct ftrace_regs *fregs, unsigned long ip)
{
struct pt_regs *regs = ftrace_get_regs(fregs);
regs->nip = ip;
}

5
arch/s390/include/asm/livepatch.h
View File

@ -11,10 +11,13 @@
#ifndef ASM_LIVEPATCH_H
#define ASM_LIVEPATCH_H
#include <linux/ftrace.h>
#include <asm/ptrace.h>
static inline void klp_arch_set_pc(struct pt_regs *regs, unsigned long ip)
static inline void klp_arch_set_pc(struct ftrace_regs *fregs, unsigned long ip)
{
struct pt_regs *regs = ftrace_get_regs(fregs);
regs->psw.addr = ip;
}

3
arch/x86/include/asm/ftrace.h
View File

@ -54,6 +54,9 @@ arch_ftrace_get_regs(struct ftrace_regs *fregs)
return NULL;
return &fregs->regs;
}
#define ftrace_instruction_pointer_set(fregs, _ip) \
do { (fregs)->regs.ip = (_ip); } while (0)
#endif
#ifdef CONFIG_DYNAMIC_FTRACE

4
arch/x86/include/asm/livepatch.h
View File

@ -12,9 +12,9 @@
#include <asm/setup.h>
#include <linux/ftrace.h>
static inline void klp_arch_set_pc(struct pt_regs *regs, unsigned long ip)
static inline void klp_arch_set_pc(struct ftrace_regs *fregs, unsigned long ip)
{
regs->ip = ip;
ftrace_instruction_pointer_set(fregs, ip);
}
#endif /* _ASM_X86_LIVEPATCH_H */

4
arch/x86/kernel/ftrace_64.S
View File

@ -157,6 +157,10 @@ SYM_INNER_LABEL(ftrace_caller_op_ptr, SYM_L_GLOBAL)
SYM_INNER_LABEL(ftrace_call, SYM_L_GLOBAL)
call ftrace_stub
/* Handlers can change the RIP */
movq RIP(%rsp), %rax
movq %rax, MCOUNT_REG_SIZE(%rsp)
restore_mcount_regs
/*

7
include/linux/ftrace.h
View File

@ -97,6 +97,13 @@ struct ftrace_regs {
};
#define arch_ftrace_get_regs(fregs) (&(fregs)->regs)
/*
* ftrace_instruction_pointer_set() is to be defined by the architecture
* if to allow setting of the instruction pointer from the ftrace_regs
* when HAVE_DYNAMIC_FTRACE_WITH_ARGS is set and it supports
* live kernel patching.
*/
#define ftrace_instruction_pointer_set(fregs, ip) do { } while (0)
#endif /* CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS */
static __always_inline struct pt_regs *ftrace_get_regs(struct ftrace_regs *fregs)

2
kernel/livepatch/Kconfig
View File

@ -6,7 +6,7 @@ config HAVE_LIVEPATCH
config LIVEPATCH
bool "Kernel Live Patching"
depends on DYNAMIC_FTRACE_WITH_REGS
depends on DYNAMIC_FTRACE_WITH_REGS || DYNAMIC_FTRACE_WITH_ARGS
depends on MODULES
depends on SYSFS
depends on KALLSYMS_ALL

9
kernel/livepatch/patch.c
View File

@ -42,7 +42,6 @@ static void notrace klp_ftrace_handler(unsigned long ip,
struct ftrace_ops *fops,
struct ftrace_regs *fregs)
{
struct pt_regs *regs = ftrace_get_regs(fregs);
struct klp_ops *ops;
struct klp_func *func;
int patch_state;
@ -118,7 +117,7 @@ static void notrace klp_ftrace_handler(unsigned long ip,
if (func->nop)
goto unlock;
klp_arch_set_pc(regs, (unsigned long)func->new_func);
klp_arch_set_pc(fregs, (unsigned long)func->new_func);
unlock:
preempt_enable_notrace();
@ -200,8 +199,10 @@ static int klp_patch_func(struct klp_func *func)
return -ENOMEM;
ops->fops.func = klp_ftrace_handler;
ops->fops.flags = FTRACE_OPS_FL_SAVE_REGS |
FTRACE_OPS_FL_DYNAMIC |
ops->fops.flags = FTRACE_OPS_FL_DYNAMIC |
#ifndef CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS
FTRACE_OPS_FL_SAVE_REGS |
#endif
FTRACE_OPS_FL_IPMODIFY |
FTRACE_OPS_FL_PERMANENT;