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.

Steven Rostedt (VMware) committed 6 years ago

Commit 2860cd81 parent 02a474c8 files · +29 −9Browse files

Unified · Split

8 files

arch/powerpc/include/asm/livepatch.h +3 −1
arch/s390/include/asm/livepatch.h +4 −1
arch/x86/include/asm/ftrace.h +3 −0
arch/x86/include/asm/livepatch.h +2 −2
arch/x86/kernel/ftrace_64.S +4 −0
include/linux/ftrace.h +7 −0
kernel/livepatch/Kconfig +1 −1
kernel/livepatch/patch.c +5 −4

arch/powerpc/include/asm/livepatch.h+3−1

@@ -12,8 +12,10 @@ · 11 unmodified lines
12	12	#include <linux/sched/task_stack.h>
13	13
14	14	#ifdef CONFIG_LIVEPATCH
15		−static inline void klp_arch_set_pc(struct pt_regs *regs, unsigned long ip)
	15	+static inline void klp_arch_set_pc(struct ftrace_regs *fregs, unsigned long ip)
16	16	{
	17	+ struct pt_regs *regs = ftrace_get_regs(fregs);
	18	+
17	19	regs->nip = ip;
18	20	}
19	21

arch/s390/include/asm/livepatch.h+4−1

@@ -11,10 +11,13 @@ · 10 unmodified lines
11	11	#ifndef ASM_LIVEPATCH_H
12	12	#define ASM_LIVEPATCH_H
13	13
	14	+#include <linux/ftrace.h>
14	15	#include <asm/ptrace.h>
15	16
16		−static inline void klp_arch_set_pc(struct pt_regs *regs, unsigned long ip)
	17	+static inline void klp_arch_set_pc(struct ftrace_regs *fregs, unsigned long ip)
17	18	{
	19	+ struct pt_regs *regs = ftrace_get_regs(fregs);
	20	+
18	21	regs->psw.addr = ip;
19	22	}
20	23

arch/x86/include/asm/ftrace.h+3−0

@@ -54,6 +54,9 @@ arch_ftrace_get_regs(struct ftrace_regs *fregs) · 53 unmodified lines
54	54	return NULL;
55	55	return &fregs->regs;
56	56	}
	57	+
	58	+#define ftrace_instruction_pointer_set(fregs, _ip) \
	59	+ do { (fregs)->regs.ip = (_ip); } while (0)
57	60	#endif
58	61
59	62	#ifdef CONFIG_DYNAMIC_FTRACE

arch/x86/include/asm/livepatch.h+2−2

@@ -12,9 +12,9 @@ · 11 unmodified lines
12	12	#include <asm/setup.h>
13	13	#include <linux/ftrace.h>
14	14
15		−static inline void klp_arch_set_pc(struct pt_regs *regs, unsigned long ip)
	15	+static inline void klp_arch_set_pc(struct ftrace_regs *fregs, unsigned long ip)
16	16	{
17		− regs->ip = ip;
	17	+ ftrace_instruction_pointer_set(fregs, ip);
18	18	}
19	19
20	20	#endif /* _ASM_X86_LIVEPATCH_H */

arch/x86/kernel/ftrace_64.S+4−0

@@ -157,6 +157,10 @@ SYM_INNER_LABEL(ftrace_caller_op_ptr, SYM_L_GLOBAL) · 156 unmodified lines
157	157	SYM_INNER_LABEL(ftrace_call, SYM_L_GLOBAL)
158	158	call ftrace_stub
159	159
	160	+ /* Handlers can change the RIP */
	161	+ movq RIP(%rsp), %rax
	162	+ movq %rax, MCOUNT_REG_SIZE(%rsp)
	163	+
160	164	restore_mcount_regs
161	165
162	166	/*

include/linux/ftrace.h+7−0

@@ -97,6 +97,13 @@ struct ftrace_regs { · 96 unmodified lines
97	97	};
98	98	#define arch_ftrace_get_regs(fregs) (&(fregs)->regs)
99	99
	100	+/*
	101	+ * ftrace_instruction_pointer_set() is to be defined by the architecture
	102	+ * if to allow setting of the instruction pointer from the ftrace_regs
	103	+ * when HAVE_DYNAMIC_FTRACE_WITH_ARGS is set and it supports
	104	+ * live kernel patching.
	105	+ */
	106	+#define ftrace_instruction_pointer_set(fregs, ip) do { } while (0)
100	107	#endif /* CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS */
101	108
102	109	static __always_inline struct pt_regs ftrace_get_regs(struct ftrace_regs fregs)

kernel/livepatch/Kconfig+1−1

@@ -6,7 +6,7 @@ config HAVE_LIVEPATCH · 5 unmodified lines
6	6
7	7	config LIVEPATCH
8	8	bool "Kernel Live Patching"
9		− depends on DYNAMIC_FTRACE_WITH_REGS
	9	+ depends on DYNAMIC_FTRACE_WITH_REGS \|\| DYNAMIC_FTRACE_WITH_ARGS
10	10	depends on MODULES
11	11	depends on SYSFS
12	12	depends on KALLSYMS_ALL

kernel/livepatch/patch.c+5−4

@@ -42,7 +42,6 @@ static void notrace klp_ftrace_handler(unsigned long ip, · 41 unmodified lines
42	42	struct ftrace_ops *fops,
43	43	struct ftrace_regs *fregs)
44	44	{
45		− struct pt_regs *regs = ftrace_get_regs(fregs);
46	45	struct klp_ops *ops;
47	46	struct klp_func *func;
48	47	int patch_state;
@@ -118,7 +117,7 @@ static void notrace klp_ftrace_handler(unsigned long ip, · 69 unmodified lines
118	117	if (func->nop)
119	118	goto unlock;
120	119
121		− klp_arch_set_pc(regs, (unsigned long)func->new_func);
	120	+ klp_arch_set_pc(fregs, (unsigned long)func->new_func);
122	121
123	122	unlock:
124	123	preempt_enable_notrace();
@@ -200,8 +199,10 @@ static int klp_patch_func(struct klp_func *func) · 75 unmodified lines
200	199	return -ENOMEM;
201	200
202	201	ops->fops.func = klp_ftrace_handler;
203		− ops->fops.flags = FTRACE_OPS_FL_SAVE_REGS \|
204		− FTRACE_OPS_FL_DYNAMIC \|
	202	+ ops->fops.flags = FTRACE_OPS_FL_DYNAMIC \|
	203	+#ifndef CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS
	204	+ FTRACE_OPS_FL_SAVE_REGS \|
	205	+#endif
205	206	FTRACE_OPS_FL_IPMODIFY \|
206	207	FTRACE_OPS_FL_PERMANENT;
207	208