Commit 7ec8a97a authored by Masami Hiramatsu's avatar Masami Hiramatsu Committed by Ingo Molnar
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kprobes/x86: Allow probe on some kprobe preparation functions 

There is no need to prohibit probing on the functions
used in preparation phase. Those are safely probed because
those are not invoked from breakpoint/fault/debug handlers,
there is no chance to cause recursive exceptions.

Following functions are now removed from the kprobes blacklist:

	can_boost
	can_probe
	can_optimize
	is_IF_modifier
	__copy_instruction
	copy_optimized_instructions
	arch_copy_kprobe
	arch_prepare_kprobe
	arch_arm_kprobe
	arch_disarm_kprobe
	arch_remove_kprobe
	arch_trampoline_kprobe
	arch_prepare_kprobe_ftrace
	arch_prepare_optimized_kprobe
	arch_check_optimized_kprobe
	arch_within_optimized_kprobe
	__arch_remove_optimized_kprobe
	arch_remove_optimized_kprobe
	arch_optimize_kprobes
	arch_unoptimize_kprobe

I tested those functions by putting kprobes on all
instructions in the functions with the bash script
I sent to LKML. See:

  https://lkml.org/lkml/2014/3/27/33



Signed-off-by: default avatarMasami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Jiri Kosina <jkosina@suse.cz>
Cc: Jonathan Lebon <jlebon@redhat.com>
Link: http://lkml.kernel.org/r/20140417081747.26341.36065.stgit@ltc230.yrl.intra.hitachi.co.jp


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent ecd50f71

arch/x86/kernel/kprobes/core.c

+10 −10
Original line number Diff line number Diff line
@@ -159,7 +159,7 @@ static kprobe_opcode_t *__kprobes skip_prefixes(kprobe_opcode_t *insn) 
 * Returns non-zero if opcode is boostable.

 * RIP relative instructions are adjusted at copying time in 64 bits mode

 */

int __kprobes can_boost(kprobe_opcode_t *opcodes)

int can_boost(kprobe_opcode_t *opcodes)

{

	kprobe_opcode_t opcode;

	kprobe_opcode_t *orig_opcodes = opcodes;
@@ -260,7 +260,7 @@ unsigned long recover_probed_instruction(kprobe_opcode_t *buf, unsigned long add 
}



/* Check if paddr is at an instruction boundary */

static int __kprobes can_probe(unsigned long paddr)

static int can_probe(unsigned long paddr)

{

	unsigned long addr, __addr, offset = 0;

	struct insn insn;
@@ -299,7 +299,7 @@ static int __kprobes can_probe(unsigned long paddr) 
/*

 * Returns non-zero if opcode modifies the interrupt flag.

 */

static int __kprobes is_IF_modifier(kprobe_opcode_t *insn)

static int is_IF_modifier(kprobe_opcode_t *insn)

{

	/* Skip prefixes */

	insn = skip_prefixes(insn);
@@ -322,7 +322,7 @@ static int __kprobes is_IF_modifier(kprobe_opcode_t *insn) 
 * If not, return null.

 * Only applicable to 64-bit x86.

 */

int __kprobes __copy_instruction(u8 *dest, u8 *src)

int __copy_instruction(u8 *dest, u8 *src)

{

	struct insn insn;

	kprobe_opcode_t buf[MAX_INSN_SIZE];
@@ -365,7 +365,7 @@ int __kprobes __copy_instruction(u8 *dest, u8 *src) 
	return insn.length;

}



static int __kprobes arch_copy_kprobe(struct kprobe *p)

static int arch_copy_kprobe(struct kprobe *p)

{

	int ret;
@@ -392,7 +392,7 @@ static int __kprobes arch_copy_kprobe(struct kprobe *p) 
	return 0;

}



int __kprobes arch_prepare_kprobe(struct kprobe *p)

int arch_prepare_kprobe(struct kprobe *p)

{

	if (alternatives_text_reserved(p->addr, p->addr))

		return -EINVAL;
@@ -407,17 +407,17 @@ int __kprobes arch_prepare_kprobe(struct kprobe *p) 
	return arch_copy_kprobe(p);

}



void __kprobes arch_arm_kprobe(struct kprobe *p)

void arch_arm_kprobe(struct kprobe *p)

{

	text_poke(p->addr, ((unsigned char []){BREAKPOINT_INSTRUCTION}), 1);

}



void __kprobes arch_disarm_kprobe(struct kprobe *p)

void arch_disarm_kprobe(struct kprobe *p)

{

	text_poke(p->addr, &p->opcode, 1);

}



void __kprobes arch_remove_kprobe(struct kprobe *p)

void arch_remove_kprobe(struct kprobe *p)

{

	if (p->ainsn.insn) {

		free_insn_slot(p->ainsn.insn, (p->ainsn.boostable == 1));
@@ -1060,7 +1060,7 @@ int __init arch_init_kprobes(void) 
	return 0;

}



int __kprobes arch_trampoline_kprobe(struct kprobe *p)

int arch_trampoline_kprobe(struct kprobe *p)

{

	return 0;

}

arch/x86/kernel/kprobes/ftrace.c

+1 −1
Original line number Diff line number Diff line
@@ -85,7 +85,7 @@ end: 
	local_irq_restore(flags);

}



int __kprobes arch_prepare_kprobe_ftrace(struct kprobe *p)

int arch_prepare_kprobe_ftrace(struct kprobe *p)

{

	p->ainsn.insn = NULL;

	p->ainsn.boostable = -1;

arch/x86/kernel/kprobes/opt.c

+12 −12
Original line number Diff line number Diff line
@@ -77,7 +77,7 @@ found: 
}



/* Insert a move instruction which sets a pointer to eax/rdi (1st arg). */

static void __kprobes synthesize_set_arg1(kprobe_opcode_t *addr, unsigned long val)

static void synthesize_set_arg1(kprobe_opcode_t *addr, unsigned long val)

{

#ifdef CONFIG_X86_64

	*addr++ = 0x48;
@@ -169,7 +169,7 @@ static void __kprobes optimized_callback(struct optimized_kprobe *op, struct pt_ 
	local_irq_restore(flags);

}



static int __kprobes copy_optimized_instructions(u8 *dest, u8 *src)

static int copy_optimized_instructions(u8 *dest, u8 *src)

{

	int len = 0, ret;
@@ -189,7 +189,7 @@ static int __kprobes copy_optimized_instructions(u8 *dest, u8 *src) 
}



/* Check whether insn is indirect jump */

static int __kprobes insn_is_indirect_jump(struct insn *insn)

static int insn_is_indirect_jump(struct insn *insn)

{

	return ((insn->opcode.bytes[0] == 0xff &&

		(X86_MODRM_REG(insn->modrm.value) & 6) == 4) || /* Jump */
@@ -224,7 +224,7 @@ static int insn_jump_into_range(struct insn *insn, unsigned long start, int len) 
}



/* Decode whole function to ensure any instructions don't jump into target */

static int __kprobes can_optimize(unsigned long paddr)

static int can_optimize(unsigned long paddr)

{

	unsigned long addr, size = 0, offset = 0;

	struct insn insn;
@@ -275,7 +275,7 @@ static int __kprobes can_optimize(unsigned long paddr) 
}



/* Check optimized_kprobe can actually be optimized. */

int __kprobes arch_check_optimized_kprobe(struct optimized_kprobe *op)

int arch_check_optimized_kprobe(struct optimized_kprobe *op)

{

	int i;

	struct kprobe *p;
@@ -290,15 +290,15 @@ int __kprobes arch_check_optimized_kprobe(struct optimized_kprobe *op) 
}



/* Check the addr is within the optimized instructions. */

int __kprobes

arch_within_optimized_kprobe(struct optimized_kprobe *op, unsigned long addr)

int arch_within_optimized_kprobe(struct optimized_kprobe *op,

				 unsigned long addr)

{

	return ((unsigned long)op->kp.addr <= addr &&

		(unsigned long)op->kp.addr + op->optinsn.size > addr);

}



/* Free optimized instruction slot */

static __kprobes

static

void __arch_remove_optimized_kprobe(struct optimized_kprobe *op, int dirty)

{

	if (op->optinsn.insn) {
@@ -308,7 +308,7 @@ void __arch_remove_optimized_kprobe(struct optimized_kprobe *op, int dirty) 
	}

}



void __kprobes arch_remove_optimized_kprobe(struct optimized_kprobe *op)

void arch_remove_optimized_kprobe(struct optimized_kprobe *op)

{

	__arch_remove_optimized_kprobe(op, 1);

}
@@ -318,7 +318,7 @@ void __kprobes arch_remove_optimized_kprobe(struct optimized_kprobe *op) 
 * Target instructions MUST be relocatable (checked inside)

 * This is called when new aggr(opt)probe is allocated or reused.

 */

int __kprobes arch_prepare_optimized_kprobe(struct optimized_kprobe *op)

int arch_prepare_optimized_kprobe(struct optimized_kprobe *op)

{

	u8 *buf;

	int ret;
@@ -372,7 +372,7 @@ int __kprobes arch_prepare_optimized_kprobe(struct optimized_kprobe *op) 
 * Replace breakpoints (int3) with relative jumps.

 * Caller must call with locking kprobe_mutex and text_mutex.

 */

void __kprobes arch_optimize_kprobes(struct list_head *oplist)

void arch_optimize_kprobes(struct list_head *oplist)

{

	struct optimized_kprobe *op, *tmp;

	u8 insn_buf[RELATIVEJUMP_SIZE];
@@ -398,7 +398,7 @@ void __kprobes arch_optimize_kprobes(struct list_head *oplist) 
}



/* Replace a relative jump with a breakpoint (int3).  */

void __kprobes arch_unoptimize_kprobe(struct optimized_kprobe *op)

void arch_unoptimize_kprobe(struct optimized_kprobe *op)

{

	u8 insn_buf[RELATIVEJUMP_SIZE];

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