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Subject[PATCH -tip v7 10/26] kprobes/x86: Allow probe on some kprobe preparation functions
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Date
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 the safety via kprobe-tracer as below;

# cd /sys/kernel/debug/tracing
# cat above-coverted-symbols-list | while read s; do
echo "p $s"; done > kprobe_events
(Note: some symbols are not found, those are inlined)
# echo 1 > events/kprobes/enable
# echo p:foo vfs_symlink >> kprobe_events
# echo p:bar vfs_symlink+5 >> kprobe_events
# echo p vfs_symlink+5 >> kprobe_events
# echo 1 > events/kprobes/foo/enable
# ln -sf /tmp/foo /tmp/bar
# echo 0 > events/kprobes/foo/enable
# echo -:foo >> kprobe_events
# head -n 20 trace
# echo 0 > events/kprobes/enable
# echo > kprobe_events
# echo > trace

Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
---
arch/x86/kernel/kprobes/core.c | 20 ++++++++++----------
arch/x86/kernel/kprobes/ftrace.c | 2 +-
arch/x86/kernel/kprobes/opt.c | 24 ++++++++++++------------
3 files changed, 23 insertions(+), 23 deletions(-)

diff --git a/arch/x86/kernel/kprobes/core.c b/arch/x86/kernel/kprobes/core.c
index 566958e..ae5aafb 100644
--- a/arch/x86/kernel/kprobes/core.c
+++ b/arch/x86/kernel/kprobes/core.c
@@ -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));
@@ -1057,7 +1057,7 @@ 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;
}
diff --git a/arch/x86/kernel/kprobes/ftrace.c b/arch/x86/kernel/kprobes/ftrace.c
index 23ef5c5..dcaa131 100644
--- a/arch/x86/kernel/kprobes/ftrace.c
+++ b/arch/x86/kernel/kprobes/ftrace.c
@@ -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;
diff --git a/arch/x86/kernel/kprobes/opt.c b/arch/x86/kernel/kprobes/opt.c
index 898160b..fba7fb0 100644
--- a/arch/x86/kernel/kprobes/opt.c
+++ b/arch/x86/kernel/kprobes/opt.c
@@ -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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