lkml.org 
[lkml]   [2017]   [Sep]   [28]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
Subject[tip:perf/core] kprobes/x86: Make insn buffer always ROX and use text_poke()
Commit-ID:  63fef14fc98a8b4fad777fd3bef4d068802b3f14
Gitweb: https://git.kernel.org/tip/63fef14fc98a8b4fad777fd3bef4d068802b3f14
Author: Masami Hiramatsu <mhiramat@kernel.org>
AuthorDate: Fri, 18 Aug 2017 17:24:00 +0900
Committer: Ingo Molnar <mingo@kernel.org>
CommitDate: Thu, 28 Sep 2017 09:23:03 +0200

kprobes/x86: Make insn buffer always ROX and use text_poke()

Make insn buffer always ROX and use text_poke() to write
the copied instructions instead of set_memory_*().
This makes instruction buffer stronger against other
kernel subsystems because there is no window time
to modify the buffer.

Suggested-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>
Cc: David S . Miller <davem@davemloft.net>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/150304463032.17009.14195368040691676813.stgit@devbox
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
arch/x86/kernel/kprobes/common.h | 6 ++--
arch/x86/kernel/kprobes/core.c | 61 ++++++++++++++++++++++++-------------
arch/x86/kernel/kprobes/opt.c | 65 +++++++++++++++++++++++-----------------
kernel/kprobes.c | 2 +-
4 files changed, 81 insertions(+), 53 deletions(-)

diff --git a/arch/x86/kernel/kprobes/common.h b/arch/x86/kernel/kprobes/common.h
index db2182d..e2c2a19 100644
--- a/arch/x86/kernel/kprobes/common.h
+++ b/arch/x86/kernel/kprobes/common.h
@@ -75,11 +75,11 @@ extern unsigned long recover_probed_instruction(kprobe_opcode_t *buf,
* Copy an instruction and adjust the displacement if the instruction
* uses the %rip-relative addressing mode.
*/
-extern int __copy_instruction(u8 *dest, u8 *src, struct insn *insn);
+extern int __copy_instruction(u8 *dest, u8 *src, u8 *real, struct insn *insn);

/* Generate a relative-jump/call instruction */
-extern void synthesize_reljump(void *from, void *to);
-extern void synthesize_relcall(void *from, void *to);
+extern void synthesize_reljump(void *dest, void *from, void *to);
+extern void synthesize_relcall(void *dest, void *from, void *to);

#ifdef CONFIG_OPTPROBES
extern int setup_detour_execution(struct kprobe *p, struct pt_regs *regs, int reenter);
diff --git a/arch/x86/kernel/kprobes/core.c b/arch/x86/kernel/kprobes/core.c
index f015371..b48e0ef 100644
--- a/arch/x86/kernel/kprobes/core.c
+++ b/arch/x86/kernel/kprobes/core.c
@@ -119,29 +119,29 @@ struct kretprobe_blackpoint kretprobe_blacklist[] = {
const int kretprobe_blacklist_size = ARRAY_SIZE(kretprobe_blacklist);

static nokprobe_inline void
-__synthesize_relative_insn(void *from, void *to, u8 op)
+__synthesize_relative_insn(void *dest, void *from, void *to, u8 op)
{
struct __arch_relative_insn {
u8 op;
s32 raddr;
} __packed *insn;

- insn = (struct __arch_relative_insn *)from;
+ insn = (struct __arch_relative_insn *)dest;
insn->raddr = (s32)((long)(to) - ((long)(from) + 5));
insn->op = op;
}

/* Insert a jump instruction at address 'from', which jumps to address 'to'.*/
-void synthesize_reljump(void *from, void *to)
+void synthesize_reljump(void *dest, void *from, void *to)
{
- __synthesize_relative_insn(from, to, RELATIVEJUMP_OPCODE);
+ __synthesize_relative_insn(dest, from, to, RELATIVEJUMP_OPCODE);
}
NOKPROBE_SYMBOL(synthesize_reljump);

/* Insert a call instruction at address 'from', which calls address 'to'.*/
-void synthesize_relcall(void *from, void *to)
+void synthesize_relcall(void *dest, void *from, void *to)
{
- __synthesize_relative_insn(from, to, RELATIVECALL_OPCODE);
+ __synthesize_relative_insn(dest, from, to, RELATIVECALL_OPCODE);
}
NOKPROBE_SYMBOL(synthesize_relcall);

@@ -346,10 +346,11 @@ static int is_IF_modifier(kprobe_opcode_t *insn)
/*
* Copy an instruction with recovering modified instruction by kprobes
* and adjust the displacement if the instruction uses the %rip-relative
- * addressing mode.
+ * addressing mode. Note that since @real will be the final place of copied
+ * instruction, displacement must be adjust by @real, not @dest.
* This returns the length of copied instruction, or 0 if it has an error.
*/
-int __copy_instruction(u8 *dest, u8 *src, struct insn *insn)
+int __copy_instruction(u8 *dest, u8 *src, u8 *real, struct insn *insn)
{
kprobe_opcode_t buf[MAX_INSN_SIZE];
unsigned long recovered_insn =
@@ -387,11 +388,11 @@ int __copy_instruction(u8 *dest, u8 *src, struct insn *insn)
* have given.
*/
newdisp = (u8 *) src + (s64) insn->displacement.value
- - (u8 *) dest;
+ - (u8 *) real;
if ((s64) (s32) newdisp != newdisp) {
pr_err("Kprobes error: new displacement does not fit into s32 (%llx)\n", newdisp);
pr_err("\tSrc: %p, Dest: %p, old disp: %x\n",
- src, dest, insn->displacement.value);
+ src, real, insn->displacement.value);
return 0;
}
disp = (u8 *) dest + insn_offset_displacement(insn);
@@ -402,20 +403,38 @@ int __copy_instruction(u8 *dest, u8 *src, struct insn *insn)
}

/* Prepare reljump right after instruction to boost */
-static void prepare_boost(struct kprobe *p, struct insn *insn)
+static int prepare_boost(kprobe_opcode_t *buf, struct kprobe *p,
+ struct insn *insn)
{
+ int len = insn->length;
+
if (can_boost(insn, p->addr) &&
- MAX_INSN_SIZE - insn->length >= RELATIVEJUMP_SIZE) {
+ MAX_INSN_SIZE - len >= RELATIVEJUMP_SIZE) {
/*
* These instructions can be executed directly if it
* jumps back to correct address.
*/
- synthesize_reljump(p->ainsn.insn + insn->length,
+ synthesize_reljump(buf + len, p->ainsn.insn + len,
p->addr + insn->length);
+ len += RELATIVEJUMP_SIZE;
p->ainsn.boostable = true;
} else {
p->ainsn.boostable = false;
}
+
+ return len;
+}
+
+/* Make page to RO mode when allocate it */
+void *alloc_insn_page(void)
+{
+ void *page;
+
+ page = module_alloc(PAGE_SIZE);
+ if (page)
+ set_memory_ro((unsigned long)page & PAGE_MASK, 1);
+
+ return page;
}

/* Recover page to RW mode before releasing it */
@@ -429,12 +448,11 @@ void free_insn_page(void *page)
static int arch_copy_kprobe(struct kprobe *p)
{
struct insn insn;
+ kprobe_opcode_t buf[MAX_INSN_SIZE];
int len;

- set_memory_rw((unsigned long)p->ainsn.insn & PAGE_MASK, 1);
-
/* Copy an instruction with recovering if other optprobe modifies it.*/
- len = __copy_instruction(p->ainsn.insn, p->addr, &insn);
+ len = __copy_instruction(buf, p->addr, p->ainsn.insn, &insn);
if (!len)
return -EINVAL;

@@ -442,15 +460,16 @@ static int arch_copy_kprobe(struct kprobe *p)
* __copy_instruction can modify the displacement of the instruction,
* but it doesn't affect boostable check.
*/
- prepare_boost(p, &insn);
-
- set_memory_ro((unsigned long)p->ainsn.insn & PAGE_MASK, 1);
+ len = prepare_boost(buf, p, &insn);

/* Check whether the instruction modifies Interrupt Flag or not */
- p->ainsn.if_modifier = is_IF_modifier(p->ainsn.insn);
+ p->ainsn.if_modifier = is_IF_modifier(buf);

/* Also, displacement change doesn't affect the first byte */
- p->opcode = p->ainsn.insn[0];
+ p->opcode = buf[0];
+
+ /* OK, write back the instruction(s) into ROX insn buffer */
+ text_poke(p->ainsn.insn, buf, len);

return 0;
}
diff --git a/arch/x86/kernel/kprobes/opt.c b/arch/x86/kernel/kprobes/opt.c
index 4f98aad..22e65f0 100644
--- a/arch/x86/kernel/kprobes/opt.c
+++ b/arch/x86/kernel/kprobes/opt.c
@@ -184,13 +184,13 @@ optimized_callback(struct optimized_kprobe *op, struct pt_regs *regs)
}
NOKPROBE_SYMBOL(optimized_callback);

-static int copy_optimized_instructions(u8 *dest, u8 *src)
+static int copy_optimized_instructions(u8 *dest, u8 *src, u8 *real)
{
struct insn insn;
int len = 0, ret;

while (len < RELATIVEJUMP_SIZE) {
- ret = __copy_instruction(dest + len, src + len, &insn);
+ ret = __copy_instruction(dest + len, src + len, real, &insn);
if (!ret || !can_boost(&insn, src + len))
return -EINVAL;
len += ret;
@@ -343,57 +343,66 @@ void arch_remove_optimized_kprobe(struct optimized_kprobe *op)
int arch_prepare_optimized_kprobe(struct optimized_kprobe *op,
struct kprobe *__unused)
{
- u8 *buf;
- int ret;
+ u8 *buf = NULL, *slot;
+ int ret, len;
long rel;

if (!can_optimize((unsigned long)op->kp.addr))
return -EILSEQ;

- op->optinsn.insn = get_optinsn_slot();
- if (!op->optinsn.insn)
+ buf = kzalloc(MAX_OPTINSN_SIZE, GFP_KERNEL);
+ if (!buf)
return -ENOMEM;

+ op->optinsn.insn = slot = get_optinsn_slot();
+ if (!slot) {
+ ret = -ENOMEM;
+ goto out;
+ }
+
/*
* Verify if the address gap is in 2GB range, because this uses
* a relative jump.
*/
- rel = (long)op->optinsn.insn - (long)op->kp.addr + RELATIVEJUMP_SIZE;
+ rel = (long)slot - (long)op->kp.addr + RELATIVEJUMP_SIZE;
if (abs(rel) > 0x7fffffff) {
- __arch_remove_optimized_kprobe(op, 0);
- return -ERANGE;
+ ret = -ERANGE;
+ goto err;
}

- buf = (u8 *)op->optinsn.insn;
- set_memory_rw((unsigned long)buf & PAGE_MASK, 1);
+ /* Copy arch-dep-instance from template */
+ memcpy(buf, &optprobe_template_entry, TMPL_END_IDX);

/* Copy instructions into the out-of-line buffer */
- ret = copy_optimized_instructions(buf + TMPL_END_IDX, op->kp.addr);
- if (ret < 0) {
- __arch_remove_optimized_kprobe(op, 0);
- return ret;
- }
+ ret = copy_optimized_instructions(buf + TMPL_END_IDX, op->kp.addr,
+ slot + TMPL_END_IDX);
+ if (ret < 0)
+ goto err;
op->optinsn.size = ret;
-
- /* Copy arch-dep-instance from template */
- memcpy(buf, &optprobe_template_entry, TMPL_END_IDX);
+ len = TMPL_END_IDX + op->optinsn.size;

/* Set probe information */
synthesize_set_arg1(buf + TMPL_MOVE_IDX, (unsigned long)op);

/* Set probe function call */
- synthesize_relcall(buf + TMPL_CALL_IDX, optimized_callback);
+ synthesize_relcall(buf + TMPL_CALL_IDX,
+ slot + TMPL_CALL_IDX, optimized_callback);

/* Set returning jmp instruction at the tail of out-of-line buffer */
- synthesize_reljump(buf + TMPL_END_IDX + op->optinsn.size,
+ synthesize_reljump(buf + len, slot + len,
(u8 *)op->kp.addr + op->optinsn.size);
-
- set_memory_ro((unsigned long)buf & PAGE_MASK, 1);
-
- flush_icache_range((unsigned long) buf,
- (unsigned long) buf + TMPL_END_IDX +
- op->optinsn.size + RELATIVEJUMP_SIZE);
- return 0;
+ len += RELATIVEJUMP_SIZE;
+
+ /* We have to use text_poke for instuction buffer because it is RO */
+ text_poke(slot, buf, len);
+ ret = 0;
+out:
+ kfree(buf);
+ return ret;
+
+err:
+ __arch_remove_optimized_kprobe(op, 0);
+ goto out;
}

/*
diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index a1606a4..15fba7f 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -117,7 +117,7 @@ enum kprobe_slot_state {
SLOT_USED = 2,
};

-static void *alloc_insn_page(void)
+void __weak *alloc_insn_page(void)
{
return module_alloc(PAGE_SIZE);
}
\
 
 \ /
  Last update: 2017-09-28 12:56    [W:0.124 / U:6.484 seconds]
©2003-2017 Jasper Spaans. hosted at Digital OceanAdvertise on this site