diff mbox

[v3,3/3] ARM: kprobes: disallow probing stack consuming instructions

Message ID 1416551731-50777-4-git-send-email-wangnan0@huawei.com
State New
Headers show

Commit Message

Wang Nan Nov. 21, 2014, 6:35 a.m. UTC 
This patch prohibit probing instructions for which the stack
requirement are unable to be determined statically. Some test cases
are found not work again after the modification, this patch also
removes them.

Signed-off-by: Wang Nan <wangnan0@huawei.com>

---

v1 -> v2:
 - Use MAX_STACK_SIZE macro instead of hard coded stack size.

v2 -> v3:
 - Commit message improvements.
---
 arch/arm/include/asm/kprobes.h     |  1 -
 arch/arm/include/asm/probes.h      | 12 ++++++++++++
 arch/arm/kernel/entry-armv.S       |  3 ++-
 arch/arm/kernel/kprobes-test-arm.c | 16 ++++++++++------
 arch/arm/kernel/kprobes.c          |  9 +++++++++
 5 files changed, 33 insertions(+), 8 deletions(-)

Comments

Jon Medhurst (Tixy) Nov. 21, 2014, 5:59 p.m. UTC | #1 
On Fri, 2014-11-21 at 14:35 +0800, Wang Nan wrote:
> This patch prohibit probing instructions for which the stack

Needs an 's' on the end of 'prohibit'

> requirement are unable to be determined statically. Some test cases

and another 's' on the end of 'requirement'

> are found not work again after the modification, this patch also
> removes them.
> 
> Signed-off-by: Wang Nan <wangnan0@huawei.com>

Reviewed-by: Jon Medhurst <tixy@linaro.org>

I think we also need to add new test cases to cover the stack store
instructions. I have already produced these (which is how I found the
Thumb decoding bugs) so I will follow up with a separate patch with
those. It would be good if you could that it to the end of your series.

Thanks
diff mbox

Patch

diff --git a/arch/arm/include/asm/kprobes.h b/arch/arm/include/asm/kprobes.h
index 49fa0df..56f9ac6 100644
--- a/arch/arm/include/asm/kprobes.h
+++ b/arch/arm/include/asm/kprobes.h
@@ -22,7 +22,6 @@ 
 
 #define __ARCH_WANT_KPROBES_INSN_SLOT
 #define MAX_INSN_SIZE			2
-#define MAX_STACK_SIZE			64	/* 32 would probably be OK */
 
 #define flush_insn_slot(p)		do { } while (0)
 #define kretprobe_blacklist_size	0
diff --git a/arch/arm/include/asm/probes.h b/arch/arm/include/asm/probes.h
index ccf9af3..f0a1ee8 100644
--- a/arch/arm/include/asm/probes.h
+++ b/arch/arm/include/asm/probes.h
@@ -19,6 +19,8 @@ 
 #ifndef _ASM_PROBES_H
 #define _ASM_PROBES_H
 
+#ifndef __ASSEMBLY__
+
 typedef u32 probes_opcode_t;
 
 struct arch_probes_insn;
@@ -41,4 +43,14 @@  struct arch_probes_insn {
 	int stack_space;
 };
 
+#endif /* __ASSEMBLY__ */
+
+/*
+ * We assume one instruction can consume at most 64 bytes stack, which is
+ * 'push {r0-r15}'. Instructions consume more or unknown stack space like
+ * 'str r0, [sp, #-80]' and 'str r0, [sp, r1]' should be prohibit to probe.
+ * Both kprobe and jprobe use this macro.
+ */
+#define MAX_STACK_SIZE			64
+
 #endif
diff --git a/arch/arm/kernel/entry-armv.S b/arch/arm/kernel/entry-armv.S
index 2f5555d..672b219 100644
--- a/arch/arm/kernel/entry-armv.S
+++ b/arch/arm/kernel/entry-armv.S
@@ -31,6 +31,7 @@ 
 
 #include "entry-header.S"
 #include <asm/entry-macro-multi.S>
+#include <asm/probes.h>
 
 /*
  * Interrupt handling.
@@ -249,7 +250,7 @@  __und_svc:
 	@ If a kprobe is about to simulate a "stmdb sp..." instruction,
 	@ it obviously needs free stack space which then will belong to
 	@ the saved context.
-	svc_entry 64
+	svc_entry MAX_STACK_SIZE
 #else
 	svc_entry
 #endif
diff --git a/arch/arm/kernel/kprobes-test-arm.c b/arch/arm/kernel/kprobes-test-arm.c
index cb14242..d8ad5bb 100644
--- a/arch/arm/kernel/kprobes-test-arm.c
+++ b/arch/arm/kernel/kprobes-test-arm.c
@@ -476,7 +476,8 @@  void kprobe_arm_test_cases(void)
 	TEST_GROUP("Extra load/store instructions")
 
 	TEST_RPR(  "strh	r",0, VAL1,", [r",1, 48,", -r",2, 24,"]")
-	TEST_RPR(  "streqh	r",14,VAL2,", [r",13,0, ", r",12, 48,"]")
+	TEST_RPR(  "streqh	r",14,VAL2,", [r",11,0, ", r",12, 48,"]")
+	TEST_UNSUPPORTED(  "streqh	r14, [r13, r12]")
 	TEST_RPR(  "strh	r",1, VAL1,", [r",2, 24,", r",3,  48,"]!")
 	TEST_RPR(  "strneh	r",12,VAL2,", [r",11,48,", -r",10,24,"]!")
 	TEST_RPR(  "strh	r",2, VAL1,", [r",3, 24,"], r",4, 48,"")
@@ -565,7 +566,8 @@  void kprobe_arm_test_cases(void)
 
 #if __LINUX_ARM_ARCH__ >= 5
 	TEST_RPR(  "strd	r",0, VAL1,", [r",1, 48,", -r",2,24,"]")
-	TEST_RPR(  "strccd	r",8, VAL2,", [r",13,0, ", r",12,48,"]")
+	TEST_RPR(  "strccd	r",8, VAL2,", [r",11,0, ", r",12,48,"]")
+	TEST_UNSUPPORTED(  "strccd r8, [r13, r12]")
 	TEST_RPR(  "strd	r",4, VAL1,", [r",2, 24,", r",3, 48,"]!")
 	TEST_RPR(  "strcsd	r",12,VAL2,", [r",11,48,", -r",10,24,"]!")
 	TEST_RPR(  "strd	r",2, VAL1,", [r",5, 24,"], r",4,48,"")
@@ -638,13 +640,15 @@  void kprobe_arm_test_cases(void)
 	TEST_RP( "str"byte"	r",2, VAL1,", [r",3, 24,"], #48")		\
 	TEST_RP( "str"byte"	r",10,VAL2,", [r",9, 64,"], #-48")		\
 	TEST_RPR("str"byte"	r",0, VAL1,", [r",1, 48,", -r",2, 24,"]")	\
-	TEST_RPR("str"byte"	r",14,VAL2,", [r",13,0, ", r",12, 48,"]")	\
+	TEST_RPR("str"byte"	r",14,VAL2,", [r",11,0, ", r",12, 48,"]")	\
+	TEST_UNSUPPORTED("str"byte" r14, [r13, r12]")	\
 	TEST_RPR("str"byte"	r",1, VAL1,", [r",2, 24,", r",3,  48,"]!")	\
 	TEST_RPR("str"byte"	r",12,VAL2,", [r",11,48,", -r",10,24,"]!")	\
 	TEST_RPR("str"byte"	r",2, VAL1,", [r",3, 24,"], r",4, 48,"")	\
 	TEST_RPR("str"byte"	r",10,VAL2,", [r",9, 48,"], -r",11,24,"")	\
 	TEST_RPR("str"byte"	r",0, VAL1,", [r",1, 24,", r",2,  32,", asl #1]")\
-	TEST_RPR("str"byte"	r",14,VAL2,", [r",13,0, ", r",12, 32,", lsr #2]")\
+	TEST_RPR("str"byte"	r",14,VAL2,", [r",11,0, ", r",12, 32,", lsr #2]")\
+	TEST_UNSUPPORTED("str"byte"	r14, [r13, r12, lsr #2]")\
 	TEST_RPR("str"byte"	r",1, VAL1,", [r",2, 24,", r",3,  32,", asr #3]!")\
 	TEST_RPR("str"byte"	r",12,VAL2,", [r",11,24,", r",10, 4,", ror #31]!")\
 	TEST_P(  "ldr"byte"	r0, [r",0,  24,", #-2]")			\
@@ -668,12 +672,12 @@  void kprobe_arm_test_cases(void)
 
 	LOAD_STORE("")
 	TEST_P(   "str	pc, [r",0,0,", #15*4]")
-	TEST_R(   "str	pc, [sp, r",2,15*4,"]")
+	TEST_UNSUPPORTED(   "str	pc, [sp, r2]")
 	TEST_BF(  "ldr	pc, [sp, #15*4]")
 	TEST_BF_R("ldr	pc, [sp, r",2,15*4,"]")
 
 	TEST_P(   "str	sp, [r",0,0,", #13*4]")
-	TEST_R(   "str	sp, [sp, r",2,13*4,"]")
+	TEST_UNSUPPORTED(   "str	sp, [sp, r2]")
 	TEST_BF(  "ldr	sp, [sp, #13*4]")
 	TEST_BF_R("ldr	sp, [sp, r",2,13*4,"]")
 
diff --git a/arch/arm/kernel/kprobes.c b/arch/arm/kernel/kprobes.c
index d7bee4b..30498436 100644
--- a/arch/arm/kernel/kprobes.c
+++ b/arch/arm/kernel/kprobes.c
@@ -115,6 +115,15 @@  int __kprobes arch_prepare_kprobe(struct kprobe *p)
 		break;
 	}
 
+	/*
+	 * Never instrument insn like 'str r0, [sp, +/-r1]'. Also, insn likes
+	 * 'str r0, [sp, #-68]' should also be prohibited.
+	 * See __und_svc.
+	 */
+	if ((p->ainsn.stack_space < 0) ||
+			(p->ainsn.stack_space > MAX_STACK_SIZE))
+		return -EINVAL;
+
 	return 0;
 }