[PATCH] kernel/kprobes: Add test to validate pt_regs

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[PATCH] kernel/kprobes: Add test to validate pt_regs

Naveen N. Rao
Add a test to verify that the registers passed in pt_regs on kprobe
(trap), optprobe (jump) and kprobe_on_ftrace (ftrace_caller) are
accurate. The tests are exercized if KPROBES_SANITY_TEST is enabled.

Implemented for powerpc64. Other architectures will have to implement
the relevant arch_* helpers and define HAVE_KPROBES_REGS_SANITY_TEST.

Signed-off-by: Naveen N. Rao <[hidden email]>
---
 arch/powerpc/include/asm/kprobes.h  |   4 +
 arch/powerpc/lib/Makefile           |   3 +-
 arch/powerpc/lib/test_kprobe_regs.S |  62 ++++++++++++
 arch/powerpc/lib/test_kprobes.c     | 115 ++++++++++++++++++++++
 include/linux/kprobes.h             |  11 +++
 kernel/test_kprobes.c               | 183 ++++++++++++++++++++++++++++++++++++
 6 files changed, 377 insertions(+), 1 deletion(-)
 create mode 100644 arch/powerpc/lib/test_kprobe_regs.S
 create mode 100644 arch/powerpc/lib/test_kprobes.c

diff --git a/arch/powerpc/include/asm/kprobes.h b/arch/powerpc/include/asm/kprobes.h
index 566da372e02b..10c91d3132a1 100644
--- a/arch/powerpc/include/asm/kprobes.h
+++ b/arch/powerpc/include/asm/kprobes.h
@@ -124,6 +124,10 @@ static inline int skip_singlestep(struct kprobe *p, struct pt_regs *regs,
  return 0;
 }
 #endif
+#if defined(CONFIG_KPROBES_SANITY_TEST) && defined(CONFIG_PPC64)
+#define HAVE_KPROBES_REGS_SANITY_TEST
+void arch_kprobe_regs_set_ptregs(struct pt_regs *regs);
+#endif
 #else
 static inline int kprobe_handler(struct pt_regs *regs) { return 0; }
 static inline int kprobe_post_handler(struct pt_regs *regs) { return 0; }
diff --git a/arch/powerpc/lib/Makefile b/arch/powerpc/lib/Makefile
index 3c3146ba62da..8a0bb8e20179 100644
--- a/arch/powerpc/lib/Makefile
+++ b/arch/powerpc/lib/Makefile
@@ -27,7 +27,8 @@ obj64-y += copypage_64.o copyuser_64.o mem_64.o hweight_64.o \
 
 obj64-$(CONFIG_SMP) += locks.o
 obj64-$(CONFIG_ALTIVEC) += vmx-helper.o
-obj64-$(CONFIG_KPROBES_SANITY_TEST) += test_emulate_step.o
+obj64-$(CONFIG_KPROBES_SANITY_TEST) += test_emulate_step.o test_kprobe_regs.o \
+       test_kprobes.o
 
 obj-y += checksum_$(BITS).o checksum_wrappers.o
 
diff --git a/arch/powerpc/lib/test_kprobe_regs.S b/arch/powerpc/lib/test_kprobe_regs.S
new file mode 100644
index 000000000000..4e95eca6dcd3
--- /dev/null
+++ b/arch/powerpc/lib/test_kprobe_regs.S
@@ -0,0 +1,62 @@
+/*
+ * test_kprobe_regs: architectural helpers for validating pt_regs
+ *     received on a kprobe.
+ *
+ * Copyright 2017 Naveen N. Rao <[hidden email]>
+ *  IBM Corporation
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; version 2
+ * of the License.
+ */
+
+#include <asm/ppc_asm.h>
+#include <asm/asm-offsets.h>
+#include <asm/ptrace.h>
+
+_GLOBAL(arch_kprobe_regs_function)
+ mflr r0
+ std r0, LRSAVE(r1)
+ stdu r1, -SWITCH_FRAME_SIZE(r1)
+
+ /* Tell pre handler about our pt_regs location */
+ addi r3, r1, STACK_FRAME_OVERHEAD
+ bl arch_kprobe_regs_set_ptregs
+
+ /* Load back our true LR */
+ ld r0, (SWITCH_FRAME_SIZE + LRSAVE)(r1)
+ mtlr r0
+
+ /* Save all SPRs that we care about */
+ mfctr r0
+ std r0, _CTR(r1)
+ mflr r0
+ std r0, _LINK(r1)
+ mfspr r0, SPRN_XER
+ std r0, _XER(r1)
+ mfcr r0
+ std r0, _CCR(r1)
+
+ /* Now, save all GPRs */
+ SAVE_2GPRS(0, r1)
+ SAVE_10GPRS(2, r1)
+ SAVE_10GPRS(12, r1)
+ SAVE_10GPRS(22, r1)
+
+ /* We're now ready to be probed */
+.global arch_kprobe_regs_probepoint
+arch_kprobe_regs_probepoint:
+ nop
+
+#ifdef CONFIG_KPROBES_ON_FTRACE
+ /* Let's also test KPROBES_ON_FTRACE */
+ bl kprobe_regs_kp_on_ftrace_target
+ nop
+#endif
+
+ /* All done */
+ addi r1, r1, SWITCH_FRAME_SIZE
+ ld r0, LRSAVE(r1)
+ mtlr r0
+ blr
diff --git a/arch/powerpc/lib/test_kprobes.c b/arch/powerpc/lib/test_kprobes.c
new file mode 100644
index 000000000000..23f7a7ffcdd6
--- /dev/null
+++ b/arch/powerpc/lib/test_kprobes.c
@@ -0,0 +1,115 @@
+/*
+ * test_kprobes: architectural helpers for validating pt_regs
+ * received on a kprobe.
+ *
+ * Copyright 2017 Naveen N. Rao <[hidden email]>
+ *  IBM Corporation
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; version 2
+ * of the License.
+ */
+
+#define pr_fmt(fmt) "Kprobe smoke test (regs): " fmt
+
+#include <asm/ptrace.h>
+#include <linux/kernel.h>
+#include <linux/kprobes.h>
+
+static struct pt_regs *r;
+
+void arch_kprobe_regs_set_ptregs(struct pt_regs *regs)
+{
+ r = regs;
+}
+
+static int validate_regs(struct kprobe *p, struct pt_regs *regs,
+ int kp_on_ftrace, int post_handler)
+{
+ int i, ret = 1;
+
+ if (!r) {
+ pr_err("pt_regs not setup!\n");
+ return 0;
+ }
+
+ if (regs->gpr[1] + STACK_FRAME_OVERHEAD != (unsigned long)r) {
+ /* We'll continue since this may just indicate an incorrect r1 */
+ pr_err("pt_regs pointer/r1 doesn't point where we expect!\n");
+ ret = 0;
+ }
+
+ for (i = 0; i < 32; i++) {
+ /* KPROBES_ON_FTRACE may have stomped r0 in the prologue */
+ if (r->gpr[i] != regs->gpr[i] && (!kp_on_ftrace || i != 0)) {
+ pr_err("gpr[%d] expected: 0x%lx, received: 0x%lx\n",
+ i, r->gpr[i], regs->gpr[i]);
+ ret = 0;
+ }
+ }
+
+ if (r->ctr != regs->ctr) {
+ pr_err("ctr expected: 0x%lx, received: 0x%lx\n",
+ r->ctr, regs->ctr);
+ ret = 0;
+ }
+
+ if (r->link != regs->link && !kp_on_ftrace) {
+ pr_err("link expected: 0x%lx, received: 0x%lx\n",
+ r->link, regs->link);
+ ret = 0;
+ }
+
+ /* KPROBES_ON_FTRACE *must* have clobbered link */
+ if (r->link == regs->link && kp_on_ftrace) {
+ pr_err("link register not clobbered for KPROBES_ON_FTRACE!\n");
+ ret = 0;
+ }
+
+ if (r->xer != regs->xer) {
+ pr_err("xer expected: 0x%lx, received: 0x%lx\n",
+ r->xer, regs->xer);
+ ret = 0;
+ }
+
+ if (r->ccr != regs->ccr) {
+ pr_err("ccr expected: 0x%lx, received: 0x%lx\n",
+ r->ccr, regs->ccr);
+ ret = 0;
+ }
+
+ if (!post_handler && regs->nip != (unsigned long)p->addr) {
+ pr_err("nip expected: 0x%lx, received: 0x%lx\n",
+ (unsigned long)p->addr, regs->nip);
+ ret = 0;
+ }
+
+ if (post_handler &&
+ regs->nip != (unsigned long)p->addr + sizeof(kprobe_opcode_t)) {
+ pr_err("post_handler: nip expected: 0x%lx, received: 0x%lx\n",
+ (unsigned long)p->addr + sizeof(kprobe_opcode_t),
+ regs->nip);
+ ret = 0;
+ }
+
+ return ret;
+}
+
+int arch_kprobe_regs_pre_handler(struct kprobe *p, struct pt_regs *regs)
+{
+ return validate_regs(p, regs, 0, 0);
+}
+
+int arch_kprobe_regs_post_handler(struct kprobe *p, struct pt_regs *regs,
+ unsigned long flags)
+{
+ return validate_regs(p, regs, 0, 1);
+}
+
+#ifdef CONFIG_KPROBES_ON_FTRACE
+int arch_kp_on_ftrace_pre_handler(struct kprobe *p, struct pt_regs *regs)
+{
+ return validate_regs(p, regs, 1, 0);
+}
+#endif
diff --git a/include/linux/kprobes.h b/include/linux/kprobes.h
index 541df0b5b815..adfbb5b27acd 100644
--- a/include/linux/kprobes.h
+++ b/include/linux/kprobes.h
@@ -253,6 +253,17 @@ static inline void kretprobe_assert(struct kretprobe_instance *ri,
 
 #ifdef CONFIG_KPROBES_SANITY_TEST
 extern int init_test_probes(void);
+#ifdef HAVE_KPROBES_REGS_SANITY_TEST
+extern void arch_kprobe_regs_function(void);
+extern void arch_kprobe_regs_probepoint(void);
+extern int arch_kprobe_regs_pre_handler(struct kprobe *p, struct pt_regs *regs);
+extern int arch_kprobe_regs_post_handler(struct kprobe *p, struct pt_regs *regs,
+ unsigned long flags);
+#ifdef CONFIG_KPROBES_ON_FTRACE
+extern void kprobe_regs_kp_on_ftrace_target(void);
+extern int arch_kp_on_ftrace_pre_handler(struct kprobe *p, struct pt_regs *regs);
+#endif
+#endif
 #else
 static inline int init_test_probes(void)
 {
diff --git a/kernel/test_kprobes.c b/kernel/test_kprobes.c
index 0dbab6d1acb4..92011726cc69 100644
--- a/kernel/test_kprobes.c
+++ b/kernel/test_kprobes.c
@@ -19,6 +19,7 @@
 #include <linux/kernel.h>
 #include <linux/kprobes.h>
 #include <linux/random.h>
+#include <linux/workqueue.h>
 
 #define div_factor 3
 
@@ -334,6 +335,166 @@ static int test_kretprobes(void)
 }
 #endif /* CONFIG_KRETPROBES */
 
+#ifdef HAVE_KPROBES_REGS_SANITY_TEST
+static int kprobe_regs_pre_handler(struct kprobe *p, struct pt_regs *regs)
+{
+ /* architectural helper returns 0 if validation fails */
+ preh_val = arch_kprobe_regs_pre_handler(p, regs);
+ return 0;
+}
+
+static void kprobe_regs_post_handler(struct kprobe *p, struct pt_regs *regs,
+ unsigned long flags)
+{
+ posth_val = arch_kprobe_regs_post_handler(p, regs, flags);
+}
+
+static struct kprobe kpr = {
+ .symbol_name = "arch_kprobe_regs_probepoint",
+ .pre_handler = kprobe_regs_pre_handler,
+ .post_handler = kprobe_regs_post_handler,
+};
+
+static int test_kprobe_regs(void)
+{
+ int ret;
+ kprobe_opcode_t *addr;
+
+ preh_val = 0;
+ posth_val = 0;
+
+ ret = register_kprobe(&kpr);
+ if (ret < 0) {
+ pr_err("register_kprobe returned %d\n", ret);
+ return ret;
+ }
+
+ /* Let's see if this probe was optimized */
+ addr = kprobe_lookup_name(kpr.symbol_name, 0);
+ if (addr && *addr != BREAKPOINT_INSTRUCTION) {
+ pr_err("kprobe with post_handler optimized\n");
+ unregister_kprobe(&kpr);
+ return -1;
+ }
+
+ arch_kprobe_regs_function();
+ unregister_kprobe(&kpr);
+
+ if (preh_val == 0) {
+ pr_err("kprobe pre_handler regs validation failed\n");
+ handler_errors++;
+ }
+
+ if (posth_val == 0) {
+ pr_err("kprobe post_handler not called\n");
+ handler_errors++;
+ }
+
+ return 0;
+}
+
+#ifdef CONFIG_KPROBES_ON_FTRACE
+void kprobe_regs_kp_on_ftrace_target(void)
+{
+ posth_val = preh_val + div_factor;
+}
+
+static int kp_on_ftrace_pre_handler(struct kprobe *p, struct pt_regs *regs)
+{
+ /* architectural helper returns 0 if validation fails */
+ preh_val = arch_kp_on_ftrace_pre_handler(p, regs);
+ return 0;
+}
+
+static struct kprobe kprf = {
+ .symbol_name = "kprobe_regs_kp_on_ftrace_target",
+ .pre_handler = kp_on_ftrace_pre_handler,
+};
+
+static int test_kp_on_ftrace_regs(void)
+{
+ int ret;
+
+ preh_val = 0;
+
+ ret = register_kprobe(&kprf);
+ if (ret < 0) {
+ pr_err("register_kprobe returned %d\n", ret);
+ return ret;
+ }
+
+ arch_kprobe_regs_function();
+ unregister_kprobe(&kprf);
+
+ if (preh_val == 0) {
+ pr_err("kp_on_ftrace pre_handler regs validation failed\n");
+ handler_errors++;
+ }
+
+ return 0;
+}
+#endif
+
+#ifdef CONFIG_OPTPROBES
+static void test_optprobe_regs(struct work_struct *work);
+static DECLARE_DELAYED_WORK(test_optprobe_regs_work, test_optprobe_regs);
+int kprobe_registered;
+
+static struct kprobe kpor = {
+ .symbol_name = "arch_kprobe_regs_probepoint",
+ .pre_handler = kprobe_regs_pre_handler,
+};
+
+static void test_optprobe_regs_setup(void)
+{
+ int ret;
+
+ ret = register_kprobe(&kpor);
+ if (ret < 0) {
+ pr_err("register_kprobe returned %d\n", ret);
+ return;
+ }
+
+ kprobe_registered = 1;
+}
+
+static void test_optprobe_regs(struct work_struct *work)
+{
+ kprobe_opcode_t *addr;
+
+ if (!kprobe_registered) {
+ errors++;
+ goto summary;
+ }
+
+ /* Let's see if this probe was optimized */
+ addr = kprobe_lookup_name(kpor.symbol_name, 0);
+ if (addr && *addr == BREAKPOINT_INSTRUCTION) {
+ pr_info("kprobe not optimized yet... skipping optprobe test\n");
+ unregister_kprobe(&kpor);
+ goto summary;
+ }
+
+ preh_val = 0;
+ arch_kprobe_regs_function();
+ unregister_kprobe(&kpor);
+
+ if (preh_val == 0) {
+ pr_err("optprobe pre_handler regs validation failed\n");
+ handler_errors++;
+ }
+
+summary:
+ if (errors)
+ pr_err("BUG: %d out of %d tests failed\n", errors, num_tests);
+ else if (handler_errors)
+ pr_err("BUG: %d error(s) running handlers\n", handler_errors);
+ else
+ pr_info("passed successfully\n");
+}
+#endif
+#endif
+
 int init_test_probes(void)
 {
  int ret;
@@ -378,12 +539,34 @@ int init_test_probes(void)
  errors++;
 #endif /* CONFIG_KRETPROBES */
 
+#ifdef HAVE_KPROBES_REGS_SANITY_TEST
+ num_tests++;
+ ret = test_kprobe_regs();
+ if (ret < 0)
+ errors++;
+
+#ifdef CONFIG_KPROBES_ON_FTRACE
+ num_tests++;
+ ret = test_kp_on_ftrace_regs();
+ if (ret < 0)
+ errors++;
+#endif
+
+#ifdef CONFIG_OPTPROBES
+ num_tests++;
+ test_optprobe_regs_setup();
+ schedule_delayed_work(&test_optprobe_regs_work, 10);
+#endif
+#endif
+
+#if !defined(HAVE_KPROBES_REGS_SANITY_TEST) || !defined(CONFIG_OPTPROBES)
  if (errors)
  pr_err("BUG: %d out of %d tests failed\n", errors, num_tests);
  else if (handler_errors)
  pr_err("BUG: %d error(s) running handlers\n", handler_errors);
  else
  pr_info("passed successfully\n");
+#endif
 
  return 0;
 }
--
2.12.2

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Re: [PATCH] kernel/kprobes: Add test to validate pt_regs

Masami Hiramatsu
On Fri,  9 Jun 2017 00:53:08 +0530
"Naveen N. Rao" <[hidden email]> wrote:

> Add a test to verify that the registers passed in pt_regs on kprobe
> (trap), optprobe (jump) and kprobe_on_ftrace (ftrace_caller) are
> accurate. The tests are exercized if KPROBES_SANITY_TEST is enabled.

Great!

>
> Implemented for powerpc64. Other architectures will have to implement
> the relevant arch_* helpers and define HAVE_KPROBES_REGS_SANITY_TEST.

Hmm, why don't you define that in arch/powerpc/Kconfig ?
Also, could you split this into 3 patches for each case ?

>
> Signed-off-by: Naveen N. Rao <[hidden email]>
> ---
>  arch/powerpc/include/asm/kprobes.h  |   4 +
>  arch/powerpc/lib/Makefile           |   3 +-
>  arch/powerpc/lib/test_kprobe_regs.S |  62 ++++++++++++
>  arch/powerpc/lib/test_kprobes.c     | 115 ++++++++++++++++++++++
>  include/linux/kprobes.h             |  11 +++
>  kernel/test_kprobes.c               | 183 ++++++++++++++++++++++++++++++++++++
>  6 files changed, 377 insertions(+), 1 deletion(-)
>  create mode 100644 arch/powerpc/lib/test_kprobe_regs.S
>  create mode 100644 arch/powerpc/lib/test_kprobes.c
>
> diff --git a/arch/powerpc/include/asm/kprobes.h b/arch/powerpc/include/asm/kprobes.h
> index 566da372e02b..10c91d3132a1 100644
> --- a/arch/powerpc/include/asm/kprobes.h
> +++ b/arch/powerpc/include/asm/kprobes.h
> @@ -124,6 +124,10 @@ static inline int skip_singlestep(struct kprobe *p, struct pt_regs *regs,
>   return 0;
>  }
>  #endif
> +#if defined(CONFIG_KPROBES_SANITY_TEST) && defined(CONFIG_PPC64)
> +#define HAVE_KPROBES_REGS_SANITY_TEST
> +void arch_kprobe_regs_set_ptregs(struct pt_regs *regs);
> +#endif
>  #else
>  static inline int kprobe_handler(struct pt_regs *regs) { return 0; }
>  static inline int kprobe_post_handler(struct pt_regs *regs) { return 0; }
> diff --git a/arch/powerpc/lib/Makefile b/arch/powerpc/lib/Makefile
> index 3c3146ba62da..8a0bb8e20179 100644
> --- a/arch/powerpc/lib/Makefile
> +++ b/arch/powerpc/lib/Makefile
> @@ -27,7 +27,8 @@ obj64-y += copypage_64.o copyuser_64.o mem_64.o hweight_64.o \
>  
>  obj64-$(CONFIG_SMP) += locks.o
>  obj64-$(CONFIG_ALTIVEC) += vmx-helper.o
> -obj64-$(CONFIG_KPROBES_SANITY_TEST) += test_emulate_step.o
> +obj64-$(CONFIG_KPROBES_SANITY_TEST) += test_emulate_step.o test_kprobe_regs.o \
> +       test_kprobes.o
>  
>  obj-y += checksum_$(BITS).o checksum_wrappers.o
>  
> diff --git a/arch/powerpc/lib/test_kprobe_regs.S b/arch/powerpc/lib/test_kprobe_regs.S
> new file mode 100644
> index 000000000000..4e95eca6dcd3
> --- /dev/null
> +++ b/arch/powerpc/lib/test_kprobe_regs.S
> @@ -0,0 +1,62 @@
> +/*
> + * test_kprobe_regs: architectural helpers for validating pt_regs
> + *     received on a kprobe.
> + *
> + * Copyright 2017 Naveen N. Rao <[hidden email]>
> + *  IBM Corporation
> + *
> + * This program is free software; you can redistribute it and/or
> + * modify it under the terms of the GNU General Public License
> + * as published by the Free Software Foundation; version 2
> + * of the License.
> + */
> +
> +#include <asm/ppc_asm.h>
> +#include <asm/asm-offsets.h>
> +#include <asm/ptrace.h>
> +
> +_GLOBAL(arch_kprobe_regs_function)
> + mflr r0
> + std r0, LRSAVE(r1)
> + stdu r1, -SWITCH_FRAME_SIZE(r1)
> +
> + /* Tell pre handler about our pt_regs location */
> + addi r3, r1, STACK_FRAME_OVERHEAD
> + bl arch_kprobe_regs_set_ptregs
> +
> + /* Load back our true LR */
> + ld r0, (SWITCH_FRAME_SIZE + LRSAVE)(r1)
> + mtlr r0
> +
> + /* Save all SPRs that we care about */
> + mfctr r0
> + std r0, _CTR(r1)
> + mflr r0
> + std r0, _LINK(r1)
> + mfspr r0, SPRN_XER
> + std r0, _XER(r1)
> + mfcr r0
> + std r0, _CCR(r1)
> +
> + /* Now, save all GPRs */
> + SAVE_2GPRS(0, r1)
> + SAVE_10GPRS(2, r1)
> + SAVE_10GPRS(12, r1)
> + SAVE_10GPRS(22, r1)
> +
> + /* We're now ready to be probed */
> +.global arch_kprobe_regs_probepoint
> +arch_kprobe_regs_probepoint:
> + nop
> +
> +#ifdef CONFIG_KPROBES_ON_FTRACE
> + /* Let's also test KPROBES_ON_FTRACE */
> + bl kprobe_regs_kp_on_ftrace_target
> + nop
> +#endif
> +
> + /* All done */
> + addi r1, r1, SWITCH_FRAME_SIZE
> + ld r0, LRSAVE(r1)
> + mtlr r0
> + blr
> diff --git a/arch/powerpc/lib/test_kprobes.c b/arch/powerpc/lib/test_kprobes.c
> new file mode 100644
> index 000000000000..23f7a7ffcdd6
> --- /dev/null
> +++ b/arch/powerpc/lib/test_kprobes.c
> @@ -0,0 +1,115 @@
> +/*
> + * test_kprobes: architectural helpers for validating pt_regs
> + * received on a kprobe.
> + *
> + * Copyright 2017 Naveen N. Rao <[hidden email]>
> + *  IBM Corporation
> + *
> + * This program is free software; you can redistribute it and/or
> + * modify it under the terms of the GNU General Public License
> + * as published by the Free Software Foundation; version 2
> + * of the License.
> + */
> +
> +#define pr_fmt(fmt) "Kprobe smoke test (regs): " fmt
> +
> +#include <asm/ptrace.h>
> +#include <linux/kernel.h>
> +#include <linux/kprobes.h>
> +
> +static struct pt_regs *r;
> +
> +void arch_kprobe_regs_set_ptregs(struct pt_regs *regs)
> +{
> + r = regs;
> +}
> +
> +static int validate_regs(struct kprobe *p, struct pt_regs *regs,
> + int kp_on_ftrace, int post_handler)
> +{
> + int i, ret = 1;
> +
> + if (!r) {
> + pr_err("pt_regs not setup!\n");
> + return 0;
> + }
> +
> + if (regs->gpr[1] + STACK_FRAME_OVERHEAD != (unsigned long)r) {
> + /* We'll continue since this may just indicate an incorrect r1 */
> + pr_err("pt_regs pointer/r1 doesn't point where we expect!\n");
> + ret = 0;
> + }
> +
> + for (i = 0; i < 32; i++) {
> + /* KPROBES_ON_FTRACE may have stomped r0 in the prologue */
> + if (r->gpr[i] != regs->gpr[i] && (!kp_on_ftrace || i != 0)) {
> + pr_err("gpr[%d] expected: 0x%lx, received: 0x%lx\n",
> + i, r->gpr[i], regs->gpr[i]);
> + ret = 0;
> + }
> + }
> +
> + if (r->ctr != regs->ctr) {
> + pr_err("ctr expected: 0x%lx, received: 0x%lx\n",
> + r->ctr, regs->ctr);
> + ret = 0;
> + }
> +
> + if (r->link != regs->link && !kp_on_ftrace) {
> + pr_err("link expected: 0x%lx, received: 0x%lx\n",
> + r->link, regs->link);
> + ret = 0;
> + }
> +
> + /* KPROBES_ON_FTRACE *must* have clobbered link */
> + if (r->link == regs->link && kp_on_ftrace) {
> + pr_err("link register not clobbered for KPROBES_ON_FTRACE!\n");
> + ret = 0;
> + }
> +
> + if (r->xer != regs->xer) {
> + pr_err("xer expected: 0x%lx, received: 0x%lx\n",
> + r->xer, regs->xer);
> + ret = 0;
> + }
> +
> + if (r->ccr != regs->ccr) {
> + pr_err("ccr expected: 0x%lx, received: 0x%lx\n",
> + r->ccr, regs->ccr);
> + ret = 0;
> + }
> +
> + if (!post_handler && regs->nip != (unsigned long)p->addr) {
> + pr_err("nip expected: 0x%lx, received: 0x%lx\n",
> + (unsigned long)p->addr, regs->nip);
> + ret = 0;
> + }
> +
> + if (post_handler &&
> + regs->nip != (unsigned long)p->addr + sizeof(kprobe_opcode_t)) {
> + pr_err("post_handler: nip expected: 0x%lx, received: 0x%lx\n",
> + (unsigned long)p->addr + sizeof(kprobe_opcode_t),
> + regs->nip);
> + ret = 0;
> + }
> +
> + return ret;
> +}
> +
> +int arch_kprobe_regs_pre_handler(struct kprobe *p, struct pt_regs *regs)
> +{
> + return validate_regs(p, regs, 0, 0);
> +}
> +
> +int arch_kprobe_regs_post_handler(struct kprobe *p, struct pt_regs *regs,
> + unsigned long flags)
> +{
> + return validate_regs(p, regs, 0, 1);
> +}
> +
> +#ifdef CONFIG_KPROBES_ON_FTRACE
> +int arch_kp_on_ftrace_pre_handler(struct kprobe *p, struct pt_regs *regs)
> +{
> + return validate_regs(p, regs, 1, 0);
> +}
> +#endif
> diff --git a/include/linux/kprobes.h b/include/linux/kprobes.h
> index 541df0b5b815..adfbb5b27acd 100644
> --- a/include/linux/kprobes.h
> +++ b/include/linux/kprobes.h
> @@ -253,6 +253,17 @@ static inline void kretprobe_assert(struct kretprobe_instance *ri,
>  
>  #ifdef CONFIG_KPROBES_SANITY_TEST
>  extern int init_test_probes(void);
> +#ifdef HAVE_KPROBES_REGS_SANITY_TEST
> +extern void arch_kprobe_regs_function(void);
> +extern void arch_kprobe_regs_probepoint(void);
> +extern int arch_kprobe_regs_pre_handler(struct kprobe *p, struct pt_regs *regs);
> +extern int arch_kprobe_regs_post_handler(struct kprobe *p, struct pt_regs *regs,
> + unsigned long flags);
> +#ifdef CONFIG_KPROBES_ON_FTRACE
> +extern void kprobe_regs_kp_on_ftrace_target(void);
> +extern int arch_kp_on_ftrace_pre_handler(struct kprobe *p, struct pt_regs *regs);
> +#endif
> +#endif
>  #else
>  static inline int init_test_probes(void)
>  {
> diff --git a/kernel/test_kprobes.c b/kernel/test_kprobes.c
> index 0dbab6d1acb4..92011726cc69 100644
> --- a/kernel/test_kprobes.c
> +++ b/kernel/test_kprobes.c
> @@ -19,6 +19,7 @@
>  #include <linux/kernel.h>
>  #include <linux/kprobes.h>
>  #include <linux/random.h>
> +#include <linux/workqueue.h>
>  
>  #define div_factor 3
>  
> @@ -334,6 +335,166 @@ static int test_kretprobes(void)
>  }
>  #endif /* CONFIG_KRETPROBES */
>  
> +#ifdef HAVE_KPROBES_REGS_SANITY_TEST
> +static int kprobe_regs_pre_handler(struct kprobe *p, struct pt_regs *regs)
> +{
> + /* architectural helper returns 0 if validation fails */
> + preh_val = arch_kprobe_regs_pre_handler(p, regs);
> + return 0;
> +}
> +
> +static void kprobe_regs_post_handler(struct kprobe *p, struct pt_regs *regs,
> + unsigned long flags)
> +{
> + posth_val = arch_kprobe_regs_post_handler(p, regs, flags);
> +}
> +
> +static struct kprobe kpr = {
> + .symbol_name = "arch_kprobe_regs_probepoint",
> + .pre_handler = kprobe_regs_pre_handler,
> + .post_handler = kprobe_regs_post_handler,
> +};
> +
> +static int test_kprobe_regs(void)
> +{
> + int ret;
> + kprobe_opcode_t *addr;
> +
> + preh_val = 0;
> + posth_val = 0;
> +
> + ret = register_kprobe(&kpr);
> + if (ret < 0) {
> + pr_err("register_kprobe returned %d\n", ret);
> + return ret;
> + }
> +
> + /* Let's see if this probe was optimized */
> + addr = kprobe_lookup_name(kpr.symbol_name, 0);
> + if (addr && *addr != BREAKPOINT_INSTRUCTION) {
> + pr_err("kprobe with post_handler optimized\n");
> + unregister_kprobe(&kpr);
> + return -1;
> + }
> +
> + arch_kprobe_regs_function();
> + unregister_kprobe(&kpr);
> +
> + if (preh_val == 0) {
> + pr_err("kprobe pre_handler regs validation failed\n");
> + handler_errors++;
> + }
> +
> + if (posth_val == 0) {
> + pr_err("kprobe post_handler not called\n");
> + handler_errors++;
> + }
> +
> + return 0;
> +}
> +
> +#ifdef CONFIG_KPROBES_ON_FTRACE
> +void kprobe_regs_kp_on_ftrace_target(void)
> +{
> + posth_val = preh_val + div_factor;
> +}
> +
> +static int kp_on_ftrace_pre_handler(struct kprobe *p, struct pt_regs *regs)
> +{
> + /* architectural helper returns 0 if validation fails */
> + preh_val = arch_kp_on_ftrace_pre_handler(p, regs);
> + return 0;
> +}
> +
> +static struct kprobe kprf = {
> + .symbol_name = "kprobe_regs_kp_on_ftrace_target",
> + .pre_handler = kp_on_ftrace_pre_handler,
> +};
> +
> +static int test_kp_on_ftrace_regs(void)
> +{
> + int ret;
> +
> + preh_val = 0;
> +
> + ret = register_kprobe(&kprf);
> + if (ret < 0) {
> + pr_err("register_kprobe returned %d\n", ret);
> + return ret;
> + }
> +
> + arch_kprobe_regs_function();
> + unregister_kprobe(&kprf);
> +
> + if (preh_val == 0) {
> + pr_err("kp_on_ftrace pre_handler regs validation failed\n");
> + handler_errors++;
> + }
> +
> + return 0;
> +}
> +#endif
> +
> +#ifdef CONFIG_OPTPROBES
> +static void test_optprobe_regs(struct work_struct *work);
> +static DECLARE_DELAYED_WORK(test_optprobe_regs_work, test_optprobe_regs);
> +int kprobe_registered;
> +
> +static struct kprobe kpor = {
> + .symbol_name = "arch_kprobe_regs_probepoint",
> + .pre_handler = kprobe_regs_pre_handler,
> +};
> +
> +static void test_optprobe_regs_setup(void)
> +{
> + int ret;
> +
> + ret = register_kprobe(&kpor);
> + if (ret < 0) {
> + pr_err("register_kprobe returned %d\n", ret);
> + return;
> + }
> +
> + kprobe_registered = 1;
> +}
> +
> +static void test_optprobe_regs(struct work_struct *work)
> +{
> + kprobe_opcode_t *addr;
> +
> + if (!kprobe_registered) {
> + errors++;
> + goto summary;
> + }
> +
> + /* Let's see if this probe was optimized */
> + addr = kprobe_lookup_name(kpor.symbol_name, 0);
> + if (addr && *addr == BREAKPOINT_INSTRUCTION) {
> + pr_info("kprobe not optimized yet... skipping optprobe test\n");

Yes, this may take a while... you may need to wait for optimizer,
like wait_for_kprobe_optimizer().

Thank you,

> + unregister_kprobe(&kpor);
> + goto summary;
> + }
> +
> + preh_val = 0;
> + arch_kprobe_regs_function();
> + unregister_kprobe(&kpor);
> +
> + if (preh_val == 0) {
> + pr_err("optprobe pre_handler regs validation failed\n");
> + handler_errors++;
> + }
> +
> +summary:
> + if (errors)
> + pr_err("BUG: %d out of %d tests failed\n", errors, num_tests);
> + else if (handler_errors)
> + pr_err("BUG: %d error(s) running handlers\n", handler_errors);
> + else
> + pr_info("passed successfully\n");
> +}
> +#endif
> +#endif
> +
>  int init_test_probes(void)
>  {
>   int ret;
> @@ -378,12 +539,34 @@ int init_test_probes(void)
>   errors++;
>  #endif /* CONFIG_KRETPROBES */
>  
> +#ifdef HAVE_KPROBES_REGS_SANITY_TEST
> + num_tests++;
> + ret = test_kprobe_regs();
> + if (ret < 0)
> + errors++;
> +
> +#ifdef CONFIG_KPROBES_ON_FTRACE
> + num_tests++;
> + ret = test_kp_on_ftrace_regs();
> + if (ret < 0)
> + errors++;
> +#endif
> +
> +#ifdef CONFIG_OPTPROBES
> + num_tests++;
> + test_optprobe_regs_setup();
> + schedule_delayed_work(&test_optprobe_regs_work, 10);
> +#endif
> +#endif
> +
> +#if !defined(HAVE_KPROBES_REGS_SANITY_TEST) || !defined(CONFIG_OPTPROBES)
>   if (errors)
>   pr_err("BUG: %d out of %d tests failed\n", errors, num_tests);
>   else if (handler_errors)
>   pr_err("BUG: %d error(s) running handlers\n", handler_errors);
>   else
>   pr_info("passed successfully\n");
> +#endif
>  
>   return 0;
>  }
> --
> 2.12.2
>


--
Masami Hiramatsu <[hidden email]>
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Re: [PATCH] kernel/kprobes: Add test to validate pt_regs

Masami Hiramatsu
On Wed, 14 Jun 2017 11:40:08 +0900
Masami Hiramatsu <[hidden email]> wrote:

> On Fri,  9 Jun 2017 00:53:08 +0530
> "Naveen N. Rao" <[hidden email]> wrote:
>
> > Add a test to verify that the registers passed in pt_regs on kprobe
> > (trap), optprobe (jump) and kprobe_on_ftrace (ftrace_caller) are
> > accurate. The tests are exercized if KPROBES_SANITY_TEST is enabled.
>
> Great!
>
> >
> > Implemented for powerpc64. Other architectures will have to implement
> > the relevant arch_* helpers and define HAVE_KPROBES_REGS_SANITY_TEST.
>
> Hmm, why don't you define that in arch/powerpc/Kconfig ?
> Also, could you split this into 3 patches for each case ?
>
> >
> > Signed-off-by: Naveen N. Rao <[hidden email]>
> > ---
> >  arch/powerpc/include/asm/kprobes.h  |   4 +
> >  arch/powerpc/lib/Makefile           |   3 +-
> >  arch/powerpc/lib/test_kprobe_regs.S |  62 ++++++++++++
> >  arch/powerpc/lib/test_kprobes.c     | 115 ++++++++++++++++++++++
> >  include/linux/kprobes.h             |  11 +++
> >  kernel/test_kprobes.c               | 183 ++++++++++++++++++++++++++++++++++++
> >  6 files changed, 377 insertions(+), 1 deletion(-)
> >  create mode 100644 arch/powerpc/lib/test_kprobe_regs.S
> >  create mode 100644 arch/powerpc/lib/test_kprobes.c
> >
> > diff --git a/arch/powerpc/include/asm/kprobes.h b/arch/powerpc/include/asm/kprobes.h
> > index 566da372e02b..10c91d3132a1 100644
> > --- a/arch/powerpc/include/asm/kprobes.h
> > +++ b/arch/powerpc/include/asm/kprobes.h
> > @@ -124,6 +124,10 @@ static inline int skip_singlestep(struct kprobe *p, struct pt_regs *regs,
> >   return 0;
> >  }
> >  #endif
> > +#if defined(CONFIG_KPROBES_SANITY_TEST) && defined(CONFIG_PPC64)
> > +#define HAVE_KPROBES_REGS_SANITY_TEST
> > +void arch_kprobe_regs_set_ptregs(struct pt_regs *regs);
> > +#endif
> >  #else
> >  static inline int kprobe_handler(struct pt_regs *regs) { return 0; }
> >  static inline int kprobe_post_handler(struct pt_regs *regs) { return 0; }
> > diff --git a/arch/powerpc/lib/Makefile b/arch/powerpc/lib/Makefile
> > index 3c3146ba62da..8a0bb8e20179 100644
> > --- a/arch/powerpc/lib/Makefile
> > +++ b/arch/powerpc/lib/Makefile
> > @@ -27,7 +27,8 @@ obj64-y += copypage_64.o copyuser_64.o mem_64.o hweight_64.o \
> >  
> >  obj64-$(CONFIG_SMP) += locks.o
> >  obj64-$(CONFIG_ALTIVEC) += vmx-helper.o
> > -obj64-$(CONFIG_KPROBES_SANITY_TEST) += test_emulate_step.o
> > +obj64-$(CONFIG_KPROBES_SANITY_TEST) += test_emulate_step.o test_kprobe_regs.o \
> > +       test_kprobes.o
> >  
> >  obj-y += checksum_$(BITS).o checksum_wrappers.o
> >  
> > diff --git a/arch/powerpc/lib/test_kprobe_regs.S b/arch/powerpc/lib/test_kprobe_regs.S
> > new file mode 100644
> > index 000000000000..4e95eca6dcd3
> > --- /dev/null
> > +++ b/arch/powerpc/lib/test_kprobe_regs.S
> > @@ -0,0 +1,62 @@
> > +/*
> > + * test_kprobe_regs: architectural helpers for validating pt_regs
> > + *     received on a kprobe.
> > + *
> > + * Copyright 2017 Naveen N. Rao <[hidden email]>
> > + *  IBM Corporation
> > + *
> > + * This program is free software; you can redistribute it and/or
> > + * modify it under the terms of the GNU General Public License
> > + * as published by the Free Software Foundation; version 2
> > + * of the License.
> > + */
> > +
> > +#include <asm/ppc_asm.h>
> > +#include <asm/asm-offsets.h>
> > +#include <asm/ptrace.h>
> > +
> > +_GLOBAL(arch_kprobe_regs_function)
> > + mflr r0
> > + std r0, LRSAVE(r1)
> > + stdu r1, -SWITCH_FRAME_SIZE(r1)
> > +
> > + /* Tell pre handler about our pt_regs location */
> > + addi r3, r1, STACK_FRAME_OVERHEAD
> > + bl arch_kprobe_regs_set_ptregs
> > +
> > + /* Load back our true LR */
> > + ld r0, (SWITCH_FRAME_SIZE + LRSAVE)(r1)
> > + mtlr r0
> > +
> > + /* Save all SPRs that we care about */
> > + mfctr r0
> > + std r0, _CTR(r1)
> > + mflr r0
> > + std r0, _LINK(r1)
> > + mfspr r0, SPRN_XER
> > + std r0, _XER(r1)
> > + mfcr r0
> > + std r0, _CCR(r1)
> > +
> > + /* Now, save all GPRs */
> > + SAVE_2GPRS(0, r1)
> > + SAVE_10GPRS(2, r1)
> > + SAVE_10GPRS(12, r1)
> > + SAVE_10GPRS(22, r1)
> > +
> > + /* We're now ready to be probed */
> > +.global arch_kprobe_regs_probepoint
> > +arch_kprobe_regs_probepoint:
> > + nop
> > +
> > +#ifdef CONFIG_KPROBES_ON_FTRACE
> > + /* Let's also test KPROBES_ON_FTRACE */
> > + bl kprobe_regs_kp_on_ftrace_target
> > + nop
> > +#endif
> > +
> > + /* All done */
> > + addi r1, r1, SWITCH_FRAME_SIZE
> > + ld r0, LRSAVE(r1)
> > + mtlr r0
> > + blr
> > diff --git a/arch/powerpc/lib/test_kprobes.c b/arch/powerpc/lib/test_kprobes.c
> > new file mode 100644
> > index 000000000000..23f7a7ffcdd6
> > --- /dev/null
> > +++ b/arch/powerpc/lib/test_kprobes.c
> > @@ -0,0 +1,115 @@
> > +/*
> > + * test_kprobes: architectural helpers for validating pt_regs
> > + * received on a kprobe.
> > + *
> > + * Copyright 2017 Naveen N. Rao <[hidden email]>
> > + *  IBM Corporation
> > + *
> > + * This program is free software; you can redistribute it and/or
> > + * modify it under the terms of the GNU General Public License
> > + * as published by the Free Software Foundation; version 2
> > + * of the License.
> > + */
> > +
> > +#define pr_fmt(fmt) "Kprobe smoke test (regs): " fmt
> > +
> > +#include <asm/ptrace.h>
> > +#include <linux/kernel.h>
> > +#include <linux/kprobes.h>
> > +
> > +static struct pt_regs *r;
> > +
> > +void arch_kprobe_regs_set_ptregs(struct pt_regs *regs)
> > +{
> > + r = regs;
> > +}
> > +
> > +static int validate_regs(struct kprobe *p, struct pt_regs *regs,
> > + int kp_on_ftrace, int post_handler)
> > +{
> > + int i, ret = 1;
> > +
> > + if (!r) {
> > + pr_err("pt_regs not setup!\n");
> > + return 0;
> > + }
> > +
> > + if (regs->gpr[1] + STACK_FRAME_OVERHEAD != (unsigned long)r) {
> > + /* We'll continue since this may just indicate an incorrect r1 */
> > + pr_err("pt_regs pointer/r1 doesn't point where we expect!\n");
> > + ret = 0;
> > + }
> > +
> > + for (i = 0; i < 32; i++) {
> > + /* KPROBES_ON_FTRACE may have stomped r0 in the prologue */
> > + if (r->gpr[i] != regs->gpr[i] && (!kp_on_ftrace || i != 0)) {
> > + pr_err("gpr[%d] expected: 0x%lx, received: 0x%lx\n",
> > + i, r->gpr[i], regs->gpr[i]);
> > + ret = 0;
> > + }
> > + }

Hmm, is this check really needed? See below(*)

> > +
> > + if (r->ctr != regs->ctr) {
> > + pr_err("ctr expected: 0x%lx, received: 0x%lx\n",
> > + r->ctr, regs->ctr);
> > + ret = 0;
> > + }
> > +
> > + if (r->link != regs->link && !kp_on_ftrace) {
> > + pr_err("link expected: 0x%lx, received: 0x%lx\n",
> > + r->link, regs->link);
> > + ret = 0;
> > + }
> > +
> > + /* KPROBES_ON_FTRACE *must* have clobbered link */
> > + if (r->link == regs->link && kp_on_ftrace) {
> > + pr_err("link register not clobbered for KPROBES_ON_FTRACE!\n");
> > + ret = 0;
> > + }
> > +
> > + if (r->xer != regs->xer) {
> > + pr_err("xer expected: 0x%lx, received: 0x%lx\n",
> > + r->xer, regs->xer);
> > + ret = 0;
> > + }
> > +
> > + if (r->ccr != regs->ccr) {
> > + pr_err("ccr expected: 0x%lx, received: 0x%lx\n",
> > + r->ccr, regs->ccr);
> > + ret = 0;
> > + }
> > +
> > + if (!post_handler && regs->nip != (unsigned long)p->addr) {
> > + pr_err("nip expected: 0x%lx, received: 0x%lx\n",
> > + (unsigned long)p->addr, regs->nip);
> > + ret = 0;
> > + }
> > +
> > + if (post_handler &&
> > + regs->nip != (unsigned long)p->addr + sizeof(kprobe_opcode_t)) {
> > + pr_err("post_handler: nip expected: 0x%lx, received: 0x%lx\n",
> > + (unsigned long)p->addr + sizeof(kprobe_opcode_t),
> > + regs->nip);
> > + ret = 0;
> > + }
> > +
> > + return ret;
> > +}
> > +
> > +int arch_kprobe_regs_pre_handler(struct kprobe *p, struct pt_regs *regs)
> > +{
> > + return validate_regs(p, regs, 0, 0);
> > +}
> > +
> > +int arch_kprobe_regs_post_handler(struct kprobe *p, struct pt_regs *regs,
> > + unsigned long flags)
> > +{
> > + return validate_regs(p, regs, 0, 1);
> > +}
> > +
> > +#ifdef CONFIG_KPROBES_ON_FTRACE
> > +int arch_kp_on_ftrace_pre_handler(struct kprobe *p, struct pt_regs *regs)
> > +{
> > + return validate_regs(p, regs, 1, 0);
> > +}
> > +#endif
> > diff --git a/include/linux/kprobes.h b/include/linux/kprobes.h
> > index 541df0b5b815..adfbb5b27acd 100644
> > --- a/include/linux/kprobes.h
> > +++ b/include/linux/kprobes.h
> > @@ -253,6 +253,17 @@ static inline void kretprobe_assert(struct kretprobe_instance *ri,
> >  
> >  #ifdef CONFIG_KPROBES_SANITY_TEST
> >  extern int init_test_probes(void);
> > +#ifdef HAVE_KPROBES_REGS_SANITY_TEST
> > +extern void arch_kprobe_regs_function(void);
> > +extern void arch_kprobe_regs_probepoint(void);
> > +extern int arch_kprobe_regs_pre_handler(struct kprobe *p, struct pt_regs *regs);
> > +extern int arch_kprobe_regs_post_handler(struct kprobe *p, struct pt_regs *regs,
> > + unsigned long flags);
> > +#ifdef CONFIG_KPROBES_ON_FTRACE
> > +extern void kprobe_regs_kp_on_ftrace_target(void);
> > +extern int arch_kp_on_ftrace_pre_handler(struct kprobe *p, struct pt_regs *regs);
> > +#endif
> > +#endif
> >  #else
> >  static inline int init_test_probes(void)
> >  {
> > diff --git a/kernel/test_kprobes.c b/kernel/test_kprobes.c
> > index 0dbab6d1acb4..92011726cc69 100644
> > --- a/kernel/test_kprobes.c
> > +++ b/kernel/test_kprobes.c
> > @@ -19,6 +19,7 @@
> >  #include <linux/kernel.h>
> >  #include <linux/kprobes.h>
> >  #include <linux/random.h>
> > +#include <linux/workqueue.h>
> >  
> >  #define div_factor 3
> >  
> > @@ -334,6 +335,166 @@ static int test_kretprobes(void)
> >  }
> >  #endif /* CONFIG_KRETPROBES */
> >  
> > +#ifdef HAVE_KPROBES_REGS_SANITY_TEST
> > +static int kprobe_regs_pre_handler(struct kprobe *p, struct pt_regs *regs)
> > +{
> > + /* architectural helper returns 0 if validation fails */
> > + preh_val = arch_kprobe_regs_pre_handler(p, regs);
> > + return 0;
> > +}
> > +
> > +static void kprobe_regs_post_handler(struct kprobe *p, struct pt_regs *regs,
> > + unsigned long flags)
> > +{
> > + posth_val = arch_kprobe_regs_post_handler(p, regs, flags);
> > +}
> > +
> > +static struct kprobe kpr = {
> > + .symbol_name = "arch_kprobe_regs_probepoint",
> > + .pre_handler = kprobe_regs_pre_handler,
> > + .post_handler = kprobe_regs_post_handler,
> > +};
> > +


> > +static int test_kprobe_regs(void)
> > +{
> > + int ret;
> > + kprobe_opcode_t *addr;
> > +
> > + preh_val = 0;
> > + posth_val = 0;
> > +
> > + ret = register_kprobe(&kpr);
> > + if (ret < 0) {
> > + pr_err("register_kprobe returned %d\n", ret);
> > + return ret;
> > + }
> > +
> > + /* Let's see if this probe was optimized */
> > + addr = kprobe_lookup_name(kpr.symbol_name, 0);

What happen if addr == NULL?
Since this already done in register_kprobe, you'd better use
kpr.addr.

> > + if (addr && *addr != BREAKPOINT_INSTRUCTION) {
> > + pr_err("kprobe with post_handler optimized\n");

Hmm, this message is not appropriate if the arch doesn't support
optprobe. Moreover, using BREAKPOINT_INSTRUCTION or not depends
on each arch. So, I suggest this as;

if (kprobe_optimized(&kpr)) {
        pr_err("kprobe with post_handler optimized\n");
        goto error;

And if you would like to check the instruction, please use
probe_kernel_read(), and introduce arch-depend helper as
below;

} else if (arch_kprobe_validate_insn(&kpr)) {
        pr_err("kprobe breakpoint is not armed\n");
        goto error;
}

Where (typical case, like ppc),

int arch_kprobe_validate_insn(struct kprobe *kp)
{
        kprobe_opcode_t buf;
        int ret;

        ret = probe_kernel_read(&buf, kp->addr, sizeof(buf));
        if (ret)
                return ret;
        if (buf != BREAKPOINT_INSTRUCTION)
                return -EINVAL;
        return 0;
}

> > + unregister_kprobe(&kpr);
> > + return -1;
> > + }
> > +
> > + arch_kprobe_regs_function();
> > + unregister_kprobe(&kpr);
> > +
> > + if (preh_val == 0) {
> > + pr_err("kprobe pre_handler regs validation failed\n");
> > + handler_errors++;
> > + }
> > +
> > + if (posth_val == 0) {
> > + pr_err("kprobe post_handler not called\n");
> > + handler_errors++;
> > + }
> > +
> > + return 0;
> > +}
> > +

> > +#ifdef CONFIG_KPROBES_ON_FTRACE
> > +void kprobe_regs_kp_on_ftrace_target(void)
> > +{
> > + posth_val = preh_val + div_factor;
> > +}
> > +
> > +static int kp_on_ftrace_pre_handler(struct kprobe *p, struct pt_regs *regs)
> > +{
> > + /* architectural helper returns 0 if validation fails */
> > + preh_val = arch_kp_on_ftrace_pre_handler(p, regs);

Here, I think you'd better to call arch_kprobe_regs_pre_handler(p, regs);
so that user can sure the handler's behavior has no difference.

(*) If you would like to check the kprobe_on_ftrace arch inplementation,
it should be a separated function, like

arch_validate_kprobe_on_ftrace(p, regs);

> > + return 0;
> > +}
> > +
> > +static struct kprobe kprf = {
> > + .symbol_name = "kprobe_regs_kp_on_ftrace_target",
> > + .pre_handler = kp_on_ftrace_pre_handler,

Also, we'd better add post_handler here so that it is able to check
compatibilty.

> > +};
> > +
> > +static int test_kp_on_ftrace_regs(void)
> > +{
> > + int ret;
> > +
> > + preh_val = 0;
> > +
> > + ret = register_kprobe(&kprf);
> > + if (ret < 0) {
> > + pr_err("register_kprobe returned %d\n", ret);
> > + return ret;
> > + }
> > +
> > + arch_kprobe_regs_function();
> > + unregister_kprobe(&kprf);
> > +
> > + if (preh_val == 0) {
> > + pr_err("kp_on_ftrace pre_handler regs validation failed\n");
> > + handler_errors++;
> > + }
> > +
> > + return 0;
> > +}
> > +#endif
> > +
> > +#ifdef CONFIG_OPTPROBES
> > +static void test_optprobe_regs(struct work_struct *work);
> > +static DECLARE_DELAYED_WORK(test_optprobe_regs_work, test_optprobe_regs);
> > +int kprobe_registered;
> > +
> > +static struct kprobe kpor = {
> > + .symbol_name = "arch_kprobe_regs_probepoint",
> > + .pre_handler = kprobe_regs_pre_handler,
> > +};
> > +
> > +static void test_optprobe_regs_setup(void)
> > +{
> > + int ret;
> > +
> > + ret = register_kprobe(&kpor);
> > + if (ret < 0) {
> > + pr_err("register_kprobe returned %d\n", ret);
> > + return;
> > + }
> > +
> > + kprobe_registered = 1;
> > +}
> > +
> > +static void test_optprobe_regs(struct work_struct *work)
> > +{
> > + kprobe_opcode_t *addr;
> > +
> > + if (!kprobe_registered) {
> > + errors++;
> > + goto summary;
> > + }
> > +
> > + /* Let's see if this probe was optimized */
> > + addr = kprobe_lookup_name(kpor.symbol_name, 0);
> > + if (addr && *addr == BREAKPOINT_INSTRUCTION) {

Here, same as above, we need arch_optprobe_validate_insn(kp).

Thank you,

--
Masami Hiramatsu <[hidden email]>