diff mbox series

arm: Add KPROBES_ON_FTRACE supported

Message ID 20240614022318.2600814-1-ruanjinjie@huawei.com (mailing list archive)
State Superseded
Headers show
Series arm: Add KPROBES_ON_FTRACE supported | expand

Commit Message

Jinjie Ruan June 14, 2024, 2:23 a.m. UTC
Add support for kprobes on ftrace call sites to avoid much of the overhead
with regular kprobes. Try it with simple steps:

	cd /sys/kernel/debug/tracing/
	echo 'p:myprobe sys_clone r0=%r0 r1=%r1 r2=%r2' > kprobe_events
	echo 1 > events/kprobes/enable
	echo  1 > events/kprobes/myprobe/enable
	cat trace
	# tracer: nop
	#
	# entries-in-buffer/entries-written: 2/2   #P:4
	#
	#                                _-----=> irqs-off/BH-disabled
	#                               / _----=> need-resched
	#                              | / _---=> hardirq/softirq
	#                              || / _--=> preempt-depth
	#                              ||| / _-=> migrate-disable
	#                              |||| /     delay
	#           TASK-PID     CPU#  |||||  TIMESTAMP  FUNCTION
	#              | |         |   |||||     |         |
	              sh-75      [000] .....    33.793362: myprobe: (sys_clone+0xc/0xa0) r0=0x1200011 r1=0x0 r2=0x0
	              sh-75      [000] .....    34.817804: myprobe: (sys_clone+0xc/0xa0) r0=0x1200011 r1=0x0 r2=0x0

	cat /sys/kernel/debug/kprobes/list
		c03453e8  k  sys_clone+0xc    [FTRACE]
					       ^^^^^^

Signed-off-by: Jinjie Ruan <ruanjinjie@huawei.com>
---
 .../debug/kprobes-on-ftrace/arch-support.txt  |  2 +-
 arch/arm/Kconfig                              |  1 +
 arch/arm/include/asm/ftrace.h                 | 17 ++++++
 arch/arm/kernel/ftrace.c                      | 17 ------
 arch/arm/probes/Makefile                      |  1 +
 arch/arm/probes/ftrace.c                      | 53 +++++++++++++++++++
 arch/arm/probes/kprobes/core.c                | 32 +++++++++++
 7 files changed, 105 insertions(+), 18 deletions(-)
 create mode 100644 arch/arm/probes/ftrace.c

Comments

kernel test robot June 15, 2024, 10:56 p.m. UTC | #1
Hi Jinjie,

kernel test robot noticed the following build errors:

[auto build test ERROR on soc/for-next]
[also build test ERROR on linus/master v6.10-rc3 next-20240613]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Jinjie-Ruan/arm-Add-KPROBES_ON_FTRACE-supported/20240614-102440
base:   https://git.kernel.org/pub/scm/linux/kernel/git/soc/soc.git for-next
patch link:    https://lore.kernel.org/r/20240614022318.2600814-1-ruanjinjie%40huawei.com
patch subject: [PATCH] arm: Add KPROBES_ON_FTRACE supported
config: arm-allmodconfig (https://download.01.org/0day-ci/archive/20240616/202406160646.J89U1UKK-lkp@intel.com/config)
compiler: arm-linux-gnueabi-gcc (GCC) 13.2.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20240616/202406160646.J89U1UKK-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202406160646.J89U1UKK-lkp@intel.com/

All error/warnings (new ones prefixed by >>):

>> drivers/gpu/drm/xe/xe_lrc.c:92: warning: "NOP" redefined
      92 | #define NOP(x) (BIT(7) | (x))
         | 
   In file included from include/linux/ftrace.h:23,
                    from include/linux/kprobes.h:28,
                    from include/linux/kgdb.h:19,
                    from include/drm/drm_util.h:36,
                    from include/drm/drm_connector.h:32,
                    from drivers/gpu/drm/i915/display/intel_display_core.h:16,
                    from drivers/gpu/drm/xe/xe_device_types.h:27,
                    from drivers/gpu/drm/xe/xe_vm_types.h:16,
                    from drivers/gpu/drm/xe/xe_bo.h:13,
                    from drivers/gpu/drm/xe/xe_lrc.c:14:
   arch/arm/include/asm/ftrace.h:39: note: this is the location of the previous definition
      39 | #define NOP             0xe28dd004      /* add   sp, sp, #4 */
         | 
--
>> drivers/gpu/drm/xe/xe_pci.c:80: warning: "NOP" redefined
      80 | #define NOP(x)  x
         | 
   In file included from include/linux/ftrace.h:23,
                    from include/linux/kprobes.h:28,
                    from include/linux/kgdb.h:19,
                    from include/drm/drm_util.h:36,
                    from drivers/gpu/drm/xe/xe_device.h:12,
                    from drivers/gpu/drm/xe/display/xe_display.h:9,
                    from drivers/gpu/drm/xe/xe_pci.c:18:
   arch/arm/include/asm/ftrace.h:39: note: this is the location of the previous definition
      39 | #define NOP             0xe28dd004      /* add   sp, sp, #4 */
         | 
--
   In file included from include/linux/ftrace.h:23,
                    from include/linux/perf_event.h:52,
                    from include/linux/trace_events.h:10,
                    from include/trace/syscall.h:7,
                    from include/linux/syscalls.h:93,
                    from drivers/scsi/aacraid/linit.c:32:
>> arch/arm/include/asm/ftrace.h:39:25: error: expected identifier before numeric constant
      39 | #define NOP             0xe28dd004      /* add   sp, sp, #4 */
         |                         ^~~~~~~~~~
   include/scsi/scsi_status.h:19:9: note: in expansion of macro 'NOP'
      19 |         NOP                     = 0x08,
         |         ^~~
   In file included from drivers/scsi/aacraid/linit.c:38:
   include/scsi/scsi_cmnd.h: In function 'scsi_msg_to_host_byte':
>> include/scsi/scsi_cmnd.h:372:14: error: 'TARGET_RESET' undeclared (first use in this function)
     372 |         case TARGET_RESET:
         |              ^~~~~~~~~~~~
   include/scsi/scsi_cmnd.h:372:14: note: each undeclared identifier is reported only once for each function it appears in


vim +39 arch/arm/include/asm/ftrace.h

    24	
    25	/*
    26	 * The compiler emitted profiling hook consists of
    27	 *
    28	 *   PUSH    {LR}
    29	 *   BL	     __gnu_mcount_nc
    30	 *
    31	 * To turn this combined sequence into a NOP, we need to restore the value of
    32	 * SP before the PUSH. Let's use an ADD rather than a POP into LR, as LR is not
    33	 * modified anyway, and reloading LR from memory is highly likely to be less
    34	 * efficient.
    35	 */
    36	#ifdef CONFIG_THUMB2_KERNEL
    37	#define	NOP		0xf10d0d04	/* add.w sp, sp, #4 */
    38	#else
  > 39	#define	NOP		0xe28dd004	/* add   sp, sp, #4 */
    40	#endif
    41
diff mbox series

Patch

diff --git a/Documentation/features/debug/kprobes-on-ftrace/arch-support.txt b/Documentation/features/debug/kprobes-on-ftrace/arch-support.txt
index 02febc883588..4ecd7d53e859 100644
--- a/Documentation/features/debug/kprobes-on-ftrace/arch-support.txt
+++ b/Documentation/features/debug/kprobes-on-ftrace/arch-support.txt
@@ -8,7 +8,7 @@ 
     -----------------------
     |       alpha: | TODO |
     |         arc: | TODO |
-    |         arm: | TODO |
+    |         arm: |  ok  |
     |       arm64: | TODO |
     |        csky: |  ok  |
     |     hexagon: | TODO |
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index ee5115252aac..ed13b1743f94 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -114,6 +114,7 @@  config ARM
 	select HAVE_KERNEL_LZO
 	select HAVE_KERNEL_XZ
 	select HAVE_KPROBES if !XIP_KERNEL && !CPU_ENDIAN_BE32 && !CPU_V7M
+	select HAVE_KPROBES_ON_FTRACE if !XIP_KERNEL && !CPU_ENDIAN_BE32 && !CPU_V7M
 	select HAVE_KRETPROBES if HAVE_KPROBES
 	select HAVE_MOD_ARCH_SPECIFIC
 	select HAVE_NMI
diff --git a/arch/arm/include/asm/ftrace.h b/arch/arm/include/asm/ftrace.h
index 5be3ddc96a50..c8e3f808b70c 100644
--- a/arch/arm/include/asm/ftrace.h
+++ b/arch/arm/include/asm/ftrace.h
@@ -22,6 +22,23 @@  struct dyn_arch_ftrace {
 #endif
 };
 
+/*
+ * The compiler emitted profiling hook consists of
+ *
+ *   PUSH    {LR}
+ *   BL	     __gnu_mcount_nc
+ *
+ * To turn this combined sequence into a NOP, we need to restore the value of
+ * SP before the PUSH. Let's use an ADD rather than a POP into LR, as LR is not
+ * modified anyway, and reloading LR from memory is highly likely to be less
+ * efficient.
+ */
+#ifdef CONFIG_THUMB2_KERNEL
+#define	NOP		0xf10d0d04	/* add.w sp, sp, #4 */
+#else
+#define	NOP		0xe28dd004	/* add   sp, sp, #4 */
+#endif
+
 static inline unsigned long ftrace_call_adjust(unsigned long addr)
 {
 	/* With Thumb-2, the recorded addresses have the lsb set */
diff --git a/arch/arm/kernel/ftrace.c b/arch/arm/kernel/ftrace.c
index a0b6d1e3812f..f0f1bdf27637 100644
--- a/arch/arm/kernel/ftrace.c
+++ b/arch/arm/kernel/ftrace.c
@@ -25,23 +25,6 @@ 
 #include <asm/stacktrace.h>
 #include <asm/patch.h>
 
-/*
- * The compiler emitted profiling hook consists of
- *
- *   PUSH    {LR}
- *   BL	     __gnu_mcount_nc
- *
- * To turn this combined sequence into a NOP, we need to restore the value of
- * SP before the PUSH. Let's use an ADD rather than a POP into LR, as LR is not
- * modified anyway, and reloading LR from memory is highly likely to be less
- * efficient.
- */
-#ifdef CONFIG_THUMB2_KERNEL
-#define	NOP		0xf10d0d04	/* add.w sp, sp, #4 */
-#else
-#define	NOP		0xe28dd004	/* add   sp, sp, #4 */
-#endif
-
 #ifdef CONFIG_DYNAMIC_FTRACE
 
 static int __ftrace_modify_code(void *data)
diff --git a/arch/arm/probes/Makefile b/arch/arm/probes/Makefile
index 8b0ea5ace100..b3c355942a21 100644
--- a/arch/arm/probes/Makefile
+++ b/arch/arm/probes/Makefile
@@ -1,6 +1,7 @@ 
 # SPDX-License-Identifier: GPL-2.0
 obj-$(CONFIG_UPROBES)		+= decode.o decode-arm.o uprobes/
 obj-$(CONFIG_KPROBES)		+= decode.o kprobes/
+obj-$(CONFIG_KPROBES_ON_FTRACE)	+= ftrace.o
 ifdef CONFIG_THUMB2_KERNEL
 obj-$(CONFIG_KPROBES)		+= decode-thumb.o
 else
diff --git a/arch/arm/probes/ftrace.c b/arch/arm/probes/ftrace.c
new file mode 100644
index 000000000000..0f54b8e5d2a6
--- /dev/null
+++ b/arch/arm/probes/ftrace.c
@@ -0,0 +1,53 @@ 
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/kprobes.h>
+
+/* Ftrace callback handler for kprobes -- called under preepmt disabled */
+void kprobe_ftrace_handler(unsigned long ip, unsigned long parent_ip,
+			   struct ftrace_ops *ops, struct ftrace_regs *regs)
+{
+	struct kprobe *p;
+	struct kprobe_ctlblk *kcb;
+
+	p = get_kprobe((kprobe_opcode_t *)ip);
+	if (unlikely(!p) || kprobe_disabled(p))
+		return;
+
+	kcb = get_kprobe_ctlblk();
+	if (kprobe_running()) {
+		kprobes_inc_nmissed_count(p);
+	} else {
+		unsigned long orig_ip = instruction_pointer(&(regs->regs));
+
+		instruction_pointer_set(&(regs->regs), ip);
+
+		__this_cpu_write(current_kprobe, p);
+		kcb->kprobe_status = KPROBE_HIT_ACTIVE;
+		if (!p->pre_handler || !p->pre_handler(p, &(regs->regs))) {
+			/*
+			 * Emulate singlestep (and also recover regs->pc)
+			 * as if there is a nop
+			 */
+			instruction_pointer_set(&(regs->regs),
+						(unsigned long)p->addr + MCOUNT_INSN_SIZE);
+			if (unlikely(p->post_handler)) {
+				kcb->kprobe_status = KPROBE_HIT_SSDONE;
+				p->post_handler(p, &(regs->regs), 0);
+			}
+			instruction_pointer_set(&(regs->regs), orig_ip);
+		}
+
+		/*
+		 * If pre_handler returns !0, it changes regs->pc. We have to
+		 * skip emulating post_handler.
+		 */
+		__this_cpu_write(current_kprobe, NULL);
+	}
+}
+NOKPROBE_SYMBOL(kprobe_ftrace_handler);
+
+int arch_prepare_kprobe_ftrace(struct kprobe *p)
+{
+	p->ainsn.insn = NULL;
+	return 0;
+}
diff --git a/arch/arm/probes/kprobes/core.c b/arch/arm/probes/kprobes/core.c
index d8238da095df..5e2f18cfd766 100644
--- a/arch/arm/probes/kprobes/core.c
+++ b/arch/arm/probes/kprobes/core.c
@@ -45,6 +45,38 @@  DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
 DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
 
 
+kprobe_opcode_t *arch_adjust_kprobe_addr(unsigned long addr, unsigned long offset,
+					 bool *on_func_entry)
+{
+#ifdef CONFIG_KPROBES_ON_FTRACE
+	unsigned long nop_offset = 0;
+	u32 insn = 0;
+
+	/*
+	 * Since 'addr' is not guaranteed to be safe to access, use
+	 * copy_from_kernel_nofault() to read the instruction:
+	 */
+	if (copy_from_kernel_nofault(&insn, (void *)(addr + nop_offset),
+				     sizeof(u32)))
+		return NULL;
+
+	while (insn != NOP) {
+		nop_offset += 4;
+		if (copy_from_kernel_nofault(&insn, (void *)(addr + nop_offset),
+					     sizeof(u32)))
+			return NULL;
+	}
+
+	*on_func_entry = offset <= nop_offset;
+	if (*on_func_entry)
+		offset = nop_offset;
+#else
+	*on_func_entry = !offset;
+#endif
+
+	return (kprobe_opcode_t *)(addr + offset);
+}
+
 int __kprobes arch_prepare_kprobe(struct kprobe *p)
 {
 	kprobe_opcode_t insn;