@@ -8,7 +8,7 @@
-----------------------
| alpha: | TODO |
| arc: | TODO |
- | arm: | TODO |
+ | arm: | ok |
| arm64: | TODO |
| csky: | ok |
| hexagon: | TODO |
@@ -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
@@ -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 FTRACE_NOP 0xf10d0d04 /* add.w sp, sp, #4 */
+#else
+#define FTRACE_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 */
@@ -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)
@@ -60,7 +43,7 @@ void arch_ftrace_update_code(int command)
static unsigned long ftrace_nop_replace(struct dyn_ftrace *rec)
{
- return NOP;
+ return FTRACE_NOP;
}
void ftrace_caller_from_init(void);
@@ -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
new file mode 100644
@@ -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;
+}
@@ -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 != FTRACE_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;
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> Reported-by: kernel test robot <lkp@intel.com> Closes: https://lore.kernel.org/oe-kbuild-all/202406160646.J89U1UKK-lkp@intel.com/ --- v2: - Fix the allmodconfig compile issue by renaming "NOP" to "FTRACE_NOP". --- .../debug/kprobes-on-ftrace/arch-support.txt | 2 +- arch/arm/Kconfig | 1 + arch/arm/include/asm/ftrace.h | 17 ++++++ arch/arm/kernel/ftrace.c | 19 +------ arch/arm/probes/Makefile | 1 + arch/arm/probes/ftrace.c | 53 +++++++++++++++++++ arch/arm/probes/kprobes/core.c | 32 +++++++++++ 7 files changed, 106 insertions(+), 19 deletions(-) create mode 100644 arch/arm/probes/ftrace.c