[RFC PATCH] kprobes: arm: enable OPTPROBES for arm 32
Wang Nan
wangnan0 at huawei.com
Tue Aug 5 00:28:17 PDT 2014
This patch introduce kprobeopt for ARM 32.
Limitations:
- Currently only kernel compiled with ARM ISA is supported.
- offset between probe point and kprobe pre_handler must not larger
than 64MiB. Masami Hiramatsu suggests replacing 2 words, it will
make things complex. Futher patch can make such optimization.
I have tested this patch on qemu vexpress a9 platform.
Kprobe opt on ARM is relatively simpler than kprobe opt on x86 because
ARM instruction is always 4 bytes aligned. This patch replace probed
instruction by a 'b', branch to trampoline code and then calls
optimized_callback(). optimized_callback() calls kprobe_handler() to
execute kprobe handler. It also emulate/simulate replaced instruction.
When unregistering kprobe, the deferred manner of unoptimizer may leave
branch instruction before optimizer is called. Different from x86_64,
which only copy the probed insn after optprobe_template_end and
reexecute them, this patch call singlestep to emulate/simulate the insn
directly. Futher patch can optimize this behavior.
Signed-off-by: Wang Nan <wangnan0 at huawei.com>
Cc: Masami Hiramatsu <masami.hiramatsu.pt at hitachi.com>
---
arch/arm/Kconfig | 1 +
arch/arm/include/asm/kprobes.h | 20 +++
arch/arm/kernel/Makefile | 1 +
arch/arm/kernel/kprobes-opt.c | 322 +++++++++++++++++++++++++++++++++++++++++
4 files changed, 344 insertions(+)
create mode 100644 arch/arm/kernel/kprobes-opt.c
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 290f02ee..2106918 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -57,6 +57,7 @@ config ARM
select HAVE_MEMBLOCK
select HAVE_MOD_ARCH_SPECIFIC if ARM_UNWIND
select HAVE_OPROFILE if (HAVE_PERF_EVENTS)
+ select HAVE_OPTPROBES if (!THUMB2_KERNEL)
select HAVE_PERF_EVENTS
select HAVE_PERF_REGS
select HAVE_PERF_USER_STACK_DUMP
diff --git a/arch/arm/include/asm/kprobes.h b/arch/arm/include/asm/kprobes.h
index 49fa0df..0f4e5c0 100644
--- a/arch/arm/include/asm/kprobes.h
+++ b/arch/arm/include/asm/kprobes.h
@@ -51,5 +51,25 @@ int kprobe_fault_handler(struct pt_regs *regs, unsigned int fsr);
int kprobe_exceptions_notify(struct notifier_block *self,
unsigned long val, void *data);
+/* optinsn template addresses */
+extern __visible kprobe_opcode_t optprobe_template_entry;
+extern __visible kprobe_opcode_t optprobe_template_val;
+extern __visible kprobe_opcode_t optprobe_template_call;
+extern __visible kprobe_opcode_t optprobe_template_end;
+
+#define MAX_OPTIMIZED_LENGTH (4)
+#define MAX_OPTINSN_SIZE \
+ (((unsigned long)&optprobe_template_end - \
+ (unsigned long)&optprobe_template_entry))
+#define RELATIVEJUMP_SIZE (4)
+
+struct arch_optimized_insn {
+ /* copy of the original instructions */
+ kprobe_opcode_t copied_insn[RELATIVEJUMP_SIZE];
+ /* detour code buffer */
+ kprobe_opcode_t *insn;
+ /* the size of instructions copied to detour code buffer */
+ size_t size;
+};
#endif /* _ARM_KPROBES_H */
diff --git a/arch/arm/kernel/Makefile b/arch/arm/kernel/Makefile
index 38ddd9f..918ee34 100644
--- a/arch/arm/kernel/Makefile
+++ b/arch/arm/kernel/Makefile
@@ -57,6 +57,7 @@ ifdef CONFIG_THUMB2_KERNEL
obj-$(CONFIG_KPROBES) += kprobes-thumb.o probes-thumb.o
else
obj-$(CONFIG_KPROBES) += kprobes-arm.o probes-arm.o
+obj-$(CONFIG_OPTPROBES) += kprobes-opt.o
endif
obj-$(CONFIG_ARM_KPROBES_TEST) += test-kprobes.o
test-kprobes-objs := kprobes-test.o
diff --git a/arch/arm/kernel/kprobes-opt.c b/arch/arm/kernel/kprobes-opt.c
new file mode 100644
index 0000000..a4aa7ed
--- /dev/null
+++ b/arch/arm/kernel/kprobes-opt.c
@@ -0,0 +1,322 @@
+/*
+ * Kernel Probes Jump Optimization (Optprobes)
+ *
+ * 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; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+ *
+ * Copyright (C) IBM Corporation, 2002, 2004
+ * Copyright (C) Hitachi Ltd., 2012
+ * Copyright (C) Huawei Inc., 2014
+ */
+
+#include <linux/kprobes.h>
+#include <linux/jump_label.h>
+#include <asm/kprobes.h>
+#include <asm/cacheflush.h>
+#include "patch.h"
+
+unsigned long
+__recover_optprobed_insn(kprobe_opcode_t *buf, unsigned long addr)
+{
+ struct optimized_kprobe *op;
+ struct kprobe *kp;
+ int i;
+ long offs;
+ for (i = 0; i < RELATIVEJUMP_SIZE; i++) {
+ kp = get_kprobe((void *)addr - i);
+ if (!kp || !kprobe_optimized(kp))
+ continue;
+ op = container_of(kp, struct optimized_kprobe, kp);
+ /* If op->list is not empty, op is under optimizing */
+ if (list_empty(&op->list))
+ goto found;
+ }
+
+ return addr;
+
+found:
+ offs = addr - (unsigned long)kp->addr;
+ memcpy(buf, op->optinsn.copied_insn + offs, RELATIVEJUMP_SIZE - offs);
+ return (unsigned long)buf;
+}
+
+static unsigned long
+__recover_probed_insn(kprobe_opcode_t *buf, unsigned long addr)
+{
+ struct kprobe *kp;
+
+ kp = get_kprobe((void *)addr);
+ /* There is no probe, return original address */
+ if (!kp)
+ return addr;
+
+ /*
+ * Basically, kp->ainsn.insn has an original instruction.
+ */
+ memcpy(buf, kp->ainsn.insn, MAX_INSN_SIZE * sizeof(kprobe_opcode_t));
+ return (unsigned long)buf;
+}
+
+/*
+ * Recover the probed instruction at addr for further analysis.
+ * Caller must lock kprobes by kprobe_mutex, or disable preemption
+ * for preventing to release referencing kprobes.
+ */
+unsigned long
+recover_probed_instruction(kprobe_opcode_t *buf, unsigned long addr)
+{
+ unsigned long __addr;
+
+ __addr = __recover_optprobed_insn(buf, addr);
+ if (__addr != addr)
+ return __addr;
+
+ return __recover_probed_insn(buf, addr);
+}
+
+
+/*
+ * recover kprobed instruction and copy to dest
+ */
+int
+__copy_instruction(u8 *dest, u8 *src)
+{
+ kprobe_opcode_t buf[MAX_INSN_SIZE];
+ memcpy(dest, (void *)recover_probed_instruction(buf, (unsigned long)src),
+ sizeof(kprobe_opcode_t) * MAX_INSN_SIZE);
+ return (sizeof(kprobe_opcode_t) * MAX_INSN_SIZE);
+}
+
+
+asm (
+ ".global optprobe_template_entry\n"
+ "optprobe_template_entry:\n"
+#ifndef CONFIG_THUMB
+ " sub sp, sp, #80\n"
+ " stmia sp, {r0 - r14} \n"
+ " add r3, sp, #80\n"
+ " str r3, [sp, #52]\n"
+ " mrs r4, cpsr\n"
+ " str r4, [sp, #64]\n"
+ " mov r1, sp\n"
+ " ldr r0, 1f\n"
+ " ldr r2, 2f\n"
+ " blx r2\n"
+ " ldr r1, [sp, #64]\n"
+ " msr cpsr_fs, r1\n"
+ " ldmia sp, {r0 - r15}\n"
+ ".global optprobe_template_val\n"
+ "optprobe_template_val:\n"
+ "1: nop\n"
+ ".global optprobe_template_call\n"
+ "optprobe_template_call:\n"
+ "2: nop\n"
+#else /* CONFIG_THUMB */
+# error optprobe for thumb is not supported.
+#endif
+ ".global optprobe_template_end\n"
+ "optprobe_template_end:\n");
+
+#define TMPL_VAL_IDX \
+ ((long)&optprobe_template_val - (long)&optprobe_template_entry)
+#define TMPL_CALL_IDX \
+ ((long)&optprobe_template_call - (long)&optprobe_template_entry)
+#define TMPL_END_IDX \
+ ((long)&optprobe_template_end - (long)&optprobe_template_entry)
+
+int arch_prepared_optinsn(struct arch_optimized_insn *optinsn)
+{
+ return optinsn->size;
+}
+
+int arch_check_optimized_kprobe(struct optimized_kprobe *op)
+{
+ int i;
+ struct kprobe *p;
+
+ for (i = 1; i < op->optinsn.size; i++) {
+ p = get_kprobe(op->kp.addr + i);
+ if (p && !kprobe_disabled(p))
+ return -EEXIST;
+ }
+
+ return 0;
+}
+
+static int can_optimize(unsigned long paddr)
+{
+ unsigned long size = 0, offset = 0;
+
+ /* Lookup symbol including addr */
+ if (!kallsyms_lookup_size_offset(paddr, &size, &offset))
+ return 0;
+
+ /* Check there is enough space for a relative jump. */
+ if (size - offset < RELATIVEJUMP_SIZE)
+ return 0;
+
+ return 1;
+}
+
+/* Free optimized instruction slot */
+static
+void __arch_remove_optimized_kprobe(struct optimized_kprobe *op, int dirty)
+{
+ if (op->optinsn.insn) {
+ free_optinsn_slot(op->optinsn.insn, dirty);
+ op->optinsn.insn = NULL;
+ op->optinsn.size = 0;
+ }
+}
+
+extern void kprobe_handler(struct pt_regs *regs);
+
+static void
+optimized_callback(struct optimized_kprobe *op, struct pt_regs *regs)
+{
+ unsigned long flags;
+
+ regs->ARM_pc = (unsigned long)op->kp.addr;
+ regs->ARM_ORIG_r0 = ~0UL;
+
+
+ local_irq_save(flags);
+ /*
+ * This is possible if op is under delayed unoptimizing.
+ * We need simulate the replaced instruction.
+ */
+ if (kprobe_disabled(&op->kp)) {
+ struct kprobe *p = &op->kp;
+ op->kp.ainsn.insn_singlestep(p->opcode, &p->ainsn, regs);
+ } else {
+ kprobe_handler(regs);
+ }
+
+ local_irq_restore(flags);
+}
+
+int arch_prepare_optimized_kprobe(struct optimized_kprobe *op)
+{
+ u8 *buf;
+ long rel;
+ unsigned long val;
+
+ if (!can_optimize((unsigned long)op->kp.addr))
+ return -EILSEQ;
+
+ op->optinsn.insn = get_optinsn_slot();
+ if (!op->optinsn.insn)
+ return -ENOMEM;
+
+ /*
+ * 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;
+ if ((abs(rel) > 0x3fffffc) || ((abs(rel) & 3) != 0)) {
+ __arch_remove_optimized_kprobe(op, 0);
+ return -ERANGE;
+ }
+
+ buf = (u8 *)op->optinsn.insn;
+
+ op->optinsn.size = RELATIVEJUMP_SIZE;
+
+ /* Copy arch-dep-instance from template */
+ memcpy(buf, &optprobe_template_entry, TMPL_END_IDX);
+
+ /* Set probe information */
+ val = (unsigned long)op;
+ memcpy(buf + TMPL_VAL_IDX, &val, sizeof(val));
+
+ /* Set probe function call */
+ val = (unsigned long)optimized_callback;
+ memcpy(buf + TMPL_CALL_IDX, &val, sizeof(val));
+
+ flush_icache_range((unsigned long) buf,
+ (unsigned long) buf + TMPL_END_IDX +
+ op->optinsn.size + RELATIVEJUMP_SIZE);
+ return 0;
+}
+
+static inline int
+arm_branch_to_addr(unsigned int *pinst, void *src, void *dest)
+{
+ unsigned int inst = 0xea000000;
+ long offset = (unsigned long)(dest) -
+ ((unsigned long)(src) + 8);
+ if ((offset > 0x3fffffc) || (offset < -0x3fffffc)) {
+ printk(KERN_WARNING "Failed to instrument %pS to %pS\n", src, dest);
+ return -EINVAL;
+ }
+
+ inst |= (((unsigned long)offset) >> 2) & (0x00ffffffUL);
+ *pinst = inst;
+ return 0;
+}
+
+void arch_optimize_kprobes(struct list_head *oplist)
+{
+ struct optimized_kprobe *op, *tmp;
+
+ list_for_each_entry_safe(op, tmp, oplist, list) {
+ int err;
+ unsigned int insn;
+ WARN_ON(kprobe_disabled(&op->kp));
+
+ /* Backup instructions which will be replaced by jump address */
+ memcpy(op->optinsn.copied_insn, op->kp.addr, RELATIVEJUMP_SIZE);
+
+ err = arm_branch_to_addr(&insn, op->kp.addr, op->optinsn.insn);
+ BUG_ON(err);
+
+ patch_text(op->kp.addr, insn);
+
+ list_del_init(&op->list);
+ }
+ return;
+}
+
+void arch_unoptimize_kprobe(struct optimized_kprobe *op)
+{
+ arch_arm_kprobe(&op->kp);
+ return;
+}
+
+/*
+ * Recover original instructions and breakpoints from relative jumps.
+ * Caller must call with locking kprobe_mutex.
+ */
+void arch_unoptimize_kprobes(struct list_head *oplist,
+ struct list_head *done_list)
+{
+ struct optimized_kprobe *op, *tmp;
+
+ list_for_each_entry_safe(op, tmp, oplist, list) {
+ arch_unoptimize_kprobe(op);
+ list_move(&op->list, done_list);
+ }
+}
+
+int arch_within_optimized_kprobe(struct optimized_kprobe *op,
+ unsigned long addr)
+{
+ return ((unsigned long)op->kp.addr <= addr &&
+ (unsigned long)op->kp.addr + op->optinsn.size > addr);
+}
+
+void arch_remove_optimized_kprobe(struct optimized_kprobe *op)
+{
+ __arch_remove_optimized_kprobe(op, 1);
+}
--
1.8.4
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