| Message ID | 1416292359-75893-3-git-send-email-wangnan0@huawei.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On 2014/11/18 14:32, Wang Nan wrote: > This patch introduce kprobeopt for ARM 32. > > Limitations: > - Currently only kernel compiled with ARM ISA is supported. > > - Offset between probe point and optinsn slot must not larger than > 32MiB. Masami Hiramatsu suggests replacing 2 words, it will make > things complex. Futher patch can make such optimization. > > Kprobe opt on ARM is relatively simpler than kprobe opt on x86 because > ARM instruction is always 4 bytes aligned and 4 bytes long. This patch > replace probed instruction by a 'b', branch to trampoline code and then > calls optimized_callback(). optimized_callback() calls opt_pre_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. > > v1 -> v2: > > - Improvement: if replaced instruction is conditional, generate a > conditional branch instruction for it; > > - Introduces RELATIVEJUMP_OPCODES due to ARM kprobe_opcode_t is 4 > bytes; > > - Removes size field in struct arch_optimized_insn; > > - Use arm_gen_branch() to generate branch instruction; > > - Remove all recover logic: ARM doesn't use tail buffer, no need > recover replaced instructions like x86; > > - Remove incorrect CONFIG_THUMB checking; > > - can_optimize() always returns true if address is well aligned; > > - Improve optimized_callback: using opt_pre_handler(); > > - Bugfix: correct range checking code and improve comments; > > - Fix commit message. > > v2 -> v3: > > - Rename RELATIVEJUMP_OPCODES to MAX_COPIED_INSNS; > > - Remove unneeded checking: > arch_check_optimized_kprobe(), can_optimize(); > > - Add missing flush_icache_range() in arch_prepare_optimized_kprobe(); > > - Remove unneeded 'return;'. > > v3 -> v4: > > - Use __mem_to_opcode_arm() to translate copied_insn to ensure it > works in big endian kernel; > > - Replace 'nop' placeholder in trampoline code template with > '.long 0' to avoid confusion: reader may regard 'nop' as an > instruction, but it is value in fact. > > v4 -> v5: > > - Don't optimize stack store operations. > > - Introduce prepared field to arch_optimized_insn to indicate whether > it is prepared. Similar to size field with x86. See v1 -> v2. > > v5 -> v6: > > - Dynamically reserve stack according to instruction. > > - Rename: kprobes-opt.c -> kprobes-opt-arm.c. > > - Set op->optinsn.insn after all works are done. > > v6 -> v7: > > - Using checker to check stack consumption. > > v7 -> v8: > > - Small code adjustments. > > Signed-off-by: Wang Nan <wangnan0@huawei.com> > Acked-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> > Cc: Jon Medhurst (Tixy) <tixy@linaro.org> > Cc: Russell King - ARM Linux <linux@arm.linux.org.uk> > Cc: Will Deacon <will.deacon@arm.com> > --- > arch/arm/Kconfig | 1 + > arch/arm/include/asm/kprobes.h | 26 ++++ > arch/arm/kernel/Makefile | 3 +- > arch/arm/kernel/kprobes-opt-arm.c | 285 ++++++++++++++++++++++++++++++++++++++ > 4 files changed, 314 insertions(+), 1 deletion(-) > create mode 100644 arch/arm/kernel/kprobes-opt-arm.c > > diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig > index 89c4b5c..8281cea 100644 > --- a/arch/arm/Kconfig > +++ b/arch/arm/Kconfig > @@ -59,6 +59,7 @@ 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 56f9ac6..c1016cb 100644 > --- a/arch/arm/include/asm/kprobes.h > +++ b/arch/arm/include/asm/kprobes.h > @@ -50,5 +50,31 @@ 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. > + * Different from x86, ARM kprobe_opcode_t is u32. > + */ > +#define MAX_COPIED_INSN ((RELATIVEJUMP_SIZE) / sizeof(kprobe_opcode_t)) > + kprobe_opcode_t copied_insn[MAX_COPIED_INSN]; > + /* detour code buffer */ > + kprobe_opcode_t *insn; > + /* > + * we always copies one instruction on arm32, > + * size always be 4, so no size field. > + */ > +}; > > #endif /* _ARM_KPROBES_H */ > diff --git a/arch/arm/kernel/Makefile b/arch/arm/kernel/Makefile > index 45aed4b..8a16fcf 100644 > --- a/arch/arm/kernel/Makefile > +++ b/arch/arm/kernel/Makefile > @@ -52,11 +52,12 @@ obj-$(CONFIG_FUNCTION_GRAPH_TRACER) += ftrace.o insn.o > obj-$(CONFIG_JUMP_LABEL) += jump_label.o insn.o patch.o > obj-$(CONFIG_KEXEC) += machine_kexec.o relocate_kernel.o > obj-$(CONFIG_UPROBES) += probes.o probes-arm.o uprobes.o uprobes-arm.o > -obj-$(CONFIG_KPROBES) += probes.o kprobes.o kprobes-common.o patch.o probes-checkers-common.o > +obj-$(CONFIG_KPROBES) += probes.o kprobes.o kprobes-common.o patch.o probes-checkers-common.o insn.o > ifdef CONFIG_THUMB2_KERNEL > obj-$(CONFIG_KPROBES) += kprobes-thumb.o probes-thumb.o probes-checkers-thumb.o > else > obj-$(CONFIG_KPROBES) += kprobes-arm.o probes-arm.o probes-checkers-arm.o > +obj-$(CONFIG_OPTPROBES) += kprobes-opt-arm.o > endif > obj-$(CONFIG_ARM_KPROBES_TEST) += test-kprobes.o > test-kprobes-objs := kprobes-test.o > diff --git a/arch/arm/kernel/kprobes-opt-arm.c b/arch/arm/kernel/kprobes-opt-arm.c > new file mode 100644 > index 0000000..55eb3ea > --- /dev/null > +++ b/arch/arm/kernel/kprobes-opt-arm.c > @@ -0,0 +1,285 @@ > +/* > + * 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> > +/* for arm_gen_branch */ > +#include "insn.h" > +/* for patch_text */ > +#include "patch.h" > + > +/* > + * NOTE: the first sub and add instruction will be modified according > + * to the stack cost of the instruction. > + */ > +asm ( > + ".global optprobe_template_entry\n" > + "optprobe_template_entry:\n" > + " sub sp, sp, #0xff\n" > + " stmia sp, {r0 - r14} \n" > + " add r3, sp, #0xff\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: .long 0\n" > + ".global optprobe_template_call\n" > + "optprobe_template_call:\n" > + "2: .long 0\n" > + ".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) > + > +/* > + * ARM can always optimize an instruction when using ARM ISA, except > + * instructions like 'str r0, [sp, r1]' which store to stack and unable > + * to determine stack space consumption statically. > + */ > +int arch_prepared_optinsn(struct arch_optimized_insn *optinsn) > +{ > + return optinsn->insn != NULL; > +} > + > +/* > + * In ARM ISA, kprobe opt always replace one instruction (4 bytes > + * aligned and 4 bytes long). It is impossiable to encounter another > + * kprobe in the address range. So always return 0. > + */ > +int arch_check_optimized_kprobe(struct optimized_kprobe *op) > +{ > + return 0; > +} > + > +/* Caller must ensure addr & 3 == 0 */ > +static int can_optimize(struct optimized_kprobe *op) > +{ > + if (op->kp.ainsn.stack_space < 0) > + return 0; > + /* > + * 255 is the biggest imm can be used in 'sub r0, r0, #<imm>'. > + * Number larger than 255 needs special encoding. > + */ > + if (op->kp.ainsn.stack_space > 255 - sizeof(struct pt_regs)) > + 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; > + } > +} > + > +extern void kprobe_handler(struct pt_regs *regs); > + > +static void > +optimized_callback(struct optimized_kprobe *op, struct pt_regs *regs) > +{ > + unsigned long flags; > + struct kprobe *p = &op->kp; > + struct kprobe_ctlblk *kcb = get_kprobe_ctlblk(); > + > + /* Save skipped registers */ > + regs->ARM_pc = (unsigned long)op->kp.addr; > + regs->ARM_ORIG_r0 = ~0UL; > + > + local_irq_save(flags); > + > + if (kprobe_running()) { > + kprobes_inc_nmissed_count(&op->kp); > + } else { > + __this_cpu_write(current_kprobe, &op->kp); > + kcb->kprobe_status = KPROBE_HIT_ACTIVE; > + opt_pre_handler(&op->kp, regs); > + __this_cpu_write(current_kprobe, NULL); > + } > + > + /* In each case, we must singlestep the replaced instruction. */ > + op->kp.ainsn.insn_singlestep(p->opcode, &p->ainsn, regs); > + > + local_irq_restore(flags); > +} > + > +int arch_prepare_optimized_kprobe(struct optimized_kprobe *op) > +{ > + u8 *buf; > + unsigned long *code; > + unsigned long rel_chk; > + unsigned long val; > + unsigned long stack_protect = sizeof(struct pt_regs); > + > + if (!can_optimize(op)) > + return -EILSEQ; > + > + buf = (u8 *)get_optinsn_slot(); > + if (!buf) > + return -ENOMEM; > + > + /* > + * Verify if the address gap is in 32MiB range, because this uses > + * a relative jump. > + * > + * kprobe opt use a 'b' instruction to branch to optinsn.insn. > + * According to ARM manual, branch instruction is: > + * > + * 31 28 27 24 23 0 > + * +------+---+---+---+---+----------------+ > + * | cond | 1 | 0 | 1 | 0 | imm24 | > + * +------+---+---+---+---+----------------+ > + * > + * imm24 is a signed 24 bits integer. The real branch offset is computed > + * by: imm32 = SignExtend(imm24:'00', 32); > + * > + * So the maximum forward branch should be: > + * (0x007fffff << 2) = 0x01fffffc = 0x1fffffc > + * The maximum backword branch should be: > + * (0xff800000 << 2) = 0xfe000000 = -0x2000000 > + * > + * We can simply check (rel & 0xfe000003): > + * if rel is positive, (rel & 0xfe000000) shoule be 0 > + * if rel is negitive, (rel & 0xfe000000) should be 0xfe000000 > + * the last '3' is used for alignment checking. > + */ > + rel_chk = (unsigned long)((long)buf - > + (long)op->kp.addr + 8) & 0xfe000003; > + > + if ((rel_chk != 0) && (rel_chk != 0xfe000000)) { > + __arch_remove_optimized_kprobe(op, 0); Here is a bug. Different from x86_64, ARM code doesn't set op->optinsn.insn here, so __arch_remove_optimized_kprobe won't do anything. In version 9 patch series I fix this problem by calling free_optinsn_slot(buf, 0) directly. However, I forgot to mention it in its commit message. > + return -ERANGE; > + } > + > + /* Copy arch-dep-instance from template. */ > + memcpy(buf, &optprobe_template_entry, TMPL_END_IDX); > + > + /* Adjust buffer according to instruction. */ > + BUG_ON(op->kp.ainsn.stack_space < 0); > + stack_protect += op->kp.ainsn.stack_space; > + > + /* Should have been filtered by can_optimize(). */ > + BUG_ON(stack_protect > 255); > + > + /* Create a 'sub sp, sp, #<stack_protect>' */ > + code = (unsigned long *)(buf); > + code[0] = __opcode_to_mem_arm(0xe24dd000 | stack_protect); > + /* Create a 'add r3, sp, #<stack_protect>' */ > + code[2] = __opcode_to_mem_arm(0xe28d3000 | stack_protect); > + > + /* 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); > + > + /* Set op->optinsn.insn means prepared */ > + op->optinsn.insn = (kprobe_opcode_t *)buf; > + return 0; > +} > + > +void arch_optimize_kprobes(struct list_head *oplist) > +{ > + struct optimized_kprobe *op, *tmp; > + > + list_for_each_entry_safe(op, tmp, oplist, list) { > + unsigned long 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); > + > + insn = arm_gen_branch((unsigned long)op->kp.addr, > + (unsigned long)op->optinsn.insn); > + BUG_ON(insn == 0); > + > + /* > + * Make it a conditional branch if replaced insn > + * is consitional > + */ > + insn = (__mem_to_opcode_arm( > + op->optinsn.copied_insn[0]) & 0xf0000000) | > + (insn & 0x0fffffff); > + > + patch_text(op->kp.addr, insn); > + > + list_del_init(&op->list); > + } > +} > + > +void arch_unoptimize_kprobe(struct optimized_kprobe *op) > +{ > + arch_arm_kprobe(&op->kp); > +} > + > +/* > + * 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 + RELATIVEJUMP_SIZE > addr); > +} > + > +void arch_remove_optimized_kprobe(struct optimized_kprobe *op) > +{ > + __arch_remove_optimized_kprobe(op, 1); > +} >
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig index 89c4b5c..8281cea 100644 --- a/arch/arm/Kconfig +++ b/arch/arm/Kconfig @@ -59,6 +59,7 @@ 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 56f9ac6..c1016cb 100644 --- a/arch/arm/include/asm/kprobes.h +++ b/arch/arm/include/asm/kprobes.h @@ -50,5 +50,31 @@ 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. + * Different from x86, ARM kprobe_opcode_t is u32. + */ +#define MAX_COPIED_INSN ((RELATIVEJUMP_SIZE) / sizeof(kprobe_opcode_t)) + kprobe_opcode_t copied_insn[MAX_COPIED_INSN]; + /* detour code buffer */ + kprobe_opcode_t *insn; + /* + * we always copies one instruction on arm32, + * size always be 4, so no size field. + */ +}; #endif /* _ARM_KPROBES_H */ diff --git a/arch/arm/kernel/Makefile b/arch/arm/kernel/Makefile index 45aed4b..8a16fcf 100644 --- a/arch/arm/kernel/Makefile +++ b/arch/arm/kernel/Makefile @@ -52,11 +52,12 @@ obj-$(CONFIG_FUNCTION_GRAPH_TRACER) += ftrace.o insn.o obj-$(CONFIG_JUMP_LABEL) += jump_label.o insn.o patch.o obj-$(CONFIG_KEXEC) += machine_kexec.o relocate_kernel.o obj-$(CONFIG_UPROBES) += probes.o probes-arm.o uprobes.o uprobes-arm.o -obj-$(CONFIG_KPROBES) += probes.o kprobes.o kprobes-common.o patch.o probes-checkers-common.o +obj-$(CONFIG_KPROBES) += probes.o kprobes.o kprobes-common.o patch.o probes-checkers-common.o insn.o ifdef CONFIG_THUMB2_KERNEL obj-$(CONFIG_KPROBES) += kprobes-thumb.o probes-thumb.o probes-checkers-thumb.o else obj-$(CONFIG_KPROBES) += kprobes-arm.o probes-arm.o probes-checkers-arm.o +obj-$(CONFIG_OPTPROBES) += kprobes-opt-arm.o endif obj-$(CONFIG_ARM_KPROBES_TEST) += test-kprobes.o test-kprobes-objs := kprobes-test.o diff --git a/arch/arm/kernel/kprobes-opt-arm.c b/arch/arm/kernel/kprobes-opt-arm.c new file mode 100644 index 0000000..55eb3ea --- /dev/null +++ b/arch/arm/kernel/kprobes-opt-arm.c @@ -0,0 +1,285 @@ +/* + * 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> +/* for arm_gen_branch */ +#include "insn.h" +/* for patch_text */ +#include "patch.h" + +/* + * NOTE: the first sub and add instruction will be modified according + * to the stack cost of the instruction. + */ +asm ( + ".global optprobe_template_entry\n" + "optprobe_template_entry:\n" + " sub sp, sp, #0xff\n" + " stmia sp, {r0 - r14} \n" + " add r3, sp, #0xff\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: .long 0\n" + ".global optprobe_template_call\n" + "optprobe_template_call:\n" + "2: .long 0\n" + ".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) + +/* + * ARM can always optimize an instruction when using ARM ISA, except + * instructions like 'str r0, [sp, r1]' which store to stack and unable + * to determine stack space consumption statically. + */ +int arch_prepared_optinsn(struct arch_optimized_insn *optinsn) +{ + return optinsn->insn != NULL; +} + +/* + * In ARM ISA, kprobe opt always replace one instruction (4 bytes + * aligned and 4 bytes long). It is impossiable to encounter another + * kprobe in the address range. So always return 0. + */ +int arch_check_optimized_kprobe(struct optimized_kprobe *op) +{ + return 0; +} + +/* Caller must ensure addr & 3 == 0 */ +static int can_optimize(struct optimized_kprobe *op) +{ + if (op->kp.ainsn.stack_space < 0) + return 0; + /* + * 255 is the biggest imm can be used in 'sub r0, r0, #<imm>'. + * Number larger than 255 needs special encoding. + */ + if (op->kp.ainsn.stack_space > 255 - sizeof(struct pt_regs)) + 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; + } +} + +extern void kprobe_handler(struct pt_regs *regs); + +static void +optimized_callback(struct optimized_kprobe *op, struct pt_regs *regs) +{ + unsigned long flags; + struct kprobe *p = &op->kp; + struct kprobe_ctlblk *kcb = get_kprobe_ctlblk(); + + /* Save skipped registers */ + regs->ARM_pc = (unsigned long)op->kp.addr; + regs->ARM_ORIG_r0 = ~0UL; + + local_irq_save(flags); + + if (kprobe_running()) { + kprobes_inc_nmissed_count(&op->kp); + } else { + __this_cpu_write(current_kprobe, &op->kp); + kcb->kprobe_status = KPROBE_HIT_ACTIVE; + opt_pre_handler(&op->kp, regs); + __this_cpu_write(current_kprobe, NULL); + } + + /* In each case, we must singlestep the replaced instruction. */ + op->kp.ainsn.insn_singlestep(p->opcode, &p->ainsn, regs); + + local_irq_restore(flags); +} + +int arch_prepare_optimized_kprobe(struct optimized_kprobe *op) +{ + u8 *buf; + unsigned long *code; + unsigned long rel_chk; + unsigned long val; + unsigned long stack_protect = sizeof(struct pt_regs); + + if (!can_optimize(op)) + return -EILSEQ; + + buf = (u8 *)get_optinsn_slot(); + if (!buf) + return -ENOMEM; + + /* + * Verify if the address gap is in 32MiB range, because this uses + * a relative jump. + * + * kprobe opt use a 'b' instruction to branch to optinsn.insn. + * According to ARM manual, branch instruction is: + * + * 31 28 27 24 23 0 + * +------+---+---+---+---+----------------+ + * | cond | 1 | 0 | 1 | 0 | imm24 | + * +------+---+---+---+---+----------------+ + * + * imm24 is a signed 24 bits integer. The real branch offset is computed + * by: imm32 = SignExtend(imm24:'00', 32); + * + * So the maximum forward branch should be: + * (0x007fffff << 2) = 0x01fffffc = 0x1fffffc + * The maximum backword branch should be: + * (0xff800000 << 2) = 0xfe000000 = -0x2000000 + * + * We can simply check (rel & 0xfe000003): + * if rel is positive, (rel & 0xfe000000) shoule be 0 + * if rel is negitive, (rel & 0xfe000000) should be 0xfe000000 + * the last '3' is used for alignment checking. + */ + rel_chk = (unsigned long)((long)buf - + (long)op->kp.addr + 8) & 0xfe000003; + + if ((rel_chk != 0) && (rel_chk != 0xfe000000)) { + __arch_remove_optimized_kprobe(op, 0); + return -ERANGE; + } + + /* Copy arch-dep-instance from template. */ + memcpy(buf, &optprobe_template_entry, TMPL_END_IDX); + + /* Adjust buffer according to instruction. */ + BUG_ON(op->kp.ainsn.stack_space < 0); + stack_protect += op->kp.ainsn.stack_space; + + /* Should have been filtered by can_optimize(). */ + BUG_ON(stack_protect > 255); + + /* Create a 'sub sp, sp, #<stack_protect>' */ + code = (unsigned long *)(buf); + code[0] = __opcode_to_mem_arm(0xe24dd000 | stack_protect); + /* Create a 'add r3, sp, #<stack_protect>' */ + code[2] = __opcode_to_mem_arm(0xe28d3000 | stack_protect); + + /* 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); + + /* Set op->optinsn.insn means prepared */ + op->optinsn.insn = (kprobe_opcode_t *)buf; + return 0; +} + +void arch_optimize_kprobes(struct list_head *oplist) +{ + struct optimized_kprobe *op, *tmp; + + list_for_each_entry_safe(op, tmp, oplist, list) { + unsigned long 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); + + insn = arm_gen_branch((unsigned long)op->kp.addr, + (unsigned long)op->optinsn.insn); + BUG_ON(insn == 0); + + /* + * Make it a conditional branch if replaced insn + * is consitional + */ + insn = (__mem_to_opcode_arm( + op->optinsn.copied_insn[0]) & 0xf0000000) | + (insn & 0x0fffffff); + + patch_text(op->kp.addr, insn); + + list_del_init(&op->list); + } +} + +void arch_unoptimize_kprobe(struct optimized_kprobe *op) +{ + arch_arm_kprobe(&op->kp); +} + +/* + * 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 + RELATIVEJUMP_SIZE > addr); +} + +void arch_remove_optimized_kprobe(struct optimized_kprobe *op) +{ + __arch_remove_optimized_kprobe(op, 1); +}
This patch introduce kprobeopt for ARM 32. Limitations: - Currently only kernel compiled with ARM ISA is supported. - Offset between probe point and optinsn slot must not larger than 32MiB. Masami Hiramatsu suggests replacing 2 words, it will make things complex. Futher patch can make such optimization. Kprobe opt on ARM is relatively simpler than kprobe opt on x86 because ARM instruction is always 4 bytes aligned and 4 bytes long. This patch replace probed instruction by a 'b', branch to trampoline code and then calls optimized_callback(). optimized_callback() calls opt_pre_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. v1 -> v2: - Improvement: if replaced instruction is conditional, generate a conditional branch instruction for it; - Introduces RELATIVEJUMP_OPCODES due to ARM kprobe_opcode_t is 4 bytes; - Removes size field in struct arch_optimized_insn; - Use arm_gen_branch() to generate branch instruction; - Remove all recover logic: ARM doesn't use tail buffer, no need recover replaced instructions like x86; - Remove incorrect CONFIG_THUMB checking; - can_optimize() always returns true if address is well aligned; - Improve optimized_callback: using opt_pre_handler(); - Bugfix: correct range checking code and improve comments; - Fix commit message. v2 -> v3: - Rename RELATIVEJUMP_OPCODES to MAX_COPIED_INSNS; - Remove unneeded checking: arch_check_optimized_kprobe(), can_optimize(); - Add missing flush_icache_range() in arch_prepare_optimized_kprobe(); - Remove unneeded 'return;'. v3 -> v4: - Use __mem_to_opcode_arm() to translate copied_insn to ensure it works in big endian kernel; - Replace 'nop' placeholder in trampoline code template with '.long 0' to avoid confusion: reader may regard 'nop' as an instruction, but it is value in fact. v4 -> v5: - Don't optimize stack store operations. - Introduce prepared field to arch_optimized_insn to indicate whether it is prepared. Similar to size field with x86. See v1 -> v2. v5 -> v6: - Dynamically reserve stack according to instruction. - Rename: kprobes-opt.c -> kprobes-opt-arm.c. - Set op->optinsn.insn after all works are done. v6 -> v7: - Using checker to check stack consumption. v7 -> v8: - Small code adjustments. Signed-off-by: Wang Nan <wangnan0@huawei.com> Acked-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Cc: Jon Medhurst (Tixy) <tixy@linaro.org> Cc: Russell King - ARM Linux <linux@arm.linux.org.uk> Cc: Will Deacon <will.deacon@arm.com> --- arch/arm/Kconfig | 1 + arch/arm/include/asm/kprobes.h | 26 ++++ arch/arm/kernel/Makefile | 3 +- arch/arm/kernel/kprobes-opt-arm.c | 285 ++++++++++++++++++++++++++++++++++++++ 4 files changed, 314 insertions(+), 1 deletion(-) create mode 100644 arch/arm/kernel/kprobes-opt-arm.c