diff options
Diffstat (limited to 'arch/arm/probes/kprobes/opt-arm.c')
| -rw-r--r-- | arch/arm/probes/kprobes/opt-arm.c | 370 |
1 files changed, 370 insertions, 0 deletions
diff --git a/arch/arm/probes/kprobes/opt-arm.c b/arch/arm/probes/kprobes/opt-arm.c new file mode 100644 index 000000000..bcdecc254 --- /dev/null +++ b/arch/arm/probes/kprobes/opt-arm.c @@ -0,0 +1,370 @@ +/* + * 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 <asm/insn.h> +/* for patch_text */ +#include <asm/patch.h> + +#include "core.h" + +/* + * See register_usage_flags. If the probed instruction doesn't use PC, + * we can copy it into template and have it executed directly without + * simulation or emulation. + */ +#define ARM_REG_PC 15 +#define can_kprobe_direct_exec(m) (!test_bit(ARM_REG_PC, &(m))) + +/* + * 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" + ".global optprobe_template_sub_sp\n" + "optprobe_template_sub_sp:" + " sub sp, sp, #0xff\n" + " stmia sp, {r0 - r14} \n" + ".global optprobe_template_add_sp\n" + "optprobe_template_add_sp:" + " 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" + /* + * AEABI requires an 8-bytes alignment stack. If + * SP % 8 != 0 (SP % 4 == 0 should be ensured), + * alloc more bytes here. + */ + " and r4, sp, #4\n" + " sub sp, sp, r4\n" +#if __LINUX_ARM_ARCH__ >= 5 + " blx r2\n" +#else + " mov lr, pc\n" + " mov pc, r2\n" +#endif + " add sp, sp, r4\n" + " ldr r1, [sp, #64]\n" + " tst r1, #"__stringify(PSR_T_BIT)"\n" + " ldrne r2, [sp, #60]\n" + " orrne r2, #1\n" + " strne r2, [sp, #60] @ set bit0 of PC for thumb\n" + " msr cpsr_cxsf, r1\n" + ".global optprobe_template_restore_begin\n" + "optprobe_template_restore_begin:\n" + " ldmia sp, {r0 - r15}\n" + ".global optprobe_template_restore_orig_insn\n" + "optprobe_template_restore_orig_insn:\n" + " nop\n" + ".global optprobe_template_restore_end\n" + "optprobe_template_restore_end:\n" + " nop\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 \ + ((unsigned long *)&optprobe_template_val - (unsigned long *)&optprobe_template_entry) +#define TMPL_CALL_IDX \ + ((unsigned long *)&optprobe_template_call - (unsigned long *)&optprobe_template_entry) +#define TMPL_END_IDX \ + ((unsigned long *)&optprobe_template_end - (unsigned long *)&optprobe_template_entry) +#define TMPL_ADD_SP \ + ((unsigned long *)&optprobe_template_add_sp - (unsigned long *)&optprobe_template_entry) +#define TMPL_SUB_SP \ + ((unsigned long *)&optprobe_template_sub_sp - (unsigned long *)&optprobe_template_entry) +#define TMPL_RESTORE_BEGIN \ + ((unsigned long *)&optprobe_template_restore_begin - (unsigned long *)&optprobe_template_entry) +#define TMPL_RESTORE_ORIGN_INSN \ + ((unsigned long *)&optprobe_template_restore_orig_insn - (unsigned long *)&optprobe_template_entry) +#define TMPL_RESTORE_END \ + ((unsigned long *)&optprobe_template_restore_end - (unsigned 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 impossible 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 kprobe *kp) +{ + if (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 (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); + } + + /* + * We singlestep the replaced instruction only when it can't be + * executed directly during restore. + */ + if (!p->ainsn.kprobe_direct_exec) + op->kp.ainsn.insn_singlestep(p->opcode, &p->ainsn, regs); + + local_irq_restore(flags); +} + +int arch_prepare_optimized_kprobe(struct optimized_kprobe *op, struct kprobe *orig) +{ + kprobe_opcode_t *code; + unsigned long rel_chk; + unsigned long val; + unsigned long stack_protect = sizeof(struct pt_regs); + + if (!can_optimize(orig)) + return -EILSEQ; + + code = get_optinsn_slot(); + if (!code) + 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)code - + (long)orig->addr + 8) & 0xfe000003; + + if ((rel_chk != 0) && (rel_chk != 0xfe000000)) { + /* + * Different from x86, we free code buf directly instead of + * calling __arch_remove_optimized_kprobe() because + * we have not fill any field in op. + */ + free_optinsn_slot(code, 0); + return -ERANGE; + } + + /* Copy arch-dep-instance from template. */ + memcpy(code, &optprobe_template_entry, + TMPL_END_IDX * sizeof(kprobe_opcode_t)); + + /* Adjust buffer according to instruction. */ + BUG_ON(orig->ainsn.stack_space < 0); + + stack_protect += orig->ainsn.stack_space; + + /* Should have been filtered by can_optimize(). */ + BUG_ON(stack_protect > 255); + + /* Create a 'sub sp, sp, #<stack_protect>' */ + code[TMPL_SUB_SP] = __opcode_to_mem_arm(0xe24dd000 | stack_protect); + /* Create a 'add r3, sp, #<stack_protect>' */ + code[TMPL_ADD_SP] = __opcode_to_mem_arm(0xe28d3000 | stack_protect); + + /* Set probe information */ + val = (unsigned long)op; + code[TMPL_VAL_IDX] = val; + + /* Set probe function call */ + val = (unsigned long)optimized_callback; + code[TMPL_CALL_IDX] = val; + + /* If possible, copy insn and have it executed during restore */ + orig->ainsn.kprobe_direct_exec = false; + if (can_kprobe_direct_exec(orig->ainsn.register_usage_flags)) { + kprobe_opcode_t final_branch = arm_gen_branch( + (unsigned long)(&code[TMPL_RESTORE_END]), + (unsigned long)(op->kp.addr) + 4); + if (final_branch != 0) { + /* + * Replace original 'ldmia sp, {r0 - r15}' with + * 'ldmia {r0 - r14}', restore all registers except pc. + */ + code[TMPL_RESTORE_BEGIN] = __opcode_to_mem_arm(0xe89d7fff); + + /* The original probed instruction */ + code[TMPL_RESTORE_ORIGN_INSN] = __opcode_to_mem_arm(orig->opcode); + + /* Jump back to next instruction */ + code[TMPL_RESTORE_END] = __opcode_to_mem_arm(final_branch); + orig->ainsn.kprobe_direct_exec = true; + } + } + + flush_icache_range((unsigned long)code, + (unsigned long)(&code[TMPL_END_IDX])); + + /* Set op->optinsn.insn means prepared. */ + op->optinsn.insn = code; + return 0; +} + +void __kprobes 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); + + /* + * Similar to __arch_disarm_kprobe, operations which + * removing breakpoints must be wrapped by stop_machine + * to avoid racing. + */ + kprobes_remove_breakpoint(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); +} |