Initial import

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);
+}