ARC: disassembly (needed by kprobes/kgdb/unaligned-access-emul)
In-kernel disassembler
Due Credits
* Orig written by Rajeshwar Ranga
* Consolidation/cleanups by Mischa Jonker
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
Cc: Rajeshwar Ranga <rajeshwar.ranga@gmail.com>
Cc: Mischa Jonker <mjonker@synopsys.com>
diff --git a/arch/arc/kernel/disasm.c b/arch/arc/kernel/disasm.c
new file mode 100644
index 0000000..254d11a
--- /dev/null
+++ b/arch/arc/kernel/disasm.c
@@ -0,0 +1,539 @@
+/*
+ * several functions that help interpret ARC instructions
+ * used for unaligned accesses, kprobes and kgdb
+ *
+ * Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com)
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/types.h>
+#include <linux/kprobes.h>
+#include <linux/slab.h>
+#include <asm/disasm.h>
+#include <asm/uaccess.h>
+
+#if defined(CONFIG_KGDB) || defined(CONFIG_MISALIGN_ACCESS) || \
+ defined(CONFIG_KPROBES)
+
+/* disasm_instr: Analyses instruction at addr, stores
+ * findings in *state
+ */
+void __kprobes disasm_instr(unsigned long addr, struct disasm_state *state,
+ int userspace, struct pt_regs *regs, struct callee_regs *cregs)
+{
+ int fieldA = 0;
+ int fieldC = 0, fieldCisReg = 0;
+ uint16_t word1 = 0, word0 = 0;
+ int subopcode, is_linked, op_format;
+ uint16_t *ins_ptr;
+ uint16_t ins_buf[4];
+ int bytes_not_copied = 0;
+
+ memset(state, 0, sizeof(struct disasm_state));
+
+ /* This fetches the upper part of the 32 bit instruction
+ * in both the cases of Little Endian or Big Endian configurations. */
+ if (userspace) {
+ bytes_not_copied = copy_from_user(ins_buf,
+ (const void __user *) addr, 8);
+ if (bytes_not_copied > 6)
+ goto fault;
+ ins_ptr = ins_buf;
+ } else {
+ ins_ptr = (uint16_t *) addr;
+ }
+
+ word1 = *((uint16_t *)addr);
+
+ state->major_opcode = (word1 >> 11) & 0x1F;
+
+ /* Check if the instruction is 32 bit or 16 bit instruction */
+ if (state->major_opcode < 0x0B) {
+ if (bytes_not_copied > 4)
+ goto fault;
+ state->instr_len = 4;
+ word0 = *((uint16_t *)(addr+2));
+ state->words[0] = (word1 << 16) | word0;
+ } else {
+ state->instr_len = 2;
+ state->words[0] = word1;
+ }
+
+ /* Read the second word in case of limm */
+ word1 = *((uint16_t *)(addr + state->instr_len));
+ word0 = *((uint16_t *)(addr + state->instr_len + 2));
+ state->words[1] = (word1 << 16) | word0;
+
+ switch (state->major_opcode) {
+ case op_Bcc:
+ state->is_branch = 1;
+
+ /* unconditional branch s25, conditional branch s21 */
+ fieldA = (IS_BIT(state->words[0], 16)) ?
+ FIELD_s25(state->words[0]) :
+ FIELD_s21(state->words[0]);
+
+ state->delay_slot = IS_BIT(state->words[0], 5);
+ state->target = fieldA + (addr & ~0x3);
+ state->flow = direct_jump;
+ break;
+
+ case op_BLcc:
+ if (IS_BIT(state->words[0], 16)) {
+ /* Branch and Link*/
+ /* unconditional branch s25, conditional branch s21 */
+ fieldA = (IS_BIT(state->words[0], 17)) ?
+ (FIELD_s25(state->words[0]) & ~0x3) :
+ FIELD_s21(state->words[0]);
+
+ state->flow = direct_call;
+ } else {
+ /*Branch On Compare */
+ fieldA = FIELD_s9(state->words[0]) & ~0x3;
+ state->flow = direct_jump;
+ }
+
+ state->delay_slot = IS_BIT(state->words[0], 5);
+ state->target = fieldA + (addr & ~0x3);
+ state->is_branch = 1;
+ break;
+
+ case op_LD: /* LD<zz> a,[b,s9] */
+ state->write = 0;
+ state->di = BITS(state->words[0], 11, 11);
+ if (state->di)
+ break;
+ state->x = BITS(state->words[0], 6, 6);
+ state->zz = BITS(state->words[0], 7, 8);
+ state->aa = BITS(state->words[0], 9, 10);
+ state->wb_reg = FIELD_B(state->words[0]);
+ if (state->wb_reg == REG_LIMM) {
+ state->instr_len += 4;
+ state->aa = 0;
+ state->src1 = state->words[1];
+ } else {
+ state->src1 = get_reg(state->wb_reg, regs, cregs);
+ }
+ state->src2 = FIELD_s9(state->words[0]);
+ state->dest = FIELD_A(state->words[0]);
+ state->pref = (state->dest == REG_LIMM);
+ break;
+
+ case op_ST:
+ state->write = 1;
+ state->di = BITS(state->words[0], 5, 5);
+ if (state->di)
+ break;
+ state->aa = BITS(state->words[0], 3, 4);
+ state->zz = BITS(state->words[0], 1, 2);
+ state->src1 = FIELD_C(state->words[0]);
+ if (state->src1 == REG_LIMM) {
+ state->instr_len += 4;
+ state->src1 = state->words[1];
+ } else {
+ state->src1 = get_reg(state->src1, regs, cregs);
+ }
+ state->wb_reg = FIELD_B(state->words[0]);
+ if (state->wb_reg == REG_LIMM) {
+ state->aa = 0;
+ state->instr_len += 4;
+ state->src2 = state->words[1];
+ } else {
+ state->src2 = get_reg(state->wb_reg, regs, cregs);
+ }
+ state->src3 = FIELD_s9(state->words[0]);
+ break;
+
+ case op_MAJOR_4:
+ subopcode = MINOR_OPCODE(state->words[0]);
+ switch (subopcode) {
+ case 32: /* Jcc */
+ case 33: /* Jcc.D */
+ case 34: /* JLcc */
+ case 35: /* JLcc.D */
+ is_linked = 0;
+
+ if (subopcode == 33 || subopcode == 35)
+ state->delay_slot = 1;
+
+ if (subopcode == 34 || subopcode == 35)
+ is_linked = 1;
+
+ fieldCisReg = 0;
+ op_format = BITS(state->words[0], 22, 23);
+ if (op_format == 0 || ((op_format == 3) &&
+ (!IS_BIT(state->words[0], 5)))) {
+ fieldC = FIELD_C(state->words[0]);
+
+ if (fieldC == REG_LIMM) {
+ fieldC = state->words[1];
+ state->instr_len += 4;
+ } else {
+ fieldCisReg = 1;
+ }
+ } else if (op_format == 1 || ((op_format == 3)
+ && (IS_BIT(state->words[0], 5)))) {
+ fieldC = FIELD_C(state->words[0]);
+ } else {
+ /* op_format == 2 */
+ fieldC = FIELD_s12(state->words[0]);
+ }
+
+ if (!fieldCisReg) {
+ state->target = fieldC;
+ state->flow = is_linked ?
+ direct_call : direct_jump;
+ } else {
+ state->target = get_reg(fieldC, regs, cregs);
+ state->flow = is_linked ?
+ indirect_call : indirect_jump;
+ }
+ state->is_branch = 1;
+ break;
+
+ case 40: /* LPcc */
+ if (BITS(state->words[0], 22, 23) == 3) {
+ /* Conditional LPcc u7 */
+ fieldC = FIELD_C(state->words[0]);
+
+ fieldC = fieldC << 1;
+ fieldC += (addr & ~0x03);
+ state->is_branch = 1;
+ state->flow = direct_jump;
+ state->target = fieldC;
+ }
+ /* For Unconditional lp, next pc is the fall through
+ * which is updated */
+ break;
+
+ case 48 ... 55: /* LD a,[b,c] */
+ state->di = BITS(state->words[0], 15, 15);
+ if (state->di)
+ break;
+ state->x = BITS(state->words[0], 16, 16);
+ state->zz = BITS(state->words[0], 17, 18);
+ state->aa = BITS(state->words[0], 22, 23);
+ state->wb_reg = FIELD_B(state->words[0]);
+ if (state->wb_reg == REG_LIMM) {
+ state->instr_len += 4;
+ state->src1 = state->words[1];
+ } else {
+ state->src1 = get_reg(state->wb_reg, regs,
+ cregs);
+ }
+ state->src2 = FIELD_C(state->words[0]);
+ if (state->src2 == REG_LIMM) {
+ state->instr_len += 4;
+ state->src2 = state->words[1];
+ } else {
+ state->src2 = get_reg(state->src2, regs,
+ cregs);
+ }
+ state->dest = FIELD_A(state->words[0]);
+ if (state->dest == REG_LIMM)
+ state->pref = 1;
+ break;
+
+ case 10: /* MOV */
+ /* still need to check for limm to extract instr len */
+ /* MOV is special case because it only takes 2 args */
+ switch (BITS(state->words[0], 22, 23)) {
+ case 0: /* OP a,b,c */
+ if (FIELD_C(state->words[0]) == REG_LIMM)
+ state->instr_len += 4;
+ break;
+ case 1: /* OP a,b,u6 */
+ break;
+ case 2: /* OP b,b,s12 */
+ break;
+ case 3: /* OP.cc b,b,c/u6 */
+ if ((!IS_BIT(state->words[0], 5)) &&
+ (FIELD_C(state->words[0]) == REG_LIMM))
+ state->instr_len += 4;
+ break;
+ }
+ break;
+
+
+ default:
+ /* Not a Load, Jump or Loop instruction */
+ /* still need to check for limm to extract instr len */
+ switch (BITS(state->words[0], 22, 23)) {
+ case 0: /* OP a,b,c */
+ if ((FIELD_B(state->words[0]) == REG_LIMM) ||
+ (FIELD_C(state->words[0]) == REG_LIMM))
+ state->instr_len += 4;
+ break;
+ case 1: /* OP a,b,u6 */
+ break;
+ case 2: /* OP b,b,s12 */
+ break;
+ case 3: /* OP.cc b,b,c/u6 */
+ if ((!IS_BIT(state->words[0], 5)) &&
+ ((FIELD_B(state->words[0]) == REG_LIMM) ||
+ (FIELD_C(state->words[0]) == REG_LIMM)))
+ state->instr_len += 4;
+ break;
+ }
+ break;
+ }
+ break;
+
+ /* 16 Bit Instructions */
+ case op_LD_ADD: /* LD_S|LDB_S|LDW_S a,[b,c] */
+ state->zz = BITS(state->words[0], 3, 4);
+ state->src1 = get_reg(FIELD_S_B(state->words[0]), regs, cregs);
+ state->src2 = get_reg(FIELD_S_C(state->words[0]), regs, cregs);
+ state->dest = FIELD_S_A(state->words[0]);
+ break;
+
+ case op_ADD_MOV_CMP:
+ /* check for limm, ignore mov_s h,b (== mov_s 0,b) */
+ if ((BITS(state->words[0], 3, 4) < 3) &&
+ (FIELD_S_H(state->words[0]) == REG_LIMM))
+ state->instr_len += 4;
+ break;
+
+ case op_S:
+ subopcode = BITS(state->words[0], 5, 7);
+ switch (subopcode) {
+ case 0: /* j_s */
+ case 1: /* j_s.d */
+ case 2: /* jl_s */
+ case 3: /* jl_s.d */
+ state->target = get_reg(FIELD_S_B(state->words[0]),
+ regs, cregs);
+ state->delay_slot = subopcode & 1;
+ state->flow = (subopcode >= 2) ?
+ direct_call : indirect_jump;
+ break;
+ case 7:
+ switch (BITS(state->words[0], 8, 10)) {
+ case 4: /* jeq_s [blink] */
+ case 5: /* jne_s [blink] */
+ case 6: /* j_s [blink] */
+ case 7: /* j_s.d [blink] */
+ state->delay_slot = (subopcode == 7);
+ state->flow = indirect_jump;
+ state->target = get_reg(31, regs, cregs);
+ default:
+ break;
+ }
+ default:
+ break;
+ }
+ break;
+
+ case op_LD_S: /* LD_S c, [b, u7] */
+ state->src1 = get_reg(FIELD_S_B(state->words[0]), regs, cregs);
+ state->src2 = FIELD_S_u7(state->words[0]);
+ state->dest = FIELD_S_C(state->words[0]);
+ break;
+
+ case op_LDB_S:
+ case op_STB_S:
+ /* no further handling required as byte accesses should not
+ * cause an unaligned access exception */
+ state->zz = 1;
+ break;
+
+ case op_LDWX_S: /* LDWX_S c, [b, u6] */
+ state->x = 1;
+ /* intentional fall-through */
+
+ case op_LDW_S: /* LDW_S c, [b, u6] */
+ state->zz = 2;
+ state->src1 = get_reg(FIELD_S_B(state->words[0]), regs, cregs);
+ state->src2 = FIELD_S_u6(state->words[0]);
+ state->dest = FIELD_S_C(state->words[0]);
+ break;
+
+ case op_ST_S: /* ST_S c, [b, u7] */
+ state->write = 1;
+ state->src1 = get_reg(FIELD_S_C(state->words[0]), regs, cregs);
+ state->src2 = get_reg(FIELD_S_B(state->words[0]), regs, cregs);
+ state->src3 = FIELD_S_u7(state->words[0]);
+ break;
+
+ case op_STW_S: /* STW_S c,[b,u6] */
+ state->write = 1;
+ state->zz = 2;
+ state->src1 = get_reg(FIELD_S_C(state->words[0]), regs, cregs);
+ state->src2 = get_reg(FIELD_S_B(state->words[0]), regs, cregs);
+ state->src3 = FIELD_S_u6(state->words[0]);
+ break;
+
+ case op_SP: /* LD_S|LDB_S b,[sp,u7], ST_S|STB_S b,[sp,u7] */
+ /* note: we are ignoring possibility of:
+ * ADD_S, SUB_S, PUSH_S, POP_S as these should not
+ * cause unaliged exception anyway */
+ state->write = BITS(state->words[0], 6, 6);
+ state->zz = BITS(state->words[0], 5, 5);
+ if (state->zz)
+ break; /* byte accesses should not come here */
+ if (!state->write) {
+ state->src1 = get_reg(28, regs, cregs);
+ state->src2 = FIELD_S_u7(state->words[0]);
+ state->dest = FIELD_S_B(state->words[0]);
+ } else {
+ state->src1 = get_reg(FIELD_S_B(state->words[0]), regs,
+ cregs);
+ state->src2 = get_reg(28, regs, cregs);
+ state->src3 = FIELD_S_u7(state->words[0]);
+ }
+ break;
+
+ case op_GP: /* LD_S|LDB_S|LDW_S r0,[gp,s11/s9/s10] */
+ /* note: ADD_S r0, gp, s11 is ignored */
+ state->zz = BITS(state->words[0], 9, 10);
+ state->src1 = get_reg(26, regs, cregs);
+ state->src2 = state->zz ? FIELD_S_s10(state->words[0]) :
+ FIELD_S_s11(state->words[0]);
+ state->dest = 0;
+ break;
+
+ case op_Pcl: /* LD_S b,[pcl,u10] */
+ state->src1 = regs->ret & ~3;
+ state->src2 = FIELD_S_u10(state->words[0]);
+ state->dest = FIELD_S_B(state->words[0]);
+ break;
+
+ case op_BR_S:
+ state->target = FIELD_S_s8(state->words[0]) + (addr & ~0x03);
+ state->flow = direct_jump;
+ state->is_branch = 1;
+ break;
+
+ case op_B_S:
+ fieldA = (BITS(state->words[0], 9, 10) == 3) ?
+ FIELD_S_s7(state->words[0]) :
+ FIELD_S_s10(state->words[0]);
+ state->target = fieldA + (addr & ~0x03);
+ state->flow = direct_jump;
+ state->is_branch = 1;
+ break;
+
+ case op_BL_S:
+ state->target = FIELD_S_s13(state->words[0]) + (addr & ~0x03);
+ state->flow = direct_call;
+ state->is_branch = 1;
+ break;
+
+ default:
+ break;
+ }
+
+ if (bytes_not_copied <= (8 - state->instr_len))
+ return;
+
+fault: state->fault = 1;
+}
+
+long __kprobes get_reg(int reg, struct pt_regs *regs,
+ struct callee_regs *cregs)
+{
+ long *p;
+
+ if (reg <= 12) {
+ p = ®s->r0;
+ return p[-reg];
+ }
+
+ if (cregs && (reg <= 25)) {
+ p = &cregs->r13;
+ return p[13-reg];
+ }
+
+ if (reg == 26)
+ return regs->r26;
+ if (reg == 27)
+ return regs->fp;
+ if (reg == 28)
+ return regs->sp;
+ if (reg == 31)
+ return regs->blink;
+
+ return 0;
+}
+
+void __kprobes set_reg(int reg, long val, struct pt_regs *regs,
+ struct callee_regs *cregs)
+{
+ long *p;
+
+ switch (reg) {
+ case 0 ... 12:
+ p = ®s->r0;
+ p[-reg] = val;
+ break;
+ case 13 ... 25:
+ if (cregs) {
+ p = &cregs->r13;
+ p[13-reg] = val;
+ }
+ break;
+ case 26:
+ regs->r26 = val;
+ break;
+ case 27:
+ regs->fp = val;
+ break;
+ case 28:
+ regs->sp = val;
+ break;
+ case 31:
+ regs->blink = val;
+ break;
+ default:
+ break;
+ }
+}
+
+/*
+ * Disassembles the insn at @pc and sets @next_pc to next PC (which could be
+ * @pc +2/4/6 (ARCompact ISA allows free intermixing of 16/32 bit insns).
+ *
+ * If @pc is a branch
+ * -@tgt_if_br is set to branch target.
+ * -If branch has delay slot, @next_pc updated with actual next PC.
+ *
+ */
+int __kprobes disasm_next_pc(unsigned long pc, struct pt_regs *regs,
+ struct callee_regs *cregs,
+ unsigned long *next_pc, unsigned long *tgt_if_br)
+{
+ struct disasm_state instr;
+
+ memset(&instr, 0, sizeof(struct disasm_state));
+ disasm_instr(pc, &instr, 0, regs, cregs);
+
+ *next_pc = pc + instr.instr_len;
+
+ /* Instruction with possible two targets branch, jump and loop */
+ if (instr.is_branch)
+ *tgt_if_br = instr.target;
+
+ /* For the instructions with delay slots, the fall through is the
+ * instruction following the instruction in delay slot.
+ */
+ if (instr.delay_slot) {
+ struct disasm_state instr_d;
+
+ disasm_instr(*next_pc, &instr_d, 0, regs, cregs);
+
+ *next_pc += instr_d.instr_len;
+ }
+
+ /* Zero Overhead Loop - end of the loop */
+ if (!(regs->status32 & STATUS32_L) && (*next_pc == regs->lp_end)
+ && (regs->lp_count > 1)) {
+ *next_pc = regs->lp_start;
+ }
+
+ return instr.is_branch;
+}
+
+#endif /* CONFIG_KGDB || CONFIG_MISALIGN_ACCESS || CONFIG_KPROBES */