Support displaced stepping in aarch64-linux

This patch is to support displaced stepping in aarch64-linux.  A
visitor is implemented for displaced stepping, and used to record
information to fixup pc after displaced stepping if needed.  Some
emit_* functions are converted to macros, and moved to
arch/aarch64-insn.{c,h} so that they can be shared.

gdb:

2015-10-12  Yao Qi  <yao.qi@linaro.org>

	* aarch64-linux-tdep.c: Include arch-utils.h.
	(aarch64_linux_init_abi): Call set_gdbarch_max_insn_length,
	set_gdbarch_displaced_step_copy_insn,
	set_gdbarch_displaced_step_fixup,
	set_gdbarch_displaced_step_free_closure,
	set_gdbarch_displaced_step_location,
	and set_gdbarch_displaced_step_hw_singlestep.
	* aarch64-tdep.c (struct displaced_step_closure): New.
	(struct aarch64_displaced_step_data): New.
	(aarch64_displaced_step_b): New function.
	(aarch64_displaced_step_b_cond): Likewise.
	(aarch64_register): Likewise.
	(aarch64_displaced_step_cb): Likewise.
	(aarch64_displaced_step_tb): Likewise.
	(aarch64_displaced_step_adr): Likewise.
	(aarch64_displaced_step_ldr_literal): Likewise.
	(aarch64_displaced_step_others): Likewise.
	(aarch64_displaced_step_copy_insn): Likewise.
	(aarch64_displaced_step_fixup): Likewise.
	(aarch64_displaced_step_hw_singlestep): Likewise.
	* aarch64-tdep.h (DISPLACED_MODIFIED_INSNS): New macro.
	(aarch64_displaced_step_copy_insn): Declare.
	(aarch64_displaced_step_fixup): Declare.
	(aarch64_displaced_step_hw_singlestep): Declare.
	* arch/aarch64-insn.c (emit_insn): Moved from
	gdbserver/linux-aarch64-low.c.
	(emit_load_store): Likewise.
	* arch/aarch64-insn.h (enum aarch64_opcodes): Moved from
	gdbserver/linux-aarch64-low.c.
	(struct aarch64_register): Likewise.
	(struct aarch64_memory_operand): Likewise.
	(ENCODE): Likewise.
	(can_encode_int32): New macro.
	(emit_b, emit_bcond, emit_cb, emit_ldr, emit_ldrsw): Likewise.
	(emit_tb, emit_nop): Likewise.
	(emit_insn): Declare.
	(emit_load_store): Declare.

gdb/gdbserver:

2015-10-12  Yao Qi  <yao.qi@linaro.org>

	* linux-aarch64-low.c (enum aarch64_opcodes): Move to
	arch/aarch64-insn.h.
	(struct aarch64_memory_operand): Likewise.
	(ENCODE): Likewise.
	(emit_insn): Move to arch/aarch64-insn.c.
	(emit_b, emit_bcond, emit_cb, emit_tb): Remove.
	(emit_load_store): Move to arch/aarch64-insn.c.
	(emit_ldr, emit_ldrb, emit_ldrsw, emit_nop): Remove.
	(can_encode_int32): Remove.

2 files changed, 290 insertions, 0 deletions

diff --git a/gdb/arch/aarch64-insn.c b/gdb/arch/aarch64-insn.c
index d0e88fa..3bc0117 100644
--- a/gdb/arch/aarch64-insn.c
+++ b/gdb/arch/aarch64-insn.c
@@ -328,3 +328,61 @@ aarch64_relocate_instruction (uint32_t insn,
   else
     visitor->others (insn, data);
 }
+
+/* Write a 32-bit unsigned integer INSN info *BUF.  Return the number of
+   instructions written (aka. 1).  */
+
+int
+emit_insn (uint32_t *buf, uint32_t insn)
+{
+  *buf = insn;
+  return 1;
+}
+
+/* Helper function emitting a load or store instruction.  */
+
+int
+emit_load_store (uint32_t *buf, uint32_t size,
+		 enum aarch64_opcodes opcode,
+		 struct aarch64_register rt,
+		 struct aarch64_register rn,
+		 struct aarch64_memory_operand operand)
+{
+  uint32_t op;
+
+  switch (operand.type)
+    {
+    case MEMORY_OPERAND_OFFSET:
+      {
+	op = ENCODE (1, 1, 24);
+
+	return emit_insn (buf, opcode | ENCODE (size, 2, 30) | op
+			  | ENCODE (operand.index >> 3, 12, 10)
+			  | ENCODE (rn.num, 5, 5)
+			  | ENCODE (rt.num, 5, 0));
+      }
+    case MEMORY_OPERAND_POSTINDEX:
+      {
+	uint32_t post_index = ENCODE (1, 2, 10);
+
+	op = ENCODE (0, 1, 24);
+
+	return emit_insn (buf, opcode | ENCODE (size, 2, 30) | op
+			  | post_index | ENCODE (operand.index, 9, 12)
+			  | ENCODE (rn.num, 5, 5) | ENCODE (rt.num, 5, 0));
+      }
+    case MEMORY_OPERAND_PREINDEX:
+      {
+	uint32_t pre_index = ENCODE (3, 2, 10);
+
+	op = ENCODE (0, 1, 24);
+
+	return emit_insn (buf, opcode | ENCODE (size, 2, 30) | op
+			  | pre_index | ENCODE (operand.index, 9, 12)
+			  | ENCODE (rn.num, 5, 5)
+			  | ENCODE (rt.num, 5, 0));
+      }
+    default:
+      return 0;
+    }
+}
diff --git a/gdb/arch/aarch64-insn.h b/gdb/arch/aarch64-insn.h
index 47f6715..01a5d73 100644
--- a/gdb/arch/aarch64-insn.h
+++ b/gdb/arch/aarch64-insn.h
@@ -21,6 +21,129 @@
 
 extern int aarch64_debug;
 
+/* List of opcodes that we need for building the jump pad and relocating
+   an instruction.  */
+
+enum aarch64_opcodes
+{
+  /* B              0001 01ii iiii iiii iiii iiii iiii iiii */
+  /* BL             1001 01ii iiii iiii iiii iiii iiii iiii */
+  /* B.COND         0101 0100 iiii iiii iiii iiii iii0 cccc */
+  /* CBZ            s011 0100 iiii iiii iiii iiii iiir rrrr */
+  /* CBNZ           s011 0101 iiii iiii iiii iiii iiir rrrr */
+  /* TBZ            b011 0110 bbbb biii iiii iiii iiir rrrr */
+  /* TBNZ           b011 0111 bbbb biii iiii iiii iiir rrrr */
+  B               = 0x14000000,
+  BL              = 0x80000000 | B,
+  BCOND           = 0x40000000 | B,
+  CBZ             = 0x20000000 | B,
+  CBNZ            = 0x21000000 | B,
+  TBZ             = 0x36000000 | B,
+  TBNZ            = 0x37000000 | B,
+  /* BLR            1101 0110 0011 1111 0000 00rr rrr0 0000 */
+  BLR             = 0xd63f0000,
+  /* RET            1101 0110 0101 1111 0000 00rr rrr0 0000 */
+  RET             = 0xd65f0000,
+  /* STP            s010 100o o0ii iiii irrr rrrr rrrr rrrr */
+  /* LDP            s010 100o o1ii iiii irrr rrrr rrrr rrrr */
+  /* STP (SIMD&VFP) ss10 110o o0ii iiii irrr rrrr rrrr rrrr */
+  /* LDP (SIMD&VFP) ss10 110o o1ii iiii irrr rrrr rrrr rrrr */
+  STP             = 0x28000000,
+  LDP             = 0x28400000,
+  STP_SIMD_VFP    = 0x04000000 | STP,
+  LDP_SIMD_VFP    = 0x04000000 | LDP,
+  /* STR            ss11 100o 00xi iiii iiii xxrr rrrr rrrr */
+  /* LDR            ss11 100o 01xi iiii iiii xxrr rrrr rrrr */
+  /* LDRSW          1011 100o 10xi iiii iiii xxrr rrrr rrrr */
+  STR             = 0x38000000,
+  LDR             = 0x00400000 | STR,
+  LDRSW           = 0x80800000 | STR,
+  /* LDAXR          ss00 1000 0101 1111 1111 11rr rrrr rrrr */
+  LDAXR           = 0x085ffc00,
+  /* STXR           ss00 1000 000r rrrr 0111 11rr rrrr rrrr */
+  STXR            = 0x08007c00,
+  /* STLR           ss00 1000 1001 1111 1111 11rr rrrr rrrr */
+  STLR            = 0x089ffc00,
+  /* MOV            s101 0010 1xxi iiii iiii iiii iiir rrrr */
+  /* MOVK           s111 0010 1xxi iiii iiii iiii iiir rrrr */
+  MOV             = 0x52800000,
+  MOVK            = 0x20000000 | MOV,
+  /* ADD            s00o ooo1 xxxx xxxx xxxx xxxx xxxx xxxx */
+  /* SUB            s10o ooo1 xxxx xxxx xxxx xxxx xxxx xxxx */
+  /* SUBS           s11o ooo1 xxxx xxxx xxxx xxxx xxxx xxxx */
+  ADD             = 0x01000000,
+  SUB             = 0x40000000 | ADD,
+  SUBS            = 0x20000000 | SUB,
+  /* AND            s000 1010 xx0x xxxx xxxx xxxx xxxx xxxx */
+  /* ORR            s010 1010 xx0x xxxx xxxx xxxx xxxx xxxx */
+  /* ORN            s010 1010 xx1x xxxx xxxx xxxx xxxx xxxx */
+  /* EOR            s100 1010 xx0x xxxx xxxx xxxx xxxx xxxx */
+  AND             = 0x0a000000,
+  ORR             = 0x20000000 | AND,
+  ORN             = 0x00200000 | ORR,
+  EOR             = 0x40000000 | AND,
+  /* LSLV           s001 1010 110r rrrr 0010 00rr rrrr rrrr */
+  /* LSRV           s001 1010 110r rrrr 0010 01rr rrrr rrrr */
+  /* ASRV           s001 1010 110r rrrr 0010 10rr rrrr rrrr */
+  LSLV             = 0x1ac02000,
+  LSRV             = 0x00000400 | LSLV,
+  ASRV             = 0x00000800 | LSLV,
+  /* SBFM           s001 0011 0nii iiii iiii iirr rrrr rrrr */
+  SBFM            = 0x13000000,
+  /* UBFM           s101 0011 0nii iiii iiii iirr rrrr rrrr */
+  UBFM            = 0x40000000 | SBFM,
+  /* CSINC          s001 1010 100r rrrr cccc 01rr rrrr rrrr */
+  CSINC           = 0x9a800400,
+  /* MUL            s001 1011 000r rrrr 0111 11rr rrrr rrrr */
+  MUL             = 0x1b007c00,
+  /* MSR (register) 1101 0101 0001 oooo oooo oooo ooor rrrr */
+  /* MRS            1101 0101 0011 oooo oooo oooo ooor rrrr */
+  MSR             = 0xd5100000,
+  MRS             = 0x00200000 | MSR,
+  /* HINT           1101 0101 0000 0011 0010 oooo ooo1 1111 */
+  HINT            = 0xd503201f,
+  SEVL            = (5 << 5) | HINT,
+  WFE             = (2 << 5) | HINT,
+  NOP             = (0 << 5) | HINT,
+};
+
+/* Representation of a general purpose register of the form xN or wN.
+
+   This type is used by emitting functions that take registers as operands.  */
+
+struct aarch64_register
+{
+  unsigned num;
+  int is64;
+};
+
+/* Representation of a memory operand, used for load and store
+   instructions.
+
+   The types correspond to the following variants:
+
+   MEMORY_OPERAND_OFFSET:    LDR rt, [rn, #offset]
+   MEMORY_OPERAND_PREINDEX:  LDR rt, [rn, #index]!
+   MEMORY_OPERAND_POSTINDEX: LDR rt, [rn], #index  */
+
+struct aarch64_memory_operand
+{
+  /* Type of the operand.  */
+  enum
+    {
+      MEMORY_OPERAND_OFFSET,
+      MEMORY_OPERAND_PREINDEX,
+      MEMORY_OPERAND_POSTINDEX,
+    } type;
+  /* Index from the base register.  */
+  int32_t index;
+};
+
+/* Helper macro to mask and shift a value into a bitfield.  */
+
+#define ENCODE(val, size, offset) \
+  ((uint32_t) ((val & ((1ULL << size) - 1)) << offset))
+
 int aarch64_decode_adr (CORE_ADDR addr, uint32_t insn, int *is_adrp,
 			unsigned *rd, int32_t *offset);
 
@@ -86,4 +209,113 @@ void aarch64_relocate_instruction (uint32_t insn,
 				   const struct aarch64_insn_visitor *visitor,
 				   struct aarch64_insn_data *data);
 
+#define can_encode_int32(val, bits)			\
+  (((val) >> (bits)) == 0 || ((val) >> (bits)) == -1)
+
+/* Write a B or BL instruction into *BUF.
+
+     B  #offset
+     BL #offset
+
+   IS_BL specifies if the link register should be updated.
+   OFFSET is the immediate offset from the current PC.  It is
+   byte-addressed but should be 4 bytes aligned.  It has a limited range of
+   +/- 128MB (26 bits << 2).  */
+
+#define emit_b(buf, is_bl, offset) \
+  emit_insn (buf, ((is_bl) ? BL : B) | (ENCODE ((offset) >> 2, 26, 0)))
+
+/* Write a BCOND instruction into *BUF.
+
+     B.COND #offset
+
+   COND specifies the condition field.
+   OFFSET is the immediate offset from the current PC.  It is
+   byte-addressed but should be 4 bytes aligned.  It has a limited range of
+   +/- 1MB (19 bits << 2).  */
+
+#define emit_bcond(buf, cond, offset)			\
+  emit_insn (buf,					\
+	     BCOND | ENCODE ((offset) >> 2, 19, 5)	\
+	     | ENCODE ((cond), 4, 0))
+
+/* Write a CBZ or CBNZ instruction into *BUF.
+
+     CBZ  rt, #offset
+     CBNZ rt, #offset
+
+   IS_CBNZ distinguishes between CBZ and CBNZ instructions.
+   RN is the register to test.
+   OFFSET is the immediate offset from the current PC.  It is
+   byte-addressed but should be 4 bytes aligned.  It has a limited range of
+   +/- 1MB (19 bits << 2).  */
+
+#define emit_cb(buf, is_cbnz, rt, offset)		\
+  emit_insn (buf,					\
+	     ((is_cbnz) ? CBNZ : CBZ)			\
+	     | ENCODE (rt.is64, 1, 31)  /* sf */	\
+	     | ENCODE (offset >> 2, 19, 5) /* imm19 */	\
+	     | ENCODE (rt.num, 5, 0))
+
+/* Write a LDR instruction into *BUF.
+
+     LDR rt, [rn, #offset]
+     LDR rt, [rn, #index]!
+     LDR rt, [rn], #index
+
+   RT is the register to store.
+   RN is the base address register.
+   OFFSET is the immediate to add to the base address.  It is limited to
+   0 .. 32760 range (12 bits << 3).  */
+
+#define emit_ldr(buf, rt, rn, operand) \
+  emit_load_store (buf, rt.is64 ? 3 : 2, LDR, rt, rn, operand)
+
+/* Write a LDRSW instruction into *BUF.  The register size is 64-bit.
+
+     LDRSW xt, [rn, #offset]
+     LDRSW xt, [rn, #index]!
+     LDRSW xt, [rn], #index
+
+   RT is the register to store.
+   RN is the base address register.
+   OFFSET is the immediate to add to the base address.  It is limited to
+   0 .. 16380 range (12 bits << 2).  */
+
+#define emit_ldrsw(buf, rt, rn, operand)		\
+  emit_load_store (buf, 3, LDRSW, rt, rn, operand)
+
+
+/* Write a TBZ or TBNZ instruction into *BUF.
+
+   TBZ  rt, #bit, #offset
+   TBNZ rt, #bit, #offset
+
+   IS_TBNZ distinguishes between TBZ and TBNZ instructions.
+   RT is the register to test.
+   BIT is the index of the bit to test in register RT.
+   OFFSET is the immediate offset from the current PC.  It is
+   byte-addressed but should be 4 bytes aligned.  It has a limited range of
+   +/- 32KB (14 bits << 2).  */
+
+#define emit_tb(buf, is_tbnz, bit, rt, offset)	       \
+  emit_insn (buf,				       \
+	     ((is_tbnz) ? TBNZ: TBZ)		       \
+	     | ENCODE (bit >> 5, 1, 31) /* b5 */       \
+	     | ENCODE (bit, 5, 19) /* b40 */	       \
+	     | ENCODE (offset >> 2, 14, 5) /* imm14 */ \
+	     | ENCODE (rt.num, 5, 0))
+
+/* Write a NOP instruction into *BUF.  */
+
+#define emit_nop(buf) emit_insn (buf, NOP)
+
+int emit_insn (uint32_t *buf, uint32_t insn);
+
+int emit_load_store (uint32_t *buf, uint32_t size,
+		     enum aarch64_opcodes opcode,
+		     struct aarch64_register rt,
+		     struct aarch64_register rn,
+		     struct aarch64_memory_operand operand);
+
 #endif