gdb/s390-linux: Step over MVCLE+JO (and similiar) as a unit.
This is needed to avoid O(n**2) complexity when recording MVCLE and other partial execution instructions. gdb/ChangeLog: PR/18376 * gdb/s390-linux-tdep.c (s390_is_partial_instruction): New function. (s390_software_single_step): New function. (s390_displaced_step_hw_singlestep): New function. (s390_gdbarch_init): Fill gdbarch slots with the above.
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@ -1,3 +1,11 @@
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2015-11-04 Marcin Kościelnicki <koriakin@0x04.net>
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PR/18376
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* gdb/s390-linux-tdep.c (s390_is_partial_instruction): New function.
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(s390_software_single_step): New function.
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(s390_displaced_step_hw_singlestep): New function.
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(s390_gdbarch_init): Fill gdbarch slots with the above.
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2015-11-04 Marcin Kościelnicki <koriakin@0x04.net>
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PR/18376
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@ -526,6 +526,119 @@ s390_pseudo_register_reggroup_p (struct gdbarch *gdbarch, int regnum,
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}
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/* A helper for s390_software_single_step, decides if an instruction
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is a partial-execution instruction that needs to be executed until
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completion when in record mode. If it is, returns 1 and writes
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instruction length to a pointer. */
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static int
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s390_is_partial_instruction (struct gdbarch *gdbarch, CORE_ADDR loc, int *len)
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{
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enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
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uint16_t insn;
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insn = read_memory_integer (loc, 2, byte_order);
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switch (insn >> 8)
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{
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case 0xa8: /* MVCLE */
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*len = 4;
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return 1;
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case 0xeb:
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{
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insn = read_memory_integer (loc + 4, 2, byte_order);
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if ((insn & 0xff) == 0x8e)
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{
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/* MVCLU */
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*len = 6;
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return 1;
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}
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}
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break;
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}
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switch (insn)
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{
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case 0xb255: /* MVST */
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case 0xb263: /* CMPSC */
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case 0xb2a5: /* TRE */
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case 0xb2a6: /* CU21 */
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case 0xb2a7: /* CU12 */
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case 0xb9b0: /* CU14 */
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case 0xb9b1: /* CU24 */
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case 0xb9b2: /* CU41 */
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case 0xb9b3: /* CU42 */
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case 0xb92a: /* KMF */
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case 0xb92b: /* KMO */
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case 0xb92f: /* KMC */
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case 0xb92d: /* KMCTR */
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case 0xb92e: /* KM */
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case 0xb93c: /* PPNO */
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case 0xb990: /* TRTT */
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case 0xb991: /* TRTO */
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case 0xb992: /* TROT */
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case 0xb993: /* TROO */
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*len = 4;
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return 1;
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}
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return 0;
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}
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/* Implement the "software_single_step" gdbarch method, needed to single step
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through instructions like MVCLE in record mode, to make sure they are
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executed to completion. Without that, record will save the full length
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of destination buffer on every iteration, even though the CPU will only
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process about 4kiB of it each time, leading to O(n**2) memory and time
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complexity. */
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static int
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s390_software_single_step (struct frame_info *frame)
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{
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struct gdbarch *gdbarch = get_frame_arch (frame);
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struct address_space *aspace = get_frame_address_space (frame);
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CORE_ADDR loc = get_frame_pc (frame);
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enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
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int len;
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uint16_t insn;
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/* Special handling only if recording. */
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if (!record_full_is_used ())
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return 0;
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/* First, match a partial instruction. */
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if (!s390_is_partial_instruction (gdbarch, loc, &len))
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return 0;
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loc += len;
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/* Second, look for a branch back to it. */
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insn = read_memory_integer (loc, 2, byte_order);
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if (insn != 0xa714) /* BRC with mask 1 */
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return 0;
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insn = read_memory_integer (loc + 2, 2, byte_order);
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if (insn != (uint16_t) -(len / 2))
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return 0;
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loc += 4;
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/* Found it, step past the whole thing. */
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insert_single_step_breakpoint (gdbarch, aspace, loc);
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return 1;
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}
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static int
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s390_displaced_step_hw_singlestep (struct gdbarch *gdbarch,
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struct displaced_step_closure *closure)
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{
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return 1;
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}
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/* Maps for register sets. */
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static const struct regcache_map_entry s390_gregmap[] =
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@ -7721,6 +7834,8 @@ s390_gdbarch_init (struct gdbarch_info info, struct gdbarch_list *arches)
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/* Stack grows downward. */
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set_gdbarch_inner_than (gdbarch, core_addr_lessthan);
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set_gdbarch_breakpoint_from_pc (gdbarch, s390_breakpoint_from_pc);
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set_gdbarch_software_single_step (gdbarch, s390_software_single_step);
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set_gdbarch_displaced_step_hw_singlestep (gdbarch, s390_displaced_step_hw_singlestep);
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set_gdbarch_skip_prologue (gdbarch, s390_skip_prologue);
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set_gdbarch_stack_frame_destroyed_p (gdbarch, s390_stack_frame_destroyed_p);
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