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gdb/s390-linux: Step over MVCLE+JO (and similiar) as a unit.

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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.
This commit is contained in:
Marcin Kościelnicki 2015-11-02 17:17:22 +01:00
parent 566c56c911
commit 6df5522640
2 changed files with 123 additions and 0 deletions
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8
gdb/ChangeLog
View file

@ -1,3 +1,11 @@
2015-11-04 Marcin Kościelnicki <koriakin@0x04.net>
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.
2015-11-04 Marcin Kościelnicki <koriakin@0x04.net>
PR/18376

115
gdb/s390-linux-tdep.c
View file

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