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PPC64: Fix gdb.arch/ppc64-atomic-inst.exp with displaced stepping

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The ppc64 displaced step code can't handle atomic sequences.  Fallback
to stepping over the breakpoint in-line if we detect one.

gdb/ChangeLog:
2015-08-07  Pedro Alves  <palves@redhat.com>

	* infrun.c (displaced_step_prepare_throw): Return -1 if
	gdbarch_displaced_step_copy_insn returns NULL.  Update intro
	comment.
	* rs6000-tdep.c (LWARX_MASK, LWARX_INSTRUCTION, LDARX_INSTRUCTION)
	(STWCX_MASK, STWCX_INSTRUCTION, STDCX_INSTRUCTION): Move higher up
	in file.
	(ppc_displaced_step_copy_insn): New function.
	(ppc_displaced_step_fixup): Update comment.
	(rs6000_gdbarch_init): Install ppc_displaced_step_copy_insn as
	gdbarch_displaced_step_copy_insn hook.
	* gdbarch.sh (displaced_step_copy_insn): Document what happens on
	NULL return.
	* gdbarch.h: Regenerate.

gdb/testsuite/ChangeLog:
2015-08-07  Pedro Alves  <palves@redhat.com>

	* gdb.arch/ppc64-atomic-inst.exp (do_test): New procedure, move
	tests here.
	(top level): Run do_test with and without displaced stepping.
This commit is contained in:
Pedro Alves
2015-08-06 18:23:00 +01:00
parent 3fc8eb30a9
commit 7f03bd92e3
7 changed files with 135 additions and 38 deletions
Download Patch File Download Diff File Expand all files Collapse all files

68
gdb/rs6000-tdep.c
View File

@@ -974,6 +974,61 @@ rs6000_breakpoint_from_pc (struct gdbarch *gdbarch, CORE_ADDR *bp_addr,
#define BXL_INSN 0x4c000000
#define BP_INSN 0x7C000008
/* Instruction masks used during single-stepping of atomic
sequences. */
#define LWARX_MASK 0xfc0007fe
#define LWARX_INSTRUCTION 0x7c000028
#define LDARX_INSTRUCTION 0x7c0000A8
#define STWCX_MASK 0xfc0007ff
#define STWCX_INSTRUCTION 0x7c00012d
#define STDCX_INSTRUCTION 0x7c0001ad
/* We can't displaced step atomic sequences. Otherwise this is just
like simple_displaced_step_copy_insn. */
static struct displaced_step_closure *
ppc_displaced_step_copy_insn (struct gdbarch *gdbarch,
CORE_ADDR from, CORE_ADDR to,
struct regcache *regs)
{
size_t len = gdbarch_max_insn_length (gdbarch);
gdb_byte *buf = xmalloc (len);
struct cleanup *old_chain = make_cleanup (xfree, buf);
enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
int insn;
read_memory (from, buf, len);
insn = extract_signed_integer (buf, PPC_INSN_SIZE, byte_order);
/* Assume all atomic sequences start with a lwarx/ldarx instruction. */
if ((insn & LWARX_MASK) == LWARX_INSTRUCTION
|| (insn & LWARX_MASK) == LDARX_INSTRUCTION)
{
if (debug_displaced)
{
fprintf_unfiltered (gdb_stdlog,
"displaced: can't displaced step "
"atomic sequence at %s\n",
paddress (gdbarch, from));
}
do_cleanups (old_chain);
return NULL;
}
write_memory (to, buf, len);
if (debug_displaced)
{
fprintf_unfiltered (gdb_stdlog, "displaced: copy %s->%s: ",
paddress (gdbarch, from), paddress (gdbarch, to));
displaced_step_dump_bytes (gdb_stdlog, buf, len);
}
discard_cleanups (old_chain);
return (struct displaced_step_closure *) buf;
}
/* Fix up the state of registers and memory after having single-stepped
a displaced instruction. */
static void
@@ -983,8 +1038,7 @@ ppc_displaced_step_fixup (struct gdbarch *gdbarch,
struct regcache *regs)
{
enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
/* Since we use simple_displaced_step_copy_insn, our closure is a
copy of the instruction. */
/* Our closure is a copy of the instruction. */
ULONGEST insn = extract_unsigned_integer ((gdb_byte *) closure,
PPC_INSN_SIZE, byte_order);
ULONGEST opcode = 0;
@@ -1077,14 +1131,6 @@ ppc_displaced_step_hw_singlestep (struct gdbarch *gdbarch,
return 1;
}
/* Instruction masks used during single-stepping of atomic sequences. */
#define LWARX_MASK 0xfc0007fe
#define LWARX_INSTRUCTION 0x7c000028
#define LDARX_INSTRUCTION 0x7c0000A8
#define STWCX_MASK 0xfc0007ff
#define STWCX_INSTRUCTION 0x7c00012d
#define STDCX_INSTRUCTION 0x7c0001ad
/* Checks for an atomic sequence of instructions beginning with a LWARX/LDARX
instruction and ending with a STWCX/STDCX instruction. If such a sequence
is found, attempt to step through it. A breakpoint is placed at the end of
@@ -5923,7 +5969,7 @@ rs6000_gdbarch_init (struct gdbarch_info info, struct gdbarch_list *arches)
/* Setup displaced stepping. */
set_gdbarch_displaced_step_copy_insn (gdbarch,
simple_displaced_step_copy_insn);
ppc_displaced_step_copy_insn);
set_gdbarch_displaced_step_hw_singlestep (gdbarch,
ppc_displaced_step_hw_singlestep);
set_gdbarch_displaced_step_fixup (gdbarch, ppc_displaced_step_fixup);