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Implement gdbarch_stack_frame_destroyed_p for aarch64

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The internal AdaCore testsuite has a test that checks that an
out-of-scope watchpoint is deleted.  This fails on some aarch64
configurations, reporting an extra stop:

    (gdb) continue
    Continuing.

    Thread 3 hit Watchpoint 2: result

    Old value = 64
    New value = 0
    0x0000000040021648 in pck.get_val (seed=0, off_by_one=false) at [...]/pck.adb:13
    13	   end Get_Val;

I believe what is happening here is that the variable is stored at:

    <efa>   DW_AT_location    : 2 byte block: 91 7c 	(DW_OP_fbreg: -4)

and the extra stop is reported just before a return, when the ldp
instruction is executed:

   0x0000000040021644 <+204>:	ldp	x29, x30, [sp], #48
   0x0000000040021648 <+208>:	ret

This instruction modifies the frame base calculation, and so the test
picks up whatever memory is pointed to in the callee frame.

Implementing the gdbarch hook gdbarch_stack_frame_destroyed_p fixes
this problem.

As usual with this sort of patch, it has passed internal testing, but
I don't have a good way to try it with dejagnu.  So, I don't know
whether some existing test covers this.  I suspect there must be one,
but it's also worth noting that this test passes for aarch64 in some
configurations -- I don't know what causes one to fail and another to
succeed.
This commit is contained in:
Tom Tromey 2022-03-07 14:06:09 -07:00
parent 0a30596cfa
commit da729c5ccd
1 changed files with 22 additions and 0 deletions
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22
gdb/aarch64-tdep.c
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@ -3396,6 +3396,25 @@ aarch64_cannot_store_register (struct gdbarch *gdbarch, int regnum)
|| regnum == AARCH64_PAUTH_CMASK_REGNUM (tdep->pauth_reg_base));
}
/* Implement the stack_frame_destroyed_p gdbarch method. */
static int
aarch64_stack_frame_destroyed_p (struct gdbarch *gdbarch, CORE_ADDR pc)
{
CORE_ADDR func_start, func_end;
if (!find_pc_partial_function (pc, NULL, &func_start, &func_end))
return 0;
enum bfd_endian byte_order_for_code = gdbarch_byte_order_for_code (gdbarch);
uint32_t insn = read_memory_unsigned_integer (pc, 4, byte_order_for_code);
aarch64_inst inst;
if (aarch64_decode_insn (insn, &inst, 1, nullptr) != 0)
return 0;
return streq (inst.opcode->name, "ret");
}
/* Initialize the current architecture based on INFO. If possible,
re-use an architecture from ARCHES, which is a list of
architectures already created during this debugging session.
@ -3602,6 +3621,9 @@ aarch64_gdbarch_init (struct gdbarch_info info, struct gdbarch_list *arches)
set_gdbarch_long_double_format (gdbarch, floatformats_ia64_quad);
set_gdbarch_type_align (gdbarch, aarch64_type_align);
/* Detect whether PC is at a point where the stack has been destroyed. */
set_gdbarch_stack_frame_destroyed_p (gdbarch, aarch64_stack_frame_destroyed_p);
/* Internal <-> external register number maps. */
set_gdbarch_dwarf2_reg_to_regnum (gdbarch, aarch64_dwarf_reg_to_regnum);