aarch64-tdep.c:379: internal-error: CORE_ADDR aarch64_analyze_prologue(gdbarch*, CORE_ADDR, CORE_ADDR, aarch64_prologue_cache*, {anonymous}::abstract_instruction_reader&): Assertion `inst.operands[0].qualifier == AARCH64_OPND_QLF_S_D' failed

Simon Marchi simon.marchi@polymtl.ca
Tue Apr 3 01:35:00 GMT 2018


On 2018-04-02 05:13, Dmitry Antipov wrote:
> IIUC a few types of STP and STR instructions are explicitly banned in
> aarch64_analyze_prologue():
> 
> f:
>         stp     x29, x30, [sp, #-160]!
>         mov     x29, sp
>         stp     q0, q1, [sp, #-16]!     ; Hmm...
>         ldp     x29, x30, [sp], #160
>         ret
> .end
> 
> The following dummy self-test...
> 
> diff --git a/gdb/aarch64-tdep.c b/gdb/aarch64-tdep.c
> index f08945ea07..42f9d00b64 100644
> --- a/gdb/aarch64-tdep.c
> +++ b/gdb/aarch64-tdep.c
> @@ -529,6 +529,22 @@ aarch64_analyze_prologue_test (void)
>    struct gdbarch *gdbarch = gdbarch_find_by_info (info);
>    SELF_CHECK (gdbarch != NULL);
> 
> +  {
> +    struct aarch64_prologue_cache cache;
> +    cache.saved_regs = trad_frame_alloc_saved_regs (gdbarch);
> +
> +    static const uint32_t insns[] = {
> +      0xa9b67bfd, /* stp       x29, x30, [sp, #-160]! */
> +      0x910003fd, /* mov       x29, sp */
> +      0xadbf87e0, /* stp       q0, q1, [sp, #-16]! */
> +      0xa8ca7bfd, /* ldp       x29, x30, [sp], #160 */
> +      0xd65f03c0  /* ret */
> +    };
> +
> +    instruction_reader_test reader (insns);
> +    (void)aarch64_analyze_prologue (gdbarch, 0, 128, &cache, reader);
> +  }
> +
> 
> ...raises gdb_assert():
> 
> (gdb) maintenance selftest
> Running selftest aarch64-analyze-prologue.
> ../../gdb/aarch64-tdep.c:379: internal-error: CORE_ADDR
> aarch64_analyze_prologue(gdbarch*, CORE_ADDR, CORE_ADDR,
> aarch64_prologue_cache*, {anonymous}::abstract_instruction_reader&):
> Assertion `inst.operands[0].qualifier == AARCH64_OPND_QLF_S_D' failed.
> 
> Can someone please explain why it is so?
> 
> Dmitry

Hi Dmitry,

My guess is that it follows this sentence from the AArch64 ABI [1]:

Registers v8-v15 must be preserved by a callee across subroutine calls; 
the remaining registers (v0-v7, v16-v31)do not need to be preserved (or 
should be preserved by the caller).  Additionally, only the bottom 
64-bits of each value stored in v8-v15 need to be preserved. The FPSR is 
a status register that holds the cumulative exception bits of the 
floating-point unit.  It contains the fields IDC, IXC, UFC, OFC, DZC, 
IOC and QC.  These fields are not preserved across a public interface 
and may have any value on entry to a subroutine.; it is the 
responsibility of the caller to preserve larger values

So it looks like the GDB code assumes that no-one would ever save the 
whole registers, because it is not necessary.  GDB should not use 
gdb_assert and crash on bad input.  I don't know what it should do 
instead in that specific case, that's the part that takes more time to 
think about :).

Simon

[1] 
http://infocenter.arm.com/help/topic/com.arm.doc.ihi0055b/IHI0055B_aapcs64.pdf



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