[PATCH 1/2] morello: Fix objdump of adrp inst with negative offset - Gnu-morello - op-lists.linaro.org

6 Dec 2023


      Hi,
I'm submitting this patch on behalf of Benjamin Teoh benjamin.teoh@arm.com.
Regression testing on aarch64-none-elf showed the patch needed the expected
disassembly for an existing test changing, I'll submit that as a follow-on fix
in 2/2.
OK for users/ARM/morello-binutils-gdb-master?
Thanks,
Alex
-- >8 --
When an adrp instruction references a symbol that is more than a page
in memory behind the instruction, it would have a negative offset.
An example of this is:
foo:
        nop
        .zero 4096
        adrp c0, foo
where adrp references 'foo' that is more than a page in memory behind
it.
In the case where the offset is negative, when translating from its
binary format, the offset was seen as an unsigned integer, which
caused a spurious high bit set in the resolved address in the adrp
instruction like in:
0000000000400078 <foo>:
 400078:   d503201f   nop
        ...
 40107c:   f0ffffe0   adrp    c0, 100400000 <__bss_end__+0xfffeeff8>
There was an issue with how the imm field of the adrp instruction was
extracted in `aarch64_ext_imm`. The value was not sign extended
correctly for capability mode targets. This was caused by the imm
field having its `P` bit being removed before the sign extension,
which is exclusive to 64-bit capability targets. This was remedied
by shortening the width of the imm field before sign extending the
imm value, resulting in:
0000000000400078 <foo>:
 400078:   d503201f   nop
        ...
 40107c:   f0ffffe0   adrp    c0, 400000 <foo-0x78>