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SubjectRe: [PATCH] scripts/decodecode: Fix decoding for AArch64 (arm64) instructions
On Thu, Sep 28, 2017 at 11:55:47AM +0100, Will Deacon wrote:
> There are a couple of problems with the decodecode script and arm64:
>
> 1. AArch64 objdump refuses to disassemble .4byte directives as instructions,
> insisting that they are data values and displaying them as:
>
> a94153f3 .word 0xa94153f3 <-- trapping instruction
>
> This is resolved by using the .inst directive instead.
>
> 2. Disassembly of branch instructions attempts to provide the target as
> an offset from a symbol, e.g.:
>
> 0: 34000082 cbz w2, 10 <.text+0x10>
>
> however this falls foul of the grep -v, which matches lines containing
> ".text" and ends up removing all branch instructions from the dump.

Any idea why this doesn't affect other arches too ... or does it?

> This patch resolves both issues by using the .inst directive for 4-byte
> quantities on arm64 and stripping the resulting binaries (as is done on
> arm already) to remove the mapping symbols.
>
> Signed-off-by: Will Deacon <will.deacon@arm.com>
>
> ---
> scripts/decodecode | 8 ++++++++
> 1 file changed, 8 insertions(+)
>
> diff --git a/scripts/decodecode b/scripts/decodecode
> index d8824f37acce..67214ec5b2cb 100755
> --- a/scripts/decodecode
> +++ b/scripts/decodecode
> @@ -58,6 +58,14 @@ disas() {
> ${CROSS_COMPILE}strip $1.o
> fi
>
> + if [ "$ARCH" = "arm64" ]; then
> + if [ $width -eq 4 ]; then
> + type=inst

Can we merge with arm here, or does arm still support toolchains that
don't have .inst? Anyway, no big deal.

> + fi
> +
> + ${CROSS_COMPILE}strip $1.o
> + fi
> +
> ${CROSS_COMPILE}objdump $OBJDUMPFLAGS -S $1.o | \
> grep -v "/tmp\|Disassembly\|\.text\|^$" > $1.dis 2>&1

FWIW,

Reviewed-by: Dave Martin <Dave.Martin@arm.com>

Here's hoping someone runs this as a CGI script somewhere ;)

Cheers
---Dave

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