Re: [PATCH v2] bpf: disasemble offsets of value 0 as "+0"

["Jose E. Marchesi" <jose.marchesi@oracle.com>]

Hi Faust.

Thanks for the patch.
OK.

> [Changes from v1:
>  - Also do the same for 32-bit offsets
>  - Add gas testsuite updates. ]
>
> This tiny patch makes the BPF disassembler to emit, e.g.
>
>   ldxdw %r1, [%r0+0]
>
> instead of
>
>   ldxdw %r1, [%r00]
>
> when the offset is 0, to avoid confusion.
>
> opcodes/
>
> 	* bpf-dis.c (print_insn_bpf): Print offsets with value 0 as "+0".
>
> gas/
>
> 	* testsuite/gas/bpf/mem.s: Add tests with offset 0.
> 	* testsuite/gas/bpf/mem-pseudoc.s: Likewise.
> 	* testsuite/gas/bpf/mem.d: Update accordingly.
> 	* testsuite/gas/bpf/mem-be.d: Likewise.
> 	* testsuite/gas/bpf/mem-pseudoc.d: Likewise.
> 	* testsuite/gas/bpf/mem-be-pseudoc.d: Likewise.
> ---
>  gas/testsuite/gas/bpf/mem-be-pseudoc.d | 2 ++
>  gas/testsuite/gas/bpf/mem-be.d         | 4 +++-
>  gas/testsuite/gas/bpf/mem-pseudoc.d    | 2 ++
>  gas/testsuite/gas/bpf/mem-pseudoc.s    | 2 ++
>  gas/testsuite/gas/bpf/mem.d            | 4 +++-
>  gas/testsuite/gas/bpf/mem.s            | 2 ++
>  opcodes/bpf-dis.c                      | 4 ++--
>  7 files changed, 16 insertions(+), 4 deletions(-)
>
> diff --git a/gas/testsuite/gas/bpf/mem-be-pseudoc.d b/gas/testsuite/gas/bpf/mem-be-pseudoc.d
> index 9a1ffc10984..5dff35c225d 100644
> --- a/gas/testsuite/gas/bpf/mem-be-pseudoc.d
> +++ b/gas/testsuite/gas/bpf/mem-be-pseudoc.d
> @@ -32,3 +32,5 @@ Disassembly of section .text:
>    a8:	89 21 7e ef 00 00 00 00 	r2=\*\(i16\*\)\(r1\+0x7eef\)
>    b0:	91 21 7e ef 00 00 00 00 	r2=\*\(i8\*\)\(r1\+0x7eef\)
>    b8:	99 21 7e ef 00 00 00 00 	r2=\*\(i64\*\)\(r1\+0x7eef\)
> +  c0:	58 05 00 00 00 00 00 00 	r0=\*\(u64\*\)skb\[r5\+0x0\]
> +  c8:	61 21 00 00 00 00 00 00 	r2=\*\(u32\*\)\(r1\+0x0\)
> diff --git a/gas/testsuite/gas/bpf/mem-be.d b/gas/testsuite/gas/bpf/mem-be.d
> index 5746b6a9485..cd7b35c60a3 100644
> --- a/gas/testsuite/gas/bpf/mem-be.d
> +++ b/gas/testsuite/gas/bpf/mem-be.d
> @@ -31,4 +31,6 @@ Disassembly of section .text:
>    a0:	81 21 7e ef 00 00 00 00 	ldxsw %r2,\[%r1\+0x7eef\]
>    a8:	89 21 7e ef 00 00 00 00 	ldxsh %r2,\[%r1\+0x7eef\]
>    b0:	91 21 7e ef 00 00 00 00 	ldxsb %r2,\[%r1\+0x7eef\]
> -  b8:	99 21 7e ef 00 00 00 00 	ldxsdw %r2,\[%r1\+0x7eef\]
> \ No newline at end of file
> +  b8:	99 21 7e ef 00 00 00 00 	ldxsdw %r2,\[%r1\+0x7eef\]
> +  c0:	79 21 00 00 00 00 00 00 	ldxdw %r2,\[%r1\+0x0\]
> +  c8:	40 03 00 00 00 00 00 00 	ldindw %r3,0x0
> diff --git a/gas/testsuite/gas/bpf/mem-pseudoc.d b/gas/testsuite/gas/bpf/mem-pseudoc.d
> index 8481048504d..ca94cef51cf 100644
> --- a/gas/testsuite/gas/bpf/mem-pseudoc.d
> +++ b/gas/testsuite/gas/bpf/mem-pseudoc.d
> @@ -32,3 +32,5 @@ Disassembly of section .text:
>    a8:	89 12 ef 7e 00 00 00 00 	r2=\*\(i16\*\)\(r1\+0x7eef\)
>    b0:	91 12 ef 7e 00 00 00 00 	r2=\*\(i8\*\)\(r1\+0x7eef\)
>    b8:	99 12 ef 7e 00 00 00 00 	r2=\*\(i64\*\)\(r1\+0x7eef\)
> +  c0:	58 50 00 00 00 00 00 00 	r0=\*\(u64\*\)skb\[r5\+0x0\]
> +  c8:	61 12 00 00 00 00 00 00 	r2=\*\(u32\*\)\(r1\+0x0\)
> diff --git a/gas/testsuite/gas/bpf/mem-pseudoc.s b/gas/testsuite/gas/bpf/mem-pseudoc.s
> index 1ffa2e25926..4a5e588b91a 100644
> --- a/gas/testsuite/gas/bpf/mem-pseudoc.s
> +++ b/gas/testsuite/gas/bpf/mem-pseudoc.s
> @@ -25,3 +25,5 @@
>          r2 = *(i16*)(r1+0x7eef)
>          r2 = *(i8*)(r1+0x7eef)
>          r2 = *(i64*)(r1+0x7eef)
> +	r0 = *(u64 *)skb[r5 + 0]
> +	r2 = *(u32 *)(r1 + 0)
> diff --git a/gas/testsuite/gas/bpf/mem.d b/gas/testsuite/gas/bpf/mem.d
> index 8b7a488ae01..9a1e7095df0 100644
> --- a/gas/testsuite/gas/bpf/mem.d
> +++ b/gas/testsuite/gas/bpf/mem.d
> @@ -31,4 +31,6 @@ Disassembly of section .text:
>    a0:	81 12 ef 7e 00 00 00 00 	ldxsw %r2,\[%r1\+0x7eef\]
>    a8:	89 12 ef 7e 00 00 00 00 	ldxsh %r2,\[%r1\+0x7eef\]
>    b0:	91 12 ef 7e 00 00 00 00 	ldxsb %r2,\[%r1\+0x7eef\]
> -  b8:	99 12 ef 7e 00 00 00 00 	ldxsdw %r2,\[%r1\+0x7eef\]
> \ No newline at end of file
> +  b8:	99 12 ef 7e 00 00 00 00 	ldxsdw %r2,\[%r1\+0x7eef\]
> +  c0:	79 12 00 00 00 00 00 00 	ldxdw %r2,\[%r1\+0x0\]
> +  c8:	40 30 00 00 00 00 00 00 	ldindw %r3,0x0
> diff --git a/gas/testsuite/gas/bpf/mem.s b/gas/testsuite/gas/bpf/mem.s
> index 6323cf1ede7..adeda473bb8 100644
> --- a/gas/testsuite/gas/bpf/mem.s
> +++ b/gas/testsuite/gas/bpf/mem.s
> @@ -26,3 +26,5 @@
>          ldxsh %r2, [%r1+0x7eef]
>          ldxsb %r2, [%r1+0x7eef]
>          ldxsdw %r2, [%r1+0x7eef]
> +	ldxdw %r2, [%r1+0]
> +	ldindw %r3, 0
> diff --git a/opcodes/bpf-dis.c b/opcodes/bpf-dis.c
> index a4dc3dc2523..4fe0efc2f96 100644
> --- a/opcodes/bpf-dis.c
> +++ b/opcodes/bpf-dis.c
> @@ -215,7 +215,7 @@ print_insn_bpf (bfd_vma pc, disassemble_info *info)
>                    if (p[1] == 'I')
>                      (*info->fprintf_styled_func) (info->stream, dis_style_immediate,
>                                                    "%s",
> -                                                  asm_obase != 10 || imm32 > 0 ? "+" : "");
> +						  asm_obase != 10 || imm32 >= 0 ? "+" : "");
>                    (*info->fprintf_styled_func) (info->stream, dis_style_immediate,
>                                                  asm_obase == 10 ? "%" PRIi32
>                                                  : asm_obase == 8 ? "%" PRIo32
> @@ -231,7 +231,7 @@ print_insn_bpf (bfd_vma pc, disassemble_info *info)
>                    if (p[1] == 'o')
>                      (*info->fprintf_styled_func) (info->stream, dis_style_immediate,
>                                                    "%s",
> -                                                  asm_obase != 10 || offset16 > 0 ? "+" : "");
> +						  asm_obase != 10 || offset16 >= 0 ? "+" : "");
>                    if (asm_obase == 16 || asm_obase == 8)
>                      (*info->fprintf_styled_func) (info->stream, dis_style_immediate,
>                                                    asm_obase == 8 ? "0%" PRIo16 : "0x%" PRIx16,