Re: [PATCH v3 binutils] Add BPF support to binutils...

[David Miller]

From: Alexei Starovoitov <a...@fb.com>
Date: Sat, 29 Apr 2017 17:48:43 -0700

> $ bld/binutils/objdump -S test.o
> 
> test.o:     file format elf64-bpfbe
> 
> Disassembly of section .text:
> 
> 0000000000000000 <bpf_prog1>:
>    0: 18 10 00 00 83 98 47 39         ldimm64 r1, 590618314553
>    8: 00 00 00 00 00 00 00 89
>   10: 7b a1 ff f8 00 00 00 00         stdw    [r10+65528], r1
>   18: 79 1a ff f8 00 00 00 00         lddw    r1, [r10+65528]
>   20: 07 10 00 00 8f ff 00 02         add     r1, -1879113726
>   28: 79 01 00 00 00 00 00 00         lddw    r0, [r1+0]
>   30: 95 00 00 00 00 00 00 00         exit
> 
> looks good except negative offsets are reported as large positive.

Some of your bugs should be fixed by this patch below, I'll add
test cases soon:

diff --git a/gas/config/tc-bpf.c b/gas/config/tc-bpf.c
index 0ba2afa..36393b7 100644
--- a/gas/config/tc-bpf.c
+++ b/gas/config/tc-bpf.c
@@ -288,6 +288,14 @@ md_assemble (char *str ATTRIBUTE_UNUSED)
          switch (*args)
            {
            case '+':
+             if (*s == '+')
+               {
+                 ++s;
+                 continue;
+               }
+             if (*s == '-')
+               continue;
+             break;
            case ',':
            case '[':
            case ']':
diff --git a/opcodes/bpf-dis.c b/opcodes/bpf-dis.c
index 92e29af..39656bf 100644
--- a/opcodes/bpf-dis.c
+++ b/opcodes/bpf-dis.c
@@ -49,7 +49,7 @@ print_insn_bpf (bfd_vma memaddr, disassemble_info *info)
   bpf_opcode_hash *op;
   int code, dest, src;
   bfd_byte buffer[8];
-  unsigned short off;
+  signed short off;
   int status, ret;
   signed int imm;
 
@@ -78,7 +78,7 @@ print_insn_bpf (bfd_vma memaddr, disassemble_info *info)
   else
     {
       getword = bfd_getl32;
-      gethalf = bfd_getl32;
+      gethalf = bfd_getl16;
     }  
 
   code = buffer[0];
@@ -128,7 +128,7 @@ print_insn_bpf (bfd_vma memaddr, disassemble_info *info)
              (*info->fprintf_func) (stream, "%d", imm);
              break;
            case 'O':
-             (*info->fprintf_func) (stream, "%d", off);
+             (*info->fprintf_func) (stream, "%d", (int) off);
              break;
            case 'L':
              info->target = memaddr + ((off - 1) * 8);