From e8fc65713d6e050348d443f9be7b61e6f54c6371 Mon Sep 17 00:00:00 2001
From: David Faust <david.faust@oracle.com>
Date: Fri, 21 Jul 2023 11:41:43 -0700
Subject: [PATCH] bpf: disasemble offsets of value 0 as "+0"

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,
-- 
2.30.2