pkg/csource: annotate syscall() args with their names

This annotates syscall arguments so they are easier to read without
having to pull out the syscall's man page. E.g:
  syscall(__NR_mmap, /*addr=*/0x21000000ul, /*len=*/0x1000ul,
/*prot=*/0ul, ...

Signed-off-by: Florent Revest <revest@chromium.org>

2 files changed, 16 insertions, 10 deletions

diff --git a/pkg/csource/csource.go b/pkg/csource/csource.go
index 0c9f78e71..54cf2fa39 100644
--- a/pkg/csource/csource.go
+++ b/pkg/csource/csource.go
@@ -351,25 +351,27 @@ func (ctx *context) fmtCallBody(call prog.ExecCall) string {
 		}
 		funcName = fmt.Sprintf("((intptr_t(*)(%v))CAST(%v))", args, callName)
 	}
-	for _, arg := range call.Args {
+	for i, arg := range call.Args {
 		switch arg := arg.(type) {
 		case prog.ExecArgConst:
 			if arg.Format != prog.FormatNative && arg.Format != prog.FormatBigEndian {
 				panic("string format in syscall argument")
 			}
+			com := ctx.argComment(call.Meta.Args[i], arg)
 			suf := ctx.literalSuffix(arg, native)
-			argsStrs = append(argsStrs, handleBigEndian(arg, ctx.constArgToStr(arg, suf)))
+			argsStrs = append(argsStrs, com+handleBigEndian(arg, ctx.constArgToStr(arg, suf)))
 		case prog.ExecArgResult:
 			if arg.Format != prog.FormatNative && arg.Format != prog.FormatBigEndian {
 				panic("string format in syscall argument")
 			}
+			com := ctx.argComment(call.Meta.Args[i], arg)
 			val := ctx.resultArgToStr(arg)
 			if native && ctx.target.PtrSize == 4 {
 				// syscall accepts args as ellipsis, resources are uint64
 				// and take 2 slots without the cast, which would be wrong.
 				val = "(intptr_t)" + val
 			}
-			argsStrs = append(argsStrs, val)
+			argsStrs = append(argsStrs, com+val)
 		default:
 			panic(fmt.Sprintf("unknown arg type: %+v", arg))
 		}
@@ -499,6 +501,10 @@ func (ctx *context) copyout(w *bytes.Buffer, call prog.ExecCall, resCopyout bool
 	}
 }
 
+func (ctx *context) argComment(field prog.Field, arg prog.ExecArg) string {
+	return "/*" + field.Name + "=" + "*/"
+}
+
 func (ctx *context) constArgToStr(arg prog.ExecArgConst, suffix string) string {
 	mask := (uint64(1) << (arg.Size * 8)) - 1
 	v := arg.Value & mask
diff --git a/pkg/csource/csource_test.go b/pkg/csource/csource_test.go
index 2eb8cd150..eb85fd77b 100644
--- a/pkg/csource/csource_test.go
+++ b/pkg/csource/csource_test.go
@@ -191,10 +191,10 @@ r0 = csource0(0x1)
 csource1(r0)
 `,
 			output: `
-res = syscall(SYS_csource0, 1);
+res = syscall(SYS_csource0, /*num=*/1);
 if (res != -1)
 	r[0] = res;
-syscall(SYS_csource1, r[0]);
+syscall(SYS_csource1, /*fd=*/r[0]);
 `,
 		},
 		{
@@ -207,15 +207,15 @@ csource6(&AUTO)
 `,
 			output: fmt.Sprintf(`
 NONFAILING(memcpy((void*)0x%x, "\x12\x34\x56\x78", 4));
-syscall(SYS_csource2, 0x%xul);
+syscall(SYS_csource2, /*buf=*/0x%xul);
 NONFAILING(memset((void*)0x%x, 0, 10));
-syscall(SYS_csource3, 0x%xul);
+syscall(SYS_csource3, /*buf=*/0x%xul);
 NONFAILING(memset((void*)0x%x, 48, 10));
-syscall(SYS_csource4, 0x%xul);
+syscall(SYS_csource4, /*buf=*/0x%xul);
 NONFAILING(memcpy((void*)0x%x, "0101010101", 10));
-syscall(SYS_csource5, 0x%xul);
+syscall(SYS_csource5, /*buf=*/0x%xul);
 NONFAILING(memcpy((void*)0x%x, "101010101010", 12));
-syscall(SYS_csource6, 0x%xul);
+syscall(SYS_csource6, /*buf=*/0x%xul);
 `,
 				target.DataOffset+0x40, target.DataOffset+0x40,
 				target.DataOffset+0x80, target.DataOffset+0x80,