executor: fix handling of big-endian bitfields

Currently we apply big-endian-ness and bitfield-ness in the wrong order in copyin.
This leads to totally bogus result. Fix this.

2 files changed, 22 insertions, 21 deletions

diff --git a/pkg/csource/csource.go b/pkg/csource/csource.go
index 49431f655..aa5f615e1 100644
--- a/pkg/csource/csource.go
+++ b/pkg/csource/csource.go
@@ -229,7 +229,7 @@ func (ctx *context) emitCall(w *bytes.Buffer, call prog.ExecCall, ci int, haveCo
 			if arg.Format != prog.FormatNative && arg.Format != prog.FormatBigEndian {
 				panic("sring format in syscall argument")
 			}
-			fmt.Fprintf(w, "%v", ctx.constArgToStr(arg))
+			fmt.Fprintf(w, "%v", ctx.constArgToStr(arg, true))
 		case prog.ExecArgResult:
 			if arg.Format != prog.FormatNative && arg.Format != prog.FormatBigEndian {
 				panic("sring format in syscall argument")
@@ -282,13 +282,17 @@ func (ctx *context) copyin(w *bytes.Buffer, csumSeq *int, copyin prog.ExecCopyin
 	switch arg := copyin.Arg.(type) {
 	case prog.ExecArgConst:
 		if arg.BitfieldOffset == 0 && arg.BitfieldLength == 0 {
-			ctx.copyinVal(w, copyin.Addr, arg.Size, ctx.constArgToStr(arg), arg.Format)
+			ctx.copyinVal(w, copyin.Addr, arg.Size, ctx.constArgToStr(arg, true), arg.Format)
 		} else {
 			if arg.Format != prog.FormatNative && arg.Format != prog.FormatBigEndian {
 				panic("bitfield+string format")
 			}
-			fmt.Fprintf(w, "\tNONFAILING(STORE_BY_BITMASK(uint%v, 0x%x, %v, %v, %v));\n",
-				arg.Size*8, copyin.Addr, ctx.constArgToStr(arg),
+			htobe := ""
+			if arg.Format == prog.FormatBigEndian {
+				htobe = fmt.Sprintf("htobe%v", arg.Size*8)
+			}
+			fmt.Fprintf(w, "\tNONFAILING(STORE_BY_BITMASK(uint%v, %v, 0x%x, %v, %v, %v));\n",
+				arg.Size*8, htobe, copyin.Addr, ctx.constArgToStr(arg, false),
 				arg.BitfieldOffset, arg.BitfieldLength)
 		}
 	case prog.ExecArgResult:
@@ -363,7 +367,7 @@ func (ctx *context) copyout(w *bytes.Buffer, call prog.ExecCall, resCopyout bool
 	}
 }
 
-func (ctx *context) constArgToStr(arg prog.ExecArgConst) string {
+func (ctx *context) constArgToStr(arg prog.ExecArgConst, handleBigEndian bool) string {
 	mask := (uint64(1) << (arg.Size * 8)) - 1
 	v := arg.Value & mask
 	val := fmt.Sprintf("%v", v)
@@ -375,7 +379,7 @@ func (ctx *context) constArgToStr(arg prog.ExecArgConst) string {
 	if ctx.opts.Procs > 1 && arg.PidStride != 0 {
 		val += fmt.Sprintf(" + procid*%v", arg.PidStride)
 	}
-	if arg.Format == prog.FormatBigEndian {
+	if handleBigEndian && arg.Format == prog.FormatBigEndian {
 		val = fmt.Sprintf("htobe%v(%v)", arg.Size*8, val)
 	}
 	return val
diff --git a/pkg/csource/generated.go b/pkg/csource/generated.go
index a7bfe74d0..0c3ecb4e8 100644
--- a/pkg/csource/generated.go
+++ b/pkg/csource/generated.go
@@ -310,19 +310,10 @@ static int event_timedwait(event_t* ev, uint64 timeout)
 #endif
 
 #if SYZ_EXECUTOR || SYZ_USE_BITMASKS
-#define BITMASK_LEN(type, bf_len) (type)((1ull << (bf_len)) - 1)
-
-#define BITMASK_LEN_OFF(type, bf_off, bf_len) (type)(BITMASK_LEN(type, (bf_len)) << (bf_off))
-
-#define STORE_BY_BITMASK(type, addr, val, bf_off, bf_len)                         \
-	if ((bf_off) == 0 && (bf_len) == 0) {                                     \
-		*(type*)(addr) = (type)(val);                                     \
-	} else {                                                                  \
-		type new_val = *(type*)(addr);                                    \
-		new_val &= ~BITMASK_LEN_OFF(type, (bf_off), (bf_len));            \
-		new_val |= ((type)(val)&BITMASK_LEN(type, (bf_len))) << (bf_off); \
-		*(type*)(addr) = new_val;                                         \
-	}
+#define BITMASK(bf_off, bf_len) (((1ull << (bf_len)) - 1) << (bf_off))
+#define STORE_BY_BITMASK(type, htobe, addr, val, bf_off, bf_len)                        \
+	*(type*)(addr) = htobe((htobe(*(type*)(addr)) & ~BITMASK((bf_off), (bf_len))) | \
+			       (((type)(val) << (bf_off)) & BITMASK((bf_off), (bf_len))))
 #endif
 
 #if SYZ_EXECUTOR || SYZ_USE_CHECKSUMS
@@ -3945,7 +3936,10 @@ static long syz_compare(long want, long want_len, long got, long got_len)
 		return -1;
 	}
 	if (memcmp((void*)want, (void*)got, want_len)) {
-		debug("syz_compare: data differs\n");
+		debug("syz_compare: data differs, want:\n");
+		debug_dump_data((char*)want, want_len);
+		debug("got:\n");
+		debug_dump_data((char*)got, got_len);
 		errno = EINVAL;
 		return -1;
 	}
@@ -4106,7 +4100,10 @@ static long syz_compare(long want, long want_len, long got, long got_len)
 		return -1;
 	}
 	if (memcmp((void*)want, (void*)got, want_len)) {
-		debug("syz_compare: data differs\n");
+		debug("syz_compare: data differs, want:\n");
+		debug_dump_data((char*)want, want_len);
+		debug("got:\n");
+		debug_dump_data((char*)got, got_len);
 		errno = EINVAL;
 		return -1;
 	}