[zbin] Change fixup semantics to support ROMs over 128k uncompressed

The option ROM header contains a one-byte field indicating the number
of 512-byte sectors in the ROM image.  Currently it is linked to
contain the number of uncompressed sectors, with an instruction to the
compressor to correct it.  This causes link failure when the
uncompressed size of the ROM image is over 128k.

Fix by replacing the SUBx compressor fixup with an ADDx fixup that
adds the total compressed output length, scaled as requested, to an
addend stored in the field where the final length value will be
placed.  This is similar to the behavior of ELF relocations, and
ensures that an overflow error will not be generated unless the
compressed size is still too large for the field.

This also allows us to do away with the _filesz_pgh and _filesz_sect
calculations exported by the linker script.

Output tested bitwise identical to the old SUBx mechanism on hd, dsk,
lkrn, and rom prefixes, on both 32-bit and 64-bit processors.

Modified-by: Michael Brown <mcb30@etherboot.org>
Signed-off-by: Michael Brown <mcb30@etherboot.org>

1 files changed, 76 insertions, 50 deletions

diff --git a/src/util/zbin.c b/src/util/zbin.c
index 1513289e..2adc35c9 100644
--- a/src/util/zbin.c
+++ b/src/util/zbin.c
@@ -38,7 +38,7 @@ struct zinfo_pack {
 	uint32_t align;
 };
 
-struct zinfo_subtract {
+struct zinfo_add {
 	char type[4];
 	uint32_t offset;
 	uint32_t divisor;
@@ -49,7 +49,7 @@ union zinfo_record {
 	struct zinfo_common common;
 	struct zinfo_copy copy;
 	struct zinfo_pack pack;
-	struct zinfo_subtract subtract;
+	struct zinfo_add add;
 };
 
 struct zinfo_file {
@@ -157,8 +157,9 @@ static int process_zinfo_copy ( struct input_file *input,
 	}
 
 	if ( DEBUG ) {
-		fprintf ( stderr, "COPY [%#zx,%#zx) to [%#zx,%#zx)\n", offset, ( offset + len ),
-			  output->len, ( output->len + len ) );
+		fprintf ( stderr, "COPY [%#zx,%#zx) to [%#zx,%#zx)\n",
+			  offset, ( offset + len ), output->len,
+			  ( output->len + len ) );
 	}
 
 	memcpy ( ( output->buf + output->len ),
@@ -194,8 +195,9 @@ static int process_zinfo_pack ( struct input_file *input,
 	}
 
 	if ( DEBUG ) {
-		fprintf ( stderr, "PACK [%#zx,%#zx) to [%#zx,%#zx)\n", offset, ( offset + len ),
-			  output->len, ( output->len + packed_len ) );
+		fprintf ( stderr, "PACK [%#zx,%#zx) to [%#zx,%#zx)\n",
+			  offset, ( offset + len ), output->len,
+			  ( output->len + packed_len ) );
 	}
 
 	output->len += packed_len;
@@ -207,78 +209,102 @@ static int process_zinfo_pack ( struct input_file *input,
 	return 0;
 }
 
-static int process_zinfo_subtract ( struct input_file *input,
-				    struct output_file *output,
-				    struct zinfo_subtract *subtract,
-				    size_t datasize ) {
-	size_t offset = subtract->offset;
+static int process_zinfo_add ( struct input_file *input,
+			       struct output_file *output,
+			       struct zinfo_add *add,
+			       size_t datasize ) {
+	size_t offset = add->offset;
 	void *target;
-	signed long raw_delta;
-	signed long delta;
-	unsigned long old;
-	unsigned long new;
+	signed long addend;
+	unsigned long size;
+	signed long val;
+	unsigned long mask;
 
 	if ( ( offset + datasize ) > output->len ) {
-		fprintf ( stderr, "Subtract at %#zx outside output buffer\n",
+		fprintf ( stderr, "Add at %#zx outside output buffer\n",
 			  offset );
 		return -1;
 	}
 
 	target = ( output->buf + offset );
-	raw_delta = ( align ( output->len, subtract->divisor ) -
-		      align ( input->len, subtract->divisor ) );
-	delta = ( raw_delta / ( ( signed long ) subtract->divisor ) );
+	size = ( align ( output->len, add->divisor ) / add->divisor );
 
 	switch ( datasize ) {
-	case 1: {
-		uint8_t *byte = target;
-		old = *byte;
-		*byte += delta;
-		new = *byte;
-		break; }
-	case 2: {
-		uint16_t *word = target;
-		old = *word;
-		*word += delta;
-		new = *word;
-		break; }
-	case 4: {
-		uint32_t *dword = target;
-		old = *dword;
-		*dword += delta;
-		new = *dword;
-		break; }
+	case 1:
+		addend = *( ( int8_t * ) target );
+		break;
+	case 2:
+		addend = *( ( int16_t * ) target );
+		break;
+	case 4:
+		addend = *( ( int32_t * ) target );
+		break;
 	default:
-		fprintf ( stderr, "Unsupported subtract datasize %d\n",
+		fprintf ( stderr, "Unsupported add datasize %d\n",
 			  datasize );
 		return -1;
 	}
 
+	val = size + addend;
+
+	/* The result of 1UL << ( 8 * sizeof(unsigned long) ) is undefined */
+	mask = ( ( datasize < sizeof ( mask ) ) ?
+		 ( ( 1UL << ( 8 * datasize ) ) - 1 ) : ~0UL );
+
+	if ( val < 0 ) {
+		fprintf ( stderr, "Add %s%#lx+%#lx at %#zx %sflows field\n",
+			  ( ( addend < 0 ) ? "-" : "" ), abs ( addend ), size,
+			  offset, ( ( addend < 0 ) ? "under" : "over" ) );
+		return -1;
+	}
+
+	if ( val & ~mask ) {
+		fprintf ( stderr, "Add %s%#lx+%#lx at %#zx overflows %d-byte "
+			  "field (%d bytes too big)\n",
+			  ( ( addend < 0 ) ? "-" : "" ), abs ( addend ), size,
+			  offset, datasize,
+			  ( ( val - mask - 1 ) * add->divisor ) );
+		return -1;
+	}
+
+	switch ( datasize ) {
+	case 1:
+		*( ( uint8_t * ) target ) = val;
+		break;
+	case 2:
+		*( ( uint16_t * ) target ) = val;
+		break;
+	case 4:
+		*( ( uint32_t * ) target ) = val;
+		break;
+	}
+
 	if ( DEBUG ) {
-		fprintf ( stderr, "SUBx [%#zx,%#zx) (%#lx+(%#lx/%#x)-(%#lx/%#x)) = %#lx\n",
-			  offset, ( offset + datasize ), old, output->len, subtract->divisor,
-			  input->len, subtract->divisor, new );
+		fprintf ( stderr, "ADDx [%#zx,%#zx) (%s%#lx+(%#lx/%#x)) = "
+			  "%#lx\n", offset, ( offset + datasize ),
+			  ( ( addend < 0 ) ? "-" : "" ), abs ( addend ),
+			  output->len, add->divisor, val );
 	}
 
 	return 0;
 }
 
-static int process_zinfo_subb ( struct input_file *input,
+static int process_zinfo_addb ( struct input_file *input,
 				struct output_file *output,
 				union zinfo_record *zinfo ) {
-	return process_zinfo_subtract ( input, output, &zinfo->subtract, 1 );
+	return process_zinfo_add ( input, output, &zinfo->add, 1 );
 }
 
-static int process_zinfo_subw ( struct input_file *input,
+static int process_zinfo_addw ( struct input_file *input,
 				struct output_file *output,
 				union zinfo_record *zinfo ) {
-	return process_zinfo_subtract ( input, output, &zinfo->subtract, 2 );
+	return process_zinfo_add ( input, output, &zinfo->add, 2 );
 }
 
-static int process_zinfo_subl ( struct input_file *input,
+static int process_zinfo_addl ( struct input_file *input,
 				struct output_file *output,
 				union zinfo_record *zinfo ) {
-	return process_zinfo_subtract ( input, output, &zinfo->subtract, 4 );
+	return process_zinfo_add ( input, output, &zinfo->add, 4 );
 }
 
 struct zinfo_processor {
@@ -291,9 +317,9 @@ struct zinfo_processor {
 static struct zinfo_processor zinfo_processors[] = {
 	{ "COPY", process_zinfo_copy },
 	{ "PACK", process_zinfo_pack },
-	{ "SUBB", process_zinfo_subb },
-	{ "SUBW", process_zinfo_subw },
-	{ "SUBL", process_zinfo_subl },
+	{ "ADDB", process_zinfo_addb },
+	{ "ADDW", process_zinfo_addw },
+	{ "ADDL", process_zinfo_addl },
 };
 
 static int process_zinfo ( struct input_file *input,