[efi] Allow for sections to be excluded from the generated PE file

Hybrid bzImage and UEFI binaries (such as wimboot) include a bzImage
header within a section starting at offset zero, with the PE header
effectively occupying unused space within this section.  This section
should not appear as a named section in the resulting PE file.

Allow for the existence of hidden sections that do not result in a
section header being written to the PE file.

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

1 files changed, 17 insertions, 6 deletions

diff --git a/src/util/elf2efi.c b/src/util/elf2efi.c
index 61ac0e277..5b3e785f5 100644
--- a/src/util/elf2efi.c
+++ b/src/util/elf2efi.c
@@ -181,6 +181,7 @@ struct pe_section {
 	struct pe_section *next;
 	EFI_IMAGE_SECTION_HEADER hdr;
 	void ( * fixup ) ( struct pe_section *section );
+	int hidden;
 	uint8_t contents[0];
 };
 
@@ -641,10 +642,12 @@ static struct pe_section * process_section ( struct elf_file *elf,
 	/* Update RVA limits */
 	start = new->hdr.VirtualAddress;
 	end = ( start + new->hdr.Misc.VirtualSize );
-	if ( ( ! *applicable_start ) || ( *applicable_start >= start ) )
-		*applicable_start = start;
-	if ( *applicable_end < end )
-		*applicable_end = end;
+	if ( ! new->hidden ) {
+		if ( ( ! *applicable_start ) || ( *applicable_start >= start ) )
+			*applicable_start = start;
+		if ( *applicable_end < end )
+			*applicable_end = end;
+	}
 	if ( data_start < code_end )
 		data_start = code_end;
 	if ( data_mid < data_start )
@@ -664,8 +667,11 @@ static struct pe_section * process_section ( struct elf_file *elf,
 		( data_end - data_mid );
 
 	/* Update remaining file header fields */
-	pe_header->nt.FileHeader.NumberOfSections++;
-	pe_header->nt.OptionalHeader.SizeOfHeaders += sizeof ( new->hdr );
+	if ( ! new->hidden ) {
+		pe_header->nt.FileHeader.NumberOfSections++;
+		pe_header->nt.OptionalHeader.SizeOfHeaders +=
+			sizeof ( new->hdr );
+	}
 	pe_header->nt.OptionalHeader.SizeOfImage =
 		efi_image_align ( data_end );
 
@@ -935,6 +941,7 @@ static void write_pe_file ( struct pe_header *pe_header,
 			    FILE *pe ) {
 	struct pe_section *section;
 	unsigned long fpos = 0;
+	unsigned int count = 0;
 
 	/* Align length of headers */
 	fpos = pe_header->nt.OptionalHeader.SizeOfHeaders =
@@ -962,12 +969,16 @@ static void write_pe_file ( struct pe_header *pe_header,
 
 	/* Write section headers */
 	for ( section = pe_sections ; section ; section = section->next ) {
+		if ( section->hidden )
+			continue;
 		if ( fwrite ( &section->hdr, sizeof ( section->hdr ),
 			      1, pe ) != 1 ) {
 			perror ( "Could not write section header" );
 			exit ( 1 );
 		}
+		count++;
 	}
+	assert ( count == pe_header->nt.FileHeader.NumberOfSections );
 
 	/* Write sections */
 	for ( section = pe_sections ; section ; section = section->next ) {