On Mon, Feb 17, 2020 at 03:48:18PM +0100, Ard Biesheuvel wrote:
> In commit
>
> c7fb93ec51d462ec ("x86/efi: Include a .bss section within the PE/COFF headers")
>
> we added a separate .bss section to the PE/COFF header of the compressed
> kernel describing the static memory footprint of the decompressor, to
> ensure that it has enough headroom to decompress itself.
>
> We can achieve the exact same result by increasing the virtual size of
> the .text section, without changing the raw size, which, as per the
> PE/COFF specification, requires the loader to zero initialize the delta.
>
> Doing so frees up a slot in the section table, which we will use later
> to describe the mixed mode entrypoint.
>
> Signed-off-by: Ard Biesheuvel <ardb@xxxxxxxxxx>
> ---
> arch/x86/boot/header.S | 21 +-----------
> arch/x86/boot/tools/build.c | 35 ++++++++------------
> 2 files changed, 14 insertions(+), 42 deletions(-)
>
> diff --git a/arch/x86/boot/tools/build.c b/arch/x86/boot/tools/build.c
> index 55e669d29e54..0c8c5a52f1f0 100644
> --- a/arch/x86/boot/tools/build.c
> +++ b/arch/x86/boot/tools/build.c
> @@ -203,10 +203,12 @@ static void update_pecoff_setup_and_reloc(unsigned int size)
> put_unaligned_le32(10, &buf[reloc_offset + 4]);
> }
>
> -static void update_pecoff_text(unsigned int text_start, unsigned int file_sz)
> +static void update_pecoff_text(unsigned int text_start, unsigned int file_sz,
> + unsigned int init_sz)
> {
> unsigned int pe_header;
> unsigned int text_sz = file_sz - text_start;
> + unsigned int bss_sz = init_sz - file_sz;
>
> pe_header = get_unaligned_le32(&buf[0x3c]);
>
> @@ -216,28 +218,19 @@ static void update_pecoff_text(unsigned int text_start, unsigned int file_sz)
> */
> put_unaligned_le32(file_sz - 512, &buf[pe_header + 0x1c]);
>
> - /*
> - * Address of entry point for PE/COFF executable
> - */
> - put_unaligned_le32(text_start + efi_pe_entry, &buf[pe_header + 0x28]);
> -
> - update_pecoff_section_header(".text", text_start, text_sz);
> -}
> -
> -static void update_pecoff_bss(unsigned int file_sz, unsigned int init_sz)
> -{
> - unsigned int pe_header;
> - unsigned int bss_sz = init_sz - file_sz;
> -
> - pe_header = get_unaligned_le32(&buf[0x3c]);
> -
> /* Size of uninitialized data */
> put_unaligned_le32(bss_sz, &buf[pe_header + 0x24]);
Should this still be populated given that there's no .bss section any
more?
