efi/x86: Drop redundant .bss section

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@kernel.org>

diff --git a/arch/x86/boot/header.S b/arch/x86/boot/header.S
index 97d9b6d6c1af4d8c7ba42eafb58f81b34a185068..d59f6604bb421b089062a49cd988e9d1b9698b68 100644 (file)
--- a/arch/x86/boot/header.S
+++ b/arch/x86/boot/header.S
@@ -106,7 +106,7 @@ coff_header:
 #else
        .word   0x8664                          # x86-64
 #endif
-       .word   4                               # nr_sections
+       .word   3                               # nr_sections
        .long   0                               # TimeDateStamp
        .long   0                               # PointerToSymbolTable
        .long   1                               # NumberOfSymbols
@@ -248,25 +248,6 @@ section_table:
        .word   0                               # NumberOfLineNumbers
        .long   0x60500020                      # Characteristics (section flags)
 
-       #
-       # The offset & size fields are filled in by build.c.
-       #
-       .ascii  ".bss"
-       .byte   0
-       .byte   0
-       .byte   0
-       .byte   0
-       .long   0
-       .long   0x0
-       .long   0                               # Size of initialized data
-                                               # on disk
-       .long   0x0
-       .long   0                               # PointerToRelocations
-       .long   0                               # PointerToLineNumbers
-       .word   0                               # NumberOfRelocations
-       .word   0                               # NumberOfLineNumbers
-       .long   0xc8000080                      # Characteristics (section flags)
-
 #endif /* CONFIG_EFI_STUB */
 
        # Kernel attributes; used by setup.  This is part 1 of the

diff --git a/arch/x86/boot/tools/build.c b/arch/x86/boot/tools/build.c
index c08db2ee4ba27e2571f090804139ef973b2a18f8..f9f5761c5d0554d1a1ea594944a241bd34b6aed4 100644 (file)
--- 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 + text_start - file_sz;
 
        pe_header = get_unaligned_le32(&buf[0x3c]);
 
@@ -214,30 +216,18 @@ static void update_pecoff_text(unsigned int text_start, unsigned int file_sz)
         * Size of code: Subtract the size of the first sector (512 bytes)
         * which includes the header.
         */
-       put_unaligned_le32(file_sz - 512, &buf[pe_header + 0x1c]);
+       put_unaligned_le32(file_sz - 512 + bss_sz, &buf[pe_header + 0x1c]);
+
+       /* Size of image */
+       put_unaligned_le32(init_sz + text_start, &buf[pe_header + 0x50]);
 
        /*
         * 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]);
-
-       /* Size of image */
-       put_unaligned_le32(init_sz, &buf[pe_header + 0x50]);
-
-       update_pecoff_section_header_fields(".bss", file_sz, bss_sz, 0, 0);
+       update_pecoff_section_header_fields(".text", text_start, text_sz + bss_sz,
+                                           text_sz, text_start);
 }
 
 static int reserve_pecoff_reloc_section(int c)
@@ -278,9 +268,8 @@ static void efi_stub_entry_update(void)
 
 static inline void update_pecoff_setup_and_reloc(unsigned int size) {}
 static inline void update_pecoff_text(unsigned int text_start,
-                                     unsigned int file_sz) {}
-static inline void update_pecoff_bss(unsigned int file_sz,
-                                    unsigned int init_sz) {}
+                                     unsigned int file_sz,
+                                     unsigned int init_sz) {}
 static inline void efi_stub_defaults(void) {}
 static inline void efi_stub_entry_update(void) {}
 
@@ -406,9 +395,8 @@ int main(int argc, char ** argv)
        buf[0x1f1] = setup_sectors-1;
        put_unaligned_le32(sys_size, &buf[0x1f4]);
 
-       update_pecoff_text(setup_sectors * 512, i + (sys_size * 16));
        init_sz = get_unaligned_le32(&buf[0x260]);
-       update_pecoff_bss(i + (sys_size * 16), init_sz + setup_sectors * 512);
+       update_pecoff_text(setup_sectors * 512, i + (sys_size * 16), init_sz);
 
        efi_stub_entry_update();