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x86/boot: Derive file size from _edata symbol 

Tweak the linker script so that the value of _edata represents the
decompressor binary's file size rounded up to the appropriate alignment.
This removes the need to calculate it in the build tool, and will make
it easier to refer to the file size from the header directly in
subsequent changes to the PE header layout.

While adding _edata to the sed regex that parses the compressed
vmlinux's symbol list, tweak the regex a bit for conciseness.

This change has no impact on the resulting bzImage binary when
configured with CONFIG_EFI_STUB=y.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20230915171623.655440-14-ardb@google.com
This commit is contained in:
Ard Biesheuvel 2023-09-15 17:16:28 +00:00 committed by Ingo Molnar
parent 093ab258e3
commit aeb92067f6
4 changed files with 12 additions and 25 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
arch/x86/boot/Makefile
View File

@ -89,7 +89,7 @@ $(obj)/vmlinux.bin: $(obj)/compressed/vmlinux FORCE
SETUP_OBJS = $(addprefix $(obj)/,$(setup-y))
sed-zoffset := -e 's/^\([0-9a-fA-F]*\) [a-zA-Z] \(startup_32\|efi32_stub_entry\|efi64_stub_entry\|efi_pe_entry\|efi32_pe_entry\|input_data\|kernel_info\|_end\|_ehead\|_text\|z_.*\)$$/\#define ZO_\2 0x\1/p'
sed-zoffset := -e 's/^\([0-9a-fA-F]*\) [a-zA-Z] \(startup_32\|efi.._stub_entry\|efi\(32\)\?_pe_entry\|input_data\|kernel_info\|_end\|_ehead\|_text\|_edata\|z_.*\)$$/\#define ZO_\2 0x\1/p'
quiet_cmd_zoffset = ZOFFSET $@
cmd_zoffset = $(NM) $< | sed -n $(sed-zoffset) > $@

3
arch/x86/boot/compressed/vmlinux.lds.S
View File

@ -47,6 +47,9 @@ SECTIONS
_data = . ;
*(.data)
*(.data.*)
/* Add 4 bytes of extra space for a CRC-32 checksum */
. = ALIGN(. + 4, 0x20);
_edata = . ;
}
. = ALIGN(L1_CACHE_BYTES);

2
arch/x86/boot/header.S
View File

@ -233,7 +233,7 @@ sentinel: .byte 0xff, 0xff /* Used to detect broken loaders */
hdr:
.byte setup_sects - 1
root_flags: .word ROOT_RDONLY
syssize: .long 0 /* Filled in by build.c */
syssize: .long ZO__edata / 16
ram_size: .word 0 /* Obsolete */
vid_mode: .word SVGA_MODE
root_dev: .word 0 /* Default to major/minor 0/0 */

30
arch/x86/boot/tools/build.c
View File

@ -52,6 +52,7 @@ u8 buf[SETUP_SECT_MAX*512];
static unsigned long efi_pe_entry;
static unsigned long efi32_pe_entry;
static unsigned long _edata;
static unsigned long _end;
/*----------------------------------------------------------------------*/
@ -308,6 +309,7 @@ static void parse_zoffset(char *fname)
while (p && *p) {
PARSE_ZOFS(p, efi_pe_entry);
PARSE_ZOFS(p, efi32_pe_entry);
PARSE_ZOFS(p, _edata);
PARSE_ZOFS(p, _end);
p = strchr(p, '\n');
@ -320,7 +322,6 @@ int main(int argc, char ** argv)
{
unsigned int i, sz, setup_sectors;
int c;
u32 sys_size;
struct stat sb;
FILE *file, *dest;
int fd;
@ -368,24 +369,14 @@ int main(int argc, char ** argv)
die("Unable to open `%s': %m", argv[2]);
if (fstat(fd, &sb))
die("Unable to stat `%s': %m", argv[2]);
sz = sb.st_size;
if (_edata != sb.st_size)
die("Unexpected file size `%s': %u != %u", argv[2], _edata,
sb.st_size);
sz = _edata - 4;
kernel = mmap(NULL, sz, PROT_READ, MAP_SHARED, fd, 0);
if (kernel == MAP_FAILED)
die("Unable to mmap '%s': %m", argv[2]);
/* Number of 16-byte paragraphs, including space for a 4-byte CRC */
sys_size = (sz + 15 + 4) / 16;
#ifdef CONFIG_EFI_STUB
/*
* COFF requires minimum 32-byte alignment of sections, and
* adding a signature is problematic without that alignment.
*/
sys_size = (sys_size + 1) & ~1;
#endif
/* Patch the setup code with the appropriate size parameters */
put_unaligned_le32(sys_size, &buf[0x1f4]);
update_pecoff_text(setup_sectors * 512, i + (sys_size * 16));
update_pecoff_text(setup_sectors * 512, i + _edata);
crc = partial_crc32(buf, i, crc);
@ -397,13 +388,6 @@ int main(int argc, char ** argv)
if (fwrite(kernel, 1, sz, dest) != sz)
die("Writing kernel failed");
/* Add padding leaving 4 bytes for the checksum */
while (sz++ < (sys_size*16) - 4) {
crc = partial_crc32_one('\0', crc);
if (fwrite("\0", 1, 1, dest) != 1)
die("Writing padding failed");
}
/* Write the CRC */
put_unaligned_le32(crc, buf);
if (fwrite(buf, 1, 4, dest) != 4)