On Mon 2019-04-01 12:24:34, Pali Rohár wrote: > Every EFI binary is in PE format. And we know that PE format needs to have > MZ MS-DOS header as there is written offset to PE header. > > Therefore generated bzImage binary with CONFIG_EFI_STUB option is MS-DOS > executable binary. > > We already know the "requirement" that Windows PE executable started in > MS-DOS must print legendary and famous message to computer screen: > "This program cannot be run in DOS mode." > > But trying to run that bzImage of Linux kernel with MZ header just cause > freezing whole MS-DOS instead of writing "the correct message" to user. > This is not the compliant behavior of PE executables! > > This patch fixes this problem. When Linux kernel compiled with > CONFIG_EFI_STUB is started in MS-DOS then it prints message: > > This program cannot be run in DOS mode. > To load Linux kernel from DOS mode use LOADLIN.EXE. > > So it also helps MS-DOS users how to "correctly" start this bzImage binary > by mentioning LOADLIN.EXE. Note that MS-DOS strings are not null-terminated > but rather dollar-terminated. > > To have error message unified bugger_off_msg for BIOS boot block code was > changed to: > > This program cannot be run in BIOS mode. > > So if you copy generated bzImage directly to boot sector and try to boot it > by BIOS you get this new updated message. > > Due to fixed offset of setup header (0x1f1), PE header was moved after > entrytext section. bstext and bsdata sections where is full MZ header and > MS-DOS code is now bigger.
Hehe, I guess the patch may have been dropped due to april's fools?
You may want to retransmit?
Pavel
> Signed-off-by: Pali Rohár <[email protected]>
> ---
> arch/x86/boot/header.S | 55
> +++++++++++++++++++++++++++++++++++++++++++-------
> arch/x86/boot/setup.ld | 1 +
> 2 files changed, 49 insertions(+), 7 deletions(-)
>
> diff --git a/arch/x86/boot/header.S b/arch/x86/boot/header.S
> index 850b8762e889..58fcab7d00c8 100644
> --- a/arch/x86/boot/header.S
> +++ b/arch/x86/boot/header.S
> @@ -45,6 +45,46 @@ bootsect_start:
> # "MZ", MS-DOS header
> .byte 0x4d
> .byte 0x5a
> +
> + # Explicitly enter this as bytes, or the assembler
> + # tries to generate a 3-byte jump here, which causes
> + # everything else to push off to the wrong offset.
> + .byte 0xeb # short (2-byte) jump
> + .byte bios_start-1f
> +1:
> +
> + .org 0x04
> + .short 3 # e_cp - Pages in file
> + .short 0 # e_crlc - Relocations
> + .short 4 # e_cparhdr - Size of header in paragraphs
> + .short 0 # e_minalloc - Minimum extra paragraphs needed
> + .short 0xffff # e_maxalloc - Maximum extra paragraphs needed
> + .short 0 # e_ss - Initial (relative) SS value
> + .short 0 # e_sp - Initial SP value
> + .short 0 # e_csum - Checksum
> + .short 0 # e_ip - Initial IP value
> + .short -4 # e_cs - Initial (relative) CS value
> + .short 0x40 # e_lfarlc - File address of relocation table
> +
> + .org 0x3c
> + .long pe_header # Offset to the PE header
> +
> + #
> + # MS-DOS start code
> + #
> + push %cs
> + pop %ds
> +
> + # Write msdos_msg string
> + mov $msdos_msg, %dx
> + mov $0x09, %ah
> + int $0x21
> +
> + # Terminate program
> + mov $0x4c01, %ax
> + int $0x21
> +
> +bios_start:
> #endif
>
> # Normalize the start address
> @@ -80,22 +120,23 @@ bs_die:
> # invoke the BIOS reset code...
> ljmp $0xf000,$0xfff0
>
> + .section ".bsdata", "a"
> #ifdef CONFIG_EFI_STUB
> - .org 0x3c
> - #
> - # Offset to the PE header.
> - #
> - .long pe_header
> +msdos_msg:
> + .ascii "This program cannot be run in DOS mode.\r\n"
> + .ascii "To load Linux kernel from DOS mode use LOADLIN.EXE.\r\r\n"
> + .ascii "$"
> #endif /* CONFIG_EFI_STUB */
>
> - .section ".bsdata", "a"
> bugger_off_msg:
> - .ascii "Use a boot loader.\r\n"
> + .ascii "This program cannot be run in BIOS mode.\r\n"
> + .ascii "To load Linux kernel from BIOS mode use a boot loader.\r\n"
> .ascii "\n"
> .ascii "Remove disk and press any key to reboot...\r\n"
> .byte 0
>
> #ifdef CONFIG_EFI_STUB
> + .section ".pedata", "a"
> pe_header:
> .ascii "PE"
> .word 0
> diff --git a/arch/x86/boot/setup.ld b/arch/x86/boot/setup.ld
> index 0149e41d42c2..c0ec2fe09d2d 100644
> --- a/arch/x86/boot/setup.ld
> +++ b/arch/x86/boot/setup.ld
> @@ -16,6 +16,7 @@ SECTIONS
> . = 495;
> .header : { *(.header) }
> .entrytext : { *(.entrytext) }
> + .pedata : { *(.pedata) }
> .inittext : { *(.inittext) }
> .initdata : { *(.initdata) }
> __end_init = .;
--
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures)
http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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