On Monday 08 April 2019 20:04:22 Pavel Machek wrote: > 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?
Yea, it was mean as first April patch :-) I tested it with MS-DOS 7.0 and DOSBox and it worked. > You may want to retransmit? Do you really think it can be useful? :-) > 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 = .; > -- Pali Rohár [email protected]
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