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efi/libstub: Fix boot argument handling in mixed mode entry code 

The mixed mode refactor actually broke mixed mode by failing to
pass the bootparam structure to startup_32(). This went unnoticed
because it apparently has a high tolerance for being passed random
junk, and still boots fine in some cases. So let's fix this by
populating %esi as required when entering via efi32_stub_entry,
and while at it, preserve the arguments themselves instead of their
address in memory (via the stack pointer) since that memory could
be clobbered before we get to it.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Arvind Sankar <nivedita@alum.mit.edu>
Cc: Matthew Garrett <mjg59@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-efi@vger.kernel.org
Link: https://lkml.kernel.org/r/20200103113953.9571-2-ardb@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Ard Biesheuvel 2020-01-03 12:39:34 +01:00 committed by Ingo Molnar
parent 57ad87ddce
commit 12dc9e154d
1 changed files with 10 additions and 7 deletions
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17
arch/x86/boot/compressed/head_64.S
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@ -208,13 +208,12 @@ SYM_FUNC_START(startup_32)
pushl $__KERNEL_CS
leal startup_64(%ebp), %eax
#ifdef CONFIG_EFI_MIXED
movl efi32_boot_args(%ebp), %ebx
cmp $0, %ebx
movl efi32_boot_args(%ebp), %edi
cmp $0, %edi
jz 1f
leal handover_entry(%ebp), %eax
movl 0(%ebx), %edi
movl 4(%ebx), %esi
movl 8(%ebx), %edx
movl %esi, %edx
movl efi32_boot_args+4(%ebp), %esi
movl $0x0, %ecx
1:
#endif
@ -232,12 +231,16 @@ SYM_FUNC_END(startup_32)
.org 0x190
SYM_FUNC_START(efi32_stub_entry)
add $0x4, %esp /* Discard return address */
popl %ecx
popl %edx
popl %esi
call 1f
1: pop %ebp
subl $1b, %ebp
movl %esp, efi32_boot_args(%ebp)
movl %ecx, efi32_boot_args(%ebp)
movl %edx, efi32_boot_args+4(%ebp)
sgdtl efi32_boot_gdt(%ebp)
/* Disable paging */
@ -628,7 +631,7 @@ SYM_DATA_START_LOCAL(gdt)
SYM_DATA_END_LABEL(gdt, SYM_L_LOCAL, gdt_end)
#ifdef CONFIG_EFI_MIXED
SYM_DATA_LOCAL(efi32_boot_args, .long 0)
SYM_DATA_LOCAL(efi32_boot_args, .long 0, 0)
#endif
/*