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efi/x86: Make efi32_pe_entry() more readable

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Set up a proper frame pointer in efi32_pe_entry() so that it's easier to
calculate offsets for arguments.

Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20200301230436.2246909-4-nivedita@alum.mit.edu
Link: https://lore.kernel.org/r/20200308080859.21568-12-ardb@kernel.org
This commit is contained in:
Arvind Sankar 2020-03-08 09:08:42 +01:00 committed by Ingo Molnar
parent 71ff44ac6c
commit 3fab43318f
1 changed files with 49 additions and 26 deletions
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75
arch/x86/boot/compressed/head_64.S
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@ -658,42 +658,65 @@ SYM_DATA(efi_is64, .byte 1)
.text
.code32
SYM_FUNC_START(efi32_pe_entry)
pushl %ebp
/*
* efi_status_t efi32_pe_entry(efi_handle_t image_handle,
* efi_system_table_32_t *sys_table)
*/
pushl %ebx
pushl %ebp
movl %esp, %ebp
pushl %eax // dummy push to allocate loaded_image
pushl %ebx // save callee-save registers
pushl %edi
call verify_cpu // check for long mode support
popl %edi
popl %ebx
testl %eax, %eax
movl $0x80000003, %eax // EFI_UNSUPPORTED
jnz 3f
call 1f
1: pop %ebp
subl $1b, %ebp
/* Get the loaded image protocol pointer from the image handle */
subl $12, %esp // space for the loaded image pointer
pushl %esp // pass its address
leal loaded_image_proto(%ebp), %eax
pushl %eax // pass the GUID address
pushl 28(%esp) // pass the image handle
movl 36(%esp), %eax // sys_table
movl ST32_boottime(%eax), %eax // sys_table->boottime
call *BS32_handle_protocol(%eax) // sys_table->boottime->handle_protocol
cmp $0, %eax
jnz 2f
movl 32(%esp), %ecx // image_handle
movl 36(%esp), %edx // sys_table
movl 12(%esp), %esi // loaded_image
call 1f
1: pop %ebx
subl $1b, %ebx
/* Get the loaded image protocol pointer from the image handle */
leal -4(%ebp), %eax
pushl %eax // &loaded_image
leal loaded_image_proto(%ebx), %eax
pushl %eax // pass the GUID address
pushl 8(%ebp) // pass the image handle
/*
* Note the alignment of the stack frame.
* sys_table
* handle <-- 16-byte aligned on entry by ABI
* return address
* frame pointer
* loaded_image <-- local variable
* saved %ebx <-- 16-byte aligned here
* saved %edi
* &loaded_image
* &loaded_image_proto
* handle <-- 16-byte aligned for call to handle_protocol
*/
movl 12(%ebp), %eax // sys_table
movl ST32_boottime(%eax), %eax // sys_table->boottime
call *BS32_handle_protocol(%eax) // sys_table->boottime->handle_protocol
addl $12, %esp // restore argument space
testl %eax, %eax
jnz 2f
movl 8(%ebp), %ecx // image_handle
movl 12(%ebp), %edx // sys_table
movl -4(%ebp), %esi // loaded_image
movl LI32_image_base(%esi), %esi // loaded_image->image_base
movl %ebx, %ebp // startup_32 for efi32_pe_stub_entry
jmp efi32_pe_stub_entry
2: addl $24, %esp
3: popl %ebp
2: popl %edi // restore callee-save registers
popl %ebx
leave
ret
SYM_FUNC_END(efi32_pe_entry)