mirror of
https://github.com/torvalds/linux.git
synced 2024-11-17 01:22:07 +00:00
b17ed48040
Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: Huang Ying <ying.huang@intel.com>
124 lines
2.7 KiB
ArmAsm
124 lines
2.7 KiB
ArmAsm
/*
|
|
* EFI call stub for IA32.
|
|
*
|
|
* This stub allows us to make EFI calls in physical mode with interrupts
|
|
* turned off.
|
|
*/
|
|
|
|
#include <linux/linkage.h>
|
|
#include <asm/page_types.h>
|
|
|
|
/*
|
|
* efi_call_phys(void *, ...) is a function with variable parameters.
|
|
* All the callers of this function assure that all the parameters are 4-bytes.
|
|
*/
|
|
|
|
/*
|
|
* In gcc calling convention, EBX, ESP, EBP, ESI and EDI are all callee save.
|
|
* So we'd better save all of them at the beginning of this function and restore
|
|
* at the end no matter how many we use, because we can not assure EFI runtime
|
|
* service functions will comply with gcc calling convention, too.
|
|
*/
|
|
|
|
.text
|
|
ENTRY(efi_call_phys)
|
|
/*
|
|
* 0. The function can only be called in Linux kernel. So CS has been
|
|
* set to 0x0010, DS and SS have been set to 0x0018. In EFI, I found
|
|
* the values of these registers are the same. And, the corresponding
|
|
* GDT entries are identical. So I will do nothing about segment reg
|
|
* and GDT, but change GDT base register in prelog and epilog.
|
|
*/
|
|
|
|
/*
|
|
* 1. Now I am running with EIP = <physical address> + PAGE_OFFSET.
|
|
* But to make it smoothly switch from virtual mode to flat mode.
|
|
* The mapping of lower virtual memory has been created in prelog and
|
|
* epilog.
|
|
*/
|
|
movl $1f, %edx
|
|
subl $__PAGE_OFFSET, %edx
|
|
jmp *%edx
|
|
1:
|
|
|
|
/*
|
|
* 2. Now on the top of stack is the return
|
|
* address in the caller of efi_call_phys(), then parameter 1,
|
|
* parameter 2, ..., param n. To make things easy, we save the return
|
|
* address of efi_call_phys in a global variable.
|
|
*/
|
|
popl %edx
|
|
movl %edx, saved_return_addr
|
|
/* get the function pointer into ECX*/
|
|
popl %ecx
|
|
movl %ecx, efi_rt_function_ptr
|
|
movl $2f, %edx
|
|
subl $__PAGE_OFFSET, %edx
|
|
pushl %edx
|
|
|
|
/*
|
|
* 3. Clear PG bit in %CR0.
|
|
*/
|
|
movl %cr0, %edx
|
|
andl $0x7fffffff, %edx
|
|
movl %edx, %cr0
|
|
jmp 1f
|
|
1:
|
|
|
|
/*
|
|
* 4. Adjust stack pointer.
|
|
*/
|
|
subl $__PAGE_OFFSET, %esp
|
|
|
|
/*
|
|
* 5. Call the physical function.
|
|
*/
|
|
jmp *%ecx
|
|
|
|
2:
|
|
/*
|
|
* 6. After EFI runtime service returns, control will return to
|
|
* following instruction. We'd better readjust stack pointer first.
|
|
*/
|
|
addl $__PAGE_OFFSET, %esp
|
|
|
|
/*
|
|
* 7. Restore PG bit
|
|
*/
|
|
movl %cr0, %edx
|
|
orl $0x80000000, %edx
|
|
movl %edx, %cr0
|
|
jmp 1f
|
|
1:
|
|
/*
|
|
* 8. Now restore the virtual mode from flat mode by
|
|
* adding EIP with PAGE_OFFSET.
|
|
*/
|
|
movl $1f, %edx
|
|
jmp *%edx
|
|
1:
|
|
|
|
/*
|
|
* 9. Balance the stack. And because EAX contain the return value,
|
|
* we'd better not clobber it.
|
|
*/
|
|
leal efi_rt_function_ptr, %edx
|
|
movl (%edx), %ecx
|
|
pushl %ecx
|
|
|
|
/*
|
|
* 10. Push the saved return address onto the stack and return.
|
|
*/
|
|
leal saved_return_addr, %edx
|
|
movl (%edx), %ecx
|
|
pushl %ecx
|
|
ret
|
|
ENDPROC(efi_call_phys)
|
|
.previous
|
|
|
|
.data
|
|
saved_return_addr:
|
|
.long 0
|
|
efi_rt_function_ptr:
|
|
.long 0
|