| /* |
| * EFI call stub for IA32. |
| * |
| * This stub allows us to make EFI calls in physical mode with interrupts |
| * turned off. Note that this implementation is different from the one in |
| * arch/x86/platform/efi/efi_stub_32.S because we're _already_ in physical |
| * mode at this point. |
| */ |
| |
| #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. Because we haven't been relocated by this point we need to |
| * use relative addressing. |
| */ |
| call 1f |
| 1: popl %edx |
| subl $1b, %edx |
| |
| /* |
| * 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 %ecx |
| movl %ecx, saved_return_addr(%edx) |
| /* get the function pointer into ECX*/ |
| popl %ecx |
| movl %ecx, efi_rt_function_ptr(%edx) |
| |
| /* |
| * 3. Call the physical function. |
| */ |
| call *%ecx |
| |
| /* |
| * 4. Balance the stack. And because EAX contain the return value, |
| * we'd better not clobber it. We need to calculate our address |
| * again because %ecx and %edx are not preserved across EFI function |
| * calls. |
| */ |
| call 1f |
| 1: popl %edx |
| subl $1b, %edx |
| |
| movl efi_rt_function_ptr(%edx), %ecx |
| pushl %ecx |
| |
| /* |
| * 10. Push the saved return address onto the stack and return. |
| */ |
| movl saved_return_addr(%edx), %ecx |
| pushl %ecx |
| ret |
| ENDPROC(efi_call_phys) |
| .previous |
| |
| .data |
| saved_return_addr: |
| .long 0 |
| efi_rt_function_ptr: |
| .long 0 |
