diff options
Diffstat (limited to 'arch/x86/platform/efi/efi_stub_32.S')
| -rw-r--r-- | arch/x86/platform/efi/efi_stub_32.S | 109 |
1 files changed, 17 insertions, 92 deletions
diff --git a/arch/x86/platform/efi/efi_stub_32.S b/arch/x86/platform/efi/efi_stub_32.S index eed8b5b441f8..75c46e7a809f 100644 --- a/arch/x86/platform/efi/efi_stub_32.S +++ b/arch/x86/platform/efi/efi_stub_32.S @@ -7,118 +7,43 @@ */ #include <linux/linkage.h> +#include <linux/init.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. - */ + __INIT +SYM_FUNC_START(efi_call_svam) + push 8(%esp) + push 8(%esp) + push %ecx + push %edx -.text -SYM_FUNC_START(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 prolog 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 prolog and - * epilog. + * Switch to the flat mapped alias of this routine, by jumping to the + * address of label '1' after subtracting PAGE_OFFSET from it. */ 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. - */ + /* disable paging */ movl %cr0, %edx andl $0x7fffffff, %edx movl %edx, %cr0 - jmp 1f -1: - /* - * 4. Adjust stack pointer. - */ + /* convert the stack pointer to a flat mapped address */ subl $__PAGE_OFFSET, %esp - /* - * 5. Call the physical function. - */ - jmp *%ecx + /* call the EFI routine */ + call *(%eax) -2: - /* - * 6. After EFI runtime service returns, control will return to - * following instruction. We'd better readjust stack pointer first. - */ - addl $__PAGE_OFFSET, %esp + /* convert ESP back to a kernel VA, and pop the outgoing args */ + addl $__PAGE_OFFSET + 16, %esp - /* - * 7. Restore PG bit - */ + /* re-enable paging */ 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 -SYM_FUNC_END(efi_call_phys) -.previous - -.data -saved_return_addr: - .long 0 -efi_rt_function_ptr: - .long 0 +SYM_FUNC_END(efi_call_svam) |