diff options
| author | Patrick Rudolph <patrick.rudolph@9elements.com> | 2023-12-28 07:44:26 +0100 |
|---|---|---|
| committer | Lean Sheng Tan <sheng.tan@9elements.com> | 2024-01-03 00:38:27 +0000 |
| commit | b4283a4fbbcc8702afa4d992789ca458a7df923a (patch) | |
| tree | c41be09ed596948596bfeda123554321c5c3fd3f /src/cpu/x86 | |
| parent | b14b96d29a5ed196b2205a1bbd239c23d684fa47 (diff) | |
cpu/x86/64bit/mode_switch: Simplify assembly code
Drop the first argument specifying the number of arguments pushed
to the stack. Instead always push the 3 arguments to stack and use
the first one as function pointer to call while in protected mode.
While on it add more comments and simplify register restore code.
Tested:
- On qemu can call x86_32 function and pass argument and return
value.
- Booted Lenovo X220 in x86_64 mode using x86_32 MRC.
Change-Id: I30809453a1800ba3c0df60acd7eca778841c520f
Signed-off-by: Patrick Rudolph <patrick.rudolph@9elements.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/79752
Reviewed-by: Arthur Heymans <arthur@aheymans.xyz>
Reviewed-by: Jérémy Compostella <jeremy.compostella@intel.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Diffstat (limited to 'src/cpu/x86')
| -rw-r--r-- | src/cpu/x86/64bit/mode_switch.S | 72 |
1 files changed, 30 insertions, 42 deletions
diff --git a/src/cpu/x86/64bit/mode_switch.S b/src/cpu/x86/64bit/mode_switch.S index c27f540ba3..f9f784e8c4 100644 --- a/src/cpu/x86/64bit/mode_switch.S +++ b/src/cpu/x86/64bit/mode_switch.S @@ -1,14 +1,13 @@ /* SPDX-License-Identifier: GPL-2.0-only */ +/* Calls a x86_32 function from x86_64 context */ .text .code64 .section ".text.protected_mode_call", "ax", @progbits - .globl protected_mode_call_narg -protected_mode_call_narg: - - push %rbp - mov %rsp, %rbp + .globl protected_mode_call_3arg +protected_mode_call_3arg: /* Preserve registers */ + push %rbp push %rbx push %r12 push %r13 @@ -19,58 +18,47 @@ protected_mode_call_narg: movl %gs, %eax push %rax - /* Arguments to stack */ - push %rdi - push %rsi - push %rdx - push %rcx - - #include <cpu/x86/64bit/exit32.inc> + /* Store stack pointer */ + mov %rsp, %rbp - movl -56(%ebp), %eax /* Argument count */ - movl -72(%ebp), %edx /* Argument 0 */ - movl -80(%ebp), %ecx /* Argument 1 */ + /* Align stack and make space for arguments */ + movabs $0xfffffffffffffff0, %rax + andq %rax, %rsp + sub $16, %rsp - /* Align the stack */ - andl $0xFFFFFFF0, %esp - test %eax, %eax - je 1f /* Zero arguments */ + /* Arguments to stack */ + movl %edi, 12(%rsp) + movl %esi, 0(%rsp) + movl %edx, 4(%rsp) + movl %ecx, 8(%rsp) - subl $1, %eax - test %eax, %eax - je 2f /* One argument */ + /* Drop to protected mode */ + #include <cpu/x86/64bit/exit32.inc> - /* Two arguments */ - subl $8, %esp - pushl %ecx /* Argument 1 */ - pushl %edx /* Argument 0 */ - jmp 1f -2: - subl $12, %esp - pushl %edx /* Argument 0 */ + /* Fetch function to call */ + movl 12(%esp), %ebx -1: - movl -64(%ebp), %ebx /* Function to call */ + /* Call function */ call *%ebx movl %eax, %ebx - /* Preserves ebx */ + /* Jump to long mode. Preserves ebx */ #include <cpu/x86/64bit/entry64.inc> /* Place return value in rax */ movl %ebx, %eax - /* Restore registers */ - mov -48(%rbp), %rbx - movl %ebx, %gs - mov -40(%rbp), %r15 - mov -32(%rbp), %r14 - mov -24(%rbp), %r13 - mov -16(%rbp), %r12 - mov -8(%rbp), %rbx - /* Restore stack pointer */ mov %rbp, %rsp + + /* Restore registers */ + pop %rbx + movl %ebx, %gs + pop %r15 + pop %r14 + pop %r13 + pop %r12 + pop %rbx pop %rbp ret |