Lean Sheng Tan has submitted this change. ( https://review.coreboot.org/c/coreboot/+/79752?usp=email )
Change subject: cpu/x86/64bit/mode_switch: Simplify assembly code ......................................................................
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 --- M src/arch/x86/include/mode_switch.h M src/cpu/x86/64bit/mode_switch.S 2 files changed, 45 insertions(+), 49 deletions(-)
Approvals: Jérémy Compostella: Looks good to me, but someone else must approve build bot (Jenkins): Verified Arthur Heymans: Looks good to me, approved
diff --git a/src/arch/x86/include/mode_switch.h b/src/arch/x86/include/mode_switch.h index 24efb1e..4235db9 100644 --- a/src/arch/x86/include/mode_switch.h +++ b/src/arch/x86/include/mode_switch.h @@ -3,10 +3,18 @@ #include <stdint.h>
#if ENV_X86_64 -int protected_mode_call_narg(uint32_t arg_count, - uint32_t func_ptr, +/* + * Assembly code that drops into protected mode and calls the function + * specified as first argument, which must have been compiled for x86_32. + * After the function returns it enters long mode again. + * The function pointer destination must be below 4GiB in physical memory. + * + * The called function has 0-3 arguments and returns an int. + */ +int protected_mode_call_3arg(uint32_t func_ptr, uint32_t opt_arg1, - uint32_t opt_arg2); + uint32_t opt_arg2, + uint32_t opt_arg3);
/* * Drops into protected mode and calls the function, which must have been compiled for x86_32. @@ -17,7 +25,7 @@ */ static inline int protected_mode_call(void *func) { - return protected_mode_call_narg(0, (uintptr_t)func, 0, 0); + return protected_mode_call_3arg((uintptr_t)func, 0, 0, 0); }
/* @@ -30,7 +38,7 @@ */ static inline int protected_mode_call_1arg(void *func, uint32_t arg1) { - return protected_mode_call_narg(1, (uintptr_t)func, arg1, 0); + return protected_mode_call_3arg((uintptr_t)func, arg1, 0, 0); }
/* @@ -43,7 +51,7 @@ */ static inline int protected_mode_call_2arg(void *func, uint32_t arg1, uint32_t arg2) { - return protected_mode_call_narg(2, (uintptr_t)func, arg1, arg2); + return protected_mode_call_3arg((uintptr_t)func, arg1, arg2, 0); } #else static inline int protected_mode_call(void *func) diff --git a/src/cpu/x86/64bit/mode_switch.S b/src/cpu/x86/64bit/mode_switch.S index c27f540..f9f784e 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 @@ movl %gs, %eax push %rax
- /* Arguments to stack */ - push %rdi - push %rsi - push %rdx - push %rcx + /* Store stack pointer */ + mov %rsp, %rbp
+ /* Align stack and make space for arguments */ + movabs $0xfffffffffffffff0, %rax + andq %rax, %rsp + sub $16, %rsp + + /* Arguments to stack */ + movl %edi, 12(%rsp) + movl %esi, 0(%rsp) + movl %edx, 4(%rsp) + movl %ecx, 8(%rsp) + + /* Drop to protected mode */ #include <cpu/x86/64bit/exit32.inc>
- movl -56(%ebp), %eax /* Argument count */ - movl -72(%ebp), %edx /* Argument 0 */ - movl -80(%ebp), %ecx /* Argument 1 */ + /* Fetch function to call */ + movl 12(%esp), %ebx
- /* Align the stack */ - andl $0xFFFFFFF0, %esp - test %eax, %eax - je 1f /* Zero arguments */ - - subl $1, %eax - test %eax, %eax - je 2f /* One argument */ - - /* Two arguments */ - subl $8, %esp - pushl %ecx /* Argument 1 */ - pushl %edx /* Argument 0 */ - jmp 1f -2: - subl $12, %esp - pushl %edx /* Argument 0 */ - -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