Move the long return to switch to 32-bit mode into the trampoline code so it can be called as an ordinary function. This will allow it to be called directly from C code in a subsequent patch. Acked-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx> Signed-off-by: Ard Biesheuvel <ardb@xxxxxxxxxx> --- arch/x86/boot/compressed/head_64.S | 46 ++++++++++---------- arch/x86/boot/compressed/pgtable.h | 2 +- 2 files changed, 23 insertions(+), 25 deletions(-) diff --git a/arch/x86/boot/compressed/head_64.S b/arch/x86/boot/compressed/head_64.S index 2ccddec2220ce914..1892679be2b6897a 100644 --- a/arch/x86/boot/compressed/head_64.S +++ b/arch/x86/boot/compressed/head_64.S @@ -446,29 +446,9 @@ SYM_CODE_START(startup_64) /* Save the trampoline address in RCX */ movq %rax, %rcx - /* Set up 32-bit addressable stack */ - leaq TRAMPOLINE_32BIT_STACK_END(%rcx), %rsp - - /* - * Load the address of trampoline_return() into RDI and push it onto - * the stack so it will survive 32-bit truncation due to the 32-bit - * protected mode switch. It will be used by the trampoline to return - * to the main code. - */ - leaq trampoline_return(%rip), %rdi - pushq %rdi - - /* Preserve other live 64-bit registers */ - pushq %r15 - pushq %rbp - pushq %rbx - - /* Switch to compatibility mode (CS.L = 0 CS.D = 1) via far return */ - pushq $__KERNEL32_CS leaq TRAMPOLINE_32BIT_CODE_OFFSET(%rax), %rax - pushq %rax - lretq -trampoline_return: + call *%rax + /* Restore the stack, the 32-bit trampoline uses its own stack */ leaq rva(boot_stack_end)(%rbx), %rsp @@ -551,15 +531,33 @@ SYM_FUNC_START_LOCAL_NOALIGN(.Lrelocated) jmp *%rax SYM_FUNC_END(.Lrelocated) - .code32 /* * This is the 32-bit trampoline that will be copied over to low memory. * - * RDI contains the return address (might be above 4G). * ECX contains the base address of the trampoline memory. * Non zero RDX means trampoline needs to enable 5-level paging. */ SYM_CODE_START(trampoline_32bit_src) + /* Grab return address */ + movq (%rsp), %rax + + /* Set up 32-bit addressable stack */ + leaq TRAMPOLINE_32BIT_STACK_END(%rcx), %rsp + + /* Preserve return address and other live 64-bit registers */ + pushq %rax + pushq %r15 + pushq %rbp + pushq %rbx + + /* Switch to compatibility mode (CS.L = 0 CS.D = 1) via far return */ + pushq $__KERNEL32_CS + leaq 0f(%rip), %rax + pushq %rax + lretq + + .code32 +0: /* Set up data and stack segments */ movl $__KERNEL_DS, %eax movl %eax, %ds diff --git a/arch/x86/boot/compressed/pgtable.h b/arch/x86/boot/compressed/pgtable.h index cc9b2529a08634b4..91dbb99203fbce2d 100644 --- a/arch/x86/boot/compressed/pgtable.h +++ b/arch/x86/boot/compressed/pgtable.h @@ -6,7 +6,7 @@ #define TRAMPOLINE_32BIT_PGTABLE_OFFSET 0 #define TRAMPOLINE_32BIT_CODE_OFFSET PAGE_SIZE -#define TRAMPOLINE_32BIT_CODE_SIZE 0x80 +#define TRAMPOLINE_32BIT_CODE_SIZE 0xA0 #define TRAMPOLINE_32BIT_STACK_END TRAMPOLINE_32BIT_SIZE -- 2.39.2
