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 <[email protected]>
Signed-off-by: Ard Biesheuvel <[email protected]>
---
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