@@ -405,10 +405,14 @@ SYM_CODE_START(startup_64)
lretq
.Lon_kernel_cs:
+ /*
+ * RSI holds a pointer to a boot_params structure provided by the
+ * loader, and this needs to be preserved across C function calls. So
+ * move it into a callee saved register.
+ */
+ movq %rsi, %r15
- pushq %rsi
call load_stage1_idt
- popq %rsi
#ifdef CONFIG_AMD_MEM_ENCRYPT
/*
@@ -421,10 +425,8 @@ SYM_CODE_START(startup_64)
* detection/setup to ensure that has been done in advance of any dependent
* code.
*/
- pushq %rsi
- movq %rsi, %rdi /* real mode address */
+ movq %r15, %rdi /* pass struct boot_params pointer */
call sev_enable
- popq %rsi
#endif
/*
@@ -437,13 +439,9 @@ SYM_CODE_START(startup_64)
* - Non zero RDX means trampoline needs to enable 5-level
* paging.
*
- * RSI holds real mode data and needs to be preserved across
- * this function call.
*/
- pushq %rsi
- movq %rsi, %rdi /* real mode address */
+ movq %r15, %rdi /* pass struct boot_params pointer */
call paging_prepare
- popq %rsi
/* Save the trampoline address in RCX */
movq %rax, %rcx
@@ -468,14 +466,9 @@ trampoline_return:
*
* RDI is address of the page table to use instead of page table
* in trampoline memory (if required).
- *
- * RSI holds real mode data and needs to be preserved across
- * this function call.
*/
- pushq %rsi
leaq rva(top_pgtable)(%rbx), %rdi
call cleanup_trampoline
- popq %rsi
/* Zero EFLAGS */
pushq $0
@@ -485,7 +478,6 @@ trampoline_return:
* Copy the compressed kernel to the end of our buffer
* where decompression in place becomes safe.
*/
- pushq %rsi
leaq (_bss-8)(%rip), %rsi
leaq rva(_bss-8)(%rbx), %rdi
movl $(_bss - startup_32), %ecx
@@ -493,7 +485,6 @@ trampoline_return:
std
rep movsq
cld
- popq %rsi
/*
* The GDT may get overwritten either during the copy we just did or
@@ -525,30 +516,27 @@ SYM_FUNC_START_LOCAL_NOALIGN(.Lrelocated)
shrq $3, %rcx
rep stosq
- pushq %rsi
call load_stage2_idt
/* Pass boot_params to initialize_identity_maps() */
- movq (%rsp), %rdi
+ movq %r15, %rdi /* pass struct boot_params pointer */
call initialize_identity_maps
- popq %rsi
/*
* Do the extraction, and jump to the new kernel..
*/
- pushq %rsi /* Save the real mode argument */
- movq %rsi, %rdi /* real mode address */
+ movq %r15, %rdi /* pass struct boot_params pointer */
leaq boot_heap(%rip), %rsi /* malloc area for uncompression */
leaq input_data(%rip), %rdx /* input_data */
movl input_len(%rip), %ecx /* input_len */
movq %rbp, %r8 /* output target address */
movl output_len(%rip), %r9d /* decompressed length, end of relocs */
call extract_kernel /* returns kernel entry point in %rax */
- popq %rsi
/*
* Jump to the decompressed kernel.
*/
+ movq %r15, %rsi
jmp *%rax
SYM_FUNC_END(.Lrelocated)
Instead of pushing and popping %RSI several times to preserve the struct boot_params pointer across the execution of the startup code, move it into a callee save register before the first call into C, and copy it back when needed. Signed-off-by: Ard Biesheuvel <ardb@kernel.org> --- arch/x86/boot/compressed/head_64.S | 34 +++++++------------- 1 file changed, 11 insertions(+), 23 deletions(-)