Move startup32_check_sev_cbit() into the .text section and turn it into an ordinary function using the ordinary 32-bit calling convention, instead of saving/restoring the registers that are known to be live at the only call site. This improves maintainability, and makes it possible to move this function out of head_64.S and into a separate compilation unit that is specific to memory encryption. Note that this requires the call site to be moved before the mixed mode check, as %eax will be live otherwise. Signed-off-by: Ard Biesheuvel <ardb@xxxxxxxxxx> --- arch/x86/boot/compressed/head_64.S | 35 +++++++++++--------- 1 file changed, 19 insertions(+), 16 deletions(-) diff --git a/arch/x86/boot/compressed/head_64.S b/arch/x86/boot/compressed/head_64.S index 97b2167f128cbefe..272b2e97456f0dcf 100644 --- a/arch/x86/boot/compressed/head_64.S +++ b/arch/x86/boot/compressed/head_64.S @@ -259,6 +259,11 @@ SYM_FUNC_START(startup_32) movl $__BOOT_TSS, %eax ltr %ax +#ifdef CONFIG_AMD_MEM_ENCRYPT + /* Check if the C-bit position is correct when SEV is active */ + call startup32_check_sev_cbit +#endif + /* * Setup for the jump to 64bit mode * @@ -276,8 +281,6 @@ SYM_FUNC_START(startup_32) leal rva(startup_64_mixed_mode)(%ebp), %eax 1: #endif - /* Check if the C-bit position is correct when SEV is active */ - call startup32_check_sev_cbit pushl $__KERNEL_CS pushl %eax @@ -732,16 +735,17 @@ SYM_DATA_END_LABEL(boot_idt, SYM_L_GLOBAL, boot_idt_end) * succeed. An incorrect C-bit position will map all memory unencrypted, so that * the compare will use the encrypted random data and fail. */ - __HEAD -SYM_FUNC_START(startup32_check_sev_cbit) #ifdef CONFIG_AMD_MEM_ENCRYPT - pushl %eax + .text +SYM_FUNC_START(startup32_check_sev_cbit) pushl %ebx - pushl %ecx - pushl %edx + pushl %ebp + + call 0f +0: popl %ebp /* Check for non-zero sev_status */ - movl rva(sev_status)(%ebp), %eax + movl (sev_status - 0b)(%ebp), %eax testl %eax, %eax jz 4f @@ -756,17 +760,18 @@ SYM_FUNC_START(startup32_check_sev_cbit) jnc 2b /* Store to memory and keep it in the registers */ - movl %eax, rva(sev_check_data)(%ebp) - movl %ebx, rva(sev_check_data+4)(%ebp) + leal (sev_check_data - 0b)(%ebp), %ebp + movl %eax, 0(%ebp) + movl %ebx, 4(%ebp) /* Enable paging to see if encryption is active */ movl %cr0, %edx /* Backup %cr0 in %edx */ movl $(X86_CR0_PG | X86_CR0_PE), %ecx /* Enable Paging and Protected mode */ movl %ecx, %cr0 - cmpl %eax, rva(sev_check_data)(%ebp) + cmpl %eax, 0(%ebp) jne 3f - cmpl %ebx, rva(sev_check_data+4)(%ebp) + cmpl %ebx, 4(%ebp) jne 3f movl %edx, %cr0 /* Restore previous %cr0 */ @@ -778,13 +783,11 @@ SYM_FUNC_START(startup32_check_sev_cbit) jmp 3b 4: - popl %edx - popl %ecx + popl %ebp popl %ebx - popl %eax -#endif RET SYM_FUNC_END(startup32_check_sev_cbit) +#endif /* * Stack and heap for uncompression -- 2.35.1
