The following commit has been merged into the x86/boot branch of tip: Commit-ID: b5d854cd4b6a314edd6c15dabc4233b84a0f8e5e Gitweb: https://git.kernel.org/tip/b5d854cd4b6a314edd6c15dabc4233b84a0f8e5e Author: Ard Biesheuvel <ardb@xxxxxxxxxx> AuthorDate: Tue, 22 Nov 2022 17:10:13 +01:00 Committer: Borislav Petkov <bp@xxxxxxx> CommitterDate: Thu, 24 Nov 2022 08:57:41 +01:00 x86/boot/compressed: Move startup32_check_sev_cbit() into .text 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> Signed-off-by: Borislav Petkov <bp@xxxxxxx> Link: https://lore.kernel.org/r/20221122161017.2426828-14-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 16cccc2..30ba541 100644 --- a/arch/x86/boot/compressed/head_64.S +++ b/arch/x86/boot/compressed/head_64.S @@ -251,6 +251,11 @@ 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 * @@ -268,8 +273,6 @@ 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 @@ -724,16 +727,17 @@ 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 @@ -748,17 +752,18 @@ 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 */ @@ -770,13 +775,11 @@ 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
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