From: Ard Biesheuvel <ardb@kernel.org>
To: linux-efi@vger.kernel.org
Cc: linux-kernel@vger.kernel.org, Ard Biesheuvel <ardb@kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
Dave Hansen <dave.hansen@linux.intel.com>,
Michael Roth <michael.roth@amd.com>
Subject: [PATCH v2 13/16] x86/compressed: move startup32_check_sev_cbit() into .text
Date: Wed, 21 Sep 2022 16:54:19 +0200 [thread overview]
Message-ID: <20220921145422.437618-14-ardb@kernel.org> (raw)
In-Reply-To: <20220921145422.437618-1-ardb@kernel.org>
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@kernel.org>
---
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 abb5a650a816..639f688e4949 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_mixedmode)(%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
--
2.35.1
next prev parent reply other threads:[~2022-09-21 14:56 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-09-21 14:54 [PATCH v2 00/16] x86: head_64.S spring cleaning Ard Biesheuvel
2022-09-21 14:54 ` [PATCH v2 01/16] x86/compressed: efi-mixed: rename efi_thunk_64.S to efi-mixed.S Ard Biesheuvel
2022-09-21 14:54 ` [PATCH v2 02/16] x86/compressed: efi-mixed: move 32-bit entrypoint code into .text section Ard Biesheuvel
2022-10-06 10:42 ` Borislav Petkov
2022-10-06 10:56 ` Ard Biesheuvel
2022-10-06 11:13 ` Borislav Petkov
2022-10-06 11:19 ` Ard Biesheuvel
2022-10-06 12:27 ` Ard Biesheuvel
2022-10-07 8:56 ` Borislav Petkov
2022-09-21 14:54 ` [PATCH v2 03/16] x86/compressed: efi-mixed: move bootargs parsing out of 32-bit startup code Ard Biesheuvel
2022-10-06 11:03 ` Borislav Petkov
2022-10-06 11:29 ` Ard Biesheuvel
2022-10-07 9:30 ` Borislav Petkov
2022-09-21 14:54 ` [PATCH v2 04/16] x86/compressed: efi-mixed: move efi32_pe_entry into .text section Ard Biesheuvel
2022-11-17 15:57 ` Borislav Petkov
2022-11-17 16:06 ` Ard Biesheuvel
2022-11-17 17:08 ` Borislav Petkov
2022-09-21 14:54 ` [PATCH v2 05/16] x86/compressed: efi-mixed: move efi32_entry out of head_64.S Ard Biesheuvel
2022-09-21 14:54 ` [PATCH v2 06/16] x86/compressed: efi-mixed: move efi32_pe_entry() " Ard Biesheuvel
2022-09-21 14:54 ` [PATCH v2 07/16] x86/compressed: efi: merge multiple definitions of image_offset into one Ard Biesheuvel
2022-09-21 14:54 ` [PATCH v2 08/16] x86/compressed: efi-mixed: simplify IDT/GDT preserve/restore Ard Biesheuvel
2022-09-21 14:54 ` [PATCH v2 09/16] x86/compressed: avoid touching ECX in startup32_set_idt_entry() Ard Biesheuvel
2022-09-21 14:54 ` [PATCH v2 10/16] x86/compressed: pull global variable ref up into startup32_load_idt() Ard Biesheuvel
2022-09-21 14:54 ` [PATCH v2 11/16] x86/compressed: move startup32_load_idt() into .text section Ard Biesheuvel
2022-11-18 16:44 ` Borislav Petkov
2022-09-21 14:54 ` [PATCH v2 12/16] x86/compressed: move startup32_load_idt() out of head_64.S Ard Biesheuvel
2022-09-21 14:54 ` Ard Biesheuvel [this message]
2022-09-21 14:54 ` [PATCH v2 14/16] x86/compressed: move startup32_check_sev_cbit() " Ard Biesheuvel
2022-09-21 14:54 ` [PATCH v2 15/16] x86/compressed: adhere to calling convention in get_sev_encryption_bit() Ard Biesheuvel
2022-09-21 14:54 ` [PATCH v2 16/16] x86/compressed: only build mem_encrypt.S if AMD_MEM_ENCRYPT=y Ard Biesheuvel
2022-11-18 18:26 ` [PATCH v2 00/16] x86: head_64.S spring cleaning Borislav Petkov
2022-11-18 23:31 ` Ard Biesheuvel
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