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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 v3 09/17] x86/compressed: avoid touching ECX in startup32_set_idt_entry()
Date: Tue, 22 Nov 2022 17:10:09 +0100	[thread overview]
Message-ID: <20221122161017.2426828-10-ardb@kernel.org> (raw)
In-Reply-To: <20221122161017.2426828-1-ardb@kernel.org>

Avoid touching register %ecx in startup32_set_idt_entry(), by folding
the MOV, SHL and ORL instructions into a single ORL which no longer
requires a temp register.

This permits ECX to be used as a function argument in a subsequent
patch.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
 arch/x86/boot/compressed/head_64.S | 8 ++------
 1 file changed, 2 insertions(+), 6 deletions(-)

diff --git a/arch/x86/boot/compressed/head_64.S b/arch/x86/boot/compressed/head_64.S
index 66ad3ab802ca9d0c..f31277f455e63f5f 100644
--- a/arch/x86/boot/compressed/head_64.S
+++ b/arch/x86/boot/compressed/head_64.S
@@ -741,7 +741,6 @@ SYM_DATA_END_LABEL(boot32_idt, SYM_L_GLOBAL, boot32_idt_end)
  */
 SYM_FUNC_START(startup32_set_idt_entry)
 	push    %ebx
-	push    %ecx
 
 	/* IDT entry address to %ebx */
 	leal    rva(boot32_idt)(%ebp), %ebx
@@ -750,10 +749,8 @@ SYM_FUNC_START(startup32_set_idt_entry)
 
 	/* Build IDT entry, lower 4 bytes */
 	movl    %eax, %edx
-	andl    $0x0000ffff, %edx	# Target code segment offset [15:0]
-	movl    $__KERNEL32_CS, %ecx	# Target code segment selector
-	shl     $16, %ecx
-	orl     %ecx, %edx
+	andl    $0x0000ffff, %edx		# Target code segment offset [15:0]
+	orl	$(__KERNEL32_CS << 16), %edx	# Target code segment selector
 
 	/* Store lower 4 bytes to IDT */
 	movl    %edx, (%ebx)
@@ -766,7 +763,6 @@ SYM_FUNC_START(startup32_set_idt_entry)
 	/* Store upper 4 bytes to IDT */
 	movl    %edx, 4(%ebx)
 
-	pop     %ecx
 	pop     %ebx
 	RET
 SYM_FUNC_END(startup32_set_idt_entry)
-- 
2.35.1


  parent reply	other threads:[~2022-11-22 16:11 UTC|newest]

Thread overview: 50+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-11-22 16:10 [PATCH v3 00/17] x86: head_64.S spring cleaning Ard Biesheuvel
2022-11-22 16:10 ` [PATCH v3 01/17] x86/compressed: efi-mixed: rename efi_thunk_64.S to efi-mixed.S Ard Biesheuvel
2022-11-24  8:12   ` [tip: x86/boot] x86/boot/compressed: Rename " tip-bot2 for Ard Biesheuvel
2022-11-22 16:10 ` [PATCH v3 02/17] x86/compressed: efi-mixed: move 32-bit entrypoint code into .text section Ard Biesheuvel
2022-11-24  8:12   ` [tip: x86/boot] x86/boot/compressed: Move " tip-bot2 for Ard Biesheuvel
2022-11-22 16:10 ` [PATCH v3 03/17] x86/compressed: efi-mixed: move bootargs parsing out of 32-bit startup code Ard Biesheuvel
2022-11-24  8:12   ` [tip: x86/boot] x86/boot/compressed: Move " tip-bot2 for Ard Biesheuvel
2022-11-22 16:10 ` [PATCH v3 04/17] x86/compressed: efi-mixed: move efi32_pe_entry into .text section Ard Biesheuvel
2022-11-24  8:12   ` [tip: x86/boot] x86/boot/compressed: Move " tip-bot2 for Ard Biesheuvel
2022-11-22 16:10 ` [PATCH v3 05/17] x86/compressed: efi-mixed: move efi32_entry out of head_64.S Ard Biesheuvel
2022-11-24  8:12   ` [tip: x86/boot] x86/boot/compressed: Move " tip-bot2 for Ard Biesheuvel
2022-11-22 16:10 ` [PATCH v3 06/17] x86/compressed: efi-mixed: move efi32_pe_entry() " Ard Biesheuvel
2022-11-24  8:12   ` [tip: x86/boot] x86/boot/compressed: Move " tip-bot2 for Ard Biesheuvel
2022-11-22 16:10 ` [PATCH v3 07/17] x86/compressed: efi: merge multiple definitions of image_offset into one Ard Biesheuvel
2022-11-24  8:12   ` [tip: x86/boot] x86/boot/compressed, efi: Merge " tip-bot2 for Ard Biesheuvel
2022-11-22 16:10 ` [PATCH v3 08/17] x86/compressed: efi-mixed: simplify IDT/GDT preserve/restore Ard Biesheuvel
2022-11-24  8:12   ` [tip: x86/boot] x86/boot/compressed: Simplify IDT/GDT preserve/restore in the EFI thunk tip-bot2 for Ard Biesheuvel
2022-11-22 16:10 ` Ard Biesheuvel [this message]
2022-11-24  8:12   ` [tip: x86/boot] x86/boot/compressed: Avoid touching ECX in startup32_set_idt_entry() tip-bot2 for Ard Biesheuvel
2022-11-22 16:10 ` [PATCH v3 10/17] x86/compressed: pull global variable ref up into startup32_load_idt() Ard Biesheuvel
2022-11-24  8:12   ` [tip: x86/boot] x86/boot/compressed: Pull global variable reference " tip-bot2 for Ard Biesheuvel
2022-11-22 16:10 ` [PATCH v3 11/17] x86/compressed: move startup32_load_idt() into .text section Ard Biesheuvel
2022-11-24  8:12   ` [tip: x86/boot] x86/boot/compressed: Move " tip-bot2 for Ard Biesheuvel
2022-11-22 16:10 ` [PATCH v3 12/17] x86/compressed: move startup32_load_idt() out of head_64.S Ard Biesheuvel
2022-11-24  8:12   ` [tip: x86/boot] x86/boot/compressed: Move " tip-bot2 for Ard Biesheuvel
2022-11-22 16:10 ` [PATCH v3 13/17] x86/compressed: move startup32_check_sev_cbit() into .text Ard Biesheuvel
2022-11-24  8:12   ` [tip: x86/boot] x86/boot/compressed: Move " tip-bot2 for Ard Biesheuvel
2022-11-22 16:10 ` [PATCH v3 14/17] x86/compressed: move startup32_check_sev_cbit() out of head_64.S Ard Biesheuvel
2022-11-24  8:12   ` [tip: x86/boot] x86/boot/compressed: Move " tip-bot2 for Ard Biesheuvel
2022-11-22 16:10 ` [PATCH v3 15/17] x86/compressed: adhere to calling convention in get_sev_encryption_bit() Ard Biesheuvel
2022-11-24  8:12   ` [tip: x86/boot] x86/boot/compressed: Adhere " tip-bot2 for Ard Biesheuvel
2022-11-22 16:10 ` [PATCH v3 16/17] x86/compressed: only build mem_encrypt.S if AMD_MEM_ENCRYPT=y Ard Biesheuvel
2022-11-24  8:11   ` [tip: x86/boot] x86/boot/compressed: Only " tip-bot2 for Ard Biesheuvel
2022-11-22 16:10 ` [PATCH v3 17/17] efi: x86: Make the deprecated EFI handover protocol optional Ard Biesheuvel
2022-11-22 18:56   ` Randy Dunlap
2022-11-24  8:11   ` [tip: x86/boot] x86/efi: " tip-bot2 for Ard Biesheuvel
2022-11-22 20:48 ` [PATCH v3 00/17] x86: head_64.S spring cleaning Tom Lendacky
2022-11-22 21:37   ` Ard Biesheuvel
2022-11-22 21:42     ` Ard Biesheuvel
2022-11-22 21:50       ` Tom Lendacky
2022-11-22 21:51         ` Ard Biesheuvel
2022-11-22 21:49     ` Tom Lendacky
2022-11-22 22:20       ` Borislav Petkov
2022-11-23 10:49       ` Borislav Petkov
2022-11-23 10:52         ` Ard Biesheuvel
2022-11-23 11:09           ` Borislav Petkov
2022-11-23 11:22             ` Ard Biesheuvel
2022-11-23 14:16           ` Tom Lendacky
2022-11-23 14:33             ` Ard Biesheuvel
2022-11-23 14:13         ` Tom Lendacky

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