mk-rootfs.sh

hc

2023-12-11 072de836f53be56a70cecf70b43ae43b7ce17376

 kernel/arch/arm64/kernel/efi-rt-wrapper.S
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@@ -1,14 +1,12 @@
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+/* SPDX-License-Identifier: GPL-2.0-only */
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 /*
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  * Copyright (C) 2018 Linaro Ltd <ard.biesheuvel@linaro.org>
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- *
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- * This program is free software; you can redistribute it and/or modify
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- * it under the terms of the GNU General Public License version 2 as
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- * published by the Free Software Foundation.
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  */
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 #include <linux/linkage.h>
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+#include <asm/assembler.h>
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-ENTRY(__efi_rt_asm_wrapper)
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+SYM_FUNC_START(__efi_rt_asm_wrapper)
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 	stp	x29, x30, [sp, #-32]!
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 	mov	x29, sp
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@@ -18,6 +16,12 @@
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 	 * (such as UEFI) should never touch it.
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 	 */
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 	stp	x1, x18, [sp, #16]
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+
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+	ldr_l	x16, efi_rt_stack_top
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+	mov	sp, x16
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+#ifdef CONFIG_SHADOW_CALL_STACK
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+	str	x18, [sp, #-16]!
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+#endif
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 	/*
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 	 * We are lucky enough that no EFI runtime services take more than
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@@ -32,19 +36,24 @@
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 	mov	x4, x6
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 	blr	x8
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+	mov	sp, x29
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 	ldp	x1, x2, [sp, #16]
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 	cmp	x2, x18
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 	ldp	x29, x30, [sp], #32
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 	b.ne	0f
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 	ret
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 0:
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-#ifdef CONFIG_SHADOW_CALL_STACK
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 	/*
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-	 * Restore x18 before returning to instrumented code. This is
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-	 * safe because the wrapper is called with preemption disabled and
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-	 * a separate shadow stack is used for interrupts.
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+	 * With CONFIG_SHADOW_CALL_STACK, the kernel uses x18 to store a
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+	 * shadow stack pointer, which we need to restore before returning to
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+	 * potentially instrumented code. This is safe because the wrapper is
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+	 * called with preemption disabled and a separate shadow stack is used
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+	 * for interrupts.
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 	 */
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-	mov	x18, x2
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+#ifdef CONFIG_SHADOW_CALL_STACK
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+	ldr_l	x18, efi_rt_stack_top
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+	ldr	x18, [x18, #-16]
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 #endif
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+
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 	b	efi_handle_corrupted_x18	// tail call
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-ENDPROC(__efi_rt_asm_wrapper)
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+SYM_FUNC_END(__efi_rt_asm_wrapper)