Attachment 225333 Details for Bug 209821 – Fix a boot hang on some systems

[patch] Fix a boot hang on some systems

0001-efi-loader-amd64-Fix-a-boot-crash-or-hang-on-some-sy.patch (text/plain), 5.79 KB, created by David Sebek on 2021-05-28 15:50:48 UTC

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Creator: David Sebek

Created: 2021-05-28 15:50:48 UTC

Size: 5.79 KB

patch

obsolete

>From 3c7acdd7ec2c526534a34442d4a0f533e6a3b62f Mon Sep 17 00:00:00 2001
>From: David Sebek <dasebek@gmail.com>
>Date: Fri, 28 May 2021 10:58:36 -0400
>Subject: [PATCH] efi: loader: amd64: Fix a boot crash or hang on some systems
>
>Instead of calling the efi_copy_finish function from amd64_tramp,
>include the copy instructions in the trampoline code itself.
>This avoids boot hangs and restarts in the cases when
>the EFI loader code and/or data segments happen to be located
>at a memory loacation that is overwritten during the copy process.
>
>Signed-off-by: David Sebek <dasebek@gmail.com>
>---
> stand/efi/loader/arch/amd64/amd64_tramp.S   | 53 +++++++++++++++++++++
> stand/efi/loader/arch/amd64/elf64_freebsd.c | 18 ++++---
> stand/efi/loader/copy.c                     |  8 ++++
> stand/efi/loader/loader_efi.h               |  1 +
> 4 files changed, 73 insertions(+), 7 deletions(-)
>
>diff --git a/stand/efi/loader/arch/amd64/amd64_tramp.S b/stand/efi/loader/arch/amd64/amd64_tramp.S
>index 877705407f9..88707ba7312 100644
>--- a/stand/efi/loader/arch/amd64/amd64_tramp.S
>+++ b/stand/efi/loader/arch/amd64/amd64_tramp.S
>@@ -61,6 +61,55 @@ amd64_tramp:
> 	ALIGN_TEXT
> amd64_tramp_end:
> 
>+/*
>+ * void amd64_tramp_inline(uint64_t stack, uint64_t kernend,
>+ *			uint64_t modulep, uint64_t pagetable, uint64_t entry,
>+ *			uint64_t copy_dst, uint64_t copy_src, uint64_t copy_src_end)
>+ */
>+	.globl	amd64_tramp_inline
>+amd64_tramp_inline:
>+	cli			/* Make sure we don't get interrupted. */
>+
>+	movq	%rsi,%r12	/* Stash the kernel values for later. */
>+	movq	%rdx,%r13
>+	movq	%rcx,%r14
>+	movq	%r8,%r15
>+
>+	/* Copy the content of the staging area to the expected location.
>+	 * A code similar to efi_copy_finish from copy.c is inlined here
>+	 * instead of calling a copy_finish function like amd64_tramp did.
>+	 * In some cases, the UEFI bootloader may be loaded to a memory location
>+	 * that happens to be overwritten during this copy process. In such a case,
>+	 * calling copy_finish could result in a system reboot or a bootloader to
>+	 * hang.
>+	 *
>+	 * while (copy_src < copy_src_end) *copy_dst++ = *copy_src++;
>+	 */
>+	movq	8(%rsp), %rax	/* rax = copy_src */
>+	movq	16(%rsp), %rcx	/* rcx = copy_src_end */
>+	cmpq	%rcx, %rax
>+	jnb	copy_done
>+	subq	%rax, %r9		/* r9 = copy_dst - copy_src */
>+loop:
>+	movq	(%rax), %rdx
>+	movq	%rdx, (%rax,%r9)
>+	addq	$8, %rax
>+	cmpq	%rax, %rcx
>+	ja	loop
>+copy_done:
>+
>+	movq	%rdi,%rsp	/* Switch to our temporary stack. */
>+
>+	pushq	%r12		/* Push kernend. */
>+	salq	$32,%r13	/* Shift modulep and push it. */
>+	pushq	%r13
>+	pushq	%r15		/* Push the entry address. */
>+	movq	%r14,%cr3	/* Switch page tables. */
>+	ret			/* "Return" to kernel entry. */
>+
>+	ALIGN_TEXT
>+amd64_tramp_inline_end:
>+
> /* void multiboot2_exec(uint64_t entry, uint64_t multiboot_info, uint64_t stack) */
> 	.globl	multiboot2_exec
> multiboot2_exec:
>@@ -74,3 +123,7 @@ multiboot2_exec:
> 	.globl	amd64_tramp_size
> amd64_tramp_size:
> 	.long	amd64_tramp_end-amd64_tramp
>+
>+	.globl	amd64_tramp_inline_size
>+amd64_tramp_inline_size:
>+	.long	amd64_tramp_inline_end-amd64_tramp_inline
>diff --git a/stand/efi/loader/arch/amd64/elf64_freebsd.c b/stand/efi/loader/arch/amd64/elf64_freebsd.c
>index a950ca55e84..852199a43f5 100644
>--- a/stand/efi/loader/arch/amd64/elf64_freebsd.c
>+++ b/stand/efi/loader/arch/amd64/elf64_freebsd.c
>@@ -84,11 +84,12 @@ static pml4_entry_t *PT4;
> static pdp_entry_t *PT3;
> static pd_entry_t *PT2;
> 
>-static void (*trampoline)(uint64_t stack, void *copy_finish, uint64_t kernend,
>-    uint64_t modulep, pml4_entry_t *pagetable, uint64_t entry);
>+static void (*trampoline)(uint64_t stack, uint64_t kernend,
>+	uint64_t modulep, pml4_entry_t *pagetable, uint64_t entry,
>+	uint64_t copy_dst, uint64_t copy_src, uint64_t copy_src_end);
> 
>-extern uintptr_t amd64_tramp;
>-extern uint32_t amd64_tramp_size;
>+extern uintptr_t amd64_tramp_inline;
>+extern uint32_t amd64_tramp_inline_size;
> 
> /*
>  * There is an ELF kernel and one or more ELF modules loaded.
>@@ -101,6 +102,7 @@ elf64_exec(struct preloaded_file *fp)
> 	struct file_metadata	*md;
> 	Elf_Ehdr 		*ehdr;
> 	vm_offset_t		modulep, kernend, trampcode, trampstack;
>+	uint64_t		copy_dst, copy_src, copy_src_end;
> 	int			err, i;
> 	ACPI_TABLE_RSDP		*rsdp;
> 	char			buf[24];
>@@ -159,7 +161,7 @@ elf64_exec(struct preloaded_file *fp)
> 	    (EFI_PHYSICAL_ADDRESS *)&trampcode);
> 	bzero((void *)trampcode, EFI_PAGE_SIZE);
> 	trampstack = trampcode + EFI_PAGE_SIZE - 8;
>-	bcopy((void *)&amd64_tramp, (void *)trampcode, amd64_tramp_size);
>+	bcopy((void *)&amd64_tramp_inline, (void *)trampcode, amd64_tramp_inline_size);
> 	trampoline = (void *)trampcode;
> 
> 	PT4 = (pml4_entry_t *)0x0000000040000000;
>@@ -200,8 +202,10 @@ elf64_exec(struct preloaded_file *fp)
> 
> 	dev_cleanup();
> 
>-	trampoline(trampstack, efi_copy_finish, kernend, modulep, PT4,
>-	    ehdr->e_entry);
>+	efi_copy_get_locations(&copy_dst, &copy_src, &copy_src_end);
>+
>+	trampoline(trampstack, kernend, modulep, PT4,
>+	    ehdr->e_entry, copy_dst, copy_src, copy_src_end);
> 
> 	panic("exec returned");
> }
>diff --git a/stand/efi/loader/copy.c b/stand/efi/loader/copy.c
>index e723b61e3bc..f063b6615bc 100644
>--- a/stand/efi/loader/copy.c
>+++ b/stand/efi/loader/copy.c
>@@ -364,3 +364,11 @@ efi_copy_finish(void)
> 	while (src < last)
> 		*dst++ = *src++;
> }
>+
>+void
>+efi_copy_get_locations(uint64_t * dst, uint64_t * src, uint64_t * src_end)
>+{
>+	*src = (uint64_t)staging;
>+	*dst = (uint64_t)(staging - stage_offset);
>+	*src_end = (uint64_t)staging_end;
>+}
>diff --git a/stand/efi/loader/loader_efi.h b/stand/efi/loader/loader_efi.h
>index 4d077514e42..f3a052a63cf 100644
>--- a/stand/efi/loader/loader_efi.h
>+++ b/stand/efi/loader/loader_efi.h
>@@ -44,5 +44,6 @@ ssize_t	efi_readin(readin_handle_t fd, vm_offset_t dest, const size_t len);
> void * efi_translate(vm_offset_t ptr);
> 
> void	efi_copy_finish(void);
>+void efi_copy_get_locations(uint64_t *dst, uint64_t *src, uint64_t *src_end);
> 
> #endif	/* _LOADER_EFI_COPY_H_ */
>-- 
>2.31.1
>

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Attachments on bug 209821: 225333 | 225480 | 230798 | 230812 | 230823