Commit b3adabae authored by David Woodhouse's avatar David Woodhouse Committed by Ingo Molnar
Browse files

x86/kexec: Drop page_list argument from relocate_kernel() 



The kernel's virtual mapping of the relocate_kernel page currently needs
to be RWX because it is written to before the %cr3 switch.

Now that the relocate_kernel page has its own .data section and local
variables, it can also have *global* variables. So eliminate the separate
page_list argument, and write the same information directly to variables
in the relocate_kernel page instead. This way, the relocate_kernel code
itself doesn't need to copy it.

Signed-off-by: default avatarDavid Woodhouse <dwmw@amazon.co.uk>
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
Cc: Baoquan He <bhe@redhat.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: Dave Young <dyoung@redhat.com>
Cc: Eric Biederman <ebiederm@xmission.com>
Cc: Ard Biesheuvel <ardb@kernel.org>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Link: https://lore.kernel.org/r/20241205153343.3275139-11-dwmw2@infradead.org
parent 8dbec5c7

arch/x86/include/asm/kexec.h

+5 −7
Original line number Diff line number Diff line
@@ -8,12 +8,6 @@ 
# define PA_PGD			2

# define PA_SWAP_PAGE		3

# define PAGES_NR		4

#else

# define PA_CONTROL_PAGE	0

# define VA_CONTROL_PAGE	1

# define PA_TABLE_PAGE		2

# define PA_SWAP_PAGE		3

# define PAGES_NR		4

#endif



# define KEXEC_CONTROL_PAGE_SIZE	4096
@@ -60,6 +54,10 @@ struct kimage; 


/* The native architecture */

# define KEXEC_ARCH KEXEC_ARCH_X86_64



extern unsigned long kexec_va_control_page;

extern unsigned long kexec_pa_table_page;

extern unsigned long kexec_pa_swap_page;

#endif



/*
@@ -122,7 +120,7 @@ relocate_kernel(unsigned long indirection_page, 
#else

unsigned long

relocate_kernel(unsigned long indirection_page,

		unsigned long page_list,

		unsigned long pa_control_page,

		unsigned long start_address,

		unsigned int preserve_context,

		unsigned int host_mem_enc_active);

arch/x86/kernel/machine_kexec_64.c

+7 −11
Original line number Diff line number Diff line
@@ -315,6 +315,11 @@ int machine_kexec_prepare(struct kimage *image) 
	result = init_pgtable(image, __pa(control_page));

	if (result)

		return result;

	kexec_va_control_page = (unsigned long)control_page;

	kexec_pa_table_page = (unsigned long)__pa(image->arch.pgd);



	if (image->type == KEXEC_TYPE_DEFAULT)

		kexec_pa_swap_page = page_to_pfn(image->swap_page) << PAGE_SHIFT;



	__memcpy(control_page, __relocate_kernel_start, reloc_end - reloc_start);
@@ -339,12 +344,11 @@ void machine_kexec_cleanup(struct kimage *image) 
void machine_kexec(struct kimage *image)

{

	unsigned long (*relocate_kernel_ptr)(unsigned long indirection_page,

					     unsigned long page_list,

					     unsigned long pa_control_page,

					     unsigned long start_address,

					     unsigned int preserve_context,

					     unsigned int host_mem_enc_active);

	unsigned long reloc_start = (unsigned long)__relocate_kernel_start;

	unsigned long page_list[PAGES_NR];

	unsigned int host_mem_enc_active;

	int save_ftrace_enabled;

	void *control_page;
@@ -382,14 +386,6 @@ void machine_kexec(struct kimage *image) 


	control_page = page_address(image->control_code_page);



	page_list[PA_CONTROL_PAGE] = virt_to_phys(control_page);

	page_list[VA_CONTROL_PAGE] = (unsigned long)control_page;

	page_list[PA_TABLE_PAGE] = (unsigned long)__pa(image->arch.pgd);



	if (image->type == KEXEC_TYPE_DEFAULT)

		page_list[PA_SWAP_PAGE] = (page_to_pfn(image->swap_page)

						<< PAGE_SHIFT);



	/*

	 * Allow for the possibility that relocate_kernel might not be at

	 * the very start of the page.
@@ -417,7 +413,7 @@ void machine_kexec(struct kimage *image) 


	/* now call it */

	image->start = relocate_kernel_ptr((unsigned long)image->head,

					   (unsigned long)page_list,

					   virt_to_phys(control_page),

					   image->start,

					   image->preserve_context,

					   host_mem_enc_active);

arch/x86/kernel/relocate_kernel_64.S

+12 −24
Original line number Diff line number Diff line
@@ -34,9 +34,9 @@ SYM_DATA_LOCAL(saved_cr0, .quad 0) 
SYM_DATA_LOCAL(saved_cr3, .quad 0)

SYM_DATA_LOCAL(saved_cr4, .quad 0)

	/* other data */

SYM_DATA_LOCAL(va_control_page, .quad 0)

SYM_DATA_LOCAL(pa_table_page, .quad 0)

SYM_DATA_LOCAL(pa_swap_page, .quad 0)

SYM_DATA(kexec_va_control_page, .quad 0)

SYM_DATA(kexec_pa_table_page, .quad 0)

SYM_DATA(kexec_pa_swap_page, .quad 0)

SYM_DATA_LOCAL(pa_backup_pages_map, .quad 0)



	.section .text.relocate_kernel,"ax";
@@ -46,7 +46,7 @@ SYM_CODE_START_NOALIGN(relocate_kernel) 
	ANNOTATE_NOENDBR

	/*

	 * %rdi indirection_page

	 * %rsi page_list

	 * %rsi pa_control_page

	 * %rdx start address

	 * %rcx preserve_context

	 * %r8  host_mem_enc_active
@@ -79,31 +79,19 @@ SYM_CODE_START_NOALIGN(relocate_kernel) 
	/* Save SME active flag */

	movq	%r8, %r12



	/*

	 * get physical and virtual address of control page now

	 * this is impossible after page table switch

	 */

	movq	PTR(PA_CONTROL_PAGE)(%rsi), %r8

	movq	PTR(VA_CONTROL_PAGE)(%rsi), %r11



	/* get physical address of page table now too */

	movq	PTR(PA_TABLE_PAGE)(%rsi), %r9



	/* get physical address of swap page now */

	movq	PTR(PA_SWAP_PAGE)(%rsi), %r10



	/* save some information for jumping back */

	movq	%r9, pa_table_page(%rip)

	movq	%r10, pa_swap_page(%rip)

	/* save indirection list for jumping back */

	movq	%rdi, pa_backup_pages_map(%rip)

	movq	%r11, va_control_page(%rip)



	/* Save the preserve_context to %r11 as swap_pages clobbers %rcx. */

	movq	%rcx, %r11



	/* Switch to the identity mapped page tables */

	movq	kexec_pa_table_page(%rip), %r9

	movq	%r9, %cr3



	/* Physical address of control page */

	movq    %rsi, %r8



	/* setup a new stack at the end of the physical control page */

	lea	PAGE_SIZE(%r8), %rsp
@@ -227,13 +215,13 @@ SYM_CODE_START_LOCAL_NOALIGN(identity_mapped) 
	/* get the re-entry point of the peer system */

	movq	0(%rsp), %rbp

	leaq	relocate_kernel(%rip), %r8

	movq	pa_swap_page(%rip), %r10

	movq	kexec_pa_swap_page(%rip), %r10

	movq	pa_backup_pages_map(%rip), %rdi

	movq	pa_table_page(%rip), %rax

	movq	kexec_pa_table_page(%rip), %rax

	movq	%rax, %cr3

	lea	PAGE_SIZE(%r8), %rsp

	call	swap_pages

	movq	va_control_page(%rip), %rax

	movq	kexec_va_control_page(%rip), %rax

	addq	$(virtual_mapped - relocate_kernel), %rax

	pushq	%rax

	ANNOTATE_UNRET_SAFE