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x86/kexec: Add data section to relocate_kernel

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Now that the relocate_kernel page is handled sanely by a linker script
we can have actual data, and just use %rip-relative addressing to access
it.

Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Signed-off-by: Ingo 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/20241205153343.3275139-10-dwmw2@infradead.org
This commit is contained in:
David Woodhouse 2024-12-05 15:05:15 +00:00 • committed by Ingo Molnar
parent cb33ff9e06
commit 8dbec5c77b
3 changed files with 38 additions and 33 deletions
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8
arch/x86/kernel/machine_kexec_64.c
View file

@ -343,6 +343,7 @@ void machine_kexec(struct kimage *image)
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;
@ -389,7 +390,12 @@ void machine_kexec(struct kimage *image)
page_list[PA_SWAP_PAGE] = (page_to_pfn(image->swap_page)
<< PAGE_SHIFT);
relocate_kernel_ptr = control_page;
/*
* Allow for the possibility that relocate_kernel might not be at
* the very start of the page.
*/
relocate_kernel_ptr = control_page + (unsigned long)relocate_kernel -
reloc_start;
/*
* The segment registers are funny things, they have both a

62
arch/x86/kernel/relocate_kernel_64.S
View file

@ -23,23 +23,21 @@
#define PAGE_ATTR (_PAGE_PRESENT | _PAGE_RW | _PAGE_ACCESSED | _PAGE_DIRTY)
/*
* control_page + KEXEC_CONTROL_CODE_MAX_SIZE
* ~ control_page + PAGE_SIZE are used as data storage and stack for
* jumping back
* The .text.relocate_kernel and .data.relocate_kernel sections are copied
* into the control page, and the remainder of the page is used as the stack.
*/
#define DATA(offset) (KEXEC_CONTROL_CODE_MAX_SIZE+(offset))
.section .data.relocate_kernel,"a";
/* Minimal CPU state */
#define RSP DATA(0x0)
#define CR0 DATA(0x8)
#define CR3 DATA(0x10)
#define CR4 DATA(0x18)
/* other data */
#define CP_PA_TABLE_PAGE DATA(0x20)
#define CP_PA_SWAP_PAGE DATA(0x28)
#define CP_PA_BACKUP_PAGES_MAP DATA(0x30)
#define CP_VA_CONTROL_PAGE DATA(0x38)
SYM_DATA_LOCAL(saved_rsp, .quad 0)
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_LOCAL(pa_backup_pages_map, .quad 0)
.section .text.relocate_kernel,"ax";
.code64
@ -63,14 +61,13 @@ SYM_CODE_START_NOALIGN(relocate_kernel)
pushq %r15
pushf
movq PTR(VA_CONTROL_PAGE)(%rsi), %r11
movq %rsp, RSP(%r11)
movq %rsp, saved_rsp(%rip)
movq %cr0, %rax
movq %rax, CR0(%r11)
movq %rax, saved_cr0(%rip)
movq %cr3, %rax
movq %rax, CR3(%r11)
movq %rax, saved_cr3(%rip)
movq %cr4, %rax
movq %rax, CR4(%r11)
movq %rax, saved_cr4(%rip)
/* Save CR4. Required to enable the right paging mode later. */
movq %rax, %r13
@ -83,10 +80,11 @@ SYM_CODE_START_NOALIGN(relocate_kernel)
movq %r8, %r12
/*
* get physical address of control page now
* 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
@ -95,10 +93,10 @@ SYM_CODE_START_NOALIGN(relocate_kernel)
movq PTR(PA_SWAP_PAGE)(%rsi), %r10
/* save some information for jumping back */
movq %r9, CP_PA_TABLE_PAGE(%r11)
movq %r10, CP_PA_SWAP_PAGE(%r11)
movq %rdi, CP_PA_BACKUP_PAGES_MAP(%r11)
movq %r11, CP_VA_CONTROL_PAGE(%r11)
movq %r9, pa_table_page(%rip)
movq %r10, pa_swap_page(%rip)
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
@ -229,13 +227,13 @@ 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 CP_PA_SWAP_PAGE(%r8), %r10
movq CP_PA_BACKUP_PAGES_MAP(%r8), %rdi
movq CP_PA_TABLE_PAGE(%r8), %rax
movq pa_swap_page(%rip), %r10
movq pa_backup_pages_map(%rip), %rdi
movq pa_table_page(%rip), %rax
movq %rax, %cr3
lea PAGE_SIZE(%r8), %rsp
call swap_pages
movq CP_VA_CONTROL_PAGE(%r8), %rax
movq va_control_page(%rip), %rax
addq $(virtual_mapped - relocate_kernel), %rax
pushq %rax
ANNOTATE_UNRET_SAFE
@ -246,11 +244,11 @@ SYM_CODE_END(identity_mapped)
SYM_CODE_START_LOCAL_NOALIGN(virtual_mapped)
UNWIND_HINT_END_OF_STACK
ANNOTATE_NOENDBR // RET target, above
movq RSP(%r8), %rsp
movq CR4(%r8), %rax
movq saved_rsp(%rip), %rsp
movq saved_cr4(%rip), %rax
movq %rax, %cr4
movq CR3(%r8), %rax
movq CR0(%r8), %r8
movq saved_cr3(%rip), %rax
movq saved_cr0(%rip), %r8
movq %rax, %cr3
movq %r8, %cr0

1
arch/x86/kernel/vmlinux.lds.S
View file

@ -101,6 +101,7 @@ const_pcpu_hot = pcpu_hot;
. = ALIGN(0x100); \
__relocate_kernel_start = .; \
*(.text.relocate_kernel); \
*(.data.relocate_kernel); \
__relocate_kernel_end = .;
ASSERT(__relocate_kernel_end - __relocate_kernel_start <= KEXEC_CONTROL_CODE_MAX_SIZE,