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: 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/20241205153343.3275139-11-dwmw2@infradead.org

diff --git a/arch/x86/include/asm/kexec.h b/arch/x86/include/asm/kexec.h
index ccb8ff37fa9d4bda2695d2279969e2422511fe73..48e4f44f794f612edf246df96afbdd934b252e97 100644 (file)
--- a/arch/x86/include/asm/kexec.h
+++ b/arch/x86/include/asm/kexec.h
@@ -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);

diff --git a/arch/x86/kernel/machine_kexec_64.c b/arch/x86/kernel/machine_kexec_64.c
index 63dca5c595f6b8ca612d56383e8b506a61fb9008..c9fd60f8f80658d522da2de3649a1c36a3534817 100644 (file)
--- a/arch/x86/kernel/machine_kexec_64.c
+++ b/arch/x86/kernel/machine_kexec_64.c
@@ -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);

diff --git a/arch/x86/kernel/relocate_kernel_64.S b/arch/x86/kernel/relocate_kernel_64.S
index f13866a068b0b98bee56d5e596f69d4060e1d00c..d52c3bb25b5e64e98999561f36bf055d6baae016 100644 (file)
--- a/arch/x86/kernel/relocate_kernel_64.S
+++ b/arch/x86/kernel/relocate_kernel_64.S
@@ -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