On November 8, 2024 6:22:41 AM GMT+01:00, David Woodhouse <dwmw2@xxxxxxxxxxxxx> wrote: >From: David Woodhouse <dwmw@xxxxxxxxxxxx> > >Now that it's handled sanely by a linker script we can have actual data, >and just use %rip-relative addressing to access it. > >If we could call the *copy* instead of the original relocate_kernel in >the kernel text, then we could use %rip-relative addressing everywhere. > >Signed-off-by: David Woodhouse <dwmw@xxxxxxxxxxxx> >--- > arch/x86/kernel/relocate_kernel_64.S | 58 ++++++++++++++++------------ > arch/x86/kernel/vmlinux.lds.S | 2 +- > 2 files changed, 35 insertions(+), 25 deletions(-) > >diff --git a/arch/x86/kernel/relocate_kernel_64.S b/arch/x86/kernel/relocate_kernel_64.S >index 1efcbd340528..577aa1672349 100644 >--- a/arch/x86/kernel/relocate_kernel_64.S >+++ b/arch/x86/kernel/relocate_kernel_64.S >@@ -27,18 +27,28 @@ > * ~ control_page + PAGE_SIZE are used as data storage and stack for > * jumping back > */ >-#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) >- >+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 */ >-#define CP_PA_TABLE_PAGE DATA(0x20) >-#define CP_PA_SWAP_PAGE DATA(0x28) >-#define CP_PA_BACKUP_PAGES_MAP DATA(0x30) >+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) >+ >+/* >+ * There are two physical copies of relocate_kernel(), one in the original >+ * Kernel text and the other copied to the control page. There is a virtual >+ * mapping of each, in the original kernel. It is the *original* which is >+ * called from machine_kexec(), largely becaose the copy isn't mapped as an >+ * executable page. Thus, this code cannot just use %rip-relative addressing >+ * until after the %cr3 change and the jump to identity_mapped(). Until >+ * then, some pointer arithmetic is required. >+ */ >+#define DATA(x) (x - relocate_kernel) > > .section .text.relocate_kernel,"ax"; > .code64 >@@ -63,13 +73,13 @@ SYM_CODE_START_NOALIGN(relocate_kernel) > pushf > > movq PTR(VA_CONTROL_PAGE)(%rsi), %r11 >- movq %rsp, RSP(%r11) >+ movq %rsp, DATA(saved_rsp)(%r11) > movq %cr0, %rax >- movq %rax, CR0(%r11) >+ movq %rax, DATA(saved_cr0)(%r11) > movq %cr3, %rax >- movq %rax, CR3(%r11) >+ movq %rax, DATA(saved_cr3)(%r11) > movq %cr4, %rax >- movq %rax, CR4(%r11) >+ movq %rax, DATA(saved_cr4)(%r11) > > /* Save CR4. Required to enable the right paging mode later. */ > movq %rax, %r13 >@@ -94,9 +104,9 @@ 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 %r9, DATA(pa_table_page)(%r11) >+ movq %r10, DATA(pa_swap_page)(%r11) >+ movq %rdi, DATA(pa_backup_pages_map)(%r11) > > /* Save the preserve_context to %r11 as swap_pages clobbers %rcx. */ > movq %rcx, %r11 >@@ -128,7 +138,7 @@ SYM_CODE_START_LOCAL_NOALIGN(identity_mapped) > /* set return address to 0 if not preserving context */ > pushq $0 > /* store the start address on the stack */ >- pushq %rdx >+ pushq start_address(%rip) > > /* > * Clear X86_CR4_CET (if it was set) such that we can clear CR0_WP >@@ -227,9 +237,9 @@ 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 >@@ -243,11 +253,11 @@ 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(%r8), %r8 > movq %rax, %cr3 > movq %r8, %cr0 > movq %rbp, %rax >diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S >index ad451371e179..65f879b31a82 100644 >--- a/arch/x86/kernel/vmlinux.lds.S >+++ b/arch/x86/kernel/vmlinux.lds.S >@@ -100,7 +100,7 @@ const_pcpu_hot = pcpu_hot; > . = ALIGN(PAGE_SIZE); \ > __relocate_kernel_start = .; \ > *(.text.relocate_kernel); \ >- *(.rodata.relocate_kernel); \ >+ *(.data.relocate_kernel); \ > __relocate_kernel_end = .; > #else > #define KEXEC_RELOCATE_KERNEL_TEXT Looks good at first glance. I'm currently traveling so I haven't fully reviewed it though. _______________________________________________ kexec mailing list kexec@xxxxxxxxxxxxxxxxxxx http://lists.infradead.org/mailman/listinfo/kexec
