From: David Woodhouse <d...@amazon.co.uk> Signed-off-by: David Woodhouse <d...@amazon.co.uk> --- arch/x86/include/asm/kexec.h | 5 ++ arch/x86/kernel/machine_kexec_64.c | 23 ++++++++ arch/x86/kernel/relocate_kernel_64.S | 82 ++++++++++++++++++++++++++++ 3 files changed, 110 insertions(+)
diff --git a/arch/x86/include/asm/kexec.h b/arch/x86/include/asm/kexec.h index 48e4f44f794f..c14b0a2704c0 100644 --- a/arch/x86/include/asm/kexec.h +++ b/arch/x86/include/asm/kexec.h @@ -8,6 +8,9 @@ # define PA_PGD 2 # define PA_SWAP_PAGE 3 # define PAGES_NR 4 +#else +/* Size of each exception handler referenced by the IDT */ +# define KEXEC_DEBUG_EXC_HANDLER_SIZE 6 /* pushi, pushi, 2-byte jmp */ #endif # define KEXEC_CONTROL_PAGE_SIZE 4096 @@ -58,6 +61,8 @@ struct kimage; extern unsigned long kexec_va_control_page; extern unsigned long kexec_pa_table_page; extern unsigned long kexec_pa_swap_page; +extern gate_desc kexec_debug_idt[]; +extern unsigned char kexec_debug_exc_vectors[]; #endif /* diff --git a/arch/x86/kernel/machine_kexec_64.c b/arch/x86/kernel/machine_kexec_64.c index 9232ad1562c8..f9a68c6ec815 100644 --- a/arch/x86/kernel/machine_kexec_64.c +++ b/arch/x86/kernel/machine_kexec_64.c @@ -304,6 +304,26 @@ static void load_segments(void) ); } +static void prepare_debug_idt(unsigned long control_page, unsigned long vec_ofs) +{ +#ifdef CONFIG_KEXEC_DEBUG + gate_desc idtentry = { 0 }; + int i; + + idtentry.bits.p = 1; + idtentry.bits.type = GATE_TRAP; + idtentry.segment = __KERNEL_CS; + idtentry.offset_low = (control_page & 0xFFFF) + vec_ofs; + idtentry.offset_middle = (control_page >> 16) & 0xFFFF; + idtentry.offset_high = control_page >> 32; + + for (i = 0; i < 16; i++) { + kexec_debug_idt[i] = idtentry; + idtentry.offset_low += KEXEC_DEBUG_EXC_HANDLER_SIZE; + } +#endif +} + int machine_kexec_prepare(struct kimage *image) { void *control_page = page_address(image->control_code_page); @@ -321,6 +341,9 @@ int machine_kexec_prepare(struct kimage *image) if (image->type == KEXEC_TYPE_DEFAULT) kexec_pa_swap_page = page_to_pfn(image->swap_page) << PAGE_SHIFT; + prepare_debug_idt((unsigned long)__pa(control_page), + (unsigned long)kexec_debug_exc_vectors - reloc_start); + __memcpy(control_page, __relocate_kernel_start, reloc_end - reloc_start); set_memory_rox((unsigned long)control_page, 1); diff --git a/arch/x86/kernel/relocate_kernel_64.S b/arch/x86/kernel/relocate_kernel_64.S index 6c6bfdccfe6a..2179f691a45b 100644 --- a/arch/x86/kernel/relocate_kernel_64.S +++ b/arch/x86/kernel/relocate_kernel_64.S @@ -49,6 +49,12 @@ SYM_DATA_START_LOCAL(kexec_debug_gdt) .quad 0x00af9a000000ffff /* __KERNEL_CS */ .quad 0x00cf92000000ffff /* __KERNEL_DS */ SYM_DATA_END_LABEL(kexec_debug_gdt, SYM_L_LOCAL, kexec_debug_gdt_end) + + .balign 8 +SYM_DATA_START(kexec_debug_idt) + .skip 0x100, 0x00 +SYM_DATA_END(kexec_debug_idt) + #endif /* CONFIG_KEXEC_DEBUG */ .section .text.relocate_kernel,"ax"; @@ -108,6 +114,11 @@ SYM_CODE_START_NOALIGN(relocate_kernel) int3 SYM_CODE_END(relocate_kernel) +#ifdef DEBUG + UNWIND_HINT_UNDEFINED + .balign 0x100 /* relocate_kernel will be overwritten with an IDT */ +#endif + SYM_CODE_START_LOCAL_NOALIGN(identity_mapped) UNWIND_HINT_END_OF_STACK /* @@ -137,6 +148,15 @@ SYM_CODE_START_LOCAL_NOALIGN(identity_mapped) /* Test that we can load segments */ movq %ds, %rax movq %rax, %ds + + /* Now an IDTR on the stack to load the IDT the kernel created */ + leaq kexec_debug_idt(%rip), %rsi + pushq %rsi + pushw $0xff + lidt (%rsp) + addq $10, %rsp + + //int3 #endif /* CONFIG_KEXEC_DEBUG */ /* @@ -346,3 +366,65 @@ SYM_CODE_START_LOCAL_NOALIGN(swap_pages) ret int3 SYM_CODE_END(swap_pages) + +#ifdef CONFIG_KEXEC_DEBUG +SYM_CODE_START_NOALIGN(kexec_debug_exc_vectors) + /* Each of these is 6 bytes. */ +.macro vec_err exc + UNWIND_HINT_ENTRY + . = kexec_debug_exc_vectors + (\exc * KEXEC_DEBUG_EXC_HANDLER_SIZE) + nop + nop + pushq $\exc + jmp exc_handler +.endm + +.macro vec_noerr exc + UNWIND_HINT_ENTRY + . = kexec_debug_exc_vectors + (\exc * KEXEC_DEBUG_EXC_HANDLER_SIZE) + pushq $0 + pushq $\exc + jmp exc_handler +.endm + + ANNOTATE_NOENDBR + vec_noerr 0 // #DE + vec_noerr 1 // #DB + vec_noerr 2 // #NMI + vec_noerr 3 // #BP + vec_noerr 4 // #OF + vec_noerr 5 // #BR + vec_noerr 6 // #UD + vec_noerr 7 // #NM + vec_err 8 // #DF + vec_noerr 9 + vec_err 10 // #TS + vec_err 11 // #NP + vec_err 12 // #SS + vec_err 13 // #GP + vec_err 14 // #PF + vec_noerr 15 +SYM_CODE_END(kexec_debug_exc_vectors) + +SYM_CODE_START_LOCAL_NOALIGN(exc_handler) + pushq %rax + pushq %rdx + movw $0x3f8, %dx + movb $'A', %al + outb %al, %dx + popq %rdx + popq %rax + + /* Only return from int3 */ + cmpq $3, (%rsp) + jne .Ldie + + addq $16, %rsp + iretq + +.Ldie: + hlt + jmp .Ldie + +SYM_CODE_END(exc_handler) +#endif /* CONFIG_KEXEC_DEBUG */ -- 2.47.0