From: David Woodhouse <dwmw@xxxxxxxxxxxx> Signed-off-by: David Woodhouse <dwmw@xxxxxxxxxxxx> --- arch/x86/kernel/relocate_kernel_64.S | 110 +++++++++++++++++++++++++++ 1 file changed, 110 insertions(+) diff --git a/arch/x86/kernel/relocate_kernel_64.S b/arch/x86/kernel/relocate_kernel_64.S index 2af4ce593645..2a2a6e693e18 100644 --- a/arch/x86/kernel/relocate_kernel_64.S +++ b/arch/x86/kernel/relocate_kernel_64.S @@ -117,6 +117,11 @@ 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 /* @@ -144,6 +149,52 @@ SYM_CODE_START_LOCAL_NOALIGN(identity_mapped) /* Test that we can load segments */ movq %ds, %rax movq %rax, %ds + + /* Load address of reloc_kernel, at start of this page, into %r8 */ + lea relocate_kernel(%rip), %r8 + + /* + * Build an IDT descriptor in %rax/%rbx. The address is in the low 16 + * and high 16 bits of %rax, and low 32 of %rbx. The niddle 32 bits + * of %rax hold the selector/ist/flags which are hard-coded below. + */ + movq %r8, %rax // 1234567890abcdef + + andq $-0xFFFF, %rax // 1234567890ab.... + shlq $16, %rax // 567890ab........ + + movq $0x8F000010, %rcx // Present, DPL0, Interrupt Gate, __KERNEL_CS. + orq %rcx, %rax // 567890ab8F000010 + shlq $16, %rax // 90ab8F000010.... + + movq %r8, %rcx + andq $0xffff, %rcx // ............cdef + orq %rcx, %rax // 90ab87000010cdef + + movq %r8, %rbx + shrq $32, %rbx + + /* + * The descriptor was built using the address of relocate_kernel. Add + * the required offset to point to the actual entry points. + */ + addq $(exc_vectors - relocate_kernel), %rax + + /* Loop 16 times to handle exception 0-15 */ + movq $16, %rcx +1: + movq %rax, (%r8) + movq %rbx, 8(%r8) + addq $16, %r8 + addq $6, %rax + loop 1b + + /* Now put an IDTR on the stack (temporarily) to load it */ + subq $0x100, %r8 + pushq %r8 + pushw $0xff + lidt (%rsp) + addq $10, %rsp #endif /* DEBUG */ /* @@ -347,6 +398,65 @@ SYM_CODE_START_LOCAL_NOALIGN(swap_pages) SYM_CODE_END(swap_pages) #ifdef DEBUG +SYM_CODE_START_LOCAL_NOALIGN(exc_vectors) + /* Each of these is 6 bytes. */ +.macro vec_err exc + UNWIND_HINT_ENTRY + . = exc_vectors + (\exc * 6) + nop + nop + pushq $\exc + jmp exc_handler +.endm + +.macro vec_noerr exc + UNWIND_HINT_ENTRY + . = exc_vectors + (\exc * 6) + pushq $0 + pushq $\exc + jmp exc_handler +.endm + + 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(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) + .Lreloc_kernel_gdt: .word 1f - .Lreloc_kernel_gdt - 1 .long 0 -- 2.44.0 _______________________________________________ kexec mailing list kexec@xxxxxxxxxxxxxxxxxxx http://lists.infradead.org/mailman/listinfo/kexec
