From: David Woodhouse <dwmw@xxxxxxxxxxxx> Signed-off-by: David Woodhouse <dwmw@xxxxxxxxxxxx> --- arch/x86/kernel/relocate_kernel_64.S | 114 +++++++++++++++++++++++++++ 1 file changed, 114 insertions(+) diff --git a/arch/x86/kernel/relocate_kernel_64.S b/arch/x86/kernel/relocate_kernel_64.S index 5c174829f794..4ace2577afc6 100644 --- a/arch/x86/kernel/relocate_kernel_64.S +++ b/arch/x86/kernel/relocate_kernel_64.S @@ -40,6 +40,9 @@ SYM_DATA(kexec_pa_swap_page, .quad 0) SYM_DATA_LOCAL(pa_backup_pages_map, .quad 0) #ifdef DEBUG + /* Size of each exception handler referenced by the IDT */ +#define EXC_HANDLER_SIZE 6 /* pushi, pushi, 2-byte jmp */ + SYM_DATA_START_LOCAL(reloc_kernel_gdt) .balign 16 .word reloc_kernel_gdt_end - reloc_kernel_gdt - 1 @@ -108,6 +111,11 @@ 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 +145,52 @@ 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 %rsi */ + lea relocate_kernel(%rip), %rsi + + /* + * 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 %rsi, %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 %rsi, %rcx + andq $0xffff, %rcx // ............cdef + orq %rcx, %rax // 90ab87000010cdef + + movq %rsi, %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, (%rsi) + movq %rbx, 8(%rsi) + addq $16, %rsi + addq $EXC_HANDLER_SIZE, %rax + loop 1b + + /* Now put an IDTR on the stack (temporarily) to load it */ + subq $0x100, %rsi + pushq %rsi + pushw $0xff + lidt (%rsp) + addq $10, %rsp #endif /* DEBUG */ /* @@ -345,3 +399,63 @@ SYM_CODE_START_LOCAL_NOALIGN(swap_pages) int3 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 * EXC_HANDLER_SIZE) + nop + nop + pushq $\exc + jmp exc_handler +.endm + +.macro vec_noerr exc + UNWIND_HINT_ENTRY + . = exc_vectors + (\exc * EXC_HANDLER_SIZE) + 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) +#endif /* DEBUG */ -- 2.47.0
