diff options
| -rw-r--r-- | payloads/libpayload/arch/x86/exception.c | 12 | ||||
| -rw-r--r-- | payloads/libpayload/arch/x86/exception_asm_64.S | 176 |
2 files changed, 158 insertions, 30 deletions
diff --git a/payloads/libpayload/arch/x86/exception.c b/payloads/libpayload/arch/x86/exception.c index fdab042902..9811be3c93 100644 --- a/payloads/libpayload/arch/x86/exception.c +++ b/payloads/libpayload/arch/x86/exception.c @@ -113,13 +113,15 @@ static void dump_stack(uintptr_t addr, size_t bytes) { int i, j; const int line = 8; - uint32_t *ptr = (uint32_t *)(addr & ~(line * sizeof(*ptr) - 1)); + uint32_t *ptr = (uint32_t *)((uintptr_t)addr & ~(line * sizeof(*ptr) - 1)); printf("Dumping stack:\n"); for (i = bytes / sizeof(*ptr); i >= 0; i -= line) { printf("%p: ", ptr + i); - for (j = i; j < i + line; j++) - printf("%08x ", *(ptr + j)); + for (j = i; j < i + line; j++) { + if ((uintptr_t)(ptr + j) >= addr && (uintptr_t)(ptr + j) < addr + bytes) + printf("%08x ", *(ptr + j)); + } printf("\n"); } } @@ -213,10 +215,6 @@ success: void exception_init(void) { - /* TODO: Add exception init code for x64, currently only supporting 32-bit code */ - if (CONFIG(LP_ARCH_X86_64)) - return; - exception_stack_end = exception_stack + ARRAY_SIZE(exception_stack); exception_init_asm(); } diff --git a/payloads/libpayload/arch/x86/exception_asm_64.S b/payloads/libpayload/arch/x86/exception_asm_64.S index ee4e9e5b76..6d91b937ac 100644 --- a/payloads/libpayload/arch/x86/exception_asm_64.S +++ b/payloads/libpayload/arch/x86/exception_asm_64.S @@ -39,10 +39,10 @@ vector: .quad 0 error_code: .quad 0 -old_rsp: - .quad 0 old_rax: .quad 0 +old_rcx: + .quad 0 .align 16 @@ -55,23 +55,23 @@ old_rax: .macro stub num exception_stub_\num: - movq $0, error_code - movq $\num, vector - jmp exception_common + movq $0, error_code + movq $\num, vector + jmp exception_common .endm .macro stub_err num exception_stub_\num: - pop error_code - movq $\num, vector - jmp exception_common + pop error_code + movq $\num, vector + jmp exception_common .endm .altmacro - .macro user_defined_stubs from, to - stub \from - .if \to-\from - user_defined_stubs %(from+1),\to + .macro user_defined_stubs from, to + stub \from + .if \to-\from + user_defined_stubs %(from+1),\to .endif .endm @@ -114,9 +114,117 @@ exception_stub_\num: user_defined_stubs 192, 255 exception_common: + /* + * At this point, on x86-64, on the stack there is: + * 0(%rsp) rip + * 8(%rsp) cs + * 16(%rsp) rflags + * 24(%rsp) rsp + * 32(%rsp) ss + * + * This section sets up the exception stack. + * It saves the old stack pointer (rsp) to preserve RIP, CS, RFLAGS and SS. + * Then sets up the new stack pointer to point to the exception stack area. + */ + movq %rax, old_rax + movq %rcx, old_rcx + + mov %rsp, %rax + movq exception_stack_end, %rsp + /* + * The `exception_state` struct is not 16-byte aligned. + * Push an extra 8 bytes to ensure the stack pointer + * is 16-byte aligned before calling exception_dispatch. + */ + push $0 + + /* + * Push values onto the top of the exception stack to form an + * exception state structure. + */ + push vector + push error_code + + /* push of the gs, fs, es, ds, ss and cs */ + mov %gs, %rcx + movl %ecx, -4(%rsp) /* gs */ + mov %fs, %rcx + movl %ecx, -8(%rsp) /* fs */ + movl $0, -12(%rsp) /* es */ + movl $0, -16(%rsp) /* ds */ + movq 32(%rax), %rcx + movl %ecx, -20(%rsp) /* ss */ + movq 8(%rax), %rcx + movl %ecx, -24(%rsp) /* cs */ + sub $24, %rsp - /* Return from the exception. */ - iretl + push 16(%rax) /* rflags */ + push (%rax) /* rip */ + push %r15 + push %r14 + push %r13 + push %r12 + push %r11 + push %r10 + push %r9 + push %r8 + push 24(%rax) /* rsp */ + push %rbp + push %rdi + push %rsi + push %rdx + push old_rcx /* rcx */ + push %rbx + push old_rax /* rax */ + + /* + * Call the C exception handler. It will find the exception state + * using the exception_state global pointer. Not + * passing parameters means we don't have to worry about what ABI + * is being used. + */ + mov %rsp, exception_state + call exception_dispatch + + /* + * Restore state from the exception state structure, including any + * changes that might have been made. + */ + pop old_rax + pop %rbx + pop old_rcx + pop %rdx + pop %rsi + pop %rdi + pop %rbp + lea exception_stack, %rax + pop 24(%rax) /* rsp */ + pop %r8 + pop %r9 + pop %r10 + pop %r11 + pop %r12 + pop %r13 + pop %r14 + pop %r15 + pop (%rax) /* rip */ + pop 16(%rax) /* rflags */ + + /* pop of the gs, fs, es, ds, ss and cs */ + movl (%rsp), %ecx + movq %rcx, 8(%rax) /* cs */ + movl 4(%rsp), %ecx + movq %rcx, 32(%rax) /* ss */ + movl 16(%rsp), %ecx + mov %rcx, %fs /* fs */ + movl 20(%rsp), %ecx + mov %rcx, %gs /* gs */ + + mov %rax, %rsp + movq old_rax, %rax + movq old_rcx, %rcx + + iretq /* * We need segment selectors for the IDT, so we need to know where things are @@ -139,18 +247,18 @@ gdt: /* selgdt 0x18, flat 4GB data segment */ .word 0xffff, 0x0000 - .byte 0x00, 0x92, 0xcf, 0x00 + .byte 0x00, 0x92, 0xcf, 0x00 /* selgdt 0x20, flat x64 code segment */ - .word 0xffff, 0x0000 - .byte 0x00, 0x9b, 0xaf, 0x00 + .word 0xffff, 0x0000 + .byte 0x00, 0x9b, 0xaf, 0x00 gdt_end: /* GDT pointer for use with lgdt */ .global gdt_ptr gdt_ptr: - .word gdt_end - gdt - 1 - .quad gdt + .word gdt_end - gdt - 1 + .quad gdt /* * Record the target and construct the actual entry at init time. This @@ -158,8 +266,11 @@ gdt_ptr: * for us. */ .macro interrupt_gate target - .quad \target - .quad \target + .word 0 /* patchable */ + .word 0x20 /* Target code segment selector */ + .word 0xee00 /* Present, Type 64-bit Interrupt Gate */ + .word 0 /* patchable */ + .quad \target /* patchable */ .endm .altmacro @@ -171,7 +282,7 @@ gdt_ptr: .endm .align 16 - .global idt + .global idt idt: interrupt_gate exception_stub_0 interrupt_gate exception_stub_1 @@ -216,6 +327,25 @@ idt_ptr: .word idt_end - idt - 1 .quad idt - .global exception_init_asm +.section .text.exception_init_asm +.globl exception_init_asm +.type exception_init_asm, @function + exception_init_asm: + /* Set up IDT entries */ + mov $idt, %rax +1: + movq 8(%rax), %rdi + movw %di, (%rax) /* procedure entry point offset bits 0..15 */ + shr $16, %rdi + movw %di, 6(%rax) /* procedure entry point offset bits 16..31 */ + shr $16, %rdi + movl %edi, 8(%rax) /* procedure entry point offset bits 32..63 */ + movl $0, 12(%rax) /* reserved */ + add $16, %rax + cmp $idt_end, %rax + jne 1b + + /* Load the IDT */ + lidt idt_ptr ret |