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/*
*
* Copyright 2024 Google Inc.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. The name of the author may not be used to endorse or promote products
* derived from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
.align 16
.global exception_stack_end
exception_stack_end:
.quad 0
.global exception_state
exception_state:
.quad 0
/* Some temporary variables which are used while saving exception state. */
vector:
.quad 0
error_code:
.quad 0
old_rax:
.quad 0
old_rcx:
.quad 0
.align 16
/*
* Each exception vector has a small stub associated with it which sets aside
* the error code, if any, records which vector we entered from, and calls
* the common exception entry point. Some exceptions have error codes and some
* don't, so we have a macro for each type.
*/
.macro stub num
exception_stub_\num:
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
.endm
.altmacro
.macro user_defined_stubs from, to
stub \from
.if \to-\from
user_defined_stubs %(from+1),\to
.endif
.endm
stub 0
stub 1
stub 2
stub 3
stub 4
stub 5
stub 6
stub 7
stub_err 8
stub 9
stub_err 10
stub_err 11
stub_err 12
stub_err 13
stub_err 14
stub 15
stub 16
stub_err 17
stub 18
stub 19
stub 20
stub 21
stub 22
stub 23
stub 24
stub 25
stub 26
stub 27
stub 28
stub 29
stub_err 30
stub 31
/* Split the macro so we avoid a stack overflow. */
user_defined_stubs 32, 63
user_defined_stubs 64, 127
user_defined_stubs 128, 191
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
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
* in the GDT. We set one up here which is pretty standard and largely copied
* from coreboot.
*/
.align 16
gdt:
/* selgdt 0, unused */
.word 0x0000, 0x0000
.byte 0x00, 0x00, 0x00, 0x00
/* selgdt 8, unused */
.word 0x0000, 0x0000
.byte 0x00, 0x00, 0x00, 0x00
/* selgdt 0x10, flat 4GB code segment */
.word 0xffff, 0x0000
.byte 0x00, 0x9b, 0xcf, 0x00
/* selgdt 0x18, flat 4GB data segment */
.word 0xffff, 0x0000
.byte 0x00, 0x92, 0xcf, 0x00
/* selgdt 0x20, flat x64 code segment */
.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
/*
* Record the target and construct the actual entry at init time. This
* is necessary because the linker doesn't want to construct the entry
* for us.
*/
.macro interrupt_gate 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
.macro user_defined_gates from, to
interrupt_gate exception_stub_\from
.if \to-\from
user_defined_gates %(from+1),\to
.endif
.endm
.align 16
.global idt
idt:
interrupt_gate exception_stub_0
interrupt_gate exception_stub_1
interrupt_gate exception_stub_2
interrupt_gate exception_stub_3
interrupt_gate exception_stub_4
interrupt_gate exception_stub_5
interrupt_gate exception_stub_6
interrupt_gate exception_stub_7
interrupt_gate exception_stub_8
interrupt_gate exception_stub_9
interrupt_gate exception_stub_10
interrupt_gate exception_stub_11
interrupt_gate exception_stub_12
interrupt_gate exception_stub_13
interrupt_gate exception_stub_14
interrupt_gate exception_stub_15
interrupt_gate exception_stub_16
interrupt_gate exception_stub_17
interrupt_gate exception_stub_18
interrupt_gate exception_stub_19
interrupt_gate exception_stub_20
interrupt_gate exception_stub_21
interrupt_gate exception_stub_22
interrupt_gate exception_stub_23
interrupt_gate exception_stub_24
interrupt_gate exception_stub_25
interrupt_gate exception_stub_26
interrupt_gate exception_stub_27
interrupt_gate exception_stub_28
interrupt_gate exception_stub_29
interrupt_gate exception_stub_30
interrupt_gate exception_stub_31
user_defined_gates 32, 63
user_defined_gates 64, 127
user_defined_gates 128, 191
user_defined_gates 192, 255
idt_end:
/* IDT pointer for use with lidt */
idt_ptr:
.word idt_end - idt - 1
.quad idt
.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
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