From 2a09d77902c5007fb30c40f9c89ecb46aedf4006 Mon Sep 17 00:00:00 2001
From: dzwdz
Date: Mon, 22 Jul 2024 18:05:07 +0200
Subject: kernel/isr: improve interrupt handling code
On the assembly side, ensure the stack frame looks always the same, by pushing
a fake "error code" for the interrupts that don't generate one.
On the C side, use a struct instead of magic indices into an "array", and
make it consistent with the current style.
---
src/kernel/arch/amd64/interrupts.h | 2 +-
src/kernel/arch/amd64/interrupts/isr.c | 61 ++++++++++++++++++-----------
src/kernel/arch/amd64/interrupts/isr_stub.s | 22 ++++++++---
3 files changed, 56 insertions(+), 29 deletions(-)
(limited to 'src')
diff --git a/src/kernel/arch/amd64/interrupts.h b/src/kernel/arch/amd64/interrupts.h
index dfc523a..288bd78 100644
--- a/src/kernel/arch/amd64/interrupts.h
+++ b/src/kernel/arch/amd64/interrupts.h
@@ -14,4 +14,4 @@ extern const char _isr_stubs;
void irq_init(void);
void irq_eoi(uint8_t line);
-void isr_stage3(uint8_t interrupt, uint64_t *stackframe);
+void isr_stage3(uint8_t interrupt, void *stackframe);
diff --git a/src/kernel/arch/amd64/interrupts/isr.c b/src/kernel/arch/amd64/interrupts/isr.c
index dd97fd4..bf84c5c 100644
--- a/src/kernel/arch/amd64/interrupts/isr.c
+++ b/src/kernel/arch/amd64/interrupts/isr.c
@@ -8,29 +8,48 @@
#include <stdint.h>
enum {
- NMI = 0x02,
- GP_FAULT = 0x0d,
- PAGE_FAULT = 0x0e,
+ Nmi = 0x02,
+ GpFault = 0x0d,
+ PageFault = 0x0e,
};
+typedef struct {
+ uint64_t ip, cs, flags;
+ /* only valid if switching from/into user mode */
+ uint64_t sp, ss;
+} IretFrame;
+
void (*irq_fn[16])(void) = {0};
-static void log_interrupt(int interrupt, uint64_t *stackframe) {
+static uint64_t
+getcr2(void)
+{
+ uint64_t cr2;
+ asm("mov %%cr2, %0" : "=r"(cr2));
+ return cr2;
+}
+
+static void
+log_interrupt(uint8_t inr, void *stackframe)
+{
+ IretFrame *iret = stackframe;
+ uint64_t *errcode = ((uint64_t*)stackframe) - 1;
kprintf("interrupt %d, rip = k/%08x, cs 0x%x, code 0x%x\n",
- interrupt, stackframe[0], stackframe[1], stackframe[-1]);
- if ((stackframe[1] & 0x3) == 0) {
- uint64_t *stack = (void*)stackframe[3];
- kprintf("kernel rip = %p, *rip = %p\n", stack, *stack);
+ inr, iret->ip, iret->cs, *errcode);
+ if ((iret->cs & 0x3) == 0) { /* ring 0? */
+ uint64_t *stack = (void*)iret->sp;
+ kprintf("kernel rsp = %p, *rsp = %p\n", stack, *stack);
}
- if (interrupt == PAGE_FAULT) {
- uint64_t addr = 0x69;
- asm("mov %%cr2, %0" : "=r"(addr));
- kprintf("addr 0x%x\n", addr);
+ if (inr == PageFault) {
+ kprintf("addr 0x%x\n", getcr2());
}
}
-void isr_stage3(uint8_t interrupt, uint64_t *stackframe) {
- uint8_t irqn = interrupt - IRQ_IBASE;
+void
+isr_stage3(uint8_t inr, void *stackframe)
+{
+ IretFrame *iret = stackframe;
+ uint8_t irqn = inr - IRQ_IBASE;
if (irqn < 16) {
if (irq_fn[irqn]) {
irq_fn[irqn]();
@@ -39,21 +58,17 @@ void isr_stage3(uint8_t interrupt, uint64_t *stackframe) {
}
}
- if (interrupt == NMI) { /* print some debugging information */
- log_interrupt(interrupt, stackframe);
+ if (inr == Nmi) { /* print some debugging information */
+ log_interrupt(inr, stackframe);
mem_debugprint();
return;
}
- if (interrupt == PAGE_FAULT || interrupt == GP_FAULT) {
- stackframe++;
- }
-
- if ((stackframe[1] & 0x3) == 0) { /* in kernel */
- log_interrupt(interrupt, stackframe);
+ if ((iret->cs & 0x3) == 0) { /* ring 0? */
+ log_interrupt(inr, stackframe);
cpu_halt();
} else { /* in user */
- proc_kill(proc_cur, interrupt);
+ proc_kill(proc_cur, inr);
proc_switch_any();
}
}
diff --git a/src/kernel/arch/amd64/interrupts/isr_stub.s b/src/kernel/arch/amd64/interrupts/isr_stub.s
index 75934d5..3134808 100644
--- a/src/kernel/arch/amd64/interrupts/isr_stub.s
+++ b/src/kernel/arch/amd64/interrupts/isr_stub.s
@@ -2,21 +2,27 @@
.global _isr_stubs
_isr_stubs:
+.set i, 0
.rept 256
.set _stub_start, .
cli
+ .if i != 8 && i != 10 && i != 11 && i != 12 && i != 13 && i != 14 && i != 17 && i != 21 && i != 29 && i != 30
+ /* no error code was pushed - push anything, just to line up the stack */
+ push %rbx
+ .endif
call _isr_stage2
.if . - _stub_start > 8
.error "isr stubs over maximum size"
.abort
.endif
- .align 8
+ .align 8, 0xCC
+ .set i, i + 1
.endr
_isr_stage2:
- // pushal order, without %esp
+ /* pushal order, without %esp. 15 in total */
push %rax
push %rcx
push %rdx
@@ -33,13 +39,19 @@ _isr_stage2:
push %r14
push %r15
// TODO FXSAVE might be required on interrupts too?
+ // on interrupts - no
+ // on syscalls - yes
+ // have fun figuring that one out
+ // basically if you're context switching, FXSAVE
- // convert the return address into the vector nr
+ /* first argument: vector nr. computed from the return address at offset
+ * 15*8 = 120 */
mov 120(%rsp), %rdi
sub $_isr_stubs, %rdi
shr $3, %rdi
- lea 128(%rsp), %rsi // second argument - IRET stack frame
+ /* second argument: IRET stack frame */
+ lea 136(%rsp), %rsi
// load kernel paging
mov %cr3, %rbx
@@ -72,7 +84,7 @@ _isr_stage2:
pop %rcx
pop %rax
- add $8, %rsp // skip call's return address
+ add $16, %rsp /* skip return address from call and the error code */
iretq
.align 8
--
cgit v1.2.3