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kcov: initial implementation

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Implement a device (/dev/kcov) that exposes coverage info for the
kernel. This will be especially useful for coverage-based fuzzing (e.g.
syzkaller).

Exclude a lot of functions which would crash/otherwise interfere in the
coverage, including only processing coverage callbacks when not handling
an irq.
This commit is contained in:
Matheus
2026-10-06 11:05:58 -03:00
parent 111a8696d8
commit e4a4896b4b
14 changed files with 581 additions and 25 deletions
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kernel-src/sys/interrupt.c
+14 -11
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@@ -2,6 +2,7 @@
#include <logging.h>
#include <arch/cpu.h>
#include <arch/context.h>
#include <kernel/kcov.h>
#include <panic.h>
void arch_interrupt_disable();
@@ -9,7 +10,7 @@ void arch_interrupt_enable();
#define DOPENDING_SAVE() arch_context_saveandcall(dopending, NULL, NULL)
static void removefromqueue(isr_t *isr) {
KCOV_DISABLED static void removefromqueue(isr_t *isr) {
if (isr->prev)
isr->prev->next = isr->next;
else
@@ -19,7 +20,7 @@ static void removefromqueue(isr_t *isr) {
isr->next->prev = isr->prev;
}
static void insertinqueue(isr_t *isr) {
KCOV_DISABLED static void insertinqueue(isr_t *isr) {
if (isr->pending)
return;
@@ -29,7 +30,7 @@ static void insertinqueue(isr_t *isr) {
current_cpu()->isrqueue = isr;
}
static void runisr(isr_t *isr, context_t *ctx) {
KCOV_DISABLED static void runisr(isr_t *isr, context_t *ctx) {
long oldipl = -1;
if (isr->priority != IPL_IGNORE)
oldipl = interrupt_raiseipl(isr->priority);
@@ -41,7 +42,7 @@ static void runisr(isr_t *isr, context_t *ctx) {
interrupt_loweripl(oldipl);
}
static void dopending(context_t *ctx, void *) {
KCOV_DISABLED static void dopending(context_t *ctx, void *) {
arch_interrupt_disable();
bool entrystatus = current_cpu()->intstatus;
current_cpu()->intstatus = false;
@@ -100,7 +101,7 @@ __attribute__((no_caller_saved_registers)) void sched_userspacecheck(context_t *
uint64_t syscallret,
uint64_t syscallerrno);
void interrupt_isr(int vec, context_t *ctx) {
KCOV_DISABLED void interrupt_isr(int vec, context_t *ctx) {
isr_t *isr = &current_cpu()->isr[vec];
current_cpu()->intstatus = false;
@@ -133,7 +134,7 @@ void interrupt_isr(int vec, context_t *ctx) {
current_cpu()->intstatus = ARCH_CONTEXT_INTSTATUS(ctx);
}
void interrupt_raise(isr_t *isr) {
KCOV_DISABLED void interrupt_raise(isr_t *isr) {
bool entrystate = interrupt_set(false);
if (isr->pending)
@@ -146,7 +147,8 @@ void interrupt_raise(isr_t *isr) {
interrupt_set(entrystate);
}
void interrupt_register(int vector, void (*func)(isr_t *self, context_t *ctx), void (*eoi)(isr_t *self), long priority) {
KCOV_DISABLED void interrupt_register(int vector, void (*func)(isr_t *self, context_t *ctx),
void (*eoi)(isr_t *self), long priority) {
bool intstatus = interrupt_set(false);
isr_t *isr = &current_cpu()->isr[vector];
@@ -159,7 +161,8 @@ void interrupt_register(int vector, void (*func)(isr_t *self, context_t *ctx), v
interrupt_set(intstatus);
}
isr_t *interrupt_allocate(void (*func)(isr_t *self, context_t *ctx), void (*eoi)(isr_t *self), long priority) {
KCOV_DISABLED isr_t *interrupt_allocate(void (*func)(isr_t *self, context_t *ctx), void (*eoi)(isr_t *self),
long priority) {
bool intstatus = interrupt_set(false);
isr_t *isr = NULL;
@@ -175,7 +178,7 @@ isr_t *interrupt_allocate(void (*func)(isr_t *self, context_t *ctx), void (*eoi)
return isr;
}
long interrupt_loweripl(long ipl) {
KCOV_DISABLED long interrupt_loweripl(long ipl) {
bool oldintstatus = interrupt_set(false);
long oldipl = current_cpu()->ipl;
if (oldipl < ipl)
@@ -185,7 +188,7 @@ long interrupt_loweripl(long ipl) {
return oldipl;
}
long interrupt_raiseipl(long ipl) {
KCOV_DISABLED long interrupt_raiseipl(long ipl) {
bool oldintstatus = interrupt_set(false);
long oldipl = current_cpu()->ipl;
@@ -197,7 +200,7 @@ long interrupt_raiseipl(long ipl) {
return oldipl;
}
bool interrupt_set(bool status) {
KCOV_DISABLED bool interrupt_set(bool status) {
arch_interrupt_disable();
bool old = current_cpu()->intstatus;