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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/include/x86-64/arch/msr.h
+3 -2
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@@ -2,6 +2,7 @@
#define _MSR_H
#include <stdint.h>
#include <kernel/kcov.h>
#define MSR_IA32APICBASE 0x1B
#define MSR_PERF_FIXED_CTR2 0x30b
@@ -20,13 +21,13 @@
#define MSR_KVM_SYSTEM_TIME_NEW 0x4b564d01
static inline uint64_t rdmsr(uint32_t which) {
KCOV_DISABLED static inline uint64_t rdmsr(uint32_t which) {
uint64_t low,high;
asm volatile("rdmsr" : "=a"(low), "=d"(high) : "c"(which));
return (high << 32) | low;
}
static inline void wrmsr(uint32_t which, uint64_t value) {
KCOV_DISABLED static inline void wrmsr(uint32_t which, uint64_t value) {
uint32_t low = value & 0xFFFFFFFF;
uint32_t high = (value >> 32) & 0xFFFFFFFF;
asm volatile("wrmsr" : : "a"(low), "d"(high), "c"(which));