kernel+userland: support build with undefined behavior sanitizer

.github/workflows/ci.yml

@@ -20,3 +20,13 @@ jobs:
               timeout-minutes: 3
             - run: grub-file --is-x86-multiboot kernel/kernel
             - run: make disk_image
+    ubsan:
+        runs-on: ubuntu-24.04
+        env:
+            CC: gcc
+        steps:
+            - uses: actions/checkout@v4
+            - run: sudo apt-get update && sudo apt-get install -y gcc-multilib cpio qemu-system-x86
+            - run: make EXTRA_CFLAGS="-Werror -fsanitize=undefined"
+            - run: make test
+              timeout-minutes: 5

common/panic.h

@@ -0,0 +1,11 @@
+#pragma once
+
+#include <stddef.h>
+#include <stdnoreturn.h>
+
+#define PANIC(...) panic(__FILE__, __LINE__, __VA_ARGS__)
+#define UNREACHABLE() PANIC("Unreachable")
+#define UNIMPLEMENTED() PANIC("Unimplemented")
+#define ASSERT(cond) ((cond) ? (void)0 : PANIC("Assertion failed: " #cond))
+
+noreturn void panic(const char* file, size_t line, const char* message, ...);

common/ubsan.c

@@ -0,0 +1,137 @@
+#include "panic.h"
+#include <stdbool.h>
+#include <stdint.h>
+
+struct source_location {
+    const char* filename;
+    uint32_t line;
+    uint32_t column;
+};
+
+struct type_descriptor {
+    uint16_t kind;
+    uint16_t info;
+    char name[];
+};
+
+struct invalid_value_data {
+    struct source_location location;
+    const struct type_descriptor* type;
+};
+
+void __ubsan_handle_load_invalid_value(const struct invalid_value_data* data,
+                                       const void* ptr) {
+    (void)ptr;
+    PANIC("ubsan: load invalid value: type=%s", data->type->name);
+}
+
+struct overflow_data {
+    struct source_location location;
+    const struct type_descriptor* type;
+};
+
+void __ubsan_handle_add_overflow(const struct overflow_data* data,
+                                 const void* lhs, const void* rhs) {
+    (void)lhs;
+    (void)rhs;
+    PANIC("ubsan: add overflow: type=%s", data->type->name);
+}
+
+void __ubsan_handle_sub_overflow(const struct overflow_data* data,
+                                 const void* lhs, const void* rhs) {
+    (void)lhs;
+    (void)rhs;
+    PANIC("ubsan: sub overflow: type=%s", data->type->name);
+}
+
+void __ubsan_handle_negate_overflow(const struct overflow_data* data,
+                                    const void* ptr) {
+    (void)ptr;
+    PANIC("ubsan: negate overflow: type=%s", data->type->name);
+}
+
+void __ubsan_handle_mul_overflow(const struct overflow_data* data,
+                                 const void* lhs, const void* rhs) {
+    (void)lhs;
+    (void)rhs;
+    PANIC("ubsan: mul overflow: type=%s", data->type->name);
+}
+
+struct shift_out_of_bounds_data {
+    struct source_location location;
+    const struct type_descriptor* lhs_type;
+    const struct type_descriptor* rhs_type;
+};
+
+void __ubsan_handle_shift_out_of_bounds(
+    const struct shift_out_of_bounds_data* data, const void* lhs,
+    const void* rhs) {
+    (void)lhs;
+    (void)rhs;
+    PANIC("ubsan: shift out of bounds: lhs=%s rhs=%s", data->lhs_type->name,
+          data->rhs_type->name);
+}
+
+void __ubsan_handle_divrem_overflow(const struct overflow_data* data,
+                                    const void* lhs, const void* rhs) {
+    (void)lhs;
+    (void)rhs;
+    PANIC("ubsan: divrem overflow: type=%s", data->type->name);
+}
+
+struct out_of_bounds_data {
+    struct source_location location;
+    const struct type_descriptor* array_type;
+    const struct type_descriptor* index_type;
+};
+
+void __ubsan_handle_out_of_bounds(const struct out_of_bounds_data* data,
+                                  const void* index) {
+    (void)index;
+    PANIC("ubsan: out of bounds: array=%s index=%s", data->array_type->name,
+          data->index_type->name);
+}
+
+struct type_mismatch_data {
+    struct source_location location;
+    const struct type_descriptor* type;
+    uint8_t log_alignment;
+    uint8_t type_check_kind;
+};
+
+void __ubsan_handle_type_mismatch_v1(const struct type_mismatch_data* data,
+                                     const void* ptr) {
+    unsigned alignment = 1U << data->log_alignment;
+    bool aligned = ((uintptr_t)ptr & (alignment - 1)) == 0;
+    PANIC("ubsan: type mismatch: ptr=%p type=%s kind=%u alignment=%u (%s)\n",
+          ptr, data->type->name, data->type_check_kind, alignment,
+          aligned ? "aligned" : "misaligned");
+}
+
+struct unreachable_data {
+    struct source_location location;
+};
+
+void __ubsan_handle_builtin_unreachable(const struct unreachable_data* data) {
+    (void)data;
+    PANIC("ubsan: builtin unreachable");
+}
+
+struct invalid_builtin_data {
+    struct source_location location;
+    uint8_t kind;
+};
+
+void __ubsan_handle_invalid_builtin(const struct invalid_builtin_data* data) {
+    PANIC("ubsan: invalid builtin: kind=%u", data->kind);
+}
+
+struct pointer_overflow_data {
+    struct source_location location;
+};
+
+void __ubsan_handle_pointer_overflow(const struct pointer_overflow_data* data,
+                                     const void* base, const void* result) {
+    (void)data;
+    PANIC("ubsan: pointer overflow: base=%p result=%p", base, result);
+}

kernel/Makefile

@@ -84,7 +84,8 @@ OBJS := \
 	../common/string.o \
 	../common/strings.o \
  	../common/stdio.o \
- 	../common/stdlib.o
+ 	../common/stdlib.o \
+	../common/ubsan.o
 
 DEPS := $(OBJS:.o=.d)
 

kernel/panic.h

@@ -1,14 +1,6 @@
 #pragma once
 
 #include "api/err.h"
-#include <common/extra.h>
-#include <stddef.h>
-#include <stdnoreturn.h>
+#include <common/panic.h>
 
-#define PANIC(...) panic(__FILE__, __LINE__, __VA_ARGS__)
-#define UNREACHABLE() PANIC("Unreachable")
-#define UNIMPLEMENTED() PANIC("Unimplemented")
-#define ASSERT(cond) ((cond) ? (void)0 : PANIC("Assertion failed: " #cond))
 #define ASSERT_OK(result) ASSERT(IS_OK(result))
-
-noreturn void panic(const char* file, size_t line, const char* message, ...);

kernel/time.c

@@ -67,7 +67,9 @@ int time_now(clockid_t clock_id, struct timespec* tp) {
     case CLOCK_MONOTONIC: {
         unsigned t = uptime;
         tp->tv_sec = t / CLK_TCK;
-        tp->tv_nsec = (t - tp->tv_sec * CLK_TCK) * NANOS / CLK_TCK;
+        tp->tv_nsec =
+            divmodi64(((uint64_t)t - (uint64_t)tp->tv_sec * CLK_TCK) * NANOS,
+                      CLK_TCK, NULL);
         break;
     }
     default:

userland/Makefile

@@ -66,6 +66,7 @@ LIB_OBJS := \
 	../common/strings.o \
  	../common/stdio.o \
  	../common/stdlib.o \
+	../common/ubsan.o \
 	lib/asm.o \
 	lib/crt0.o \
 	lib/dirent.o \

userland/lib/panic.h

@@ -1,13 +1,6 @@
 #pragma once
 
-#include <stddef.h>
-#include <stdnoreturn.h>
+#include <common/panic.h>
 
-#define PANIC(...) panic(__FILE__, __LINE__, __VA_ARGS__)
-#define UNREACHABLE() PANIC("Unreachable")
-#define UNIMPLEMENTED() PANIC("Unimplemented")
-#define ASSERT(cond) ((cond) ? (void)0 : PANIC("Assertion failed: " #cond))
 #define ASSERT_OK(result) ASSERT((result) >= 0)
 #define ASSERT_ERR(result) ASSERT((result) < 0)
-
-noreturn void panic(const char* file, size_t line, const char* message, ...);