Utilities+Tests: Convert test_efault to be LibTest based

This test exposed a kernel panic in is_user_range calculations, so let's
convert it to be a LibTest test so we can prevent regressions in mmap,
the page allocator, and the memory manager.

1 files changed, 98 insertions, 0 deletions

diff --git a/Tests/Kernel/TestEFault.cpp b/Tests/Kernel/TestEFault.cpp
new file mode 100644
index 0000000000..831f843cc1
--- /dev/null
+++ b/Tests/Kernel/TestEFault.cpp
@@ -0,0 +1,98 @@
+/*
+ * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
+ * Copyright (c) 2021, Andrew Kaster <akaster@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <AK/Assertions.h>
+#include <AK/Format.h>
+#include <AK/Types.h>
+#include <LibTest/TestCase.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <sys/mman.h>
+#include <unistd.h>
+
+#define EXPECT_OK(syscall, address, size)                                                                                         \
+    do {                                                                                                                          \
+        rc = syscall(fd, (void*)(address), (size_t)(size));                                                                       \
+        EXPECT(rc >= 0);                                                                                                          \
+        if (rc < 0) {                                                                                                             \
+            warnln("Expected success: " #syscall "({:p}, {}), got rc={}, errno={}", (void*)(address), (size_t)(size), rc, errno); \
+        }                                                                                                                         \
+    } while (0)
+
+#define EXPECT_EFAULT(syscall, address, size)                                                                                    \
+    do {                                                                                                                         \
+        rc = syscall(fd, (void*)(address), (size_t)(size));                                                                      \
+        EXPECT(rc < 0);                                                                                                          \
+        EXPECT_EQ(errno, EFAULT);                                                                                                \
+        if (rc >= 0 || errno != EFAULT) {                                                                                        \
+            warnln("Expected EFAULT: " #syscall "({:p}, {}), got rc={}, errno={}", (void*)(address), (size_t)(size), rc, errno); \
+        }                                                                                                                        \
+    } while (0)
+
+#define EXPECT_EFAULT_NO_FD(syscall, address, size)                                                                              \
+    do {                                                                                                                         \
+        rc = syscall((address), (size_t)(size));                                                                                 \
+        EXPECT(rc < 0);                                                                                                          \
+        EXPECT_EQ(errno, EFAULT);                                                                                                \
+        if (rc >= 0 || errno != EFAULT) {                                                                                        \
+            warnln("Expected EFAULT: " #syscall "({:p}, {}), got rc={}, errno={}", (void*)(address), (size_t)(size), rc, errno); \
+        }                                                                                                                        \
+    } while (0)
+
+TEST_CASE(test_efault)
+{
+    int fd = open("/dev/zero", O_RDONLY);
+    int rc = -1;
+
+    // Test a one-page mapping (4KB)
+    u8* one_page = (u8*)mmap(nullptr, 4096, PROT_READ | PROT_WRITE, MAP_ANONYMOUS | MAP_PRIVATE, 0, 0);
+    VERIFY(one_page);
+    EXPECT_OK(read, one_page, 4096);
+    EXPECT_EFAULT(read, one_page, 4097);
+    EXPECT_EFAULT(read, one_page - 1, 4096);
+
+    // Test a two-page mapping (8KB)
+    u8* two_page = (u8*)mmap(nullptr, 8192, PROT_READ | PROT_WRITE, MAP_ANONYMOUS | MAP_PRIVATE, 0, 0);
+    VERIFY(two_page);
+
+    EXPECT_OK(read, two_page, 4096);
+    EXPECT_OK(read, two_page + 4096, 4096);
+    EXPECT_OK(read, two_page, 8192);
+    EXPECT_OK(read, two_page + 4095, 4097);
+    EXPECT_OK(read, two_page + 1, 8191);
+    EXPECT_EFAULT(read, two_page, 8193);
+    EXPECT_EFAULT(read, two_page - 1, 1);
+
+    // Check validation of pages between the first and last address.
+    ptrdiff_t distance = two_page - one_page;
+    EXPECT_EFAULT(read, one_page, (u32)distance + 1024);
+
+    // Test every kernel page just because.
+    constexpr auto user_range_ceiling = 0xbe000000u;
+    u8* jerk_page = nullptr;
+    for (u64 kernel_address = user_range_ceiling; kernel_address <= 0xffffffff; kernel_address += PAGE_SIZE) {
+        jerk_page = (u8*)mmap((void*)kernel_address, PAGE_SIZE, PROT_READ | PROT_WRITE, MAP_ANONYMOUS | MAP_PRIVATE | MAP_FIXED, 0, 0);
+        EXPECT_EQ(jerk_page, MAP_FAILED);
+        EXPECT_EQ(errno, EFAULT);
+    }
+
+    // Test the page just below where the user VM ends.
+    jerk_page = (u8*)mmap((void*)(user_range_ceiling - PAGE_SIZE), PAGE_SIZE, PROT_READ | PROT_WRITE, MAP_ANONYMOUS | MAP_PRIVATE | MAP_FIXED, 0, 0);
+    EXPECT_EQ(jerk_page, MAP_FAILED);
+    EXPECT_EQ(errno, EFAULT);
+
+    // Test the page just before that
+    jerk_page = (u8*)mmap((void*)(user_range_ceiling - (2 * PAGE_SIZE)), PAGE_SIZE, PROT_READ | PROT_WRITE, MAP_ANONYMOUS | MAP_PRIVATE | MAP_FIXED, -1, 0);
+    EXPECT_EQ(jerk_page, (u8*)(user_range_ceiling - (2 * PAGE_SIZE)));
+
+    EXPECT_OK(read, jerk_page, 4096);
+    EXPECT_EFAULT(read, jerk_page, 4097);
+
+    // Test something that would wrap around the 2^32 mark.
+    EXPECT_EFAULT(read, jerk_page, 0x50000000);
+}