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//===-- sanitizer_coverage.cc ---------------------------------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// Sanitizer Coverage.
// This file implements run-time support for a poor man's coverage tool.
//
// Compiler instrumentation:
// For every interesting basic block the compiler injects the following code:
// if (*Guard) {
// __sanitizer_cov();
// *Guard = 1;
// }
// It's fine to call __sanitizer_cov more than once for a given block.
//
// Run-time:
// - __sanitizer_cov(): record that we've executed the PC (GET_CALLER_PC).
// - __sanitizer_cov_dump: dump the coverage data to disk.
// For every module of the current process that has coverage data
// this will create a file module_name.PID.sancov. The file format is simple:
// it's just a sorted sequence of 4-byte offsets in the module.
//
// Eventually, this coverage implementation should be obsoleted by a more
// powerful general purpose Clang/LLVM coverage instrumentation.
// Consider this implementation as prototype.
//
// FIXME: support (or at least test with) dlclose.
//===----------------------------------------------------------------------===//
#include "sanitizer_allocator_internal.h"
#include "sanitizer_common.h"
#include "sanitizer_libc.h"
#include "sanitizer_mutex.h"
#include "sanitizer_procmaps.h"
#include "sanitizer_stacktrace.h"
#include "sanitizer_flags.h"
atomic_uint32_t dump_once_guard; // Ensure that CovDump runs only once.
// pc_array is the array containing the covered PCs.
// To make the pc_array thread- and async-signal-safe it has to be large enough.
// 128M counters "ought to be enough for anybody" (4M on 32-bit).
// pc_array is allocated with MmapNoReserveOrDie and so it uses only as
// much RAM as it really needs.
static const uptr kPcArraySize = FIRST_32_SECOND_64(1 << 22, 1 << 27);
static uptr *pc_array;
static atomic_uintptr_t pc_array_index;
static bool cov_sandboxed = false;
static int cov_fd = kInvalidFd;
static unsigned int cov_max_block_size = 0;
namespace __sanitizer {
// Simply add the pc into the vector under lock. If the function is called more
// than once for a given PC it will be inserted multiple times, which is fine.
static void CovAdd(uptr pc) {
if (!pc_array) return;
uptr idx = atomic_fetch_add(&pc_array_index, 1, memory_order_relaxed);
CHECK_LT(idx, kPcArraySize);
pc_array[idx] = pc;
}
void CovInit() {
pc_array = reinterpret_cast<uptr *>(
MmapNoReserveOrDie(sizeof(uptr) * kPcArraySize, "CovInit"));
}
static inline bool CompareLess(const uptr &a, const uptr &b) {
return a < b;
}
// Block layout for packed file format: header, followed by module name (no
// trailing zero), followed by data blob.
struct CovHeader {
int pid;
unsigned int module_name_length;
unsigned int data_length;
};
static void CovWritePacked(int pid, const char *module, const void *blob,
unsigned int blob_size) {
CHECK_GE(cov_fd, 0);
unsigned module_name_length = internal_strlen(module);
CovHeader header = {pid, module_name_length, blob_size};
if (cov_max_block_size == 0) {
// Writing to a file. Just go ahead.
internal_write(cov_fd, &header, sizeof(header));
internal_write(cov_fd, module, module_name_length);
internal_write(cov_fd, blob, blob_size);
} else {
// Writing to a socket. We want to split the data into appropriately sized
// blocks.
InternalScopedBuffer<char> block(cov_max_block_size);
CHECK_EQ((uptr)block.data(), (uptr)(CovHeader *)block.data());
uptr header_size_with_module = sizeof(header) + module_name_length;
CHECK_LT(header_size_with_module, cov_max_block_size);
unsigned int max_payload_size =
cov_max_block_size - header_size_with_module;
char *block_pos = block.data();
internal_memcpy(block_pos, &header, sizeof(header));
block_pos += sizeof(header);
internal_memcpy(block_pos, module, module_name_length);
block_pos += module_name_length;
char *block_data_begin = block_pos;
char *blob_pos = (char *)blob;
while (blob_size > 0) {
unsigned int payload_size = Min(blob_size, max_payload_size);
blob_size -= payload_size;
internal_memcpy(block_data_begin, blob_pos, payload_size);
blob_pos += payload_size;
((CovHeader *)block.data())->data_length = payload_size;
internal_write(cov_fd, block.data(),
header_size_with_module + payload_size);
}
}
}
// Dump the coverage on disk.
static void CovDump() {
if (!common_flags()->coverage) return;
#if !SANITIZER_WINDOWS
if (atomic_fetch_add(&dump_once_guard, 1, memory_order_relaxed))
return;
uptr size = atomic_load(&pc_array_index, memory_order_relaxed);
InternalSort(&pc_array, size, CompareLess);
InternalMmapVector<u32> offsets(size);
const uptr *vb = pc_array;
const uptr *ve = vb + size;
MemoryMappingLayout proc_maps(/*cache_enabled*/true);
uptr mb, me, off, prot;
InternalScopedBuffer<char> module(4096);
InternalScopedBuffer<char> path(4096 * 2);
for (int i = 0;
proc_maps.Next(&mb, &me, &off, module.data(), module.size(), &prot);
i++) {
if ((prot & MemoryMappingLayout::kProtectionExecute) == 0)
continue;
while (vb < ve && *vb < mb) vb++;
if (vb >= ve) break;
if (*vb < me) {
offsets.clear();
const uptr *old_vb = vb;
CHECK_LE(off, *vb);
for (; vb < ve && *vb < me; vb++) {
uptr diff = *vb - (i ? mb : 0) + off;
CHECK_LE(diff, 0xffffffffU);
offsets.push_back(static_cast<u32>(diff));
}
char *module_name = StripModuleName(module.data());
if (cov_sandboxed) {
CovWritePacked(internal_getpid(), module_name, offsets.data(),
offsets.size() * sizeof(u32));
VReport(1, " CovDump: %zd PCs written to packed file\n", vb - old_vb);
} else {
// One file per module per process.
internal_snprintf((char *)path.data(), path.size(), "%s.%zd.sancov",
module_name, internal_getpid());
uptr fd = OpenFile(path.data(), true);
if (internal_iserror(fd)) {
Report(" CovDump: failed to open %s for writing\n", path.data());
} else {
internal_write(fd, offsets.data(), offsets.size() * sizeof(u32));
internal_close(fd);
VReport(1, " CovDump: %s: %zd PCs written\n", path.data(),
vb - old_vb);
}
}
InternalFree(module_name);
}
}
if (cov_fd >= 0)
internal_close(cov_fd);
#endif // !SANITIZER_WINDOWS
}
static void OpenPackedFileForWriting() {
CHECK(cov_fd == kInvalidFd);
InternalScopedBuffer<char> path(1024);
internal_snprintf((char *)path.data(), path.size(), "%zd.sancov.packed",
internal_getpid());
uptr fd = OpenFile(path.data(), true);
if (internal_iserror(fd)) {
Report(" Coverage: failed to open %s for writing\n", path.data());
Die();
}
cov_fd = fd;
}
void CovPrepareForSandboxing(__sanitizer_sandbox_arguments *args) {
if (!args) return;
if (!common_flags()->coverage) return;
cov_sandboxed = args->coverage_sandboxed;
if (!cov_sandboxed) return;
cov_fd = args->coverage_fd;
cov_max_block_size = args->coverage_max_block_size;
if (cov_fd < 0)
// Pre-open the file now. The sandbox won't allow us to do it later.
OpenPackedFileForWriting();
}
} // namespace __sanitizer
extern "C" {
SANITIZER_INTERFACE_ATTRIBUTE void __sanitizer_cov() {
CovAdd(StackTrace::GetPreviousInstructionPc(GET_CALLER_PC()));
}
SANITIZER_INTERFACE_ATTRIBUTE void __sanitizer_cov_dump() { CovDump(); }
SANITIZER_INTERFACE_ATTRIBUTE void __sanitizer_cov_init() { CovInit(); }
} // extern "C"
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