clang-p2996/compiler-rt/lib/esan/esan.cpp

//===-- esan.cpp ----------------------------------------------------------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file is a part of EfficiencySanitizer, a family of performance tuners.
//
// Main file (entry points) for the Esan run-time.
//===----------------------------------------------------------------------===//

#include "esan.h"
#include "esan_interface_internal.h"
#include "esan_shadow.h"
#include "sanitizer_common/sanitizer_common.h"
#include "sanitizer_common/sanitizer_flag_parser.h"
#include "sanitizer_common/sanitizer_flags.h"

// See comment below.
extern "C" {
extern void __cxa_atexit(void (*function)(void));
}

namespace __esan {

bool EsanIsInitialized;
ToolType WhichTool;
ShadowMapping Mapping;

static const char EsanOptsEnv[] = "ESAN_OPTIONS";

// We are combining multiple performance tuning tools under the umbrella of
// one EfficiencySanitizer super-tool.  Most of our tools have very similar
// memory access instrumentation, shadow memory mapping, libc interception,
// etc., and there is typically more shared code than distinct code.
//
// We are not willing to dispatch on tool dynamically in our fastpath
// instrumentation: thus, which tool to use is a static option selected
// at compile time and passed to __esan_init().
//
// We are willing to pay the overhead of tool dispatch in the slowpath to more
// easily share code.  We expect to only come here rarely.
// If this becomes a performance hit, we can add separate interface
// routines for each subtool (e.g., __esan_cache_frag_aligned_load_4).
// But for libc interceptors, we'll have to do one of the following:
// A) Add multiple-include support to sanitizer_common_interceptors.inc,
//    instantiate it separately for each tool, and call the selected
//    tool's intercept setup code.
// B) Build separate static runtime libraries, one for each tool.
// C) Completely split the tools into separate sanitizers.

void processRangeAccess(uptr PC, uptr Addr, int Size, bool IsWrite) {
  VPrintf(3, "in esan::%s %p: %c %p %d\n", __FUNCTION__, PC,
          IsWrite ? 'w' : 'r', Addr, Size);
  if (WhichTool == ESAN_CacheFrag) {
    // TODO(bruening): add shadow mapping and update shadow bits here.
    // We'll move this to cache_frag.cpp once we have something.
  }
}

#if SANITIZER_DEBUG
static bool verifyShadowScheme() {
  // Sanity checks for our shadow mapping scheme.
  for (int Scale = 0; Scale < 8; ++Scale) {
    Mapping.initialize(Scale);
    uptr AppStart, AppEnd;
    for (int i = 0; getAppRegion(i, &AppStart, &AppEnd); ++i) {
      DCHECK(isAppMem(AppStart));
      DCHECK(!isAppMem(AppStart - 1));
      DCHECK(isAppMem(AppEnd - 1));
      DCHECK(!isAppMem(AppEnd));
      DCHECK(!isShadowMem(AppStart));
      DCHECK(!isShadowMem(AppEnd - 1));
      DCHECK(isShadowMem(appToShadow(AppStart)));
      DCHECK(isShadowMem(appToShadow(AppEnd - 1)));
      // Double-shadow checks.
      DCHECK(!isShadowMem(appToShadow(appToShadow(AppStart))));
      DCHECK(!isShadowMem(appToShadow(appToShadow(AppEnd - 1))));
    }
    // Ensure no shadow regions overlap each other.
    uptr ShadowAStart, ShadowBStart, ShadowAEnd, ShadowBEnd;
    for (int i = 0; getShadowRegion(i, &ShadowAStart, &ShadowAEnd); ++i) {
      for (int j = 0; getShadowRegion(j, &ShadowBStart, &ShadowBEnd); ++j) {
        DCHECK(i == j || ShadowAStart >= ShadowBEnd ||
               ShadowAEnd <= ShadowBStart);
      }
    }
  }
  return true;
}
#endif

static void initializeShadow() {
  DCHECK(verifyShadowScheme());

  if (WhichTool == ESAN_CacheFrag)
    Mapping.initialize(2); // 4B:1B, so 4 to 1 == >>2.
  else
    UNREACHABLE("unknown tool shadow mapping");

  VPrintf(1, "Shadow scale=%d offset=%p\n", Mapping.Scale, Mapping.Offset);

  uptr ShadowStart, ShadowEnd;
  for (int i = 0; getShadowRegion(i, &ShadowStart, &ShadowEnd); ++i) {
    VPrintf(1, "Shadow #%d: [%zx-%zx) (%zuGB)\n", i, ShadowStart, ShadowEnd,
            (ShadowEnd - ShadowStart) >> 30);

    uptr Map = (uptr)MmapFixedNoReserve(ShadowStart, ShadowEnd - ShadowStart,
                                        "shadow");
    if (Map != ShadowStart) {
      Printf("FATAL: EfficiencySanitizer failed to map its shadow memory.\n");
      Die();
    }

    if (common_flags()->no_huge_pages_for_shadow)
      NoHugePagesInRegion(ShadowStart, ShadowEnd - ShadowStart);
    if (common_flags()->use_madv_dontdump)
      DontDumpShadowMemory(ShadowStart, ShadowEnd - ShadowStart);

    // TODO: Call MmapNoAccess() on in-between regions.
  }
}

static void initializeFlags() {
  // Once we add our own flags we'll parse them here.
  // For now the common ones are sufficient.
  FlagParser Parser;
  SetCommonFlagsDefaults();
  RegisterCommonFlags(&Parser);
  Parser.ParseString(GetEnv(EsanOptsEnv));
  InitializeCommonFlags();
  if (Verbosity())
    ReportUnrecognizedFlags();
  if (common_flags()->help)
    Parser.PrintFlagDescriptions();
  __sanitizer_set_report_path(common_flags()->log_path);
}

void initializeLibrary(ToolType Tool) {
  // We assume there is only one thread during init.
  if (EsanIsInitialized) {
    CHECK(Tool == WhichTool);
    return;
  }
  WhichTool = Tool;
  SanitizerToolName = "EfficiencySanitizer";
  initializeFlags();

  // Intercepting libc _exit or exit via COMMON_INTERCEPTOR_ON_EXIT only
  // finalizes on an explicit exit call by the app.  To handle a normal
  // exit we register an atexit handler.
  ::__cxa_atexit((void (*)())finalizeLibrary);

  VPrintf(1, "in esan::%s\n", __FUNCTION__);
  if (WhichTool != ESAN_CacheFrag) {
    Printf("ERROR: unknown tool %d requested\n", WhichTool);
    Die();
  }

  initializeShadow();
  initializeInterceptors();

  EsanIsInitialized = true;
}

int finalizeLibrary() {
  VPrintf(1, "in esan::%s\n", __FUNCTION__);
  if (WhichTool == ESAN_CacheFrag) {
    // FIXME NYI: we need to add sampling + callstack gathering and have a
    // strategy for how to generate a final report.
    // We'll move this to cache_frag.cpp once we have something.
    Report("%s is not finished: nothing yet to report\n", SanitizerToolName);
  }
  return 0;
}

} // namespace __esan