[PATCH] D58379: [compiler-rt] Intercept the bcmp() function.

[Vitaly Buka via Phabricator via llvm-commits]

vitalybuka added inline comments.


================
Comment at: lib/sanitizer_common/sanitizer_common_interceptors.inc:874
+  void *ctx;
+  COMMON_INTERCEPTOR_ENTER(ctx, bcmp, a1, a2, size);
+  if (common_flags()->intercept_memcmp) {
----------------
courbet wrote:
> vitalybuka wrote:
> > courbet wrote:
> > > krytarowski wrote:
> > > > Can we reuse code with memcmp(3)? bcmp(3) is a subset of memcmp(3).
> > > Looking at `COMMON_INTERCEPTOR_ENTER` implementation for, e.g.  tsan:
> > > 
> > > ```
> > > 
> > > #define SCOPED_TSAN_INTERCEPTOR(func, ...) \
> > >     SCOPED_INTERCEPTOR_RAW(func, __VA_ARGS__); \
> > >     if (REAL(func) == 0) { \
> > >       Printf("FATAL: ThreadSanitizer: failed to intercept %s\n", #func); \
> > >       Die(); \
> > >     } \
> > >     if (thr->in_rtl > 1) \
> > >       return REAL(func)(__VA_ARGS__); 
> > > 
> > > 
> > > #define COMMON_INTERCEPTOR_ENTER(ctx, func, ...)      \
> > >   SCOPED_TSAN_INTERCEPTOR(func, __VA_ARGS__);         \
> > >   TsanInterceptorContext _ctx = {thr, caller_pc, pc}; \
> > >   ctx = (void *)&_ctx;                                \
> > >   (void) ctx;
> > > 
> > > ```
> > > 
> > > Given that the implementation calls `REAL(func)`, it feels preferable to call the real `bcmp` instead of real `memcmp`, even though calling memcmp does work. But again, I'm not familiar with how you guys typically approach this, so you tell me :)
> > > 
> > Sometimes we do macro
> > But I'd prefer inline function, e.g.
> > 
> > int memcpy_interceptor_impl(ctx, a1, a2, size, real_fn_ptr) {
> > ....
> > }
> I'm not sure I understand your suggestion correctly, but if you're suggesting we refactor using a function, then the issue is that REAL(x) only works with x a macro parameter, not if `x` is a function pointer:
> 
> ```
> # define PTR_TO_REAL(x) real_##x
> ...
> # define REAL(x) __interception::PTR_TO_REAL(x)
> ```
> 
> Refactoring using a macro would be possible, but it would look quite ugly.
Looks like you can easily extract into a function code before REAL call


Repository:
  rCRT Compiler Runtime

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  https://reviews.llvm.org/D58379/new/

https://reviews.llvm.org/D58379