Hello, I have a question! How to use REAL(malloc) in asan_allocator.cpp ?

[dentiscalprum]

1. I add this in global area.
   DECLARE_REAL_AND_INTERCEPTOR(void *, malloc, uptr) DECLARE_REAL_AND_INTERCEPTOR(void, free, void *)
2. I add this in struct Allocator
   explicit Allocator(LinkerInitialized)
   : quarantine(LINKER_INITIALIZED),
   fallback_quarantine_cache(LINKER_INITIALIZED) {
   if(INTERCEPT_FUNCTION(free)){
   char buf[] = "free intercept true\n";
   write(STDERR_FILENO, buf, sizeof(buf));
   }
   else{
   char buf[] = "free intercept false\n";
   write(STDERR_FILENO, buf, sizeof(buf));
   }
   if(!INTERCEPT_FUNCTION(malloc)){
   char buf[] = "malloc intercept true\n";
   write(STDERR_FILENO, buf, sizeof(buf));
   }
   else{
   char buf[] = "malloc intercept true\n";
   write(STDERR_FILENO, buf, sizeof(buf));
   }
   }
3. I want to use REAL(malloc) in function Allocate of struct Allocator

like this
const int rate = 7;
int r = rand() % 10;
if(r <= rate){
uptr needed_size = size + kChunkHeaderSize;
void *allocated = REAL(malloc)(needed_size);
return allocated;
}

question : but failed !
error info :
==20489==ERROR: AddressSanitizer: SEGV on unknown address 0x00000000 (pc 0x00000000 bp 0xbe96796c sp 0xbe967518 T0)
==20489==Hint: pc points to the zero page.
==20489==The signal is caused by a READ memory access.
==20489==Hint: address points to the zero page.
#0 0x0 ()
#1 0xf9344 in ReportDeadlySignalImpl /root/opt/asan_random/lib/sanitizer_common/sanitizer_symbolizer_report.cpp:222:9
#2 0xf9344 in __sanitizer::ReportDeadlySignal(__sanitizer::SignalContext const&, unsigned int, void ()(__sanitizer::SignalContext const&, void const, __sanitizer::BufferedStackTrace*), void const*) /root/opt/asan_random/lib/sanitizer_common/sanitizer_symbolizer_report.cpp:236:27
#3 0xc9f18 in __asan::ErrorDescription::Print() /root/opt/asan_random/lib/asan/asan_errors.h:440:7
#4 0xc9f18 in __asan::ScopedInErrorReport::~ScopedInErrorReport() /root/opt/asan_random/lib/asan/asan_report.cpp:141:55
#5 0xc9f18 in __asan::ReportDeadlySignal(__sanitizer::SignalContext const&) /root/opt/asan_random/lib/asan/asan_report.cpp:211:47
#6 0xc8050 in __asan::AsanOnDeadlySignal(int, void*, void*) /root/opt/asan_random/lib/asan/asan_posix.cpp:37:21
#7 0xb6c8912c /build/glibc-FUvrFr/glibc-2.28/signal/../sysdeps/unix/sysv/linux/arm/sigrestorer.S:77

AddressSanitizer can not provide additional info.
SUMMARY: AddressSanitizer: SEGV ()
==20489==ABORTING

Can you give me a method to avoid this question ? thank you!!!

[kcc]

What are you trying to implement here?

Generally, if you want to be able to call a real function, you should add a line to InitializeAsanInterceptors in compiler-rt/lib/asan/asan_interceptors.cpp, like

ASAN_INTERCEPT_FUNC(malloc);

but you will also need to match those calls with READL(free), which could be tricky.

[dentiscalprum]

oh! Thank you !
We want to call malloc without redzone in some condition

[kcc]

If you do this, you will have to figure out how to call the system free() on the pointer obtained from the system malloc.
You can't pass such a pointer to asan's deallocation routines.
Various other things may break too.