Re: [PATCH v3] Add asan and ubsan support on NetBSD/amd64

[Kamil Rytarowski <n54 at gmx dot com>]

On 31.10.2017 19:45, Jakub Jelinek wrote:
> On Tue, Oct 31, 2017 at 07:28:23PM +0100, Kamil Rytarowski wrote:
>> I'm giving it a try. I took the asan part and skipped
>> "%{!shared:libasan_preinit%O%s} ". If I understand this correctly, it
>> attempts to use the ELF section with preinit property in order to
>> bootstrap asan quickly. The preinit sections are not enabled on
>> NetBSD/amd64. From my understanding, there is a design choice in NetBSD
>> to not include extensional sections unless they are requested by ABI.
> 
> ??  SHT_PREINIT_ARRAY/DT_PREINIT_ARRAY/DT_PREINIT_ARRAYSZ is not any
> kind of extension, it is an integral part of the ELF gABI:
> http://www.sco.com/developers/gabi/latest/ch5.dynamic.html#dynamic_section
> And that is quite essential for proper asan behavior, because the library
> interposes a lot of functions and if they are invoked before the library
> is initialized, they crash (of course better would be to fix the library
> not to rely on that and initialize the minimal stuff needed for
> interposition if they are called before the initialization, but that is
> unlikely to happen upstream).
> 
> 	Jakub
> 

Right now this is only Linux-specific at least in asan/LLVM.

// We can use .preinit_array section on Linux to call sanitizer
initialization
// functions very early in the process startup (unless PIC macro is
defined).
// FIXME: do we have anything like this on Mac?
#if SANITIZER_LINUX && !SANITIZER_ANDROID && !defined(PIC)
# define SANITIZER_CAN_USE_PREINIT_ARRAY 1
#else
# define SANITIZER_CAN_USE_PREINIT_ARRAY 0
#endif

-- lib/sanitizer_common/sanitizer_internal_defs.h

NetBSD needs to use different ways to initialize, like through
interception of a call and during this stage bootstrap initialization
bits. The tricky part is that we cannot initialize a sanitizer before
sufficient libc+libpthread bootstrap and this is my current obstacle
with tsan.

Specifying new LIBASAN_EARLY_SPEC does not fix the "AddressSanitizer can
not provide additional info." problem.

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