zend_alloc adding a ǹodump (p)emalloc calls.
#8878
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Aim is to discard an address content to appear in a core dump with systems supporting (Linux/FreeBSD for now), with a concealed usage in the openssl ext for now.
| static zend_always_inline void zend_mm_nodump(void* ptr, size_t size) | ||
| { | ||
| #if defined(MADV_DONTDUMP) | ||
| (void)madvise(ptr, size, MADV_DONTDUMP); |
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From https://linux.die.net/man/2/madvise:
MADV_DONTDUMP (since Linux 3.4)
Exclude from a core dump those pages in the range specified by addr and length. This is useful in applications that have large areas of memory that are known not to be useful in a core dump.
And https://stackoverflow.com/a/46663007/1320374:
You can't and even if you could do it in certain cases with certain flags (and the flags you're trying to use here should be relatively harmless), you shouldn't. madvise operates on memory from lower level allocations than malloc gives you and messing with the memory from malloc will likely break malloc.
If you want some block of memory that you can call madvise on, you should obtain it using mmap.
So, for Linux, the memory passed to madvise should be page aligned and probably provided by mmap. I'm not sure if this is different on FreeBSD.
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yes will try to think of something else.
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Aim is to discard an address content to appear in a core dump with
systems supporting (Linux/FreeBSD for now), with a concealed usage
in the openssl ext for now.