You have a terminally buggy piece of shit compiler.
Lookie here:
- the bug happens on this:
char c = *p++;
- which has been compiled into
8b 3a mov (%edx),%edi
which is a *word* access.
- the pointer is at the end of a page (very much on purpose):
edx: f2a3fffe
- and as a result you get an exception on the *next* page:
BUG: unable to handle kernel paging request at virtual address f2a40000
and btw, there is no question what-so-ever about whether your compiler
might be doing a legal optimization - the compiler really is wrong, and is
total shit. You need to make a gcc bug-report. Because this is not a
question of "the standard is ambiguous", this is a question of "the
compiler turned good code into code that could SIGSEGV in user space too,
if 'malloc()' happened to return a pointer at the end of an allocation".
Linus
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