Date: Mon, 6 Jan 2020 17:24:35 +0100 From: d.dorau@....de To: "Rich Felker" <dalias@...c.org> Cc: musl@...ts.openwall.com Subject: Re: Issue with musl and valgrind "Rich Felker" <dalias@...ifal.cx> schrieb am 06.01.2020 14:56:23: [...] > > This is really a bug in valgrind, that it's relying on a mix of the > dynamic linker and its own mechanism for interposing malloc. Either > the interposition should not take place until after line 1913 of > __dls3 in dynlink.c (this is what would happen if you did it via > LD_PRELOAD without valgrind), or valgrind should do its own loading > and relocation of vgpreload_memcheck-*.so independent of the tracee's > dynamic linker. > > On most archs, the problem does not manifest as things are setup so > that it's safe to call free in an unrelocated context. However > realloc is gratuitously not safe and Adélie Linux has a patch for it > to do it like free: > > https://code.foxkit.us/adelie/packages/blob/master/user/valgrind/realloc.patch > > But on MIPS, where there are no PC-relative references and everything > goes through the GOT, this blows up. > > I'm not sure how practical it is to get valgrind to fix this upstream. > In the either/or above, if the first course of action is taken, the > mechanism should probably be by inserting a breakpoint (or valgrind's > equivalent) at the main program's e_entry address and not doing the > replacement hack until then. Alternatively, it could just rely on > LD_PRELOAD working without trying to do additional tricks, but maybe > they have a good reason they're not doing that. > > Rich I was not aware of this when debugging the crash, but after looking at additional debug statements and valgrind code my current understanding is that valgrind actually inserts LD_PRELOAD=" /usr/lib/valgrind/vgpreload_core-mips32-linux.so:/usr/lib/valgrind/vgpreload_memcheck-mips32-linux.so" into the environment before loading the executable to test. (coregrind/m_initimg/initimg-linux.c:123) 425:11:32:696 --4757:1: main Split up command line 425:11:32:696 --4757:1: main (early_) Process Valgrind's command line options 425:11:32:696 --4757:1: main Create initial image 425:11:32:712 --4757:1: initimg Loading client 425:11:32:712 --4757:1: initimg Setup client env 425:11:32:712 --4757:2: initimg preload_string: 425:11:32:728 --4757:2: initimg "/usr/lib/valgrind/vgpreload_core-mips32-linux.so:/usr/lib/valgrind/vgpreload_memcheck-mips32-linux.so" 425:11:32:728 --4757:1: initimg Setup client stack: size will be 1048576 Is my understanding correct that you would expect it to not run into the crash I described earlier then? Daniel Content of type "text/html" skipped
Powered by blists - more mailing lists
Confused about mailing lists and their use? Read about mailing lists on Wikipedia and check out these guidelines on proper formatting of your messages.