| Summary: | getrlimit on MacOSX | ||
|---|---|---|---|
| Product: | [Developer tools] valgrind | Reporter: | Dan Kegel <dank> |
| Component: | general | Assignee: | Julian Seward <jseward> |
| Status: | RESOLVED FIXED | ||
| Severity: | normal | CC: | mark, njn, rohitrao |
| Priority: | NOR | ||
| Version: | unspecified | ||
| Target Milestone: | --- | ||
| Platform: | Unlisted Binaries | ||
| OS: | macOS | ||
| URL: | http://codereview.chromium.org/109052 | ||
| Latest Commit: | Version Fixed In: | ||
| Sentry Crash Report: | |||
| Attachments: |
Patch that seems to fix the problem.
testcase to demonstate problem |
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You say "Darwin will sometimes set _RLIMIT_POSIX_FLAG"... any more detail about the "sometimes"? Also, can you attach a test program that fails without the patch? Thanks. Created attachment 33415 [details]
testcase to demonstate problem
The attached program should show the problem. Run with something like:
$ gcc rlimit_test.c -o rlimit_test
$ ulimit -a
open files (-n) 256
$ ./rlimit_test
RLIMIT_NOFILE is 256
$ valgrind ./rlimit_test
RLIMIT_NOFILE is 266
Valgrind with the patch should output:
RLIMIT_NOFILE is 256
(Apologies for the double-mail. Couldn't figure out how to reply and attach at the same time.) OS X 10.5 and later ORs in the posix flag. See http://www.opensource.apple.com/darwinsource/10.5/Libc-498/sys/getrlimit.c . 10.4 and earlier does not do this. (Thanks to Mark Mentovai for finding that.) In coregrind/m_libcproc.c we have this:
Int VG_(setrlimit) (Int resource, const struct vki_rlimit *rlim)
{
SysRes res;
/* res = setrlimit( resource, rlim ); */
res = VG_(do_syscall2)(__NR_setrlimit, resource, (UWord)rlim);
return sr_isError(res) ? -1 : sr_Res(res);
}
Should that be adjusted too?
To answer my own question: no. The kernel masks out the posix flag if present. (Its presence/non-presence changes some of the behaviour of the syscall, but not in any way that affects us.) Patch and test committed as r9790 on the DARWIN branch. Thanks. Depends on who calls VG_(setrlimit). The getrlimit and setrlimit syscall wrappers in libSystem, when in POSIX-conformant mode, OR in the strict POSIX bit. Anything on the "far" (kernel) side of that needs to be prepared for that bit to be set. Anything that replaces the libSystem syscall wrappers (bypassing them) should implement similar logic. I don't know what VG_(setrlimit) is. If it's replacing the libSystem setrlimit syscall wrapper, then it should mimic what's done in libSystem: it should set the strict POSIX bit before doing the syscall, but only in POSIX-conformant mode. Unfortunately, that last bit might complicate matters: the POSIX compliance level is selected at compile time, and winds up baked into the object code by symbol: POSIX conformance uses _setrlimit$UNIX2003, and compatibility mode uses undecorated _setrlimit. 'Course, it's possible that VG_(setrlimit) does something entirely different. If VG_(setrlimit) is in fact a replacement for libSystem's setrlimit syscall wrapper, then ignoring the issue in this function will possibly result in subtly different behavior for this syscall in Valgrind and uninstrumented. VG_(setrlimit)() is used within Valgrind itself. It's not used at all to emulate setrlimit() in the client. So I think we're safe. Great, then I agree. Thanks. Looks like I forgot to close this one. Doing so now. |
Created attachment 33385 [details] Patch that seems to fix the problem. Darwin will sometimes set _RLIMIT_POSIX_FLAG on getrlimit/setrlimit calls; valgrind doesn't currently handle that properly. Rohit Rao filed this as a bug in the chromium bug tracker, and came up with a patch for valgrind; I've attached it here.