glibc/malloc, branch vdso

linux: Add support for getrandom vDSO

2024-09-27T18:25:36Z

Linux 6.11 has getrandom() in vDSO. It operates on a thread-local opaque state allocated with mmap using flags specified by the vDSO. Multiple states are allocated at once, as many as fit into a page, and these are held in an array of available states to be doled out to each thread upon first use, and recycled when a thread terminates. As these states run low, more are allocated. To make this procedure async-signal-safe, a simple guard is used in the LSB of the opaque state address, falling back to the syscall if there's reentrancy contention. Also, _Fork() is handled by blocking signals on opaque state allocation (so _Fork() always sees a consistent state even if it interrupts a getrandom() call) and by iterating over the thread stack cache on reclaim_stack. Each opaque state will be in the free states list (grnd_alloc.states) or allocated to a running thread. The cancellation is handled by always using GRND_NONBLOCK flags while calling the vDSO, and falling back to the cancellable syscall if the kernel returns EAGAIN (would block). Since getrandom is not defined by POSIX and cancellation is supported as an extension, the cancellation is handled as 'may occur' instead of 'shall occur' [1], meaning that if vDSO does not block (the expected behavior) getrandom will not act as a cancellation entrypoint. It avoids a pthread_testcancel call on the fast path (different than 'shall occur' functions, like sem_wait()). It is currently enabled for x86_64, which is available in Linux 6.11, and aarch64, powerpc32, powerpc64, loongarch64, and s390x, which are available in Linux 6.12. Link: https://pubs.opengroup.org/onlinepubs/9799919799/nframe.html [1] Co-developed-by: Jason A. Donenfeld Tested-by: Jason A. Donenfeld # x86_64 Tested-by: Adhemerval Zanella # x86_64, aarch64 Tested-by: Xi Ruoyao # x86_64, aarch64, loongarch64 Tested-by: Stefan Liebler # s390x

malloc: Link threading tests with $(shared-thread-library)

2024-08-20T14:16:25Z

Fixes build failures on Hurd.

malloc: Link threading tests with $(shared-thread-library)

2024-07-27T14:46:49Z

Fixes build failures on Hurd.

malloc: add multi-threaded tests for aligned_alloc/calloc/malloc

2024-07-22T09:54:46Z

Improve aligned_alloc/calloc/malloc test coverage by adding multi-threaded tests with random memory allocations and with/without cross-thread memory deallocations. Perform a number of memory allocation calls with random sizes limited to 0xffff. Use the existing DSO ('malloc/tst-aligned_alloc-lib.c') to randomize allocator selection. The multi-threaded allocation/deallocation is staged as described below: - Stage 1: Half of the threads will be allocating memory and the other half will be waiting for them to finish the allocation. - Stage 2: Half of the threads will be allocating memory and the other half will be deallocating memory. - Stage 3: Half of the threads will be deallocating memory and the second half waiting on them to finish. Add 'malloc/tst-aligned-alloc-random-thread.c' where each thread will deallocate only the memory that was previously allocated by itself. Add 'malloc/tst-aligned-alloc-random-thread-cross.c' where each thread will deallocate memory that was previously allocated by another thread. The intention is to be able to utilize existing malloc testing to ensure that similar allocation APIs are also exposed to the same rigors. Reviewed-by: Arjun Shankar

malloc: avoid global locks in tst-aligned_alloc-lib.c

2024-07-22T09:54:46Z

Make sure the DSO used by aligned_alloc/calloc/malloc tests does not get a global lock on multithreaded tests. Reviewed-by: Arjun Shankar

Fix usage of _STACK_GROWS_DOWN and _STACK_GROWS_UP defines [BZ 31989]

2024-07-19T14:10:17Z

Signed-off-by: John David Anglin Reviewed-By: Andreas K. Hüttel

mtrace: make shell commands robust against meta characters

2024-06-24T07:33:49Z

Use the list form of the open function to avoid interpreting meta characters in the arguments.

malloc: Replace shell/Perl gate in mtrace

2024-06-20T18:55:10Z

The previous version expanded $0 and $@ twice. The new version defines a q no-op shell command. The Perl syntax error is masked by the eval Perl function. The q { … } construct is executed by the shell without errors because the q shell function was defined, but treated as a non-expanding quoted string by Perl, effectively hiding its context from the Perl interpreter. As before the script is read by require instead of executed directly, to avoid infinite recursion because the #! line contains /bin/sh. Introduce the “fatal” function to produce diagnostics that are not suppressed by “do”. Use “do” instead of “require” because it has fewer requirements on the executed script than “require”. Prefix relative paths with './' because “do” (and “require“ before) searches for the script in @INC if the path is relative and does not start with './'. Use $_ to make the trampoline shorter. Add an Emacs mode marker to indentify the script as a Perl script.

malloc: Always install mtrace (bug 31892)

2024-06-20T08:32:16Z

Generation of the Perl script does not depend on Perl, so we can always install it even if $(PERL) is not set during the build. Change the malloc/mtrace.pl text substition not to rely on $(PERL). Instead use PATH at run time to find the Perl interpreter. The Perl interpreter cannot execute directly a script that starts with “#! /bin/sh”: it always executes it with /bin/sh. There is no perl command line switch to disable this behavior. Instead, use the Perl require function to execute the script. The additional shift calls remove the “.” shell arguments. Perl interprets the “.” as a string concatenation operator, making the expression syntactically valid. Reviewed-by: Carlos O'Donell

malloc: New test to check malloc alternate path using memory obstruction

2024-06-04T16:00:29Z

The test aims to ensure that malloc uses the alternate path to allocate memory when sbrk() or brk() fails.To achieve this, the test first creates an obstruction at current program break, tests that obstruction with a failing sbrk(), then checks if malloc is still returning a valid ptr thus inferring that malloc() used mmap() instead of brk() or sbrk() to allocate the memory. Reviewed-by: Arjun Shankar Reviewed-by: Zack Weinberg