go/src/syscall/exec_linux.go, branch fix-runtime-test-GOMAXPROCS

runtime: add valgrind instrumentation

2025-05-21T17:08:08Z

Add build tag gated Valgrind annotations to the runtime which let it understand how the runtime manages memory. This allows for Go binaries to be run under Valgrind without emitting spurious errors. Instead of adding the Valgrind headers to the tree, and using cgo to call the various Valgrind client request macros, we just add an assembly function which emits the necessary instructions to trigger client requests. In particular we add instrumentation of the memory allocator, using a two-level mempool structure (as described in the Valgrind manual [0]). We also add annotations which allow Valgrind to track which memory we use for stacks, which seems necessary to let it properly function. We describe the memory model to Valgrind as follows: we treat heap arenas as a "pool" created with VALGRIND_CREATE_MEMPOOL_EXT (so that we can use VALGRIND_MEMPOOL_METAPOOL and VALGRIND_MEMPOOL_AUTO_FREE). Within the pool we treat spans as "superblocks", annotated with VALGRIND_MEMPOOL_ALLOC. We then allocate individual objects within spans with VALGRIND_MALLOCLIKE_BLOCK. It should be noted that running binaries under Valgrind can be _quite slow_, and certain operations, such as running the GC, can be _very slow_. It is recommended to run programs with GOGC=off. Additionally, async preemption should be turned off, since it'll cause strange behavior (GODEBUG=asyncpreemptoff=1). Running Valgrind with --leak-check=yes will result in some errors resulting from some things not being marked fully free'd. These likely need more annotations to rectify, but for now it is recommended to run with --leak-check=off. Updates #73602 [0] https://valgrind.org/docs/manual/mc-manual.html#mc-manual.mempools Change-Id: I71b26c47d7084de71ef1e03947ef6b1cc6d38301 Reviewed-on: https://go-review.googlesource.com/c/go/+/674077 LUCI-TryBot-Result: Go LUCI Reviewed-by: Michael Knyszek

all: gofmt -w

2025-02-25T19:49:16Z

Change-Id: Ie30a780cbd98bab1e80035b3dfddf92eb281759e GitHub-Last-Rev: 369ada24ffc297efb47768e430b1bd0216706998 GitHub-Pull-Request: golang/go#71898 Reviewed-on: https://go-review.googlesource.com/c/go/+/651795 LUCI-TryBot-Result: Go LUCI Reviewed-by: Ian Lance Taylor Reviewed-by: Michael Pratt Reviewed-by: Rob Pike Auto-Submit: Ian Lance Taylor

runtime: use WCLONE when waiting on pidfd test child

2025-02-21T16:57:04Z

As of CL 650835, the pidfd test child no longer sends SIGCHLD on exit. Per clone(2), "If [the child termination] signal is specified as anything other than SIGCHLD, then the parent process must specify the __WALL or __WCLONE options when waiting for the child with wait(2)." Align with this requirement. For #71828. Change-Id: I6a6a636c739e4a59abe1533fe429a433e8588939 Reviewed-on: https://go-review.googlesource.com/c/go/+/651415 Reviewed-by: Ian Lance Taylor Auto-Submit: Michael Pratt Reviewed-by: Ian Lance Taylor LUCI-TryBot-Result: Go LUCI

syscall: don't send child signal when testing pidfd

2025-02-20T17:20:38Z

Avoid a spurious SIGCHLD the first time we start a process. Fixes #71828 Change-Id: I744100d21bf6aaaaafc99bc5eec9f9f807a50682 Reviewed-on: https://go-review.googlesource.com/c/go/+/650835 Auto-Submit: Ian Lance Taylor Reviewed-by: Michael Knyszek Reviewed-by: Michael Pratt LUCI-TryBot-Result: Go LUCI

syscall: use SYS_EXIT_GROUP in CLONE_PIDFD feature check child

2024-10-03T13:57:21Z

Inside Google we have seen issues with QEMU user mode failing to wake a parent waitid when this child exits with SYS_EXIT. This bug appears to not affect SYS_EXIT_GROUP. It is currently unclear if this is a general QEMU or specific to Google's configuration, but SYS_EXIT and SYS_EXIT_GROUP are semantically equivalent here, so we can use the latter here in case this is a general QEMU bug. For #68976. Change-Id: I34e51088c9a6b7493a060e2a719a3cc4a3d54aa0 Reviewed-on: https://go-review.googlesource.com/c/go/+/617417 Reviewed-by: Ian Lance Taylor LUCI-TryBot-Result: Go LUCI

syscall: gofmt after CL 592078

2024-10-02T14:23:34Z

Change-Id: I328760f7752f1f5ec100f151c7e13e3f804c0e10 Reviewed-on: https://go-review.googlesource.com/c/go/+/617355 Auto-Submit: Ian Lance Taylor Reviewed-by: Michael Knyszek Reviewed-by: Ian Lance Taylor Auto-Submit: Tobias Klauser LUCI-TryBot-Result: Go LUCI

os: add clone(CLONE_PIDFD) check to pidfd feature check

2024-09-12T15:45:38Z

clone(CLONE_PIDFD) was added in Linux 5.2 and pidfd_open was added in Linux 5.3. Thus our feature check for pidfd_open should be sufficient to ensure that clone(CLONE_PIDFD) works. Unfortuantely, some alternative Linux implementations may not follow this strict ordering. For example, QEMU 7.2 (Dec 2022) added pidfd_open, but clone(CLONE_PIDFD) was only added in QEMU 8.0 (Apr 2023). Debian bookworm provides QEMU 7.2 by default. Fixes #69259. Change-Id: Ie3f3dc51f0cd76944871bf98690abf59f68fd7bf Reviewed-on: https://go-review.googlesource.com/c/go/+/592078 LUCI-TryBot-Result: Go LUCI Reviewed-by: Cherry Mui

syscall: on exec failure, close pidfd

2024-09-10T22:35:31Z

Fixes #69284 Change-Id: I6350209302778ba5e44fa03d0b9e680d2b4ec192 Reviewed-on: https://go-review.googlesource.com/c/go/+/611495 LUCI-TryBot-Result: Go LUCI Reviewed-by: roger peppe Reviewed-by: Tim King Auto-Submit: Ian Lance Taylor Reviewed-by: Dmitri Shuralyov

syscall: honor prlimit set by a different process

2024-08-30T19:55:07Z

On Linux one process can call prlimit to change the resource limit of another process. With this change we treat that as though the current process called prlimit (or setrlimit) to set its own limit. The cost is one additional getrlimit system call per fork/exec, for cases in which the rlimit Cur and Max values differ at startup. This revealed a bug: the setrlimit (not Setrlimit) function should not change the cached rlimit. That means that it must call prlimit1, not prlimit. Fixes #66797 Change-Id: I46bfd06e09ab7273fe8dd9b5b744dffdf31d828b Reviewed-on: https://go-review.googlesource.com/c/go/+/607516 Auto-Submit: Ian Lance Taylor Reviewed-by: Damien Neil Reviewed-by: Ian Lance Taylor Reviewed-by: Aleksa Sarai Reviewed-by: Kirill Kolyshkin LUCI-TryBot-Result: Go LUCI Auto-Submit: Ian Lance Taylor

syscall: always use prlimit for getrlimit/setrlimit on Linux

2024-08-30T19:26:45Z

Linux added the prlimit system call in version 2.6.36. As our minimum Linux kernel version is now 3.2, simplify the various getrlimit/setlrimit implementations to just always use prlimit. For #67001 Change-Id: I2512c21c947d0bc83f8f9077c143163fd8d83be3 Reviewed-on: https://go-review.googlesource.com/c/go/+/609178 Reviewed-by: Cherry Mui Reviewed-by: Damien Neil Auto-Submit: Ian Lance Taylor Reviewed-by: Tobias Klauser LUCI-TryBot-Result: Go LUCI