From eb6f2c24cd17c0ca1df7e343f8d9187eef7d6e13 Mon Sep 17 00:00:00 2001 From: "Jason A. Donenfeld" Date: Sun, 22 Sep 2024 03:45:29 +0200 Subject: runtime: use vDSO for getrandom() on linux MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Linux 6.11 supports calling getrandom() from the vDSO. It operates on a thread-local opaque state allocated with mmap using flags specified by the vDSO. Opaque states are allocated in chunks, ideally ncpu at a time as a hint, rounding up to as many fit in a complete page. On first use, a state is assigned to an m, which owns that state, until the m exits, at which point it is given back to the pool. Performance appears to be quite good: │ sec/op │ sec/op vs base │ Read/4-16 222.45n ± 3% 27.13n ± 6% -87.80% (p=0.000 n=10) │ B/s │ B/s vs base │ Read/4-16 17.15Mi ± 3% 140.61Mi ± 6% +719.82% (p=0.000 n=10) Fixes #69577. Change-Id: Ib6f44e8f2f3940c94d970eaada0eb566ec297dc7 Reviewed-on: https://go-review.googlesource.com/c/go/+/614835 Reviewed-by: Filippo Valsorda Reviewed-by: Cuong Manh Le Auto-Submit: Jason Donenfeld Reviewed-by: Paul Murphy LUCI-TryBot-Result: Go LUCI Reviewed-by: David Chase Reviewed-by: Michael Pratt --- src/internal/syscall/unix/getrandom.go | 10 ++++++++++ 1 file changed, 10 insertions(+) (limited to 'src/internal') diff --git a/src/internal/syscall/unix/getrandom.go b/src/internal/syscall/unix/getrandom.go index 4270898b7e..2dbe19887c 100644 --- a/src/internal/syscall/unix/getrandom.go +++ b/src/internal/syscall/unix/getrandom.go @@ -12,6 +12,9 @@ import ( "unsafe" ) +//go:linkname vgetrandom runtime.vgetrandom +func vgetrandom(p []byte, flags uint32) (ret int, supported bool) + var getrandomUnsupported atomic.Bool // GetRandomFlag is a flag supported by the getrandom system call. @@ -19,6 +22,13 @@ type GetRandomFlag uintptr // GetRandom calls the getrandom system call. func GetRandom(p []byte, flags GetRandomFlag) (n int, err error) { + ret, supported := vgetrandom(p, uint32(flags)) + if supported { + if ret < 0 { + return 0, syscall.Errno(-ret) + } + return ret, nil + } if getrandomUnsupported.Load() { return 0, syscall.ENOSYS } -- cgit v1.3-5-g9baa