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/runtime/sys_linux_arm64.s | 45 +++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 45 insertions(+) (limited to 'src/runtime/sys_linux_arm64.s') diff --git a/src/runtime/sys_linux_arm64.s b/src/runtime/sys_linux_arm64.s index 51c87bea05..7a81d5479e 100644 --- a/src/runtime/sys_linux_arm64.s +++ b/src/runtime/sys_linux_arm64.s @@ -785,3 +785,48 @@ TEXT runtime·sbrk0(SB),NOSPLIT,$0-8 SVC MOVD R0, ret+0(FP) RET + +// func vgetrandom1(buf *byte, length uintptr, flags uint32, state uintptr, stateSize uintptr) int +TEXT runtime·vgetrandom1(SB),NOSPLIT,$16-48 + MOVD RSP, R20 + + MOVD runtime·vdsoGetrandomSym(SB), R8 + MOVD g_m(g), R21 + + MOVD m_vdsoPC(R21), R9 + MOVD R9, 8(RSP) + MOVD m_vdsoSP(R21), R9 + MOVD R9, 16(RSP) + MOVD LR, m_vdsoPC(R21) + MOVD $buf-8(FP), R9 + MOVD R9, m_vdsoSP(R21) + + MOVD RSP, R9 + BIC $15, R9 + MOVD R9, RSP + + MOVBU runtime·iscgo(SB), R9 + CBNZ R9, nosaveg + MOVD m_gsignal(R21), R9 + CBZ R9, nosaveg + CMP g, R9 + BEQ nosaveg + MOVD (g_stack+stack_lo)(R9), R22 + MOVD g, (R22) + + BL (R8) + + MOVD ZR, (R22) + B restore + +nosaveg: + BL (R8) + +restore: + MOVD R20, RSP + MOVD 16(RSP), R1 + MOVD R1, m_vdsoSP(R21) + MOVD 8(RSP), R1 + MOVD R1, m_vdsoPC(R21) + NOP R0 // Satisfy go vet, since the return value comes from the vDSO function. + RET -- cgit v1.3