diff options
Diffstat (limited to 'vendor/golang.org/x/sys/cpu/cpu_linux_riscv64.go')
| -rw-r--r-- | vendor/golang.org/x/sys/cpu/cpu_linux_riscv64.go | 137 |
1 files changed, 0 insertions, 137 deletions
diff --git a/vendor/golang.org/x/sys/cpu/cpu_linux_riscv64.go b/vendor/golang.org/x/sys/cpu/cpu_linux_riscv64.go deleted file mode 100644 index cb4a0c572..000000000 --- a/vendor/golang.org/x/sys/cpu/cpu_linux_riscv64.go +++ /dev/null @@ -1,137 +0,0 @@ -// Copyright 2024 The Go Authors. All rights reserved. -// Use of this source code is governed by a BSD-style -// license that can be found in the LICENSE file. - -package cpu - -import ( - "syscall" - "unsafe" -) - -// RISC-V extension discovery code for Linux. The approach here is to first try the riscv_hwprobe -// syscall falling back to HWCAP to check for the C extension if riscv_hwprobe is not available. -// -// A note on detection of the Vector extension using HWCAP. -// -// Support for the Vector extension version 1.0 was added to the Linux kernel in release 6.5. -// Support for the riscv_hwprobe syscall was added in 6.4. It follows that if the riscv_hwprobe -// syscall is not available then neither is the Vector extension (which needs kernel support). -// The riscv_hwprobe syscall should then be all we need to detect the Vector extension. -// However, some RISC-V board manufacturers ship boards with an older kernel on top of which -// they have back-ported various versions of the Vector extension patches but not the riscv_hwprobe -// patches. These kernels advertise support for the Vector extension using HWCAP. Falling -// back to HWCAP to detect the Vector extension, if riscv_hwprobe is not available, or simply not -// bothering with riscv_hwprobe at all and just using HWCAP may then seem like an attractive option. -// -// Unfortunately, simply checking the 'V' bit in AT_HWCAP will not work as this bit is used by -// RISC-V board and cloud instance providers to mean different things. The Lichee Pi 4A board -// and the Scaleway RV1 cloud instances use the 'V' bit to advertise their support for the unratified -// 0.7.1 version of the Vector Specification. The Banana Pi BPI-F3 and the CanMV-K230 board use -// it to advertise support for 1.0 of the Vector extension. Versions 0.7.1 and 1.0 of the Vector -// extension are binary incompatible. HWCAP can then not be used in isolation to populate the -// HasV field as this field indicates that the underlying CPU is compatible with RVV 1.0. -// -// There is a way at runtime to distinguish between versions 0.7.1 and 1.0 of the Vector -// specification by issuing a RVV 1.0 vsetvli instruction and checking the vill bit of the vtype -// register. This check would allow us to safely detect version 1.0 of the Vector extension -// with HWCAP, if riscv_hwprobe were not available. However, the check cannot -// be added until the assembler supports the Vector instructions. -// -// Note the riscv_hwprobe syscall does not suffer from these ambiguities by design as all of the -// extensions it advertises support for are explicitly versioned. It's also worth noting that -// the riscv_hwprobe syscall is the only way to detect multi-letter RISC-V extensions, e.g., Zba. -// These cannot be detected using HWCAP and so riscv_hwprobe must be used to detect the majority -// of RISC-V extensions. -// -// Please see https://docs.kernel.org/arch/riscv/hwprobe.html for more information. - -// golang.org/x/sys/cpu is not allowed to depend on golang.org/x/sys/unix so we must -// reproduce the constants, types and functions needed to make the riscv_hwprobe syscall -// here. - -const ( - // Copied from golang.org/x/sys/unix/ztypes_linux_riscv64.go. - riscv_HWPROBE_KEY_IMA_EXT_0 = 0x4 - riscv_HWPROBE_IMA_C = 0x2 - riscv_HWPROBE_IMA_V = 0x4 - riscv_HWPROBE_EXT_ZBA = 0x8 - riscv_HWPROBE_EXT_ZBB = 0x10 - riscv_HWPROBE_EXT_ZBS = 0x20 - riscv_HWPROBE_KEY_CPUPERF_0 = 0x5 - riscv_HWPROBE_MISALIGNED_FAST = 0x3 - riscv_HWPROBE_MISALIGNED_MASK = 0x7 -) - -const ( - // sys_RISCV_HWPROBE is copied from golang.org/x/sys/unix/zsysnum_linux_riscv64.go. - sys_RISCV_HWPROBE = 258 -) - -// riscvHWProbePairs is copied from golang.org/x/sys/unix/ztypes_linux_riscv64.go. -type riscvHWProbePairs struct { - key int64 - value uint64 -} - -const ( - // CPU features - hwcap_RISCV_ISA_C = 1 << ('C' - 'A') -) - -func doinit() { - // A slice of key/value pair structures is passed to the RISCVHWProbe syscall. The key - // field should be initialised with one of the key constants defined above, e.g., - // RISCV_HWPROBE_KEY_IMA_EXT_0. The syscall will set the value field to the appropriate value. - // If the kernel does not recognise a key it will set the key field to -1 and the value field to 0. - - pairs := []riscvHWProbePairs{ - {riscv_HWPROBE_KEY_IMA_EXT_0, 0}, - {riscv_HWPROBE_KEY_CPUPERF_0, 0}, - } - - // This call only indicates that extensions are supported if they are implemented on all cores. - if riscvHWProbe(pairs, 0) { - if pairs[0].key != -1 { - v := uint(pairs[0].value) - RISCV64.HasC = isSet(v, riscv_HWPROBE_IMA_C) - RISCV64.HasV = isSet(v, riscv_HWPROBE_IMA_V) - RISCV64.HasZba = isSet(v, riscv_HWPROBE_EXT_ZBA) - RISCV64.HasZbb = isSet(v, riscv_HWPROBE_EXT_ZBB) - RISCV64.HasZbs = isSet(v, riscv_HWPROBE_EXT_ZBS) - } - if pairs[1].key != -1 { - v := pairs[1].value & riscv_HWPROBE_MISALIGNED_MASK - RISCV64.HasFastMisaligned = v == riscv_HWPROBE_MISALIGNED_FAST - } - } - - // Let's double check with HWCAP if the C extension does not appear to be supported. - // This may happen if we're running on a kernel older than 6.4. - - if !RISCV64.HasC { - RISCV64.HasC = isSet(hwCap, hwcap_RISCV_ISA_C) - } -} - -func isSet(hwc uint, value uint) bool { - return hwc&value != 0 -} - -// riscvHWProbe is a simplified version of the generated wrapper function found in -// golang.org/x/sys/unix/zsyscall_linux_riscv64.go. We simplify it by removing the -// cpuCount and cpus parameters which we do not need. We always want to pass 0 for -// these parameters here so the kernel only reports the extensions that are present -// on all cores. -func riscvHWProbe(pairs []riscvHWProbePairs, flags uint) bool { - var _zero uintptr - var p0 unsafe.Pointer - if len(pairs) > 0 { - p0 = unsafe.Pointer(&pairs[0]) - } else { - p0 = unsafe.Pointer(&_zero) - } - - _, _, e1 := syscall.Syscall6(sys_RISCV_HWPROBE, uintptr(p0), uintptr(len(pairs)), uintptr(0), uintptr(0), uintptr(flags), 0) - return e1 == 0 -} |