root/src/pkg/runtime/os_linux_arm.c

DEFINITIONS

1. runtime·checkgoarm
2. runtime·setup_auxv
3. runtime·cputicks

// Copyright 2009 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.

#include "runtime.h"
#include "defs_GOOS_GOARCH.h"
#include "os_GOOS.h"
#include "../../cmd/ld/textflag.h"

#define AT_NULL         0
#define AT_PLATFORM     15 // introduced in at least 2.6.11
#define AT_HWCAP        16 // introduced in at least 2.6.11
#define AT_RANDOM       25 // introduced in 2.6.29
#define HWCAP_VFP       (1 << 6) // introduced in at least 2.6.11
#define HWCAP_VFPv3     (1 << 13) // introduced in 2.6.30
static uint32 runtime·randomNumber;
uint8  runtime·armArch = 6;    // we default to ARMv6
uint32 runtime·hwcap;  // set by setup_auxv
extern uint8  runtime·goarm;   // set by 5l

void
runtime·checkgoarm(void)
{
        if(runtime·goarm > 5 && !(runtime·hwcap & HWCAP_VFP)) {
                runtime·printf("runtime: this CPU has no floating point hardware, so it cannot run\n");
                runtime·printf("this GOARM=%d binary. Recompile using GOARM=5.\n", runtime·goarm);
                runtime·exit(1);
        }
        if(runtime·goarm > 6 && !(runtime·hwcap & HWCAP_VFPv3)) {
                runtime·printf("runtime: this CPU has no VFPv3 floating point hardware, so it cannot run\n");
                runtime·printf("this GOARM=%d binary. Recompile using GOARM=6.\n", runtime·goarm);
                runtime·exit(1);
        }
}

#pragma textflag NOSPLIT
void
runtime·setup_auxv(int32 argc, byte **argv)
{
        byte **envp;
        byte *rnd;
        uint32 *auxv;
        uint32 t;

        // skip envp to get to ELF auxiliary vector.
        for(envp = &argv[argc+1]; *envp != nil; envp++)
                ;
        envp++;
        
        for(auxv=(uint32*)envp; auxv[0] != AT_NULL; auxv += 2) {
                switch(auxv[0]) {
                case AT_RANDOM: // kernel provided 16-byte worth of random data
                        if(auxv[1]) {
                                rnd = (byte*)auxv[1];
                                runtime·randomNumber = rnd[4] | rnd[5]<<8 | rnd[6]<<16 | rnd[7]<<24;
                        }
                        break;
                case AT_PLATFORM: // v5l, v6l, v7l
                        if(auxv[1]) {
                                t = *(uint8*)(auxv[1]+1);
                                if(t >= '5' && t <= '7')
                                        runtime·armArch = t - '0';
                        }
                        break;
                case AT_HWCAP: // CPU capability bit flags
                        runtime·hwcap = auxv[1];
                        break;
                }
        }
}

#pragma textflag NOSPLIT
int64
runtime·cputicks(void)
{
        // Currently cputicks() is used in blocking profiler and to seed runtime·fastrand1().
        // runtime·nanotime() is a poor approximation of CPU ticks that is enough for the profiler.
        // runtime·randomNumber provides better seeding of fastrand1.
        return runtime·nanotime() + runtime·randomNumber;
}