• Shenghou Ma's avatar
    syscall: fix mkall.sh, mksyscall_linux.pl, and regen for Linux/ARM · 6e211225
    Shenghou Ma authored
    CL 3075041 says ARM is not little-endian, but my test suggests otherwise.
    My test program is:
    
        package main
        import ("fmt"; "syscall"; "os")
        func main() {
           err := syscall.Fallocate(1, 1/*FALLOC_FL_KEEP_SIZE*/, 0, int64(40960));
           fmt.Fprintln(os.Stderr, err)
        }
    
    Without this CL, ./test > testfile will show: file too large; and strace shows:
        fallocate(1, 01, 0, 175921860444160)    = -1 EFBIG (File too large)
    With this CL, ./test > testfile will show: <nil>; and strace shows:
        fallocate(1, 01, 0, 40960)              = 0
    
    Quoting rsc:
    "[It turns out that] ARM syscall ABI requires 64-bit arguments to use an
    (even, odd) register pair, not an (odd, even) pair. Switching to "big-endian"
    worked because it ended up using the high 32-bits (always zero in the tests
    we had) as the padding word, because the 64-bit argument was the last one,
    and because we fill in zeros for the rest of the system call arguments, up to
    six. So it happened to work."
    
    I updated mksyscall_linux.pl to accommodate the register pair ABI requirement,
    and removed all hand-tweaked syscall routines in favor of the auto-generated
    ones. These including: Ftruncate, Truncate, Pread and Pwrite.
    
    Some recent Linux/ARM distributions do not bundle kernel asm headers,
    so instead we always get latest asm/unistd.h from git.kernel.org (just like
    what we do for FreeBSD).
    
    R=ken, r, rsc, r, dave, iant
    CC=golang-dev
    https://golang.org/cl/5726051
    6e211225
mksyscall.pl 6.57 KB