runtime: expose auxv for use by x/sys/cpu

Updates #57336

Change-Id: I181885f59bac59360b855d3990326ea2b268bd28
Reviewed-on: https://go-review.googlesource.com/c/go/+/458256
Reviewed-by: Michael Pratt <mpratt@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Auto-Submit: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Austin Clements <austin@google.com>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

diff --git a/src/runtime/os3_solaris.go b/src/runtime/os3_solaris.go
index ffac4b6492b87cc51ded27da824f05373e1adba0..2a8677b48f64a7fa2601bdd9b7434e02a5675114 100644 (file)
--- a/src/runtime/os3_solaris.go
+++ b/src/runtime/os3_solaris.go
@@ -601,8 +601,9 @@ func sysargs(argc int32, argv **byte) {
        n++
 
        // now argv+n is auxv
-       auxv := (*[1 << 28]uintptr)(add(unsafe.Pointer(argv), uintptr(n)*goarch.PtrSize))
-       sysauxv(auxv[:])
+       auxvp := (*[1 << 28]uintptr)(add(unsafe.Pointer(argv), uintptr(n)*goarch.PtrSize))
+       pairs := sysauxv(auxvp[:])
+       auxv = auxvp[: pairs*2 : pairs*2]
 }
 
 const (
@@ -611,8 +612,9 @@ const (
        _AT_SUN_EXECNAME = 2014 // exec() path name
 )
 
-func sysauxv(auxv []uintptr) {
-       for i := 0; auxv[i] != _AT_NULL; i += 2 {
+func sysauxv(auxv []uintptr) (pairs int) {
+       var i int
+       for i = 0; auxv[i] != _AT_NULL; i += 2 {
                tag, val := auxv[i], auxv[i+1]
                switch tag {
                case _AT_PAGESZ:
@@ -621,6 +623,7 @@ func sysauxv(auxv []uintptr) {
                        executablePath = gostringnocopy((*byte)(unsafe.Pointer(val)))
                }
        }
+       return i / 2
 }
 
 // sigPerThreadSyscall is only used on linux, so we assign a bogus signal

diff --git a/src/runtime/os_dragonfly.go b/src/runtime/os_dragonfly.go
index e467578c32a8c0e4c5958663c33dbca1ef807777..fa480be029c0dbd7f36e08e7b3e7dac87494dae1 100644 (file)
--- a/src/runtime/os_dragonfly.go
+++ b/src/runtime/os_dragonfly.go
@@ -296,8 +296,9 @@ func sysargs(argc int32, argv **byte) {
        // skip NULL separator
        n++
 
-       auxv := (*[1 << 28]uintptr)(add(unsafe.Pointer(argv), uintptr(n)*goarch.PtrSize))
-       sysauxv(auxv[:])
+       auxvp := (*[1 << 28]uintptr)(add(unsafe.Pointer(argv), uintptr(n)*goarch.PtrSize))
+       pairs := sysauxv(auxvp[:])
+       auxv = auxvp[: pairs*2 : pairs*2]
 }
 
 const (
@@ -305,14 +306,16 @@ const (
        _AT_PAGESZ = 6
 )
 
-func sysauxv(auxv []uintptr) {
-       for i := 0; auxv[i] != _AT_NULL; i += 2 {
+func sysauxv(auxv []uintptr) (pairs int) {
+       var i int
+       for i = 0; auxv[i] != _AT_NULL; i += 2 {
                tag, val := auxv[i], auxv[i+1]
                switch tag {
                case _AT_PAGESZ:
                        physPageSize = val
                }
        }
+       return i / 2
 }
 
 // raise sends a signal to the calling thread.

diff --git a/src/runtime/os_freebsd.go b/src/runtime/os_freebsd.go
index f53cb115a157df9d83ec737344313c84c5c485a6..d5f02d9da5ab9c5210f22c8601aff9747860e99b 100644 (file)
--- a/src/runtime/os_freebsd.go
+++ b/src/runtime/os_freebsd.go
@@ -409,8 +409,9 @@ func sysargs(argc int32, argv **byte) {
        n++
 
        // now argv+n is auxv
-       auxv := (*[1 << 28]uintptr)(add(unsafe.Pointer(argv), uintptr(n)*goarch.PtrSize))
-       sysauxv(auxv[:])
+       auxvp := (*[1 << 28]uintptr)(add(unsafe.Pointer(argv), uintptr(n)*goarch.PtrSize))
+       pairs := sysauxv(auxvp[:])
+       auxv = auxvp[: pairs*2 : pairs*2]
 }
 
 const (
@@ -421,8 +422,9 @@ const (
        _AT_HWCAP2   = 26 // CPU feature flags 2
 )
 
-func sysauxv(auxv []uintptr) {
-       for i := 0; auxv[i] != _AT_NULL; i += 2 {
+func sysauxv(auxv []uintptr) (pairs int) {
+       var i int
+       for i = 0; auxv[i] != _AT_NULL; i += 2 {
                tag, val := auxv[i], auxv[i+1]
                switch tag {
                // _AT_NCPUS from auxv shouldn't be used due to golang.org/issue/15206
@@ -434,6 +436,7 @@ func sysauxv(auxv []uintptr) {
 
                archauxv(tag, val)
        }
+       return i / 2
 }
 
 // sysSigaction calls the sigaction system call.

diff --git a/src/runtime/os_linux.go b/src/runtime/os_linux.go
index 37cd8e648293172e012672d61d3e2e40a7918d87..194d698798c9a0de68115326dabc243fbc1b323d 100644 (file)
--- a/src/runtime/os_linux.go
+++ b/src/runtime/os_linux.go
@@ -226,6 +226,8 @@ var addrspace_vec [1]byte
 
 func mincore(addr unsafe.Pointer, n uintptr, dst *byte) int32
 
+var auxvreadbuf [128]uintptr
+
 func sysargs(argc int32, argv **byte) {
        n := argc + 1
 
@@ -238,8 +240,10 @@ func sysargs(argc int32, argv **byte) {
        n++
 
        // now argv+n is auxv
-       auxv := (*[1 << 28]uintptr)(add(unsafe.Pointer(argv), uintptr(n)*goarch.PtrSize))
-       if sysauxv(auxv[:]) != 0 {
+       auxvp := (*[1 << 28]uintptr)(add(unsafe.Pointer(argv), uintptr(n)*goarch.PtrSize))
+
+       if pairs := sysauxv(auxvp[:]); pairs != 0 {
+               auxv = auxvp[: pairs*2 : pairs*2]
                return
        }
        // In some situations we don't get a loader-provided
@@ -269,23 +273,24 @@ func sysargs(argc int32, argv **byte) {
                munmap(p, size)
                return
        }
-       var buf [128]uintptr
-       n = read(fd, noescape(unsafe.Pointer(&buf[0])), int32(unsafe.Sizeof(buf)))
+
+       n = read(fd, noescape(unsafe.Pointer(&auxvreadbuf[0])), int32(unsafe.Sizeof(auxvreadbuf)))
        closefd(fd)
        if n < 0 {
                return
        }
        // Make sure buf is terminated, even if we didn't read
        // the whole file.
-       buf[len(buf)-2] = _AT_NULL
-       sysauxv(buf[:])
+       auxvreadbuf[len(auxvreadbuf)-2] = _AT_NULL
+       pairs := sysauxv(auxvreadbuf[:])
+       auxv = auxvreadbuf[: pairs*2 : pairs*2]
 }
 
 // startupRandomData holds random bytes initialized at startup. These come from
 // the ELF AT_RANDOM auxiliary vector.
 var startupRandomData []byte
 
-func sysauxv(auxv []uintptr) int {
+func sysauxv(auxv []uintptr) (pairs int) {
        var i int
        for ; auxv[i] != _AT_NULL; i += 2 {
                tag, val := auxv[i], auxv[i+1]

diff --git a/src/runtime/os_netbsd.go b/src/runtime/os_netbsd.go
index ce59618af4adb581ae21379e60fe8e9137b4100e..7f8c6bc4e3b4ab24bdf1332c94fe12d7d1603b12 100644 (file)
--- a/src/runtime/os_netbsd.go
+++ b/src/runtime/os_netbsd.go
@@ -402,8 +402,9 @@ func sysargs(argc int32, argv **byte) {
        n++
 
        // now argv+n is auxv
-       auxv := (*[1 << 28]uintptr)(add(unsafe.Pointer(argv), uintptr(n)*goarch.PtrSize))
-       sysauxv(auxv[:])
+       auxvp := (*[1 << 28]uintptr)(add(unsafe.Pointer(argv), uintptr(n)*goarch.PtrSize))
+       pairs := sysauxv(auxvp[:])
+       auxv = auxvp[: pairs*2 : pairs*2]
 }
 
 const (
@@ -411,14 +412,16 @@ const (
        _AT_PAGESZ = 6 // Page size in bytes
 )
 
-func sysauxv(auxv []uintptr) {
-       for i := 0; auxv[i] != _AT_NULL; i += 2 {
+func sysauxv(auxv []uintptr) (pairs int) {
+       var i int
+       for i = 0; auxv[i] != _AT_NULL; i += 2 {
                tag, val := auxv[i], auxv[i+1]
                switch tag {
                case _AT_PAGESZ:
                        physPageSize = val
                }
        }
+       return i / 2
 }
 
 // raise sends signal to the calling thread.

diff --git a/src/runtime/runtime.go b/src/runtime/runtime.go
index f240d7ae70d4821e0cbe68d5b1b22e6c3fb474a1..0822d0e8054e7b53f6347f8bcdbb1228dd82d80a 100644 (file)
--- a/src/runtime/runtime.go
+++ b/src/runtime/runtime.go
@@ -151,3 +151,12 @@ func syscall_runtimeUnsetenv(key string) {
 func writeErrStr(s string) {
        write(2, unsafe.Pointer(unsafe.StringData(s)), int32(len(s)))
 }
+
+// auxv is populated on relevant platforms but defined here for all platforms
+// so x/sys/cpu can assume the getAuxv symbol exists without keeping its list
+// of auxv-using GOOS build tags in sync.
+//
+// It contains an even number of elements, (tag, value) pairs.
+var auxv []uintptr
+
+func getAuxv() []uintptr { return auxv } // accessed from x/sys/cpu; see issue 57336