issue9400_linux.go

     1  // Copyright 2014 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  // Test that SIGSETXID runs on signal stack, since it's likely to
     6  // overflow if it runs on the Go stack.
     7  
     8  package cgotest
     9  
    10  /*
    11  #include <sys/types.h>
    12  #include <unistd.h>
    13  */
    14  import "C"
    15  
    16  import (
    17  	"runtime"
    18  	"runtime/debug"
    19  	"sync/atomic"
    20  	"testing"
    21  
    22  	"cgotest/issue9400"
    23  )
    24  
    25  func test9400(t *testing.T) {
    26  	// We synchronize through a shared variable, so we need two procs
    27  	defer runtime.GOMAXPROCS(runtime.GOMAXPROCS(2))
    28  
    29  	// Start signaller
    30  	atomic.StoreInt32(&issue9400.Baton, 0)
    31  	go func() {
    32  		// Wait for RewindAndSetgid
    33  		for atomic.LoadInt32(&issue9400.Baton) == 0 {
    34  			runtime.Gosched()
    35  		}
    36  		// Broadcast SIGSETXID
    37  		runtime.LockOSThread()
    38  		C.setgid(0)
    39  		// Indicate that signalling is done
    40  		atomic.StoreInt32(&issue9400.Baton, 0)
    41  	}()
    42  
    43  	// Grow the stack and put down a test pattern
    44  	const pattern = 0x123456789abcdef
    45  	var big [1024]uint64 // len must match assembly
    46  	for i := range big {
    47  		big[i] = pattern
    48  	}
    49  
    50  	// Disable GC for the duration of the test.
    51  	// This avoids a potential GC deadlock when spinning in uninterruptable ASM below #49695.
    52  	defer debug.SetGCPercent(debug.SetGCPercent(-1))
    53  	// SetGCPercent waits until the mark phase is over, but the runtime
    54  	// also preempts at the start of the sweep phase, so make sure that's
    55  	// done too. See #49695.
    56  	runtime.GC()
    57  
    58  	// Temporarily rewind the stack and trigger SIGSETXID
    59  	issue9400.RewindAndSetgid()
    60  
    61  	// Check test pattern
    62  	for i := range big {
    63  		if big[i] != pattern {
    64  			t.Fatalf("entry %d of test pattern is wrong; %#x != %#x", i, big[i], uint64(pattern))
    65  		}
    66  	}
    67  }
    68
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