github.com/xyproto/u-root@v6.0.1-0.20200302025726-5528e0c77a3c+incompatible/pkg/strace/print.go (about)

     1  // Copyright 2018 Google LLC.
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  //
     7  //     http://www.apache.org/licenses/LICENSE-2.0
     8  //
     9  // Unless required by applicable law or agreed to in writing, software
    10  // distributed under the License is distributed on an "AS IS" BASIS,
    11  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    12  // See the License for the specific language governing permissions and
    13  // limitations under the License.
    14  //
    15  // Changes are Copyright 2018 the u-root Authors.
    16  
    17  package strace
    18  
    19  import (
    20  	"fmt"
    21  	"strings"
    22  
    23  	"golang.org/x/sys/unix"
    24  )
    25  
    26  // DefaultLogMaximumSize is the default LogMaximumSize.
    27  const DefaultLogMaximumSize = 1024
    28  
    29  // LogMaximumSize determines the maximum display size for data blobs (read,
    30  // write, etc.).
    31  var LogMaximumSize uint = DefaultLogMaximumSize
    32  
    33  // EventMaximumSize determines the maximum size for data blobs (read, write,
    34  // etc.) sent over the event channel. Default is 0 because most clients cannot
    35  // do anything useful with binary text dump of byte array arguments.
    36  var EventMaximumSize uint
    37  
    38  func dump(t *Tracer, addr Addr, size uint, maximumBlobSize uint) string {
    39  	origSize := size
    40  	if size > maximumBlobSize {
    41  		size = maximumBlobSize
    42  	}
    43  	if size == 0 {
    44  		return ""
    45  	}
    46  
    47  	b := make([]byte, size)
    48  	amt, err := t.Read(addr, b)
    49  	if err != nil {
    50  		return fmt.Sprintf("%#x (error decoding string: %s)", addr, err)
    51  	}
    52  
    53  	dot := ""
    54  	if uint(amt) < origSize {
    55  		// ... if we truncated the dump.
    56  		dot = "..."
    57  	}
    58  
    59  	return fmt.Sprintf("%#x %q%s", addr, b[:amt], dot)
    60  }
    61  
    62  func iovecs(t *Tracer, addr Addr, iovcnt int, printContent bool, maxBytes uint64) string {
    63  	if iovcnt < 0 || iovcnt > 0x10 /*unix.MSG_MAXIOVLEN*/ {
    64  		return fmt.Sprintf("%#x (error decoding iovecs: invalid iovcnt)", addr)
    65  	}
    66  	v := make([]iovec, iovcnt)
    67  	_, err := t.Read(addr, v)
    68  	if err != nil {
    69  		return fmt.Sprintf("%#x (error decoding iovecs: %v)", addr, err)
    70  	}
    71  
    72  	var totalBytes uint64
    73  	var truncated bool
    74  	iovs := make([]string, iovcnt)
    75  	for i, vv := range v {
    76  		if vv.S == 0 || !printContent {
    77  			iovs[i] = fmt.Sprintf("{base=%#x, len=%d}", vv.P, vv.S)
    78  			continue
    79  		}
    80  
    81  		size := uint64(vv.S)
    82  		if truncated || totalBytes+size > maxBytes {
    83  			truncated = true
    84  			size = maxBytes - totalBytes
    85  		} else {
    86  			totalBytes += uint64(vv.S)
    87  		}
    88  
    89  		b := make([]byte, size)
    90  		amt, err := t.Read(vv.P, b)
    91  		if err != nil {
    92  			iovs[i] = fmt.Sprintf("{base=%#x, len=%d, %q..., error decoding string: %v}", vv.P, vv.S, b[:amt], err)
    93  			continue
    94  		}
    95  
    96  		dot := ""
    97  		if truncated {
    98  			// Indicate truncation.
    99  			dot = "..."
   100  		}
   101  		iovs[i] = fmt.Sprintf("{base=%#x, len=%d, %q%s}", vv.P, vv.S, b[:amt], dot)
   102  	}
   103  
   104  	return fmt.Sprintf("%#x %s", addr, strings.Join(iovs, ", "))
   105  }
   106  
   107  func fdpair(t *Tracer, addr Addr) string {
   108  	var fds [2]int32
   109  	_, err := t.Read(addr, &fds)
   110  	if err != nil {
   111  		return fmt.Sprintf("%#x (error decoding fds: %s)", addr, err)
   112  	}
   113  
   114  	return fmt.Sprintf("%#x [%d %d]", addr, fds[0], fds[1])
   115  }
   116  
   117  func uname(t *Tracer, addr Addr) string {
   118  	var u unix.Utsname
   119  	if _, err := t.Read(addr, &u); err != nil {
   120  		return fmt.Sprintf("%#x (error decoding utsname: %s)", addr, err)
   121  	}
   122  
   123  	return fmt.Sprintf("%#x %v", addr, u)
   124  }
   125  
   126  // AlignUp rounds a length up to an alignment. align must be a power of 2.
   127  func AlignUp(length int, align uint) int {
   128  	return (length + int(align) - 1) & ^(int(align) - 1)
   129  }
   130  
   131  // AlignDown rounds a down to an alignment. align must be a power of 2.
   132  func AlignDown(length int, align uint) int {
   133  	return length & ^(int(align) - 1)
   134  }