More helpful help message

tools/inject.py

@@ -295,6 +295,21 @@ def attach(self, bpf):
 
 
 class Tool:
+
+ examples ="""
+EXAMPLES:
+# ./inject.py kmalloc -v 'SyS_mount()'
+ Fails all calls to syscall mount
+# ./inject.py kmalloc -v '(true) => SyS_mount()(true)'
+ Explicit rewriting of above
+# ./inject.py kmalloc -v 'mount_subtree() => btrfs_mount()'
+ Fails btrfs mounts only
+# ./inject.py kmalloc -v 'd_alloc_parallel(struct dentry *parent, const struct \\
+ qstr *name)(STRCMP(name->name, 'bananas'))'
+ Fails dentry allocations of files named 'bananas'
+# ./inject.py kmalloc -v -P 0.01 'SyS_mount()'
+ Fails calls to syscall mount with 1% probability
+ """
  # add cases as necessary
  error_injection_mapping = {
  "kmalloc": "should_failslab(struct kmem_cache *s, gfp_t gfpflags)",
@@ -304,8 +319,9 @@ class Tool:
  def __init__(self):
  parser = argparse.ArgumentParser(description="Fail specified kernel" +
  " functionality when call chain and predicates are met",
- formatter_class=argparse.RawDescriptionHelpFormatter)
- parser.add_argument(metavar="mode", dest="mode",
+ formatter_class=argparse.RawDescriptionHelpFormatter,
+ epilog=Tool.examples)
+ parser.add_argument(dest="mode", choices=['kmalloc','bio'],
  help="indicate which base kernel function to fail")
  parser.add_argument(metavar="spec", dest="spec",
  help="specify call chain")
@@ -316,7 +332,7 @@ def __init__(self):
  metavar="probability", type=float,
  help="probability that this call chain will fail")
  parser.add_argument("-v", "--verbose", action="store_true",
- help="print BPF program")
+  help="print BPF program")
  self.args = parser.parse_args()
 
  self.program = ""

tools/inject_example.txt

@@ -115,12 +115,12 @@ fail our mounts half the time:
 # ./inject.py kmalloc -v -P 0.01 'SyS_mount()'
 
 USAGE message:
-usage: inject.py [-h] [-I header] [-P probability] [-v] mode spec
+usage: inject.py [-h] [-I header] [-P probability] [-v] {kmalloc,bio} spec
 
 Fail specified kernel functionality when call chain and predicates are met
 
 positional arguments:
- mode  indicate which base kernel function to fail
+ {kmalloc,bio} indicate which base kernel function to fail
  spec specify call chain
 
 optional arguments:
@@ -130,3 +130,16 @@ optional arguments:
  -P probability, --probability probability
  probability that this call chain will fail
  -v, --verbose print BPF program
+
+EXAMPLES:
+# ./inject.py kmalloc -v 'SyS_mount()'
+ Fails all calls to syscall mount
+# ./inject.py kmalloc -v '(true) => SyS_mount()(true)'
+ Explicit rewriting of above
+# ./inject.py kmalloc -v 'mount_subtree() => btrfs_mount()'
+ Fails btrfs mounts only
+# ./inject.py kmalloc -v 'd_alloc_parallel(struct dentry *parent, const struct \
+ qstr *name)(STRCMP(name->name, 'bananas'))'
+ Fails dentry allocations of files named 'bananas'
+# ./inject.py kmalloc -v -P 0.01 'SyS_mount()'
+ Fails calls to syscall mount with 1% probability