diff options
Diffstat (limited to 'stap.1.in')
| -rw-r--r-- | stap.1.in | 17 |
1 files changed, 11 insertions, 6 deletions
@@ -467,11 +467,12 @@ For prologue style alias, the statement block that follows an alias definition is implicitly added as a prologue to any probe that refers to the alias. While for the epilogue style alias, the statement block that follows an alias definition is implicitly added as an epilogue to -any probe that refers to the alias. For example: +any probe that refers to the alias. For example: .SAMPLE probe syscall.read = kernel.function("sys_read") { fildes = $fd + if (execname == "init") next # skip rest of probe } .ESAMPLE defines a new probe point @@ -482,19 +483,23 @@ which expands to .nh .IR kernel.function("sys_read") , .hy -with the given statement as a prologue. And +with the given statement as a prologue, which is useful to predefine +some variables for the alias user and/or to skip probe processing +entirely based on some conditions. And .SAMPLE probe syscall.read += kernel.function("sys_read") { - fildes = $fd + if (tracethis) println ($fd) } .ESAMPLE -defines a new probe point with the given statement as an epilogue. +defines a new probe point with the given statement as an epilogue, which +is useful to take actions based upon variables set or left over by the +the alias user. -Another probe definition -may use the alias like this: +An alias is used just like a built-in probe type. .SAMPLE probe syscall.read { printf("reading fd=%d\n", fildes) + if (fildes > 10) tracethis = 1 } .ESAMPLE |