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Diffstat (limited to 'stap.1.in')
| -rw-r--r-- | stap.1.in | 76 |
1 files changed, 76 insertions, 0 deletions
@@ -153,6 +153,41 @@ Start the probes, run CMD, and exit when CMD finishes. .BI \-x " PID" Sets target() to PID. This allows scripts to be written that filter on a specific process. +.TP +.B \-\-kelf +For names and addresses of functions to probe, +consult the symbol tables in the kernel and modules. +This can be useful if your kernel and/or modules were compiled +without debugging information, or the function you want to probe +is in an assembly-language file built without debugging information. +See the +.B "MAKING DO WITH SYMBOL TABLES" +section for more information. +.TP +.BI \-\-kmap [=FILE] +For names and addresses of kernel functions to probe, +consult the symbol table in the indicated text file. +The default is /boot/System.map-VERSION. +The contents of this file should be in the form of the default output from +.IR nm (1). +Only symbols of type T or t are used. +If you specify /proc/kallsyms or some other file in that format, +where lines for module symbols contain a fourth column, +reading of the symbol table stops with the first module symbol +(which should be right after the last kernel symbol). +As with +.BR \-\-kelf , +the symbol table in each module's .ko file will also be consulted. +See the +.B "MAKING DO WITH SYMBOL TABLES" +section for more information. +.TP +.B \-\-ignore\-vmlinux +For testing, act as though neither the uncompressed kernel (vmlinux) +nor the kernel debugging information can be found. +.TP +.B \-\-ignore\-dwarf +For testing, act as though vmlinux and modules lack debugging information. .SH ARGUMENTS @@ -916,6 +951,47 @@ have overloaded the system and an exit is triggered. By default, overload processing is turned on for all modules. If you would like to disable overload processing, define STP_NO_OVERLOAD. +.SH MAKING DO WITH SYMBOL TABLES +Systemtap performs best when it has access to the debugging information +associated with your kernel and modules. +However, if this information is not available, +systemtap can still support probing of function entries and returns +using symbols read from vmlinux and/or the modules in /lib/modules. +Systemtap can also read the kernel symbol table from a text file +such as /boot/System.map or /proc/kallsyms. +See the +.B \-\--kelf +and +.B \-\--kmap +options. +.PP +If systemtap finds relevant debugging information, +it will use it even if you specify +.B \-\--kelf +or +.BR \-\--kmap . +.PP +Without debugging information, systemtap cannot support the +following types of language constructs: +.IP \(bu 4 +probe specifications that refer to source files or line numbers +.IP \(bu 4 +probe specifications that refer to inline functions +.IP \(bu 4 +statements that refer to $target variables +.IP \(bu 4 +tapset-defined variables defined using any of the above constructs. +In particular, at this writing, +the prologue blocks for certain aliases in the syscall tapset +(e.g., syscall.open) contain "if" statements that refer to $target variables. +If your script refers to any such aliases, +systemtap must have access to the kernel's debugging information. +.PP +Most T and t symbols correspond to function entry points, but some do not. +Based only on the symbol table, systemtap cannot tell the difference. +Placing return probes on symbols that aren't entry points +will most likely lead to kernel stack corruption. + .SH FILES .\" consider autoconf-substituting these directories .TP |