Go to main content

Oracle® Solaris 11.4 DTrace (Dynamic Tracing) Guide

Exit Print View

Updated: September 2020

pid Provider

The pid provider enables tracing of the entry and return of any function in a user process as well as any instruction as specified by an absolute address or function offset. The pid provider has no probe effect when probes are not enabled. When probes are enabled, the probes only induce probe effect on those processes that are traced.

Note -  When the compiler inlines a function, the pid provider's probe does not fire. Use one of the following methods to compile a particular C function so that it will not be inlined.
  • Oracle Developer Studio: #pragma no_inline (funcname[, funcname])

  • gcc: funcname __attribute__ ((noinline))

    Consult your compiler documentation for updates.

Naming pid Probes

The pid provider actually defines a class of providers. Each process can potentially have its own associated pid provider. A process with ID 123, for example, would be traced by using the pid123 provider. For probes from one of these providers, the module portion of the probe description refers to an object loaded in the corresponding process's address space. The following example uses mdb to display a list of objects:

$ mdb -p 1234
Loading modules: [ ld.so.1 libc.so.1 ]
> ::objects
   10000    34000    24000 /usr/bin/csh
ff3c0000 ff3e8000    28000 /lib/ld.so.1
ff200000 ff2be000    be000 /lib/libc.so.1
ff3a0000 ff3a2000     2000 /lib/libdl.so.1

In the probe description, you name the object by the name of the file, not its full path name. You can also omit the .1 or so.1 suffix. All of the following examples name the same probe:


The first example is the actual name of the probe. The other examples are convenient aliases that are replaced with the full load object name internally.

For the load object of the executable, you can use the alias a.out. The following two probe descriptions name the same probe:


As with all anchored DTrace probes, the function field of the probe description names a function in the module field. A user application binary might have several names for the same function. For example, mutex_lock might be an alternate name for the function pthread_mutex_lock in libc.so.1. DTrace chooses one canonical name for such functions and uses that name internally. The following example shows how DTrace internally remaps module and function names to a canonical form:

# dtrace -q -n pid101267:libc:mutex_lock:entry'{ \
    printf("%s:%s:%s:%s\n", probeprov, probemod, probefunc, probename); }'

This automatic renaming means that the names of the probes you enable may be slightly different than those actually enabled. The canonical name will always be consistent between runs of DTrace on systems running the same Oracle Solaris release.

For examples about how to use the pid provider effectively, see User Process Tracing..

pid Function Boundary Probes

The pid provider enables you to trace function entry and return in user programs just as the fbt provider provides that capability for the kernel. Most of the examples in this guide that use the FBT provider to trace kernel function calls can be modified slightly to apply to user processes.

pid entry Probes

An entry probe fires when the traced function is invoked. The arguments to entry probes are the values of the arguments to the traced function.

pid return Probes

A return probe fires when the traced function returns or makes a tail call to another function. The value for arg0 is the offset in the function of the return instruction; arg1 holds the return value.

In 32-bit processes, for functions that return either a signed long long or an unsigned long long type, arg1 contains only half of the total bits in the return value. The other half of the total bits returned is available in arg2. On SPARC systems, arg1 contains the upper 32-bits of the return value and arg2 contains the lower 32-bits of the return value. On x86 systems, arg1 contains the lower 32-bits of the return value and arg2 contains the upper 32-bits of the return value.

pid Function Offset Probes

The pid provider lets you trace any instruction in a function. For example to trace the instruction 4 bytes into a function main, you can use the following command:


Every time the program executes the instruction at address main+4, this probe will be activated. The arguments for offset probes are undefined. The uregs[] array will help you to examine process state at these probe sites. For more information, see uregs[] Array.

pid Stability

The pid provider uses stability mechanism of DTrace to describe its stabilities, as shown in the following table. For more information about the stability mechanism, see DTrace Stability Mechanisms.

Table 41  Stability Mechanism for the pid Provider
Name Stability
Data Stability
Dependency Class