---
name: "pmc_get_msr"
section: "3"
platform: "freebsd"
package: "base"
version: "16.0-CURRENT-20261027-61c70dc16a79"
release: "FreeBSD 16.0-CURRENT (2026-10-27)"
platforms: ["freebsd"]
url: "https://new.carta.tech/pmc_get_msr"
---

# pmc\_get\_msr(3)

x86 architecture-specific PMC operations

## NAME

**pmc\_get\_msr** – x86 architecture-specific PMC operations

## LIBRARY

library “libpmc”

## SYNOPSIS

**#include \<pmc.h\>**

*int*\

**pmc\_get\_msr**(*pmc\_id\_t pmc*, *uint32\_t \*msr*);

## DESCRIPTION

The function **pmc\_get\_msr**() returns the processor model specific register number associated with a PMC for subsequent use with RDPMC instructions. Argument *pmc* specifies a process scope counting PMC. The function will write the model specific register number associated with the PMC to the location pointed to by argument *msr*.

After successful completion of this function, applications can directly read the contents of PMC hardware using RDPMC instructions.

## RETURN VALUES

The **pmc\_get\_msr()** function returns the value 0 if successful; otherwise the value -1 is returned and the global variable errno is set to indicate the error.

## ERRORS

A call to **pmc\_get\_msr**() may fail with the following errors:

- \[EINVAL\]

  The PMC handle specified was invalid.

- \[EINVAL\]

  The PMC specified did not have process scope or counting mode.

- \[EINVAL\]

  The PMC specified was allocated with the PMC\_F\_DESCENDANTS flag.

- \[EINVAL\]

  The specified PMC is already attached to target processes other than the owner.

- \[ENOSYS\]

  The underlying hardware does not support an RDPMC instruction.

## SEE ALSO

[pmc(3)](/pmc/3.md), [hwpmc(4)](/hwpmc/4.md)