KSYMS(4)

KSYMS(4) | Device Drivers Manual | KSYMS(4)

# NAME

`ksyms` — kernel symbol table interface

# SYNOPSIS

`pseudo-device ksyms`

# DESCRIPTION

The /dev/ksyms character device provides a read-only interface to the current kernel symbol table. It can be accessed either as a sequential file, where it looks like an executable file but with zero-sized text and data segments, or via ioctl(2).

/dev/ksyms represents the symbol table at the time when the device is opened, and may not change until it is closed.

The in-kernel symbol manager is designed to be able to handle any type of symbol table. However, only elf(5) symbol tables are currently dealt with.

# IOCTLS

The ioctl(2) command codes below are defined in `<sys/ksyms.h>`.

The (third) argument to the ioctl(2) should be a pointer to the type indicated.

`KIOCGSIZE` (int)
  Returns the total size of the current symbol table. This should be used when allocating a buffer to read in the whole symbol table to memory.
`KIOCGVALUE` (struct ksyms_gvalue)
  Returns the value for the given symbol name in a symtab-independent fashion.

      struct ksyms_gvalue {
              const char *kv_name;
              uint64_t kv_value;
      };

  The struct member kv_name should be set to the name of the requested value, and upon return kv_value contains the symbol value.

`KIOCGSYMBOL` (struct ksyms_gsymbol)
  Returns the complete symbol for the given symbol name.

      struct ksyms_gsymbol {
              const char *kg_name;
              void *kg_sym;
      };

  The struct member kg_name should be set to the name of the requested symbol, and the found symbol will be written to the kg_sym address. It is the callers responsibility to ensure that enough space for the symbol is allocated.

# FILES

/dev/ksyms

# SEE ALSO

ioctl(2), nlist(3), elf(5)

# HISTORY

A `ksyms` device exists in many different operating systems. This implementation is modelled in function after Solaris `ksyms`. This `ksyms` driver was written by Anders Magnusson for NetBSD.

The `ksyms` driver first appeared in NetBSD 2.0.

July 27, 2024 | NetBSD 11.0