NAME

       getunwind - copy the unwind data to caller's buffer

LIBRARY

       Standard C library (libc, -lc)

SYNOPSIS

       #include <linux/unwind.h>
       #include <sys/syscall.h>      /* Definition of SYS_* constants */
       #include <unistd.h>

       [[deprecated]] long syscall(SYS_getunwind, void buf[.buf_size],
                                   size_t buf_size);

DESCRIPTION

       Note: this system call is obsolete.

       The  IA-64-specific  getunwind()  system  call copies the kernel's call frame unwind data into the buffer
       pointed to by buf and returns the size of the unwind data; this data describes the gate page (kernel code
       that is mapped into user space).

       The size of the buffer buf is specified in buf_size.  The data is copied only if buf_size is greater than
       or equal to the size of the unwind data and buf is not NULL; otherwise, no data is copied, and  the  call
       succeeds, returning the size that would be needed to store the unwind data.

       The  first  part  of  the  unwind data contains an unwind table.  The rest contains the associated unwind
       information, in no particular order.  The unwind table contains entries of the following form:

           u64 start;      (64-bit address of start of function)
           u64 end;        (64-bit address of end of function)
           u64 info;       (BUF-relative offset to unwind info)

       An entry whose start value is zero indicates the end of  the  table.   For  more  information  about  the
       format, see the IA-64 Software Conventions and Runtime Architecture manual.

RETURN VALUE

       On  success,  getunwind() returns the size of the unwind data.  On error, -1 is returned and errno is set
       to indicate the error.

ERRORS

       getunwind() fails with the error EFAULT if the unwind info can't be stored in the space specified by buf.

STANDARDS

       Linux on IA-64.

HISTORY

       Linux 2.4.

       This system call has been deprecated.  The modern way to obtain the  kernel's  unwind  data  is  via  the
       vdso(7).

SEE ALSO

       getauxval(3)