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GETUNWIND(2) Linux Programmer's Manual GETUNWIND(2)
NAME
getunwind - copy the unwind data to caller's buffer
SYNOPSIS
#include <linux/unwind.h>
#include <sys/syscall.h> /* Definition of SYS_* constants */
#include <unistd.h>
long syscall(SYS_getunwind, void *buf, size_t buf_size);
Note: glibc provides no wrapper for getunwind(), necessitating the use of syscall(2).
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Note: this system call is obsolete.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 con‐
tains 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 Archi‐
tecture 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.
VERSIONS
This system call is available since Linux 2.4.
CONFORMING TO
This system call is Linux-specific, and is available only on the IA-64 architecture.
NOTES
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)
Linux 2021-03-22 GETUNWIND(2)