getunwind(2)

1getunwind(2)                  System Calls Manual                 getunwind(2)
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NAME

6       getunwind - copy the unwind data to caller's buffer
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LIBRARY

9       Standard C library (libc, -lc)
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SYNOPSIS

12       #include <linux/unwind.h>
13       #include <sys/syscall.h>      /* Definition of SYS_* constants */
14       #include <unistd.h>
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16       [[deprecated]] long syscall(SYS_getunwind, void buf[.buf_size],
17                                   size_t buf_size);
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DESCRIPTION

20       Note: this system call is obsolete.
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22       The  IA-64-specific  getunwind()  system  call copies the kernel's call
23       frame unwind data into the buffer pointed to by  buf  and  returns  the
24       size of the unwind data; this data describes the gate page (kernel code
25       that is mapped into user space).
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27       The size of the buffer buf is  specified  in  buf_size.   The  data  is
28       copied only if buf_size is greater than or equal to the size of the un‐
29       wind data and buf is not NULL; otherwise, no data is  copied,  and  the
30       call succeeds, returning the size that would be needed to store the un‐
31       wind data.
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33       The first part of the unwind data contains an unwind table.   The  rest
34       contains  the  associated  unwind  information, in no particular order.
35       The unwind table contains entries of the following form:
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37           u64 start;      (64-bit address of start of function)
38           u64 end;        (64-bit address of end of function)
39           u64 info;       (BUF-relative offset to unwind info)
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41       An entry whose start value is zero indicates the end of the table.  For
42       more  information  about the format, see the IA-64 Software Conventions
43       and Runtime Architecture manual.
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RETURN VALUE

46       On success, getunwind() returns the size of the unwind data.  On error,
47       -1 is returned and errno is set to indicate the error.
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ERRORS

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

54       Linux on IA-64.
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HISTORY

57       Linux 2.4.
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59       This system call has been deprecated.  The modern  way  to  obtain  the
60       kernel's unwind data is via the vdso(7).
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