man2/getunwind.2

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  27 .TH GETUNWIND 2 2017-09-15 Linux "Linux Programmer's Manual"
  28 .SH NAME
  29 getunwind \- copy the unwind data to caller's buffer
  30 .SH SYNOPSIS
  31 .nf
  32 .B #include <syscall.h>
  33 .B #include <linux/unwind.h>
  34 .PP
  35 .BI "long getunwind(void " *buf ", size_t " buf_size );
  36 .fi
  37 .PP
  38 .IR Note :
  39 There is no glibc wrapper for this system call; see NOTES.
  40 .SH DESCRIPTION
  41 .I Note: this function is obsolete.
  42 .PP
  43 The
  44 IA-64-specific
  45 .BR getunwind ()
  46 system call copies the kernel's call frame
  47 unwind data into the buffer pointed to by
  48 .I buf
  49 and returns the size of the unwind data;
  50 this data describes the gate page (kernel code that
  51 is mapped into user space).
  52 .PP
  53 The size of the buffer
  54 .I buf
  55 is specified in
  56 .IR buf_size .
  57 The data is copied only if
  58 .I buf_size
  59 is greater than or equal to the size of the unwind data and
  60 .I buf
  61 is not NULL;
  62 otherwise, no data is copied, and the call succeeds,
  63 returning the size that would be needed to store the unwind data.
  64 .PP
  65 The first part of the unwind data contains an unwind table.
  66 The rest contains the associated unwind information, in no particular order.
  67 The unwind table contains entries of the following form:
  68 .PP
  69 .in +4n
  70 .EX
  71 u64 start;      (64-bit address of start of function)
  72 u64 end;        (64-bit address of end of function)
  73 u64 info;       (BUF-relative offset to unwind info)
  74 .EE
  75 .in
  76 .PP
  77 An entry whose
  78 .I start
  79 value is zero indicates the end of the table.
  80 For more information about the format, see the
  81 .I IA-64 Software Conventions and Runtime Architecture
  82 manual.
  83 .SH RETURN VALUE
  84 On success,
  85 .BR getunwind ()
  86 returns the size of the unwind data.
  87 On error, \-1 is returned and
  88 .I errno
  89 is set to indicate the error.
  90 .SH ERRORS
  91 .BR getunwind ()
  92 fails with the error
  93 .B EFAULT
  94 if the unwind info can't be stored in the space specified by
  95 .IR buf .
  96 .SH VERSIONS
  97 This system call is available since Linux 2.4.
  98 .SH CONFORMING TO
  99 This system call is Linux-specific,
 100 and is available only on the IA-64 architecture.
 101 .SH NOTES
 102 This system call has been deprecated.
 103 The modern way to obtain the kernel's unwind data is via the
 104 .BR vdso (7).
 105 .PP
 106 Glibc does not provide a wrapper for this system call;
 107 in the unlikely event that you want to call it, use
 108 .BR syscall (2).
 109 .SH SEE ALSO
 110 .BR getauxval (3)