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2 .\" Written by Marcela Maslanova <mmaslano@redhat.com>
3 .\" and Copyright 2013, Michael Kerrisk <mtk.manpages@gmail.com>
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7 .TH GETUNWIND 2 2021-03-22 "Linux man-pages (unreleased)"
9 getunwind \- copy the unwind data to caller's buffer
12 .RI ( libc ", " \-lc )
15 .B #include <linux/unwind.h>
16 .BR "#include <sys/syscall.h>" " /* Definition of " SYS_* " constants */"
17 .B #include <unistd.h>
19 .BI "long syscall(SYS_getunwind, void " *buf ", size_t " buf_size );
23 glibc provides no wrapper for
25 necessitating the use of
28 .I Note: this system call is obsolete.
33 system call copies the kernel's call frame
34 unwind data into the buffer pointed to by
36 and returns the size of the unwind data;
37 this data describes the gate page (kernel code that
38 is mapped into user space).
40 The size of the buffer
44 The data is copied only if
46 is greater than or equal to the size of the unwind data and
49 otherwise, no data is copied, and the call succeeds,
50 returning the size that would be needed to store the unwind data.
52 The first part of the unwind data contains an unwind table.
53 The rest contains the associated unwind information, in no particular order.
54 The unwind table contains entries of the following form:
58 uint64_t start; (64\-bit address of start of function)
59 uint64_t end; (64\-bit address of end of function)
60 uint64_t info; (BUF\-relative offset to unwind info)
66 value is zero indicates the end of the table.
67 For more information about the format, see the
68 .I IA-64 Software Conventions and Runtime Architecture
73 returns the size of the unwind data.
74 On error, \-1 is returned and
76 is set to indicate the error.
81 if the unwind info can't be stored in the space specified by
84 This system call is available since Linux 2.4.
86 This system call is Linux-specific,
87 and is available only on the IA-64 architecture.
89 This system call has been deprecated.
90 The modern way to obtain the kernel's unwind data is via the