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100 lines
3.6 KiB
TeX
100 lines
3.6 KiB
TeX
\documentclass{article}
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\usepackage[fancyhdr,pdf]{latex2man}
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\input{common.tex}
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\begin{document}
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\begin{Name}{3}{unw\_resume}{David Mosberger-Tang}{Programming Library}{unw\_resume}unw\_resume -- resume execution in a particular stack frame
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\end{Name}
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\section{Synopsis}
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\File{\#include $<$libunwind.h$>$}\\
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\Type{int} \Func{unw\_resume}(\Type{unw\_cursor\_t~*}\Var{cp});\\
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\section{Description}
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The \Func{unw\_resume}() routine resumes execution at the stack frame
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identified by \Var{cp}. The behavior of this routine differs
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slightly for local and remote unwinding.
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For local unwinding, \Func{unw\_resume}() restores the machine state
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and then directly resumes execution in the target stack frame. Thus
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\Func{unw\_resume}() does not return in this case. Restoring the
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machine state normally involves restoring the ``preserved''
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(callee-saved) registers. However, if execution in any of the stack
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frames younger (more deeply nested) than the one identified by
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\Var{cp} was interrupted by a signal, then \Func{unw\_resume}() will
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restore all registers as well as the signal mask. Attempting to call
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\Func{unw\_resume}() on a cursor which identifies the stack frame of
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another thread results in undefined behavior (e.g., the program may
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crash).
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For remote unwinding, \Func{unw\_resume}() installs the machine state
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identified by the cursor by calling the \Func{access\_reg} and
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\Func{access\_fpreg} accessor callbacks as needed. Once that is
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accomplished, the \Func{resume} accessor callback is invoked. The
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\Func{unw\_resume} routine then returns normally (that is, unlikely
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for local unwinding, \Func{unw\_resume} will always return for remote
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unwinding).
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Most platforms reserve some registers to pass arguments to exception
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handlers (e.g., IA-64 uses \texttt{r15}-\texttt{r18} for this
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purpose). These registers are normally treated like ``scratch''
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registers. However, if \Prog{libunwind} is used to set an exception
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argument register to a particular value (e.g., via
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\Func{unw\_set\_reg}()), then \Func{unw\_resume}() will install this
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value as the contents of the register. In other words, the exception
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handling arguments are installed even in cases where normally only the
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``preserved'' registers are restored.
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Note that \Func{unw\_resume}() does \emph{not} invoke any unwind
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handlers (aka, ``personality routines''). If a program needs this, it
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will have to do so on its own by obtaining the \Type{unw\_proc\_info\_t}
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of each unwound frame and appropriately processing its unwind handler
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and language-specific data area (lsda). These steps are generally
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dependent on the target-platform and are regulated by the
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processor-specific ABI (application-binary interface).
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\section{Return Value}
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For local unwinding, \Func{unw\_resume}() does not return on success.
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For remote unwinding, it returns 0 on success. On failure, the
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negative value of one of the errors below is returned.
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\section{Thread and Signal Safety}
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\Func{unw\_resume}() is thread-safe as well as safe to use from a
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signal handler.
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\section{Errors}
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\begin{Description}
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\item[\Const{UNW\_EUNSPEC}] An unspecified error occurred.
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\item[\Const{UNW\_EBADREG}] A register needed by \Func{unw\_resume}() wasn't
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accessible.
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\item[\Const{UNW\_EINVALIDIP}] The instruction pointer identified by
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\Var{cp} is not valid.
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\item[\Const{UNW\_BADFRAME}] The stack frame identified by
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\Var{cp} is not valid.
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\end{Description}
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\section{See Also}
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\SeeAlso{libunwind(3)},
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\SeeAlso{unw\_set\_reg(3)},
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sigprocmask(2)
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\section{Author}
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\noindent
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David Mosberger-Tang\\
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Hewlett-Packard Labs\\
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Palo-Alto, CA 94304\\
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Email: \Email{davidm@hpl.hp.com}\\
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WWW: \URL{http://www.hpl.hp.com/research/linux/libunwind/}.
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\LatexManEnd
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\end{document}
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