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    25 .\" ident	"@(#)sigsegv_install_handler.3	1.2	10/03/16 SMI"

    26 .\"

    27 .TH sigsegv_install_handler 3 "13 Jan 2009" "SunOS 5.11"

    28 .SH NAME

    29 sigsegv_install_handler, sigsegv_deinstall_handler - Install and deinstall a global SIGSEGV handler

    30 .sp

    31 .SH SYNOPSIS

    32 .sp

    33 #include <\fBsigsegv.h\fR>

    34 .sp

    35 int \fBsigsegv_install_handler\fR (\fIsigsegv_handler_t handler\fR);

    36 .sp

    37 void \fBsigsegv_deinstall_handler\fR (\fIvoid\fR);

    38 .sp

    39 .SH DESCRIPTION

    40 .sp

    41 .LP

    42 Pageable virtual memory is usually done in the operating system's kernel. This library helps in implementing the others.

    43 .sp

    44 .LP

    45 Installing a page fault handler is usually more efficient than doing access checks in software at every access, because it's effectively the hardware (the MMU) which checks whether a page is present or not.

    46 .sp

    47 .LP

    48 Note that if you use system calls (like read()) to write into write-protected pages, the system will react by returning -1 and setting errno to EFAULT, instead of signalling SIGSEGV and restarting the system call. In this case, the program has to do what the SIGSEGV handler would do, and then restart the read() operation.

    49 .sp

    50 .LP

    51 \fBSigsegv_install_handler\fR installs a global SIGSEGV handler. This should be called once only, and it ignores any previously installed SIGSEGV handler.

    52 .sp

    53 .LP

    54 \fBSigsegv_deinstall_handler\fR deinstalls the global SIGSEGV handler. This goes back to the state where no SIGSEGV handler is installed.

    55 .sp

    56 .SH OPERANDS

    57 .sp

    58 .LP

    59 typedef int (*\fBsigsegv_handler_t\fR) (\fIvoid* fault_address\fR,

    60 .RS +34

    61 \fIint serious\fR);

    62 .RE

    63 .sp

    64 \fISigsegv_handler_t\fR is the type of a global SIGSEGV handler.The fault address is passed as argument. The access type (read access or write access) is not passed; your handler has to know itself how to distinguish these two cases. The second argument is 0, meaning it could also be a stack overflow, or 1, meaning the handler should seriously try to fix the fault. The return value should be nonzero if the handler has done its job and no other handler should be called, or 0 if the handler declines responsibility for the given address.

    65 .sp

    66 .LP

    67 The handler is run at a moment when nothing about the global state of the program is known. Therefore it cannot use facilities that manipulate global variables or locks. In particular, it cannot use malloc(); use mmap() instead. It cannot use fopen(); use open() instead. Etc. All global variables that are accessed by the handler should be marked 'volatile'.

    68 .sp

    69 .SH EXIT STATUS

    70 .sp

    71 .LP

    72 If success, sigsegv_install_handler returns 0, or -1 if the system doesn't support catching SIGSEGV.

    73 .sp

    74 .SH ATTRIBUTES

    75 See

    76 .BR attributes(5)

    77 for descriptions of the  following  attributes:

    78 .sp

    79 .TS

    80 tab() box;

    81 cw(2.75i) |cw(2.75i) 

    82 lw(2.75i) |lw(2.75i) 

    83 .

    84 ATTRIBUTE TYPEATTRIBUTE VALUE

    85 _

    86 Availabilitylibrary/libsigsegv

    87 _

    88 Interface StabilityUncommitted

    89 _

    90 StandardSee \fBstandards\fR(5).

    91 .TE

    92 

    93 .SH SEE ALSO

    94 .sp

    95 .LP

    96 \fBattributes\fR(5), \fBsigsegv\fR(3), \fBstandards\fR(5)

    97 

    98 .SH NOTES

    99 The libsigsegv project is located at http://libsigsegv.sourceforge.net.

   100 .sp

   101 Source for libsigsegv is available on http://opensolaris.org.