The function for detecting stack smashing is implemented by the -Xstack_protector option, -Xstack_protector_all option, or the #pragma directives described in this section.
Generates a code for detection of stack smashing at the entry and end of a function. A code for detection of stack smashing indicates the instructions for executing the three processes shown below. |
(1) A 4-byte area is allocated just before the local variable area (in the direction towards address 0xFFFFFFFF) at the entry to a function, and the value specified by <number> is stored in the allocated area.
(2) At the end of the function, whether the 4-byte area in which <number> was stored has been rewritten is checked.
(3) If the value has been rewritten in (2), the __stack_chk_fail function is called as the stack has been smashed.
A decimal number from 0 to 4294967295 should be specified in <number>. If the specification of <number> is omitted, the compiler automatically specifies the number. |
The __stack_chk_fail function needs to be defined by the user and the processing to be executed upon detection of stack smashing should be written. |
The only possible type of return value is void and the __stack_chk_fail function does not have formal parameters. |
The __stack_chk_fail function does not generate a code for detection of stack smashing regardless of the -Xstack_protector and -Xstack_protector_all options, and #pragma stack_protector. |
Prevent returning to the caller, that is, the function where stack smashing was detected by taking measures such as calling abort() in the __stack_chk_fail function to terminate the program. |
When this facility is used for a function for which PIC (see "8.6 PIC/PID Facility") is performed, PIC should also be performed for the __stack_chk_fail function. |
A code for detection of stack smashing is not generated for a function for which #pragma no_stack_protector has been specified regardless of the -Xstack_protector option and -Xstack_protector_all option. |
If this option is used simultaneously with #pragma stack_protector, the -Xstack_protector option, or the -Xstack_protector_all option, the specification by #pragma becomes valid. |
#pragma inline_asm, #pragma inline, #pragma stack_protector, #pragma no_stack_protector
#pragma no_stack_protector cannot be specified simultaneously with the following #pragma directives. |
#pragma stack_protector, #pragma no_stack_protector