syscall_entrypoint.h

#ifndef SYSCALL_ENTRYPOINT_H_
#define SYSCALL_ENTRYPOINT_H_

#include "abstract_data/compiler.h"

/**
 * The entrypoint for making a system call.
 */
extern void syscall_enter_with_frame() __internal;

/**
* Normally, when we rewrite code to intercept a system call, we set up a
* special call frame that can later help in identifying call stacks.  In
* particular, we keep track both of the actual address that we need to return
* to (this is still part of our intercepted code), and we keep track of the
* address where the un-modified system call would have returned to.
* Furthermore, we set up a chain of frame pointers that ends in 0xDEADBEEF.
*
* Programs such as breakpad can use this information to remove all traces of
* the seccomp sandbox from the core files that they generate. This helps when
* debugging with "gdb", which otherwise gets confused by seeing executable
* code outside of the .text segment.
*
* There are a few special situations, though, were we want to call the system
* call entrypoint without having had a chance to initialize our special call
* frame. This happens, whenever we don't actually need to instrument
* instructions (e.g. because there already is a perfectly good "CALL"
* instructions). In that case, we call the syscall_enter_no_frame function.
* It sets up the extra return address in the stack frame prior to falling
* through to the syscall_enter_with_frame function.
*/
extern void syscall_enter_without_frame() __internal;

#endif /* SYSCALL_ENTRYPOINT_H_ */