![]() ![]() In summary, this is what happens during a system call: Machine setup, attach gdb to a running kernel, add a breakpoint to the To demonstrate the system call flow we are going to use the virtual * Handles int $0x80 */ _visible void do_int80_syscall_32 ( struct pt_regs * regs ) Parameters) on stack and then it will continue with executing the The system call entry point will save registers (which contains valuesįrom user space, including system call number and system call Similar to how interrupts and exceptions are handled (in fact on someĪrchitectures this transition happens as a result of an exception). Interrupted and it is transferred to a kernel entry point. When a user to kernel mode transition occurs, the execution flow is libc) offers functions that implement theĪctual system calls in order to make it easier for applications to use Stored in the EAX register, while parameters in registers EBX, ECX, The parameters are stored in certain registers.įor example, on 32bit x86 architecture, the system call identifier is In Linux, system calls are identified by numbers and the parametersįor system calls are machine word sized (32 or 64 bit). setup information to identify the system call and its parameters.Not function calls, but specific assembly instructions (architectureĪnd kernel specific) that do the following: However, on a closer look, we can see that system calls are actually User applications and they resemble library APIs in that they areĭescribed as a function call with a name, parameters, and return value. At a high level system calls are "services" offered by the kernel to ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |