What is the problem with ptrace?

Communications between the controller and target take place using repeated calls of ptrace, passing a small fixed-size block of memory between the two (necessitating two context switches per call); this is acutely inefficient when accessing large amounts of the target’s memory, as this can only be done in word sized …

What is ptrace used for in Linux?

The ptrace() system call provides a means by which one process (the “tracer”) may observe and control the execution of another process (the “tracee”), and examine and change the tracee’s memory and registers. It is primarily used to implement breakpoint debugging and system call tracing.

Does ltrace use ptrace?

ltrace also relies on the ptrace system call, but tracing library functions works differently than tracing system calls and this is where the tools differ.

How is ptrace implemented?

The ptrace system call allows the parent process to inspect the attached child. For example, in Linux, strace (which is implemented with the ptrace system call) can inspect the system calls invoked by the child process. When the attached child process invokes a system call, the ptracing parent process can be notified.

How do I get out of strace?

The trace may be terminated at any time by a keyboard interrupt signal (CTRL-C). strace will respond by detaching itself from the traced process(es) leaving it (them) to continue running.

What is the difference between ltrace and strace?

Both ltrace and strace give you similar information, but with an important difference: strace intercepts system calls make by the glibc and other libraries directly into the Linux Kernel. ltrace intercepts library calls and system calls made by your application to C libraries such as the glibc.

How does ptrace work to intercept system calls?

It’s also the usual approach for implementing strace — system call trace. With Ptrace, tracers can pause tracees, inspect and set registers and memory , monitor system calls, or even intercept system calls. By intercept, I mean that the tracer can mutate system call arguments, mutate the system call return value, or even block certain system calls.

What is the return value of ptrace _ syscall?

Print the system call return value. The PTRACE_SYSCALL request is used in both waiting for the next system call to begin, and waiting for that system call to exit. As before, a wait (2) is needed to wait for the tracee to enter the desired state.

What does the call to ptrace do in Linux?

The call to ptrace, with a first argument of PTRACE_SYSCALL, makes the kernel stop the child process whenever a system call entry or exit is made. It’s equivalent to doing a PTRACE_CONT and stopping at the next system call entry/exit.

What are the arguments of the ptrace function?

PTRACE_SYSCALL: Continue, but stop at the next system call entrance or exit. PTRACE_GETREGS: Get a copy of the tracee’s registers. The other two fields, addr and data, serve as generic arguments for the selected Ptrace function.