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Kernel: Add 'ptrace' syscall

Browse source 
This commit adds a basic implementation of
the ptrace syscall, which allows one process
(the tracer) to control another process (the tracee).

While a process is being traced, it is stopped whenever a signal is
received (other than SIGCONT).

The tracer can start tracing another thread with PT_ATTACH,
which causes the tracee to stop.

From there, the tracer can use PT_CONTINUE
to continue the execution of the tracee,
or use other request codes (which haven't been implemented yet)
to modify the state of the tracee.

Additional request codes are PT_SYSCALL, which causes the tracee to
continue exection but stop at the next entry or exit from a syscall,
and PT_GETREGS which fethces the last saved register set of the tracee
(can be used to inspect syscall arguments and return value).

A special request code is PT_TRACE_ME, which is issued by the tracee
and causes it to stop when it calls execve and wait for the
tracer to attach.
This commit is contained in:
Itamar 2020-03-28 11:47:16 +03:00 • committed by Andreas Kling
parent c9396be83f
commit 6b74d38aab
13 changed files with 300 additions and 102 deletions
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17
Kernel/Syscall.cpp
View file

@ -26,9 +26,9 @@
#include <Kernel/Arch/i386/CPU.h>
#include <Kernel/Process.h>
#include <Kernel/ProcessTracer.h>
#include <Kernel/Random.h>
#include <Kernel/Syscall.h>
#include <Kernel/ThreadTracer.h>
#include <Kernel/VM/MemoryManager.h>
namespace Kernel {
@ -92,8 +92,6 @@ int handle(RegisterState& regs, u32 function, u32 arg1, u32 arg2, u32 arg3)
if (function == SC_exit || function == SC_exit_thread) {
// These syscalls need special handling since they never return to the caller.
cli();
if (auto* tracer = process.tracer())
tracer->did_syscall(function, arg1, arg2, arg3, 0);
if (function == SC_exit)
process.sys$exit((int)arg1);
else
@ -132,6 +130,11 @@ void syscall_handler(RegisterState& regs)
return;
}
if (Thread::current->tracer() && Thread::current->tracer()->is_tracing_syscalls()) {
Thread::current->tracer()->set_trace_syscalls(false);
Thread::current->tracer_trap(regs);
}
// Make sure SMAP protection is enabled on syscall entry.
clac();
@ -168,8 +171,12 @@ void syscall_handler(RegisterState& regs)
u32 arg2 = regs.ecx;
u32 arg3 = regs.ebx;
regs.eax = (u32)Syscall::handle(regs, function, arg1, arg2, arg3);
if (auto* tracer = process.tracer())
tracer->did_syscall(function, arg1, arg2, arg3, regs.eax);
if (Thread::current->tracer() && Thread::current->tracer()->is_tracing_syscalls()) {
Thread::current->tracer()->set_trace_syscalls(false);
Thread::current->tracer_trap(regs);
}
process.big_lock().unlock();
// Check if we're supposed to return to userspace or just die.