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Kernel: Add 'ptrace' syscall

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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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10
Kernel/Thread.h
View file

@ -122,6 +122,7 @@ public:
virtual ~Blocker() {}
virtual bool should_unblock(Thread&, time_t now_s, long us) = 0;
virtual const char* state_string() const = 0;
virtual bool is_reason_signal() const { return false; }
void set_interrupted_by_death() { m_was_interrupted_by_death = true; }
bool was_interrupted_by_death() const { return m_was_interrupted_by_death; }
void set_interrupted_by_signal() { m_was_interrupted_while_blocked = true; }
@ -253,6 +254,7 @@ public:
}
ASSERT_NOT_REACHED();
}
virtual bool is_reason_signal() const override { return m_reason == Reason::Signal; }
private:
Reason m_reason;
@ -356,6 +358,7 @@ public:
void terminate_due_to_signal(u8 signal);
bool should_ignore_signal(u8 signal) const;
bool has_signal_handler(u8 signal) const;
bool has_pending_signal(u8 signal) const { return m_pending_signals & (1 << (signal - 1)); }
FPUState& fpu_state() { return *m_fpu_state; }
@ -431,6 +434,11 @@ public:
static constexpr u32 default_kernel_stack_size = 65536;
static constexpr u32 default_userspace_stack_size = 4 * MB;
ThreadTracer* tracer() { return m_tracer.ptr(); }
void start_tracing_from(pid_t tracer);
void stop_tracing();
void tracer_trap(const RegisterState&);
private:
IntrusiveListNode m_runnable_list_node;
IntrusiveListNode m_wait_queue_node;
@ -491,6 +499,8 @@ private:
bool m_dump_backtrace_on_finalization { false };
bool m_should_die { false };
OwnPtr<ThreadTracer> m_tracer;
void yield_without_holding_big_lock();
};