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Correctly handle cases when a thread single-steps into the kernel as it can

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happen on syscalls or "int" instructions. The debug exception handler sets
the thread debug flags B_THREAD_DEBUG_STOP and
B_THREAD_DEBUG_NOTIFY_SINGLE_STEP (new) and lets the thread continue. Before
leaving the kernel the thread is stopped and a single-step notification is
sent. Fixes #3487.


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@35620 a95241bf-73f2-0310-859d-f6bbb57e9c96
This commit is contained in:
Ingo Weinhold 2010-02-25 20:20:16 +00:00
parent a304e08905
commit 8b3d3d8a15
3 changed files with 63 additions and 13 deletions
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17
headers/private/kernel/user_debugger.h
View File

@ -154,17 +154,18 @@ enum {
// thread debugging flags (user-specifiable flags are in <debugger.h>)
enum {
B_THREAD_DEBUG_INITIALIZED = 0x0001,
B_THREAD_DEBUG_DYING = 0x0002,
B_THREAD_DEBUG_STOP = 0x0004,
B_THREAD_DEBUG_STOPPED = 0x0008,
B_THREAD_DEBUG_SINGLE_STEP = 0x0010,
B_THREAD_DEBUG_INITIALIZED = 0x0001,
B_THREAD_DEBUG_DYING = 0x0002,
B_THREAD_DEBUG_STOP = 0x0004,
B_THREAD_DEBUG_STOPPED = 0x0008,
B_THREAD_DEBUG_SINGLE_STEP = 0x0010,
B_THREAD_DEBUG_NOTIFY_SINGLE_STEP = 0x0020,
B_THREAD_DEBUG_NUB_THREAD = 0x0020, // marks the nub thread
B_THREAD_DEBUG_NUB_THREAD = 0x0040, // marks the nub thread
B_THREAD_DEBUG_KERNEL_FLAG_MASK = 0xffff,
B_THREAD_DEBUG_KERNEL_FLAG_MASK = 0xffff,
B_THREAD_DEBUG_DEFAULT_FLAGS = 0,
B_THREAD_DEBUG_DEFAULT_FLAGS = 0,
};
// messages sent from the debug nub thread to a debugged thread

37
src/system/kernel/arch/x86/arch_user_debugger.cpp
View File

@ -886,7 +886,42 @@ x86_handle_debug_exception(struct iframe *frame)
// it, but we don't want it when continuing otherwise.
frame->flags &= ~(1 << X86_EFLAGS_TF);
panic("kernel single step");
// Determine whether the exception occurred at a syscall/trap
// kernel entry or whether this is genuine kernel single-stepping.
bool inKernel = true;
struct thread* thread = thread_get_current_thread();
if (thread->team != team_get_kernel_team()
&& i386_get_user_iframe() == NULL) {
// TODO: This is not yet fully correct, since a newly created
// thread that doesn't have entered userland yet also has this
// property.
inKernel = false;
}
if (inKernel) {
panic("kernel single step");
} else {
// The thread is a userland thread and it just entered the
// kernel when the single-step exception occurred. This happens
// e.g. when sysenter is called with single-stepping enabled.
// We need to ignore the exception now and send a single-step
// notification later, when the thread wants to return from the
// kernel.
InterruptsSpinLocker threadLocker(gThreadSpinlock);
// Check whether the team is still being debugged and set
// the B_THREAD_DEBUG_NOTIFY_SINGLE_STEP and
// B_THREAD_DEBUG_STOP flags, so that the thread will be
// stopped when it is going to leave the kernel and notify the
// debugger about the single-step event.
int32 teamDebugFlags
= atomic_get(&thread->team->debug_info.flags);
if (teamDebugFlags & B_TEAM_DEBUG_DEBUGGER_INSTALLED) {
atomic_or(&thread->debug_info.flags,
B_THREAD_DEBUG_NOTIFY_SINGLE_STEP
| B_THREAD_DEBUG_STOP);
}
}
}
} else if (dr6 & (1 << X86_DR6_BT)) {
// task switch

22
src/system/kernel/debug/user_debugger.cpp
View File

@ -954,11 +954,25 @@ user_debug_handle_signal(int signal, struct sigaction *handler, bool deadly)
void
user_debug_stop_thread()
{
// prepare the message
debug_thread_debugged message;
// check whether this is actually an emulated single-step notification
InterruptsSpinLocker threadsLocker(gThreadSpinlock);
struct thread* thread = thread_get_current_thread();
bool singleStepped = false;
if ((atomic_and(&thread->debug_info.flags,
~B_THREAD_DEBUG_NOTIFY_SINGLE_STEP)
& B_THREAD_DEBUG_NOTIFY_SINGLE_STEP) != 0) {
singleStepped = true;
}
thread_hit_serious_debug_event(B_DEBUGGER_MESSAGE_THREAD_DEBUGGED, &message,
sizeof(message));
threadsLocker.Unlock();
if (singleStepped) {
user_debug_single_stepped();
} else {
debug_thread_debugged message;
thread_hit_serious_debug_event(B_DEBUGGER_MESSAGE_THREAD_DEBUGGED,
&message, sizeof(message));
}
}