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CPU: Handle Debug exception

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We currently only care about debug exceptions that are triggered
by the single-step execution mode.

The debug exception is translated to a SIGTRAP, which can be caught
and handled by the tracing thread.
This commit is contained in:
Itamar 2020-04-13 16:37:47 +03:00 • committed by Andreas Kling
parent 1191ab9500
commit d04409b444
2 changed files with 32 additions and 3 deletions
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33
Kernel/Arch/i386/CPU.cpp
View file

@ -297,11 +297,31 @@ void page_fault_handler(RegisterState regs)
} }
} }
EH_ENTRY_NO_CODE(1, debug);
void debug_handler(RegisterState regs)
{
clac();
if (!Process::current || (regs.cs & 3) == 0) {
klog() << "Debug Exception in Ring0";
hang();
return;
}
constexpr u8 REASON_SINGLESTEP = 14;
bool is_reason_singlestep = (read_dr6() & (1 << REASON_SINGLESTEP));
if (!is_reason_singlestep)
return;
if (Thread::current->tracer()) {
Thread::current->tracer()->set_regs(regs);
}
Thread::current->send_urgent_signal_to_self(SIGTRAP);
}
EH_ENTRY_NO_CODE(3, breakpoint); EH_ENTRY_NO_CODE(3, breakpoint);
void breakpoint_handler(RegisterState regs) void breakpoint_handler(RegisterState regs)
{ {
clac(); clac();
if (!Process::current || Process::current->is_ring0()) { if (!Process::current || (regs.cs & 3) == 0) {
klog() << "Breakpoint Trap in Ring0"; klog() << "Breakpoint Trap in Ring0";
hang(); hang();
return; return;
@ -329,7 +349,6 @@ void breakpoint_handler(RegisterState regs)
hang(); \ hang(); \
} }
EH(1, "Debug exception")
EH(2, "Unknown error") EH(2, "Unknown error")
EH(4, "Overflow") EH(4, "Overflow")
EH(5, "Bounds check") EH(5, "Bounds check")
@ -498,7 +517,7 @@ void idt_init()
register_interrupt_handler(i, unimp_trap); register_interrupt_handler(i, unimp_trap);
register_interrupt_handler(0x00, divide_error_asm_entry); register_interrupt_handler(0x00, divide_error_asm_entry);
register_interrupt_handler(0x01, _exception1); register_user_callable_interrupt_handler(0x01, debug_asm_entry);
register_interrupt_handler(0x02, _exception2); register_interrupt_handler(0x02, _exception2);
register_user_callable_interrupt_handler(0x03, breakpoint_asm_entry); register_user_callable_interrupt_handler(0x03, breakpoint_asm_entry);
register_interrupt_handler(0x04, _exception4); register_interrupt_handler(0x04, _exception4);
@ -828,6 +847,14 @@ void write_cr3(u32 cr3)
: "memory"); : "memory");
} }
u32 read_dr6()
{
u32 dr6;
asm("movl %%dr6, %%eax"
: "=a"(dr6));
return dr6;
}
} }
#ifdef DEBUG #ifdef DEBUG

2
Kernel/Arch/i386/CPU.h
View file

@ -480,6 +480,8 @@ inline FlatPtr offset_in_page(const void* address)
u32 read_cr3(); u32 read_cr3();
void write_cr3(u32); void write_cr3(u32);
u32 read_dr6();
class CPUID { class CPUID {
public: public:
CPUID(u32 function) { asm volatile("cpuid" CPUID(u32 function) { asm volatile("cpuid"