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Kernel: Add debug register handling

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This patch adds functions to read/write from the debug registers,
and implements storing/loading them across context switches.
This commit is contained in:
FalseHonesty 2021-04-15 12:29:00 -04:00 • committed by Andreas Kling
parent c84107a1ab
commit 97a4c627cb
3 changed files with 97 additions and 11 deletions
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81
Kernel/Arch/i386/CPU.cpp
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@ -855,19 +855,70 @@ FlatPtr read_cr4()
return cr4;
}
FlatPtr read_dr6()
void read_debug_registers_into(DebugRegisterState& state)
{
FlatPtr dr6;
#if ARCH(I386)
asm("mov %%dr6, %%eax"
: "=a"(dr6));
#else
asm("mov %%dr6, %%rax"
: "=a"(dr6));
#endif
return dr6;
state.dr0 = read_dr0();
state.dr1 = read_dr1();
state.dr2 = read_dr2();
state.dr3 = read_dr3();
state.dr6 = read_dr6();
state.dr7 = read_dr7();
}
void write_debug_registers_from(const DebugRegisterState& state)
{
write_dr0(state.dr0);
write_dr1(state.dr1);
write_dr2(state.dr2);
write_dr3(state.dr3);
write_dr6(state.dr6);
write_dr7(state.dr7);
}
void clear_debug_registers()
{
write_dr0(0);
write_dr1(0);
write_dr2(0);
write_dr3(0);
write_dr7(1 << 10); // Bit 10 is reserved and must be set to 1.
}
#if ARCH(I386)
# define DEFINE_DEBUG_REGISTER(index) \
FlatPtr read_dr##index() \
{ \
FlatPtr value; \
asm("mov %%dr" #index ", %%eax" \
: "=a"(value)); \
return value; \
} \
void write_dr##index(FlatPtr value) \
{ \
asm volatile("mov %%eax, %%dr" #index ::"a"(value)); \
}
#else
# define DEFINE_DEBUG_REGISTER(index) \
FlatPtr read_dr##index() \
{ \
FlatPtr value; \
asm("mov %%dr" #index ", %%rax" \
: "=a"(value)); \
return value; \
} \
void write_dr##index(FlatPtr value) \
{ \
asm volatile("mov %%rax, %%dr" #index ::"a"(value)); \
}
#endif
DEFINE_DEBUG_REGISTER(0);
DEFINE_DEBUG_REGISTER(1);
DEFINE_DEBUG_REGISTER(2);
DEFINE_DEBUG_REGISTER(3);
DEFINE_DEBUG_REGISTER(6);
DEFINE_DEBUG_REGISTER(7);
#define XCR_XFEATURE_ENABLED_MASK 0
UNMAP_AFTER_INIT u64 read_xcr0()
@ -1391,6 +1442,15 @@ extern "C" void enter_thread_context(Thread* from_thread, Thread* to_thread)
set_fs(to_tss.fs);
set_gs(to_tss.gs);
if (from_thread->process().is_traced())
read_debug_registers_into(from_thread->debug_register_state());
if (to_thread->process().is_traced()) {
write_debug_registers_from(to_thread->debug_register_state());
} else {
clear_debug_registers();
}
auto& processor = Processor::current();
auto& tls_descriptor = processor.get_gdt_entry(GDT_SELECTOR_TLS);
tls_descriptor.set_base(to_thread->thread_specific_data());
@ -1404,7 +1464,6 @@ extern "C" void enter_thread_context(Thread* from_thread, Thread* to_thread)
asm volatile("fxrstor %0" ::"m"(to_thread->fpu_state()));
// TODO: debug registers
// TODO: ioperm?
}