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kern: optimize hw-single-step management

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Michael Scire 2021-07-27 14:05:32 -07:00 • committed by SciresM
parent 05ea0c53d7
commit 9e7b56b33c
7 changed files with 102 additions and 125 deletions
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48
libraries/libmesosphere/source/arch/arm64/kern_exception_handlers.cpp
View file

@ -109,6 +109,15 @@ namespace ams::kern::arch::arm64 {
break;
}
/* If we should, clear the thread's state as single-step. */
#if defined(MESOSPHERE_ENABLE_HARDWARE_SINGLE_STEP)
if (AMS_UNLIKELY(GetCurrentThread().IsSingleStep())) {
GetCurrentThread().ClearSingleStep();
cpu::MonitorDebugSystemControlRegisterAccessor().SetSoftwareStep(false).Store();
cpu::EnsureInstructionConsistency();
}
#endif
/* If we should process the user exception (and it's not a breakpoint), try to enter. */
const bool is_software_break = (ec == EsrEc_Unknown || ec == EsrEc_IllegalExecution || ec == EsrEc_BkptInstruction || ec == EsrEc_BrkInstruction);
const bool is_breakpoint = (ec == EsrEc_BreakPointEl0 || ec == EsrEc_SoftwareStepEl0 || ec == EsrEc_WatchPointEl0);
@ -290,16 +299,40 @@ namespace ams::kern::arch::arm64 {
return;
}
/* Print that an exception occurred. */
MESOSPHERE_RELEASE_LOG("Exception occurred. %016lx\n", GetCurrentProcess().GetProgramId());
#if defined(MESOSPHERE_ENABLE_HARDWARE_SINGLE_STEP)
{
/* Print the current thread's registers. */
KDebug::PrintRegister();
if (ec != EsrEc_SoftwareStepEl0) {
/* If the exception wasn't single-step, print details. */
MESOSPHERE_RELEASE_LOG("Exception occurred. %016lx\n", GetCurrentProcess().GetProgramId());
/* Print a backtrace. */
KDebug::PrintBacktrace();
{
/* Print the current thread's registers. */
KDebug::PrintRegister();
/* Print a backtrace. */
KDebug::PrintBacktrace();
}
} else {
/* If the exception was single-step and we have no debug object, we should just return. */
if (AMS_UNLIKELY(!cur_process.IsAttachedToDebugger())) {
return;
}
}
}
#else
{
/* Print that an exception occurred. */
MESOSPHERE_RELEASE_LOG("Exception occurred. %016lx\n", GetCurrentProcess().GetProgramId());
{
/* Print the current thread's registers. */
KDebug::PrintRegister();
/* Print a backtrace. */
KDebug::PrintBacktrace();
}
}
#endif
/* If the SVC is handled, handle it. */
if (!svc::ResultNotHandled::Includes(result)) {
@ -559,6 +592,7 @@ namespace ams::kern::arch::arm64 {
KDpcManager::HandleDpc();
}
}
/* Note that we're no longer in an exception handler. */
GetCurrentThread().ClearInExceptionHandler();
}

38
libraries/libmesosphere/source/arch/arm64/svc/kern_svc_exception_asm.s
View file

@ -15,39 +15,6 @@
*/
#include <mesosphere/kern_select_assembly_offsets.h>
#if defined(MESOSPHERE_ENABLE_HARDWARE_SINGLE_STEP)
.macro disable_single_step, scratch
/* Clear MDSCR_EL1.SS. */
mrs \scratch, mdscr_el1
bic \scratch, \scratch, #1
msr mdscr_el1, \scratch
.endm
.macro check_enable_single_step, scratch1, scratch2, spsr_value
/* Check if single-step is requested. */
ldrb \scratch1, [sp, #(EXCEPTION_CONTEXT_SIZE + THREAD_STACK_PARAMETERS_IS_SINGLE_STEP)]
tbz \scratch1, #0, .skip_single_step\@
/* If single-step is requested, enable the single-step machine by setting MDSCR_EL1.SS. */
mrs \scratch2, mdscr_el1
orr \scratch2, \scratch2, #1
msr mdscr_el1, \scratch2
/* Since we're returning from an exception, set SPSR.SS so we actually advance an instruction. */
orr \spsr_value, \spsr_value, #(1 << 21)
isb
.skip_single_step\@:
.endm
#else
.macro disable_single_step, scratch
.endm
.macro check_enable_single_step, scratch1, scratch2, spsr_value
.endm
#endif
/* ams::kern::svc::CallReturnFromException64(Result result) */
.section .text._ZN3ams4kern3svc25CallReturnFromException64Ev, "ax", %progbits
.global _ZN3ams4kern3svc25CallReturnFromException64Ev
@ -123,7 +90,10 @@ _ZN3ams4kern3svc14RestoreContextEm:
ldp x9, x10, [sp, #(EXCEPTION_CONTEXT_PC_PSR)]
ldr x11, [sp, #(EXCEPTION_CONTEXT_TPIDR)]
check_enable_single_step w0, x0, x10
#if defined(MESOSPHERE_ENABLE_HARDWARE_SINGLE_STEP)
/* Since we're returning from an exception, set SPSR.SS so that we advance an instruction if single-stepping. */
orr x22, x22, #(1 << 21)
#endif
msr sp_el0, x8
msr elr_el1, x9

59
libraries/libmesosphere/source/arch/arm64/svc/kern_svc_handlers_asm.s
View file

@ -16,39 +16,6 @@
#include <mesosphere/kern_build_config.hpp>
#include <mesosphere/kern_select_assembly_offsets.h>
#if defined(MESOSPHERE_ENABLE_HARDWARE_SINGLE_STEP)
.macro disable_single_step, scratch
/* Clear MDSCR_EL1.SS. */
mrs \scratch, mdscr_el1
bic \scratch, \scratch, #1
msr mdscr_el1, \scratch
.endm
.macro check_enable_single_step, scratch1, scratch2, spsr_value
/* Check if single-step is requested. */
ldrb \scratch1, [sp, #(EXCEPTION_CONTEXT_SIZE + THREAD_STACK_PARAMETERS_IS_SINGLE_STEP)]
tbz \scratch1, #0, .skip_single_step\@
/* If single-step is requested, enable the single-step machine by setting MDSCR_EL1.SS. */
mrs \scratch2, mdscr_el1
orr \scratch2, \scratch2, #1
msr mdscr_el1, \scratch2
/* Since we're returning from an SVC, make sure SPSR.SS is cleared so we break instantly on the instruction after the SVC. */
bic \spsr_value, \spsr_value, #(1 << 21)
isb
.skip_single_step\@:
.endm
#else
.macro disable_single_step, scratch
.endm
.macro check_enable_single_step, scratch1, scratch2, spsr_value
.endm
#endif
/* ams::kern::arch::arm64::SvcHandler64() */
.section .text._ZN3ams4kern4arch5arm6412SvcHandler64Ev, "ax", %progbits
.global _ZN3ams4kern4arch5arm6412SvcHandler64Ev
@ -84,9 +51,6 @@ _ZN3ams4kern4arch5arm6412SvcHandler64Ev:
stp x8, x9, [sp, #(EXCEPTION_CONTEXT_SP_PC)]
stp x10, x11, [sp, #(EXCEPTION_CONTEXT_PSR_TPIDR)]
/* Disable single-step. */
disable_single_step x8
/* Check if the SVC index is out of range. */
mrs x8, esr_el1
and x8, x8, #0xFF
@ -191,7 +155,10 @@ _ZN3ams4kern4arch5arm6412SvcHandler64Ev:
ldp x9, x10, [sp, #(EXCEPTION_CONTEXT_PC_PSR)]
ldr x11, [sp, #(EXCEPTION_CONTEXT_TPIDR)]
check_enable_single_step w0, x0, x10
#if defined(MESOSPHERE_ENABLE_HARDWARE_SINGLE_STEP)
/* Since we're returning from an SVC, make sure SPSR.SS is cleared so that if we're single-stepping we break instantly on the instruction after the SVC. */
bic x10, x10, #(1 << 21)
#endif
msr sp_el0, x8
msr elr_el1, x9
@ -243,7 +210,10 @@ _ZN3ams4kern4arch5arm6412SvcHandler64Ev:
ldr x11, [sp, #(EXCEPTION_CONTEXT_TPIDR)]
ldr x18, [sp, #(EXCEPTION_CONTEXT_X18)]
check_enable_single_step w12, x12, x10
#if defined(MESOSPHERE_ENABLE_HARDWARE_SINGLE_STEP)
/* Since we're returning from an SVC, make sure SPSR.SS is cleared so that if we're single-stepping we break instantly on the instruction after the SVC. */
bic x10, x10, #(1 << 21)
#endif
msr sp_el0, x8
msr elr_el1, x9
@ -302,9 +272,6 @@ _ZN3ams4kern4arch5arm6412SvcHandler32Ev:
stp x12, x13, [sp, #(EXCEPTION_CONTEXT_X12_X13)]
stp x14, xzr, [sp, #(EXCEPTION_CONTEXT_X14_X15)]
/* Disable single-step. */
disable_single_step x8
/* Check if the SVC index is out of range. */
mrs x16, esr_el1
and x16, x16, #0xFF
@ -405,7 +372,10 @@ _ZN3ams4kern4arch5arm6412SvcHandler32Ev:
ldp x17, x20, [sp, #(EXCEPTION_CONTEXT_PC_PSR)]
ldr x19, [sp, #(EXCEPTION_CONTEXT_TPIDR)]
check_enable_single_step w0, x0, x20
#if defined(MESOSPHERE_ENABLE_HARDWARE_SINGLE_STEP)
/* Since we're returning from an SVC, make sure SPSR.SS is cleared so that if we're single-stepping we break instantly on the instruction after the SVC. */
bic x20, x20, #(1 << 21)
#endif
msr elr_el1, x17
msr spsr_el1, x20
@ -451,7 +421,10 @@ _ZN3ams4kern4arch5arm6412SvcHandler32Ev:
ldp x17, x20, [sp, #(EXCEPTION_CONTEXT_PC_PSR)]
ldr x19, [sp, #(EXCEPTION_CONTEXT_TPIDR)]
check_enable_single_step w21, x21, x20
#if defined(MESOSPHERE_ENABLE_HARDWARE_SINGLE_STEP)
/* Since we're returning from an SVC, make sure SPSR.SS is cleared so that if we're single-stepping we break instantly on the instruction after the SVC. */
bic x20, x20, #(1 << 21)
#endif
msr elr_el1, x17
msr spsr_el1, x20

5
libraries/libmesosphere/source/kern_k_debug_base.cpp
View file

@ -372,6 +372,7 @@ namespace ams::kern {
new_state = state;
}
#if defined(MESOSPHERE_ENABLE_HARDWARE_SINGLE_STEP)
/* Clear single step on all threads. */
{
auto end = target->GetThreadList().end();
@ -379,6 +380,7 @@ namespace ams::kern {
it->ClearSingleStep();
}
}
#endif
/* Detach from the process. */
target->ClearDebugObject(new_state);
@ -900,8 +902,10 @@ namespace ams::kern {
{
auto end = process->GetThreadList().end();
for (auto it = process->GetThreadList().begin(); it != end; ++it) {
#if defined(MESOSPHERE_ENABLE_HARDWARE_SINGLE_STEP)
/* Clear the thread's single-step state. */
it->ClearSingleStep();
#endif
if (resume) {
/* If the process isn't crashed, resume threads. */
@ -993,7 +997,6 @@ namespace ams::kern {
/* If the event is an exception, set the result and clear single step. */
if (event == ams::svc::DebugEvent_Exception) {
GetCurrentThread().SetDebugExceptionResult(ResultSuccess());
GetCurrentThread().ClearSingleStep();
}
/* Exit our retry loop. */