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kern: swap tpidr_el1/cntv_cval_el0 as scratch vs exception stack

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Michael Scire 2021-04-07 08:36:03 -07:00 • committed by SciresM
parent 2f930c2d5f
commit c216f92a91
7 changed files with 34 additions and 28 deletions
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4
mesosphere/kernel/source/arch/arm64/init/kern_init_core.cpp
View file

@ -125,9 +125,6 @@ namespace ams::kern::init {
/* Ensure our first argument is page aligned (as we will map it if it is non-zero). */
MESOSPHERE_INIT_ABORT_UNLESS(util::IsAligned(misc_unk_debug_phys_addr, PageSize));
/* Clear TPIDR_EL1 to zero. */
cpu::ThreadIdRegisterAccessor(0).Store();
/* Restore the page allocator state setup by kernel loader. */
g_initial_page_allocator.InitializeFromState(initial_page_allocator_state);
@ -476,6 +473,7 @@ namespace ams::kern::init {
void InitializeExceptionVectors() {
cpu::SetVbarEl1(reinterpret_cast<uintptr_t>(::ams::kern::ExceptionVectors));
cpu::SetTpidrEl1(0);
cpu::SetExceptionThreadStackTop(0);
cpu::EnsureInstructionConsistency();
}

4
mesosphere/kernel/source/arch/arm64/init/start.s
View file

@ -227,9 +227,9 @@ _ZN3ams4kern4init16InvokeEntrypointEPKNS1_14KInitArgumentsE:
/* Ensure that the exception vectors are setup. */
bl _ZN3ams4kern4init26InitializeExceptionVectorsEv
/* Setup the exception stack in tpidr_el1. */
/* Setup the exception stack in cntv_cval_el0. */
ldr x1, [x20, #0x58]
msr tpidr_el1, x1
msr cntv_cval_el0, x1
/* Jump to the entrypoint. */
ldr x1, [x20, #0x40]

36
mesosphere/kernel/source/arch/arm64/kern_exception_handlers_asm.s
View file

@ -281,8 +281,8 @@ _ZN3ams4kern4arch5arm6430EL0SynchronousExceptionHandlerEv:
.global _ZN3ams4kern4arch5arm6430EL1SynchronousExceptionHandlerEv
.type _ZN3ams4kern4arch5arm6430EL1SynchronousExceptionHandlerEv, %function
_ZN3ams4kern4arch5arm6430EL1SynchronousExceptionHandlerEv:
/* Nintendo uses the "unused" virtual timer compare value as a scratch register. */
msr cntv_cval_el0, x0
/* Nintendo uses tpidr_el1 as a scratch register. */
msr tpidr_el1, x0
/* Get and parse the exception syndrome register. */
mrs x0, esr_el1
@ -297,18 +297,21 @@ _ZN3ams4kern4arch5arm6430EL1SynchronousExceptionHandlerEv:
b.eq 5f
1: /* The exception is not a data abort or instruction abort caused by a TLB conflict. */
/* Load the exception stack top from tpidr_el1. */
mrs x0, tpidr_el1
/* Load the exception stack top from otherwise "unused" virtual timer compare value. */
mrs x0, cntv_cval_el0
/* Setup the stack for a generic exception handle */
lsl x0, x0, #8
asr x0, x0, #8
sub x0, x0, #0x20
str x1, [x0, #16]
str x1, [x0, #8]
mov x1, sp
str x1, [x0]
mov sp, x0
ldr x1, [x0, #16]
mrs x0, cntv_cval_el0
ldr x1, [x0, #8]
mrs x0, tpidr_el1
str x0, [sp, #8]
str x1, [sp, #16]
/* Check again if this is a data abort from EL1. */
mrs x0, esr_el1
@ -406,7 +409,7 @@ _ZN3ams4kern4arch5arm6430EL1SynchronousExceptionHandlerEv:
isb
/* Restore x0 from scratch. */
mrs x0, cntv_cval_el0
mrs x0, tpidr_el1
/* Return from the exception. */
eret
@ -474,21 +477,22 @@ _ZN3ams4kern4arch5arm6425FpuAccessExceptionHandlerEv:
.global _ZN3ams4kern4arch5arm6421EL1SystemErrorHandlerEv
.type _ZN3ams4kern4arch5arm6421EL1SystemErrorHandlerEv, %function
_ZN3ams4kern4arch5arm6421EL1SystemErrorHandlerEv:
/* Nintendo uses the "unused" virtual timer compare value as a scratch register. */
msr cntv_cval_el0, x0
/* Nintendo uses tpidr_el1 as a scratch register. */
msr tpidr_el1, x0
/* Load the exception stack top from tpidr_el1. */
mrs x0, tpidr_el1
/* Load the exception stack top from otherwise "unused" virtual timer compare value. */
mrs x0, cntv_cval_el0
/* Setup the stack for a generic exception handle */
lsl x0, x0, #8
asr x0, x0, #8
sub x0, x0, #0x20
str x1, [x0, #16]
str x1, [x0, #8]
mov x1, sp
str x1, [x0]
mov sp, x0
ldr x1, [x0, #16]
mrs x0, cntv_cval_el0
str x0, [sp, #8]
ldr x1, [x0, #8]
mrs x0, tpidr_el1
/* Create a KExceptionContext to pass to HandleException. */
sub sp, sp, #0x120

3
mesosphere/kernel_ldr/source/arch/arm64/start.s
View file

@ -89,7 +89,8 @@ _main:
bl _ZN3ams4kern4init3Elf18CallInitArrayFuncsEmm
/* Setup system registers, for detection of errors during init later. */
msr tpidr_el1, xzr /* Clear TPIDR_EL1 */
msr tpidr_el1, xzr
msr cntv_cval_el0, xzr
adr x0, __external_references
adr x1, _start
ldr x0, [x0, #0x30]