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Arm fault handler: add emulation of MRS instruction #2088

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merged 3 commits into from
Jan 10, 2025
Merged

Arm fault handler: add emulation of MRS instruction #2088

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9deffdc
Arm is_illegal_instruction(): add check for trapped instructions
francescolavra Dec 22, 2024
2d7b130
unix_fault_handler(): add context_frame local variable
francescolavra Dec 22, 2024
92df866
Arm unix_fault_handler(): add emulation of MRS instruction
francescolavra Dec 22, 2024
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5 changes: 5 additions & 0 deletions src/aarch64/crt0.S
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Original file line number Diff line number Diff line change
Expand Up @@ -180,6 +180,11 @@ context_suspend:
ldr x0, [x18]
b context_suspend_finish

.globl sysreg_get_id_aa64zfr0
sysreg_get_id_aa64zfr0:
.long (INSN_MRS(0) | SYSREG_ID_AA64ZFR0_EL1)
ret

.globl arm_hvc
arm_hvc:
// incomplete, just enough to issue power off
Expand Down
27 changes: 27 additions & 0 deletions src/aarch64/kernel_machine.c
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Expand Up @@ -88,6 +88,33 @@ void clone_frame_pstate(context_frame dest, context_frame src)
runtime_memcpy(dest, src, sizeof(u64) * FRAME_N_PSTATE);
}

boolean insn_emulate(context_frame f)
{
#define CASE_SYSREG(id) case SYSREG_##id: val = read_psr(id); break

u32 *insn_ptr = (u32 *)frame_fault_pc(f);
u32 insn = *insn_ptr;
if ((insn & 0xfff80000) == 0xd5380000) {
/* read from non-debug system registers and special-purpose registers (op0 = 3) */
u64 val;
switch (insn & 0x001fffe0) {
CASE_SYSREG(ID_AA64PFR0_EL1);
CASE_SYSREG(ID_AA64ISAR0_EL1);
CASE_SYSREG(ID_AA64ISAR1_EL1);
case SYSREG_ID_AA64ZFR0_EL1:
val = sysreg_get_id_aa64zfr0();
break;
default:
return false;
}
u64 *dest = &f[FRAME_X0] + (insn & 0x0000001f); /* destination register */
*dest = val;
frame_set_insn_ptr(f, u64_from_pointer(insn_ptr + 1)); /* go to next instruction */
return true;
}
return false;
}

void interrupt_exit(void)
{
gic_eoi(gic_dispatch_int());
Expand Down
22 changes: 21 additions & 1 deletion src/aarch64/kernel_machine.h
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Original file line number Diff line number Diff line change
Expand Up @@ -21,6 +21,16 @@

#define VIRTUAL_ADDRESS_BITS 48

#define INSN_MRS(Rt) (0xd5300000 | Rt)

#define SYSREG(op0, op1, CRn, CRm, op2) \
(((op0) << 19) | ((op1) << 16) | ((CRn) << 12) | ((CRm) << 8) | ((op2) << 5))

#define SYSREG_ID_AA64PFR0_EL1 SYSREG(3, 0, 0, 4, 0)
#define SYSREG_ID_AA64ZFR0_EL1 SYSREG(3, 0, 0, 4, 4)
#define SYSREG_ID_AA64ISAR0_EL1 SYSREG(3, 0, 0, 6, 0)
#define SYSREG_ID_AA64ISAR1_EL1 SYSREG(3, 0, 0, 6, 1)

#define CNTV_CTL_EL0_ISTATUS 4
#define CNTV_CTL_EL0_MASK 2
#define CNTV_CTL_EL0_ENABLE 1
Expand All @@ -38,6 +48,7 @@
#define ESR_EC_UNKNOWN 0x00
#define ESR_EC_ILL_EXEC 0x0e
#define ESR_EC_SVC_AARCH64 0x15
#define ESR_EC_MSR_MRS 0x18
#define ESR_EC_INST_ABRT_LEL 0x20
#define ESR_EC_INST_ABRT 0x21
#define ESR_EC_PC_ALIGN_FAULT 0x22
Expand Down Expand Up @@ -239,6 +250,10 @@ MK_MMIO_WRITE(64, "", "x");
#define read_psr_s(rstr) ({ register u64 r; asm volatile("mrs %0, " rstr : "=r"(r)); r;})
#define write_psr_s(rstr, v) do { asm volatile("msr " rstr ", %0" : : "r"((u64)(v))); } while (0)

/* Manually encoded system register access instructions for registers that are not supported with
* the processor features enabled in the `-march` compiler flags. */
u64 sysreg_get_id_aa64zfr0(void);

struct cpuinfo_machine {
/*** Fields accessed by low-level entry points. ***/
/* Don't move these without updating x18-relative accesses in crt0.s ***/
Expand Down Expand Up @@ -272,6 +287,8 @@ static inline cpuinfo current_cpu(void)
extern void clone_frame_pstate(context_frame dest, context_frame src);
extern void init_extended_frame(context_frame f);

boolean insn_emulate(context_frame f);

static inline boolean is_pte_error(context_frame f)
{
// arm equivalent?
Expand Down Expand Up @@ -367,8 +384,11 @@ static inline boolean is_illegal_instruction(context_frame f)
{
u64 esr = esr_from_frame(f);
u32 ec = field_from_u64(esr, ESR_EC);
if (ec == ESR_EC_UNKNOWN)
switch (ec) {
case ESR_EC_UNKNOWN:
case ESR_EC_MSR_MRS:
return true;
}
return false;
}

Expand Down
2 changes: 2 additions & 0 deletions src/riscv64/kernel_machine.h
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Expand Up @@ -195,6 +195,8 @@ static inline cpuinfo current_cpu(void)

extern void clone_frame_pstate(context_frame dest, context_frame src);

#define insn_emulate(f) false

static inline boolean is_pte_error(context_frame f)
{
// riscv equivalent?
Expand Down
32 changes: 17 additions & 15 deletions src/unix/unix.c
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Original file line number Diff line number Diff line change
Expand Up @@ -251,12 +251,13 @@ closure_func_basic(fault_handler, context, unix_fault_handler,
context ctx)
{
sstring errmsg = sstring_empty();
u64 fault_pc = frame_fault_pc(ctx->frame);
context_frame f = ctx->frame;
u64 fault_pc = frame_fault_pc(f);
boolean user = (current_cpu()->state == cpu_user);
process p = struct_from_field(closure_self(), process, fault_handler);
thread t = user ? (thread)ctx : 0;

if (is_div_by_zero(ctx->frame)) {
if (is_div_by_zero(f)) {
if (user) {
deliver_fault_signal(SIGFPE, t, fault_pc, FPE_INTDIV);
schedule_thread(t);
Expand All @@ -265,30 +266,31 @@ closure_func_basic(fault_handler, context, unix_fault_handler,
errmsg = ss("Divide by zero occurs in kernel mode");
goto bug;
}
} else if (is_illegal_instruction(ctx->frame)) {
} else if (is_illegal_instruction(f)) {
if (user) {
pf_debug("invalid opcode fault in user mode, rip 0x%lx", fault_pc);
deliver_fault_signal(SIGILL, t, fault_pc, ILL_ILLOPC);
if (!insn_emulate(f))
deliver_fault_signal(SIGILL, t, fault_pc, ILL_ILLOPC);
schedule_thread(t);
return 0;
} else {
errmsg = ss("Illegal instruction in kernel mode");
goto bug;
}
} else if (is_trap(ctx->frame)) {
} else if (is_trap(f)) {
if (user) {
pf_debug("trap in user mode, rip 0x%lx", fault_pc);
if (!ltrace_handle_trap(ctx->frame))
if (!ltrace_handle_trap(f))
deliver_fault_signal(SIGTRAP, t, fault_pc,
is_breakpoint(ctx->frame) ? TRAP_BRKPT : TRAP_TRACE);
is_breakpoint(f) ? TRAP_BRKPT : TRAP_TRACE);
schedule_thread(t);
return 0;
} else {
errmsg = ss("Breakpoint in kernel mode");
goto bug;
}
} else if (is_page_fault(ctx->frame)) {
u64 vaddr = frame_fault_address(ctx->frame);
} else if (is_page_fault(f)) {
u64 vaddr = frame_fault_address(f);
vmap_lock(p);
vmap vm;
if (vaddr >= MIN(p->mmap_min_addr, PAGESIZE) && vaddr < USER_LIMIT)
Expand All @@ -313,21 +315,21 @@ closure_func_basic(fault_handler, context, unix_fault_handler,
return 0;
}

if (is_pte_error(ctx->frame)) {
if (is_pte_error(f)) {
vmap_unlock(p);
/* no SEGV on reserved PTEs */
errmsg = ss("bug: pte entries reserved or corrupt");
dump_page_tables(vaddr, 8);
goto bug;
}

if (is_instruction_fault(ctx->frame) && !user) {
if (is_instruction_fault(f) && !user) {
vmap_unlock(p);
msg_err("%s: kernel instruction fault", func_ss);
goto bug;
}

if (is_protection_fault(ctx->frame)) {
if (is_protection_fault(f)) {
if (handle_protection_fault(ctx, vaddr, vm)) {
vmap_unlock(p);
if (!is_thread_context(ctx))
Expand All @@ -354,7 +356,7 @@ closure_func_basic(fault_handler, context, unix_fault_handler,
}
/* XXX arch dep */
#ifdef __x86_64__
else if (ctx->frame[FRAME_VECTOR] == 13) {
else if (f[FRAME_VECTOR] == 13) {
if (user) {
pf_debug("general protection fault in user mode, rip 0x%lx", fault_pc);
deliver_fault_signal(SIGSEGV, t, 0, SI_KERNEL);
Expand All @@ -367,7 +369,7 @@ closure_func_basic(fault_handler, context, unix_fault_handler,
error:
if (context_err_is_set(ctx)) {
kernel_context kc = (kernel_context)ctx;
err_frame_apply(kc->err_frame, ctx->frame);
err_frame_apply(kc->err_frame, f);
context_clear_err(ctx);
return ctx;
}
Expand All @@ -377,7 +379,7 @@ closure_func_basic(fault_handler, context, unix_fault_handler,
rprintf("\n%s\n", errmsg);
rprintf("cpu: %d, context type: %d\n", current_cpu()->id, ctx->type);
dump_context(ctx);
ctx->frame[FRAME_FULL] = false;
f[FRAME_FULL] = false;

if (get(p->process_root, sym(fault))) {
rputs("TODO: in-kernel gdb needs revisiting\n");
Expand Down
2 changes: 2 additions & 0 deletions src/x86_64/kernel_machine.h
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Original file line number Diff line number Diff line change
Expand Up @@ -365,6 +365,8 @@ static inline void frame_disable_interrupts(context_frame f)
extern void xsave(context_frame f);
extern void clone_frame_pstate(context_frame dest, context_frame src);

#define insn_emulate(f) false

static inline boolean is_protection_fault(context_frame f)
{
return (f[FRAME_ERROR_CODE] & FRAME_ERROR_PF_P) != 0;
Expand Down