@@ -146,6 +146,21 @@ extern char __smccc_workaround_1_smc[__SMCCC_WORKAROUND_1_SMC_SZ];
kern_hyp_va \vcpu
.endm
+/*
+ * KVM extable for unexpected exceptions.
+ * In the same format _asm_extable, but output to a different section so that
+ * it can be mapped to EL2. The KVM version is not sorted. The caller must
+ * ensure:
+ * x18 has the hypervisor value to allow any Shadow-Call-Stack instrumented
+ * code to write to it, and that SPSR_EL2 and ELR_EL2 are restored by the fixup.
+ */
+.macro _kvm_extable, from, to
+ .pushsection __kvm_ex_table, "a"
+ .align 3
+ .long (\from - .), (\to - .)
+ .popsection
+.endm
+
#endif
#endif /* __ARM_KVM_ASM_H__ */
@@ -21,6 +21,13 @@ ENTRY(_text)
jiffies = jiffies_64;
+
+#define HYPERVISOR_EXTABLE \
+ . = ALIGN(SZ_8); \
+ __start___kvm_ex_table = .; \
+ *(__kvm_ex_table) \
+ __stop___kvm_ex_table = .;
+
#define HYPERVISOR_TEXT \
/* \
* Align to 4 KB so that \
@@ -36,6 +43,7 @@ jiffies = jiffies_64;
__hyp_idmap_text_end = .; \
__hyp_text_start = .; \
*(.hyp.text) \
+ HYPERVISOR_EXTABLE \
__hyp_text_end = .;
#define IDMAP_TEXT \
@@ -198,20 +198,23 @@ alternative_endif
// This is our single instruction exception window. A pending
// SError is guaranteed to occur at the earliest when we unmask
// it, and at the latest just after the ISB.
- .global abort_guest_exit_start
abort_guest_exit_start:
isb
- .global abort_guest_exit_end
abort_guest_exit_end:
msr daifset, #4 // Mask aborts
+ ret
+
+ _kvm_extable abort_guest_exit_start, 9997f
+ _kvm_extable abort_guest_exit_end, 9997f
+9997:
+ msr daifset, #4 // Mask aborts
+ mov x0, #(1 << ARM_EXIT_WITH_SERROR_BIT)
- // If the exception took place, restore the EL1 exception
- // context so that we can report some information.
- // Merge the exception code with the SError pending bit.
- tbz x0, #ARM_EXIT_WITH_SERROR_BIT, 1f
+ // restore the EL1 exception context so that we can report some
+ // information. Merge the exception code with the SError pending bit.
msr elr_el2, x2
msr esr_el2, x3
msr spsr_el2, x4
@@ -15,6 +15,30 @@
#include <asm/kvm_mmu.h>
#include <asm/mmu.h>
+.macro save_caller_saved_regs_vect
+ /* x0 and x1 were saved in the vector entry */
+ stp x2, x3, [sp, #-16]!
+ stp x4, x5, [sp, #-16]!
+ stp x6, x7, [sp, #-16]!
+ stp x8, x9, [sp, #-16]!
+ stp x10, x11, [sp, #-16]!
+ stp x12, x13, [sp, #-16]!
+ stp x14, x15, [sp, #-16]!
+ stp x16, x17, [sp, #-16]!
+.endm
+
+.macro restore_caller_saved_regs_vect
+ ldp x16, x17, [sp], #16
+ ldp x14, x15, [sp], #16
+ ldp x12, x13, [sp], #16
+ ldp x10, x11, [sp], #16
+ ldp x8, x9, [sp], #16
+ ldp x6, x7, [sp], #16
+ ldp x4, x5, [sp], #16
+ ldp x2, x3, [sp], #16
+ ldp x0, x1, [sp], #16
+.endm
+
.text
.pushsection .hyp.text, "ax"
@@ -156,27 +180,14 @@ el2_sync:
el2_error:
- ldp x0, x1, [sp], #16
+ save_caller_saved_regs_vect
+ stp x29, x30, [sp, #-16]!
+
+ bl kvm_unexpected_el2_exception
+
+ ldp x29, x30, [sp], #16
+ restore_caller_saved_regs_vect
- /*
- * Only two possibilities:
- * 1) Either we come from the exit path, having just unmasked
- * PSTATE.A: change the return code to an EL2 fault, and
- * carry on, as we're already in a sane state to handle it.
- * 2) Or we come from anywhere else, and that's a bug: we panic.
- *
- * For (1), x0 contains the original return code and x1 doesn't
- * contain anything meaningful at that stage. We can reuse them
- * as temp registers.
- * For (2), who cares?
- */
- mrs x0, elr_el2
- adr x1, abort_guest_exit_start
- cmp x0, x1
- adr x1, abort_guest_exit_end
- ccmp x0, x1, #4, ne
- b.ne __hyp_panic
- mov x0, #(1 << ARM_EXIT_WITH_SERROR_BIT)
eret
sb
@@ -14,6 +14,7 @@
#include <asm/barrier.h>
#include <asm/cpufeature.h>
+#include <asm/extable.h>
#include <asm/kprobes.h>
#include <asm/kvm_asm.h>
#include <asm/kvm_emulate.h>
@@ -24,6 +25,9 @@
#include <asm/processor.h>
#include <asm/thread_info.h>
+extern struct exception_table_entry __start___kvm_ex_table;
+extern struct exception_table_entry __stop___kvm_ex_table;
+
/* Check whether the FP regs were dirtied while in the host-side run loop: */
static bool __hyp_text update_fp_enabled(struct kvm_vcpu *vcpu)
{
@@ -934,3 +938,30 @@ void __hyp_text __noreturn hyp_panic(struct kvm_cpu_context *host_ctxt)
unreachable();
}
+
+asmlinkage void __hyp_text kvm_unexpected_el2_exception(void)
+{
+ unsigned long addr, fixup;
+ struct kvm_cpu_context *host_ctxt;
+ struct exception_table_entry *entry, *end;
+ unsigned long elr_el2 = read_sysreg(elr_el2);
+
+ entry = hyp_symbol_addr(__start___kvm_ex_table);
+ end = hyp_symbol_addr(__stop___kvm_ex_table);
+ host_ctxt = &__hyp_this_cpu_ptr(kvm_host_data)->host_ctxt;
+
+ while (entry < end) {
+ addr = (unsigned long)&entry->insn + entry->insn;
+ fixup = (unsigned long)&entry->fixup + entry->fixup;
+
+ if (addr != elr_el2) {
+ entry++;
+ continue;
+ }
+
+ write_sysreg(fixup, elr_el2);
+ return;
+ }
+
+ hyp_panic(host_ctxt);
+}