The branch main has been updated by markj:
URL:
https://cgit.FreeBSD.org/src/commit/?id=c226f193515c8c0665610cb519fe381987f8ee24
commit c226f193515c8c0665610cb519fe381987f8ee24
Author: Mark Johnston <ma...@freebsd.org>
AuthorDate: 2024-12-10 15:07:28 +0000
Commit: Mark Johnston <ma...@freebsd.org>
CommitDate: 2024-12-10 15:07:28 +0000
riscv: Permit spurious faults in kernel mode
Right now, pmap_enter() does not issue an sfence.vma after overwriting
an invalid PTE, so the kernel can trigger a page fault when accessing a
freshly created mapping. In this case, pmap_fault() can handle the
exception, but we may panic before that. Move the check; this is
consistent with arm64 and serves to ensure that we don't call vm_fault()
etc. from a context where that's not permitted.
Also fix a related bug: don't enable interrupts if they were disabled in
the context where the exception occurred.
Reviewed by: br
Tested by: br
MFC after: 2 weeks
Differential Revision: https://reviews.freebsd.org/D47688
---
sys/riscv/riscv/trap.c | 13 +++++++------
1 file changed, 7 insertions(+), 6 deletions(-)
diff --git a/sys/riscv/riscv/trap.c b/sys/riscv/riscv/trap.c
index 3bb1fc7f1010..a1a30eb58220 100644
--- a/sys/riscv/riscv/trap.c
+++ b/sys/riscv/riscv/trap.c
@@ -227,11 +227,6 @@ page_fault_handler(struct trapframe *frame, int usermode)
pcb = td->td_pcb;
stval = frame->tf_stval;
- if (td->td_critnest != 0 || td->td_intr_nesting_level != 0 ||
- WITNESS_CHECK(WARN_SLEEPOK | WARN_GIANTOK, NULL,
- "Kernel page fault") != 0)
- goto fatal;
-
if (usermode) {
if (!VIRT_IS_VALID(stval)) {
call_trapsignal(td, SIGSEGV, SEGV_MAPERR, (void *)stval,
@@ -244,7 +239,8 @@ page_fault_handler(struct trapframe *frame, int usermode)
* Enable interrupts for the duration of the page fault. For
* user faults this was done already in do_trap_user().
*/
- intr_enable();
+ if ((frame->tf_sstatus & SSTATUS_SIE) != 0)
+ intr_enable();
if (stval >= VM_MIN_KERNEL_ADDRESS) {
map = kernel_map;
@@ -268,6 +264,11 @@ page_fault_handler(struct trapframe *frame, int usermode)
if (VIRT_IS_VALID(va) && pmap_fault(map->pmap, va, ftype))
goto done;
+ if (td->td_critnest != 0 || td->td_intr_nesting_level != 0 ||
+ WITNESS_CHECK(WARN_SLEEPOK | WARN_GIANTOK, NULL,
+ "Kernel page fault") != 0)
+ goto fatal;
+
error = vm_fault_trap(map, va, ftype, VM_FAULT_NORMAL, &sig, &ucode);
if (error != KERN_SUCCESS) {
if (usermode) {
