Fixes from lfcode.cariscv

PMP enforecement from Qemu breaks boot cycle. This fix is from
upstream repo here: https://github.com/lf-/xv6-riscv/

1 files changed, 23 insertions, 0 deletions

diff --git a/kernel/riscv.h b/kernel/riscv.h
index 0aec003..25614b1 100644
--- a/kernel/riscv.h
+++ b/kernel/riscv.h
@@ -38,6 +38,29 @@ w_mepc(uint64 x)
   asm volatile("csrw mepc, %0" : : "r" (x));
 }
 
+// physical memory protection CSRs
+#define PMP_R (1L << 0)
+#define PMP_W (1L << 1)
+#define PMP_X (1L << 2)
+// naturally aligned power of two
+#define PMP_MATCH_NAPOT (3L << 3)
+
+// we only implement accessing one PMP register
+
+// write to the first 8 PMP configuration registers
+static inline void
+w_pmpcfg0(uint64 x)
+{
+  asm volatile("csrw pmpcfg0, %0" : : "r" (x));
+}
+
+// write to the address for PMP region 0
+static inline void
+w_pmpaddr0(uint64 x)
+{
+  asm volatile("csrw pmpaddr0, %0" : : "r" (x));
+}
+
 // Supervisor Status Register, sstatus
 
 #define SSTATUS_SPP (1L << 8)  // Previous mode, 1=Supervisor, 0=User