debug/programs/mprv.S

   1 #include "../../env/encoding.h"
   2 #define PGSHIFT         12
   3
   4         .global         main
   5
   6         .section        .text
   7 main:
   8         # Set up a page table entry that maps 0x0... to 0x8...
   9         la      t0, page_table
  10         srli    t0, t0, PGSHIFT
  11         csrw    CSR_SPTBR, t0
  12
  13         # update mstatus
  14         csrr    t1, CSR_MSTATUS
  15         li      t0, (MSTATUS_MPRV | (VM_SV39 << 24))
  16         #li      t0, ((VM_SV39 << 24))
  17         or      t1, t0, t1
  18         csrw    CSR_MSTATUS, t1
  19
  20         la      t0, (loop - 0x80000000)
  21         csrw    CSR_MEPC, t0
  22
  23         # Exit supervisor mode, entering user mode at loop.
  24         mret
  25
  26 loop:
  27         la      t0, data
  28         lw      t1, 0(t0)
  29         j       loop
  30
  31         .section        .data
  32 data:
  33         .word   0xbead
  34
  35         .balign 0x1000
  36 page_table:
  37         .word   ((0x80000000 >> 2) | PTE_V | PTE_TYPE_URWX_SRWX)
  38         .word   0