sPMP implementation

sPMP Implementation

Register

• cpu_bits.h
  • csr_spmpcfg03 **0x1a00x1a3**
  • csr_spmpaddr015 **0x1b00x1bf**
  • csr_spmpexcp 0x145

Data structure

• cpu.h
  • MAX_RISCV_SPMPS
  • spmp_state
• pmp.h
  • date structures for spmp_table_t

Enable sPMP

• cpu.h

  • add RISCV_FEATURE_SPMP
  • add cpu->cfg.spmp

• cpu.c

  • set_feature(env, RISCV_FEATURE_SPMP)
  • set cpu -> cfg.spmp
  • add riscv_cpu_properties -> spmp

• cpu_helper.c

  • check riscv_feature && spmp_hart_has_privs
    • get physical addr
    • tlb fill
  • add spmp_violation

• csr.c
  • csr function table
  • define spmp_csr access priv to spmp

Main logic

• csr.c

• read\write_spmp_cfg

• read\write_spmp_addr

• pmp.c

  • Everything except pmp_get_a_field and pmp_decode_napot

Test

• sPMP read/write

  • set region0
    • cfg0 = 0b00001111 -> 0x0f
    • spmpaddr0 = 0x22000000
    • try to read the spmpcfg and spmpaddr

• sPMP L-bit test

  • test write ignore

    • cfg0 = 0b10011101 -> 0x9d
    • spmpaddr = 0x208ccdff
    • re-write spmpcfg and spmpaddr
    • write should be ignored

  • test access without proper permission

    • cfg0 = 0b11011101 -> 0xdd
    • access paddr = 0x82333000
    • kernel should panic

• SMAP

  • access region0 with U-bit set
    • cfg0 = 0b01011111 -> 0x5f
    • spmpaddr0 = 0x208ccdff
    • set SUM in sstatus to 1
    • access 0x82333000 in region0 shall succeed
    • set SUM in sstatus to 0
    • attempt to access 0x82333000 in region0
    • kernel should panic

• SMEP

  • excute code in region0 with U-bit set
    • inject code in paddr 0x82333000
      • 0xe900893 (li a7, 233)
      • little-endian -> 0x9308900e
    • cfg0 = 0b01011111 -> 0x5f
    • spmpaddr0 = 0x208ccdff
    • attempt to execute code at 0x82333000
    • kernel should panic