xref: /dports/emulators/riscv-isa-sim/riscv-isa-sim-4f12984/riscv/csrs.h

// See LICENSE for license details.
#ifndef _RISCV_CSRS_H
#define _RISCV_CSRS_H

// For reg_t:
#include "decode.h"
// For std::shared_ptr
#include <memory>
// For access_type:
#include "memtracer.h"

class processor_t;
struct state_t;

// Parent, abstract class for all CSRs
class csr_t {
 public:
  csr_t(processor_t* const proc, const reg_t addr);

  // Throw exception if read/write disallowed.
  virtual void verify_permissions(insn_t insn, bool write) const;

  // read() returns the architectural value of this CSR. No permission
  // checking needed or allowed. Side effects not allowed.
  virtual reg_t read() const noexcept = 0;

  // write() updates the architectural value of this CSR. No
  // permission checking needed or allowed.
  // Child classes must implement unlogged_write()
  void write(const reg_t val) noexcept;

  virtual ~csr_t();

 protected:
  // Return value indicates success; false means no write actually occurred
  virtual bool unlogged_write(const reg_t val) noexcept = 0;

  // Record this CSR update (which has already happened) in the commit log
  void log_write() const noexcept;

  // Record a write to an alternate CSR (e.g. minstreth instead of minstret)
  void log_special_write(const reg_t address, const reg_t val) const noexcept;

  // What value was written to this reg? Default implementation simply
  // calls read(), but a few CSRs are special.
  virtual reg_t written_value() const noexcept;

  processor_t* const proc;
  state_t* const state;
 public:
  const reg_t address;
 private:
  const unsigned csr_priv;
  const bool csr_read_only;
};

typedef std::shared_ptr<csr_t> csr_t_p;


// Basic CSRs, with XLEN bits fully readable and writable.
class basic_csr_t: public csr_t {
 public:
  basic_csr_t(processor_t* const proc, const reg_t addr, const reg_t init);
  virtual reg_t read() const noexcept override;
 protected:
  virtual bool unlogged_write(const reg_t val) noexcept override;
 private:
  reg_t val;
};


class pmpaddr_csr_t: public csr_t {
 public:
  pmpaddr_csr_t(processor_t* const proc, const reg_t addr);
  virtual void verify_permissions(insn_t insn, bool write) const override;
  virtual reg_t read() const noexcept override;

  // Does a 4-byte access at the specified address match this PMP entry?
  bool match4(reg_t addr) const noexcept;

  // Does the specified range match only a proper subset of this page?
  bool subset_match(reg_t addr, reg_t len) const noexcept;

  // Is the specified access allowed given the pmpcfg privileges?
  bool access_ok(access_type type, reg_t mode) const noexcept;

 protected:
  virtual bool unlogged_write(const reg_t val) noexcept override;
 private:
  // Assuming this is configured as TOR, return address for top of
  // range. Also forms bottom-of-range for next-highest pmpaddr
  // register if that one is TOR.
  reg_t tor_paddr() const noexcept;

  // Assuming this is configured as TOR, return address for bottom of
  // range. This is tor_paddr() from the previous pmpaddr register.
  reg_t tor_base_paddr() const noexcept;

  // Assuming this is configured as NAPOT or NA4, return mask for paddr.
  // E.g. for 4KiB region, returns 0xffffffff_fffff000.
  reg_t napot_mask() const noexcept;

  bool next_locked_and_tor() const noexcept;
  reg_t val;
  friend class pmpcfg_csr_t;  // so he can access cfg
  uint8_t cfg;
  const size_t pmpidx;
};

typedef std::shared_ptr<pmpaddr_csr_t> pmpaddr_csr_t_p;

class pmpcfg_csr_t: public csr_t {
 public:
  pmpcfg_csr_t(processor_t* const proc, const reg_t addr);
  virtual reg_t read() const noexcept override;
 protected:
  virtual bool unlogged_write(const reg_t val) noexcept override;
};


// For CSRs that have a virtualized copy under another name. Each
// instance of virtualized_csr_t will read/write one of two CSRs,
// based on state.v. E.g. sscratch, stval, etc.
//
// Example: sscratch and vsscratch are both instances of basic_csr_t.
// The csrmap will contain a virtualized_csr_t under sscratch's
// address, plus the vsscratch basic_csr_t under its address.

class virtualized_csr_t: public csr_t {
 public:
  virtualized_csr_t(processor_t* const proc, csr_t_p orig, csr_t_p virt);

  virtual reg_t read() const noexcept override;
  // Instead of using state.v, explicitly request original or virtual:
  reg_t readvirt(bool virt) const noexcept;
 protected:
  virtual bool unlogged_write(const reg_t val) noexcept override;
  csr_t_p orig_csr;
  csr_t_p virt_csr;
};

typedef std::shared_ptr<virtualized_csr_t> virtualized_csr_t_p;

// For mepc, sepc, and vsepc
class epc_csr_t: public csr_t {
 public:
  epc_csr_t(processor_t* const proc, const reg_t addr);

  virtual reg_t read() const noexcept override;
 protected:
  virtual bool unlogged_write(const reg_t val) noexcept override;
 private:
  reg_t val;
};


// For mtvec, stvec, and vstvec
class tvec_csr_t: public csr_t {
 public:
  tvec_csr_t(processor_t* const proc, const reg_t addr);

  virtual reg_t read() const noexcept override;
 protected:
  virtual bool unlogged_write(const reg_t val) noexcept override;
 private:
  reg_t val;
};


// For mcause, scause, and vscause
class cause_csr_t: public basic_csr_t {
 public:
  cause_csr_t(processor_t* const proc, const reg_t addr);

  virtual reg_t read() const noexcept override;
};


// For *status family of CSRs
class base_status_csr_t: public csr_t {
 public:
  base_status_csr_t(processor_t* const proc, const reg_t addr);
  // Return true if the specified bits are not 00 (Off)
  bool enabled(const reg_t which);
 protected:
  reg_t adjust_sd(const reg_t val) const noexcept;
  void maybe_flush_tlb(const reg_t newval) noexcept;
  const bool has_page;
  const reg_t sstatus_write_mask;
  const reg_t sstatus_read_mask;
 private:
  reg_t compute_sstatus_write_mask() const noexcept;
};

typedef std::shared_ptr<base_status_csr_t> base_status_csr_t_p;


// For vsstatus, which is its own separate architectural register
// (unlike sstatus)
class vsstatus_csr_t: public base_status_csr_t {
 public:
  vsstatus_csr_t(processor_t* const proc, const reg_t addr);
  virtual reg_t read() const noexcept override;
 protected:
  virtual bool unlogged_write(const reg_t val) noexcept override;
 private:
  reg_t val;
};

typedef std::shared_ptr<vsstatus_csr_t> vsstatus_csr_t_p;


class sstatus_proxy_csr_t: public base_status_csr_t {
 public:
  sstatus_proxy_csr_t(processor_t* const proc, const reg_t addr, csr_t_p mstatus);
  virtual reg_t read() const noexcept override;
 protected:
  virtual bool unlogged_write(const reg_t val) noexcept override;
 private:
  csr_t_p mstatus;
};


class mstatus_csr_t: public base_status_csr_t {
 public:
  mstatus_csr_t(processor_t* const proc, const reg_t addr);
  virtual reg_t read() const noexcept override;
 protected:
  virtual bool unlogged_write(const reg_t val) noexcept override;
 private:
  reg_t val;
  friend class mstatush_csr_t;
};

typedef std::shared_ptr<mstatus_csr_t> mstatus_csr_t_p;


class mstatush_csr_t: public csr_t {
 public:
  mstatush_csr_t(processor_t* const proc, const reg_t addr, mstatus_csr_t_p mstatus);
  virtual reg_t read() const noexcept override;
 protected:
  virtual bool unlogged_write(const reg_t val) noexcept override;
 private:
  mstatus_csr_t_p mstatus;
  const reg_t mask;
};


class sstatus_csr_t: public virtualized_csr_t {
 public:
  sstatus_csr_t(processor_t* const proc, base_status_csr_t_p orig, base_status_csr_t_p virt);

  // Set FS, VS, or XS bits to dirty
  void dirty(const reg_t dirties);
  // Return true if the specified bits are not 00 (Off)
  bool enabled(const reg_t which);
 private:
  base_status_csr_t_p orig_sstatus;
  base_status_csr_t_p virt_sstatus;
};

typedef std::shared_ptr<sstatus_csr_t> sstatus_csr_t_p;


class misa_csr_t: public basic_csr_t {
 public:
  misa_csr_t(processor_t* const proc, const reg_t addr, const reg_t max_isa);
  bool extension_enabled(unsigned char ext) const noexcept;
  bool extension_enabled_const(unsigned char ext) const noexcept;
 protected:
  virtual bool unlogged_write(const reg_t val) noexcept override;
 private:
  const reg_t max_isa;
  const reg_t write_mask;
};

typedef std::shared_ptr<misa_csr_t> misa_csr_t_p;


class mip_or_mie_csr_t: public csr_t {
 public:
  mip_or_mie_csr_t(processor_t* const proc, const reg_t addr);
  virtual reg_t read() const noexcept override final;

  void write_with_mask(const reg_t mask, const reg_t val) noexcept;

 protected:
  virtual bool unlogged_write(const reg_t val) noexcept override final;
  reg_t val;
 private:
  virtual reg_t write_mask() const noexcept = 0;
};


// mip is special because some of the bits are driven by hardware pins
class mip_csr_t: public mip_or_mie_csr_t {
 public:
  mip_csr_t(processor_t* const proc, const reg_t addr);

  // Does not log. Used by external things (clint) that wiggle bits in mip.
  void backdoor_write_with_mask(const reg_t mask, const reg_t val) noexcept;
 private:
  virtual reg_t write_mask() const noexcept override;
};

typedef std::shared_ptr<mip_csr_t> mip_csr_t_p;


class mie_csr_t: public mip_or_mie_csr_t {
 public:
  mie_csr_t(processor_t* const proc, const reg_t addr);
 private:
  virtual reg_t write_mask() const noexcept override;
};

typedef std::shared_ptr<mie_csr_t> mie_csr_t_p;


// For sip, hip, hvip, vsip, sie, hie, vsie which are all just (masked
// & shifted) views into mip or mie. Each pair will have one of these
// objects describing the view, e.g. one for sip+sie, one for hip+hie,
// etc.
class generic_int_accessor_t {
 public:
  generic_int_accessor_t(state_t* const state,
                         const reg_t read_mask,
                         const reg_t ip_write_mask,
                         const reg_t ie_write_mask,
                         const bool mask_mideleg,
                         const bool mask_hideleg,
                         const int shiftamt);
  reg_t ip_read() const noexcept;
  void ip_write(const reg_t val) noexcept;
  reg_t ie_read() const noexcept;
  void ie_write(const reg_t val) noexcept;
 private:
  state_t* const state;
  const reg_t read_mask;
  const reg_t ip_write_mask;
  const reg_t ie_write_mask;
  const bool mask_mideleg;
  const bool mask_hideleg;
  const int shiftamt;
  reg_t deleg_mask() const;
};

typedef std::shared_ptr<generic_int_accessor_t> generic_int_accessor_t_p;


// For all CSRs that are simply (masked & shifted) views into mip
class mip_proxy_csr_t: public csr_t {
 public:
  mip_proxy_csr_t(processor_t* const proc, const reg_t addr, generic_int_accessor_t_p accr);
  virtual reg_t read() const noexcept override;
 protected:
  virtual bool unlogged_write(const reg_t val) noexcept override;
 private:
  generic_int_accessor_t_p accr;
};

// For all CSRs that are simply (masked & shifted) views into mie
class mie_proxy_csr_t: public csr_t {
 public:
  mie_proxy_csr_t(processor_t* const proc, const reg_t addr, generic_int_accessor_t_p accr);
  virtual reg_t read() const noexcept override;
 protected:
  virtual bool unlogged_write(const reg_t val) noexcept override;
 private:
  generic_int_accessor_t_p accr;
};



class mideleg_csr_t: public basic_csr_t {
 public:
  mideleg_csr_t(processor_t* const proc, const reg_t addr);
  virtual void verify_permissions(insn_t insn, bool write) const override;
  virtual reg_t read() const noexcept override;
 protected:
  virtual bool unlogged_write(const reg_t val) noexcept override;
};


class medeleg_csr_t: public basic_csr_t {
 public:
  medeleg_csr_t(processor_t* const proc, const reg_t addr);
  virtual void verify_permissions(insn_t insn, bool write) const override;
 protected:
  virtual bool unlogged_write(const reg_t val) noexcept override;
 private:
  const reg_t hypervisor_exceptions;
};


// For CSRs with certain bits hardwired
class masked_csr_t: public basic_csr_t {
 public:
  masked_csr_t(processor_t* const proc, const reg_t addr, const reg_t mask, const reg_t init);
 protected:
  virtual bool unlogged_write(const reg_t val) noexcept override;
 private:
  const reg_t mask;
};


// For satp and vsatp
// These are three classes in order to handle the [V]TVM bits permission checks
class base_atp_csr_t: public basic_csr_t {
 public:
  base_atp_csr_t(processor_t* const proc, const reg_t addr);
  bool satp_valid(reg_t val) const noexcept;
 protected:
  virtual bool unlogged_write(const reg_t val) noexcept override;
 private:
  reg_t compute_new_satp(reg_t val) const noexcept;
};

class satp_csr_t: public base_atp_csr_t {
 public:
  satp_csr_t(processor_t* const proc, const reg_t addr);
  virtual void verify_permissions(insn_t insn, bool write) const override;
};

typedef std::shared_ptr<satp_csr_t> satp_csr_t_p;

class virtualized_satp_csr_t: public virtualized_csr_t {
 public:
  virtualized_satp_csr_t(processor_t* const proc, satp_csr_t_p orig, csr_t_p virt);
  virtual void verify_permissions(insn_t insn, bool write) const override;
 protected:
  virtual bool unlogged_write(const reg_t val) noexcept override;
 private:
  satp_csr_t_p orig_satp;
};


// For minstret, which is always 64 bits, but in RV32 is split into
// high and low halves. The first class always holds the full 64-bit
// value.
class minstret_csr_t: public csr_t {
 public:
  minstret_csr_t(processor_t* const proc, const reg_t addr);
  // Always returns full 64-bit value
  virtual reg_t read() const noexcept override;
  void bump(const reg_t howmuch) noexcept;
  void write_upper_half(const reg_t val) noexcept;
 protected:
  virtual bool unlogged_write(const reg_t val) noexcept override;
  virtual reg_t written_value() const noexcept override;
 private:
  reg_t val;
};

typedef std::shared_ptr<minstret_csr_t> minstret_csr_t_p;


// A simple proxy to read/write the upper half of minstret
class minstreth_csr_t: public csr_t {
 public:
  minstreth_csr_t(processor_t* const proc, const reg_t addr, minstret_csr_t_p minstret);
  virtual reg_t read() const noexcept override;
 protected:
  virtual bool unlogged_write(const reg_t val) noexcept override;
 private:
  minstret_csr_t_p minstret;
};

typedef std::shared_ptr<minstreth_csr_t> minstreth_csr_t_p;


// For a CSR that is an alias of another
class proxy_csr_t: public csr_t {
 public:
  proxy_csr_t(processor_t* const proc, const reg_t addr, csr_t_p delegate);
  virtual reg_t read() const noexcept override;
 protected:
  bool unlogged_write(const reg_t val) noexcept override;
 private:
  csr_t_p delegate;
};


// For a CSR with a fixed, unchanging value
class const_csr_t: public csr_t {
 public:
  const_csr_t(processor_t* const proc, const reg_t addr, reg_t val);
  virtual reg_t read() const noexcept override;
 protected:
  bool unlogged_write(const reg_t val) noexcept override;
 private:
  const reg_t val;
};


// For a CSR that is an unprivileged accessor of a privileged counter
class counter_proxy_csr_t: public proxy_csr_t {
 public:
  counter_proxy_csr_t(processor_t* const proc, const reg_t addr, csr_t_p delegate);
  virtual void verify_permissions(insn_t insn, bool write) const override;
 private:
  bool myenable(csr_t_p counteren) const noexcept;
};


// For machine-level CSRs that only exist with Hypervisor
class hypervisor_csr_t: public basic_csr_t {
 public:
  hypervisor_csr_t(processor_t* const proc, const reg_t addr);
  virtual void verify_permissions(insn_t insn, bool write) const override;
};


class hgatp_csr_t: public basic_csr_t {
 public:
  hgatp_csr_t(processor_t* const proc, const reg_t addr);
  virtual void verify_permissions(insn_t insn, bool write) const override;
 protected:
  virtual bool unlogged_write(const reg_t val) noexcept override;
};


class tselect_csr_t: public basic_csr_t {
 public:
  tselect_csr_t(processor_t* const proc, const reg_t addr);
 protected:
  virtual bool unlogged_write(const reg_t val) noexcept override;
};


class tdata1_csr_t: public csr_t {
 public:
  tdata1_csr_t(processor_t* const proc, const reg_t addr);
  virtual reg_t read() const noexcept override;
 protected:
  virtual bool unlogged_write(const reg_t val) noexcept override;
};

class tdata2_csr_t: public csr_t {
 public:
  tdata2_csr_t(processor_t* const proc, const reg_t addr, const size_t count);
  virtual reg_t read() const noexcept override;
  reg_t read(const size_t idx) const noexcept;
 protected:
  virtual bool unlogged_write(const reg_t val) noexcept override;
 private:
  std::vector<reg_t> vals;
};

// For CSRs that are only writable from debug mode
class debug_mode_csr_t: public basic_csr_t {
 public:
  debug_mode_csr_t(processor_t* const proc, const reg_t addr);
  virtual void verify_permissions(insn_t insn, bool write) const override;
};

typedef std::shared_ptr<tdata2_csr_t> tdata2_csr_t_p;


class dpc_csr_t: public epc_csr_t {
 public:
  dpc_csr_t(processor_t* const proc, const reg_t addr);
  virtual void verify_permissions(insn_t insn, bool write) const override;
};

class dcsr_csr_t: public csr_t {
 public:
  dcsr_csr_t(processor_t* const proc, const reg_t addr);
  virtual void verify_permissions(insn_t insn, bool write) const override;
  virtual reg_t read() const noexcept override;
  void write_cause_and_prv(uint8_t cause, reg_t prv) noexcept;
 protected:
  virtual bool unlogged_write(const reg_t val) noexcept override;
 public:
  uint8_t prv;
  bool step;
  bool ebreakm;
  bool ebreakh;
  bool ebreaks;
  bool ebreaku;
  bool halt;
  uint8_t cause;
};

typedef std::shared_ptr<dcsr_csr_t> dcsr_csr_t_p;


class float_csr_t: public masked_csr_t {
 public:
  float_csr_t(processor_t* const proc, const reg_t addr, const reg_t mask, const reg_t init);
  virtual void verify_permissions(insn_t insn, bool write) const override;
 protected:
  virtual bool unlogged_write(const reg_t val) noexcept override;
};


// For a CSR like FCSR, that is actually a view into multiple
// underlying registers.
class composite_csr_t: public csr_t {
 public:
  // We assume the lower_csr maps to bit 0.
  composite_csr_t(processor_t* const proc, const reg_t addr, csr_t_p upper_csr, csr_t_p lower_csr, const unsigned upper_lsb);
  virtual void verify_permissions(insn_t insn, bool write) const override;
  virtual reg_t read() const noexcept override;
 protected:
  virtual bool unlogged_write(const reg_t val) noexcept override;
 private:
  csr_t_p upper_csr;
  csr_t_p lower_csr;
  const unsigned upper_lsb;
};


class sentropy_csr_t: public csr_t {
 public:
  sentropy_csr_t(processor_t* const proc, const reg_t addr);
  virtual void verify_permissions(insn_t insn, bool write) const override;
  virtual reg_t read() const noexcept override;
 protected:
  virtual bool unlogged_write(const reg_t val) noexcept override;
};


class vector_csr_t: public basic_csr_t {
 public:
  vector_csr_t(processor_t* const proc, const reg_t addr, const reg_t mask, const reg_t init=0);
  virtual void verify_permissions(insn_t insn, bool write) const override;
  // Write without regard to mask, and without touching mstatus.VS
  void write_raw(const reg_t val) noexcept;
 protected:
  virtual bool unlogged_write(const reg_t val) noexcept override;
 private:
  reg_t mask;
};

typedef std::shared_ptr<vector_csr_t> vector_csr_t_p;


// For CSRs shared between Vector and P extensions (vxsat)
class vxsat_csr_t: public masked_csr_t {
 public:
  vxsat_csr_t(processor_t* const proc, const reg_t addr);
  virtual void verify_permissions(insn_t insn, bool write) const override;
 protected:
  virtual bool unlogged_write(const reg_t val) noexcept override;
};

#endif