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Clean up memory checking functions slightly
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* Move `write_knd_of_flags` into its own function.
* Wrap really long lines
* Move PMP check into `phys_access_check` function. This is needed for two reasons:
  - The CBO extension needs to do explicit access checks.
  - In future it will also check PMAs so the name needs changing.
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@Timmmm @billmcspadden-riscv
Timmmm authored and billmcspadden-riscv committed Apr 9, 2024
1 parent a2ffa85 commit 5c7d1f2
Showing 1 changed file with 73 additions and 65 deletions.
138 changes: 73 additions & 65 deletions model/riscv_mem.sail
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Original file line number Diff line number Diff line change
Expand Up @@ -50,6 +50,19 @@ function read_kind_of_flags (aq : bool, rl : bool, res : bool) -> option(read_ki
(false, true, true) => None()
}

function write_kind_of_flags (aq : bool, rl : bool, con : bool) -> write_kind =
match (aq, rl, con) {
(false, false, false) => Write_plain,
(false, true, false) => Write_RISCV_release,
(false, false, true) => Write_RISCV_conditional,
(false, true , true) => Write_RISCV_conditional_release,
(true, true, false) => Write_RISCV_strong_release,
(true, true , true) => Write_RISCV_conditional_strong_release,
// throw an illegal instruction here?
(true, false, false) => throw(Error_not_implemented("store.aq")),
(true, false, true) => throw(Error_not_implemented("sc.aq"))
}

// only used for actual memory regions, to avoid MMIO effects
function phys_mem_read forall 'n, 0 < 'n <= max_mem_access . (t : AccessType(ext_access_type), paddr : xlenbits, width : int('n), aq : bool, rl: bool, res : bool, meta : bool) -> MemoryOpResult((bits(8 * 'n), mem_meta)) = {
let result = (match read_kind_of_flags(aq, rl, res) {
Expand All @@ -66,28 +79,39 @@ function phys_mem_read forall 'n, 0 < 'n <= max_mem_access . (t : AccessType(ext
}
}

/* dispatches to MMIO regions or physical memory regions depending on physical memory map */
function checked_mem_read forall 'n, 0 < 'n <= max_mem_access . (t : AccessType(ext_access_type), paddr : xlenbits, width : int('n), aq : bool, rl : bool, res: bool, meta : bool) -> MemoryOpResult((bits(8 * 'n), mem_meta)) =
if within_mmio_readable(paddr, width)
then MemoryOpResult_add_meta(mmio_read(t, paddr, width), default_meta)
else if within_phys_mem(paddr, width)
then match ext_check_phys_mem_read(t, paddr, width, aq, rl, res, meta) {
Ext_PhysAddr_OK() => phys_mem_read(t, paddr, width, aq, rl, res, meta),
Ext_PhysAddr_Error(e) => MemException(e)
} else match t {
Execute() => MemException(E_Fetch_Access_Fault()),
Read(Data) => MemException(E_Load_Access_Fault()),
_ => MemException(E_SAMO_Access_Fault())
}
// Check if access is permitted according to PMPs and PMAs.
val phys_access_check : forall 'n, 0 < 'n <= max_mem_access . (AccessType(ext_access_type), Privilege, xlenbits, int('n)) -> option(ExceptionType)
function phys_access_check (t, p, paddr, width) = {
let pmpError : option(ExceptionType) = if sys_pmp_count() == 0 then None() else pmpCheck(paddr, width, t, p);
// TODO: Also check PMAs and select the highest priority fault.
pmpError
}

/* PMP checks if enabled */
function pmp_mem_read forall 'n, 0 < 'n <= max_mem_access . (t : AccessType(ext_access_type), p : Privilege, paddr : xlenbits, width : int('n), aq : bool, rl : bool, res: bool, meta : bool) -> MemoryOpResult((bits(8 * 'n), mem_meta)) =
if sys_pmp_count() == 0
then checked_mem_read(t, paddr, width, aq, rl, res, meta)
else {
match pmpCheck(paddr, width, t, p) {
None() => checked_mem_read(t, paddr, width, aq, rl, res, meta),
Some(e) => MemException(e)
/* dispatches to MMIO regions or physical memory regions depending on physical memory map */
function checked_mem_read forall 'n, 0 < 'n <= max_mem_access . (
t : AccessType(ext_access_type),
priv : Privilege,
paddr : xlenbits,
width : int('n),
aq : bool,
rl : bool,
res: bool,
meta : bool,
) -> MemoryOpResult((bits(8 * 'n), mem_meta)) =
match phys_access_check(t, priv, paddr, width) {
Some(e) => MemException(e),
None() => {
if within_mmio_readable(paddr, width)
then MemoryOpResult_add_meta(mmio_read(t, paddr, width), default_meta)
else if within_phys_mem(paddr, width)
then match ext_check_phys_mem_read(t, paddr, width, aq, rl, res, meta) {
Ext_PhysAddr_OK() => phys_mem_read(t, paddr, width, aq, rl, res, meta),
Ext_PhysAddr_Error(e) => MemException(e)
} else match t {
Execute() => MemException(E_Fetch_Access_Fault()),
Read(Data) => MemException(E_Load_Access_Fault()),
_ => MemException(E_SAMO_Access_Fault())
}
}
}

Expand Down Expand Up @@ -133,7 +157,7 @@ function mem_read_priv_meta (typ, priv, paddr, width, aq, rl, res, meta) = {
else match (aq, rl, res) {
(false, true, false) => throw(Error_not_implemented("load.rl")),
(false, true, true) => throw(Error_not_implemented("lr.rl")),
(_, _, _) => pmp_mem_read(typ, priv, paddr, width, aq, rl, res, meta)
(_, _, _) => checked_mem_read(typ, priv, paddr, width, aq, rl, res, meta)
};
rvfi_read(paddr, width, result);
result
Expand All @@ -151,21 +175,10 @@ function mem_read (typ, paddr, width, aq, rel, res) =
mem_read_priv(typ, effectivePrivilege(typ, mstatus, cur_privilege), paddr, width, aq, rel, res)

val mem_write_ea : forall 'n, 0 < 'n <= max_mem_access . (xlenbits, int('n), bool, bool, bool) -> MemoryOpResult(unit)

function mem_write_ea (addr, width, aq, rl, con) = {
function mem_write_ea (addr, width, aq, rl, con) =
if (rl | con) & not(is_aligned_addr(addr, width))
then MemException(E_SAMO_Addr_Align())
else match (aq, rl, con) {
(false, false, false) => MemValue(write_ram_ea(Write_plain, addr, width)),
(false, true, false) => MemValue(write_ram_ea(Write_RISCV_release, addr, width)),
(false, false, true) => MemValue(write_ram_ea(Write_RISCV_conditional, addr, width)),
(false, true , true) => MemValue(write_ram_ea(Write_RISCV_conditional_release, addr, width)),
(true, false, false) => throw(Error_not_implemented("store.aq")),
(true, true, false) => MemValue(write_ram_ea(Write_RISCV_strong_release, addr, width)),
(true, false, true) => throw(Error_not_implemented("sc.aq")),
(true, true , true) => MemValue(write_ram_ea(Write_RISCV_conditional_strong_release, addr, width))
}
}
else MemValue(write_ram_ea(write_kind_of_flags(aq, rl, con), addr, width))

$ifdef RVFI_DII
val rvfi_write : forall 'n, 0 < 'n <= max_mem_access . (xlenbits, int('n), bits(8 * 'n), mem_meta, MemoryOpResult(bool)) -> unit
Expand Down Expand Up @@ -198,24 +211,30 @@ function phys_mem_write forall 'n, 0 < 'n <= max_mem_access . (wk : write_kind,
}

/* dispatches to MMIO regions or physical memory regions depending on physical memory map */
function checked_mem_write forall 'n, 0 < 'n <= max_mem_access . (wk : write_kind, paddr : xlenbits, width : int('n), data: bits(8 * 'n), meta: mem_meta) -> MemoryOpResult(bool) =
if within_mmio_writable(paddr, width)
then mmio_write(paddr, width, data)
else if within_phys_mem(paddr, width)
then match ext_check_phys_mem_write (wk, paddr, width, data, meta) {
Ext_PhysAddr_OK() => phys_mem_write(wk, paddr, width, data, meta),
Ext_PhysAddr_Error(e) => MemException(e)
}
else MemException(E_SAMO_Access_Fault())

/* PMP checks if enabled */
function pmp_mem_write forall 'n, 0 < 'n <= max_mem_access . (wk: write_kind, paddr : xlenbits, width : int('n), data: bits(8 * 'n), typ: AccessType(ext_access_type), priv: Privilege, meta: mem_meta) -> MemoryOpResult(bool) =
if sys_pmp_count() == 0
then checked_mem_write(wk, paddr, width, data, meta)
else {
match pmpCheck(paddr, width, typ, priv) {
None() => checked_mem_write(wk, paddr, width, data, meta),
Some(e) => MemException(e)
function checked_mem_write forall 'n, 0 < 'n <= max_mem_access . (
paddr : xlenbits,
width : int('n),
data: bits(8 * 'n),
typ : AccessType(ext_access_type),
priv : Privilege,
meta: mem_meta,
aq : bool,
rl : bool,
con : bool,
) -> MemoryOpResult(bool) =
match phys_access_check(typ, priv, paddr, width) {
Some(e) => MemException(e),
None() => {
if within_mmio_writable(paddr, width)
then mmio_write(paddr, width, data)
else if within_phys_mem(paddr, width)
then {
let wk = write_kind_of_flags(aq, rl, con);
match ext_check_phys_mem_write (wk, paddr, width, data, meta) {
Ext_PhysAddr_OK() => phys_mem_write(wk, paddr, width, data, meta),
Ext_PhysAddr_Error(e) => MemException(e),
}
} else MemException(E_SAMO_Access_Fault())
}
}

Expand All @@ -231,18 +250,7 @@ function mem_write_value_priv_meta (paddr, width, value, typ, priv, meta, aq, rl
if (rl | con) & not(is_aligned_addr(paddr, width))
then MemException(E_SAMO_Addr_Align())
else {
let wk : write_kind = match (aq, rl, con) {
(false, false, false) => Write_plain,
(false, true, false) => Write_RISCV_release,
(false, false, true) => Write_RISCV_conditional,
(false, true , true) => Write_RISCV_conditional_release,
(true, true, false) => Write_RISCV_strong_release,
(true, true , true) => Write_RISCV_conditional_strong_release,
// throw an illegal instruction here?
(true, false, false) => throw(Error_not_implemented("store.aq")),
(true, false, true) => throw(Error_not_implemented("sc.aq"))
};
let result = pmp_mem_write(wk, paddr, width, value, typ, priv, meta);
let result = checked_mem_write(paddr, width, value, typ, priv, meta, aq, rl, con);
rvfi_write(paddr, width, value, meta, result);
result
}
Expand Down

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