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Add Zicfilp register state and flows
- Add elp state register and its initialization - xLPE to track if landing pads enabled at priv x - Functions that implement ELP state management - LPAD instruction
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| /*=======================================================================================*/ | ||
| /* RISCV Sail Model */ | ||
| /* */ | ||
| /* This Sail RISC-V architecture model, comprising all files and */ | ||
| /* directories except for the snapshots of the Lem and Sail libraries */ | ||
| /* in the prover_snapshots directory (which include copies of their */ | ||
| /* licences), is subject to the BSD two-clause licence below. */ | ||
| /* */ | ||
| /* Copyright (c) 2017-2023 */ | ||
| /* Prashanth Mundkur */ | ||
| /* Rishiyur S. Nikhil and Bluespec, Inc. */ | ||
| /* Jon French */ | ||
| /* Brian Campbell */ | ||
| /* Robert Norton-Wright */ | ||
| /* Alasdair Armstrong */ | ||
| /* Thomas Bauereiss */ | ||
| /* Shaked Flur */ | ||
| /* Christopher Pulte */ | ||
| /* Peter Sewell */ | ||
| /* Alexander Richardson */ | ||
| /* Hesham Almatary */ | ||
| /* Jessica Clarke */ | ||
| /* Microsoft, for contributions by Robert Norton-Wright and Nathaniel Wesley Filardo */ | ||
| /* Peter Rugg */ | ||
| /* Aril Computer Corp., for contributions by Scott Johnson */ | ||
| /* Philipp Tomsich */ | ||
| /* VRULL GmbH, for contributions by its employees */ | ||
| /* Ved Shanbhogue */ | ||
| /* */ | ||
| /* All rights reserved. */ | ||
| /* */ | ||
| /* This software was developed by the above within the Rigorous */ | ||
| /* Engineering of Mainstream Systems (REMS) project, partly funded by */ | ||
| /* EPSRC grant EP/K008528/1, at the Universities of Cambridge and */ | ||
| /* Edinburgh. */ | ||
| /* */ | ||
| /* This software was developed by SRI International and the University of */ | ||
| /* Cambridge Computer Laboratory (Department of Computer Science and */ | ||
| /* Technology) under DARPA/AFRL contract FA8650-18-C-7809 ("CIFV"), and */ | ||
| /* under DARPA contract HR0011-18-C-0016 ("ECATS") as part of the DARPA */ | ||
| /* SSITH research programme. */ | ||
| /* */ | ||
| /* This project has received funding from the European Research Council */ | ||
| /* (ERC) under the European Union’s Horizon 2020 research and innovation */ | ||
| /* programme (grant agreement 789108, ELVER). */ | ||
| /* */ | ||
| /* */ | ||
| /* Redistribution and use in source and binary forms, with or without */ | ||
| /* modification, are permitted provided that the following conditions */ | ||
| /* are met: */ | ||
| /* 1. Redistributions of source code must retain the above copyright */ | ||
| /* notice, this list of conditions and the following disclaimer. */ | ||
| /* 2. Redistributions in binary form must reproduce the above copyright */ | ||
| /* notice, this list of conditions and the following disclaimer in */ | ||
| /* the documentation and/or other materials provided with the */ | ||
| /* distribution. */ | ||
| /* */ | ||
| /* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' */ | ||
| /* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED */ | ||
| /* TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A */ | ||
| /* PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR */ | ||
| /* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, */ | ||
| /* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT */ | ||
| /* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF */ | ||
| /* USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND */ | ||
| /* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, */ | ||
| /* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT */ | ||
| /* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF */ | ||
| /* SUCH DAMAGE. */ | ||
| /*=======================================================================================*/ | ||
|
|
||
| /* ****************************************************************** */ | ||
| /* This file specifies the instructions in the 'Zicfilp' extension. */ | ||
| /* ****************************************************************** */ | ||
| /* Forward-edge CFI: Landing pads */ | ||
| val get_MPELP : (unit) -> elp_state | ||
| /* Sail does not yet support H extension - this needs to be updated to | ||
| support henvcfg for VS when H extension support is included */ | ||
| function zicfilp_xLPE() -> bool = { | ||
| /* When S-mode is implemented | ||
| * Priv xLPE | ||
| * M mseccfg.MLPE | ||
| * S/HS menvcfg.LPE | ||
| * VS henvcfg.LPE | ||
| * U/VU senvcfg.LPE | ||
| * When S-mode is not implemented | ||
| * Priv xLPE | ||
| * M mseccfg.MLPE | ||
| * U menvcfg.LPE | ||
| */ | ||
| if not(haveZicfilp()) | ||
| then false | ||
| else if cur_privilege == Machine | ||
| then mseccfg[MLPE] == 0b1 | ||
| else if cur_privilege == Supervisor | ||
| then menvcfg[LPE] == 0b1 | ||
| else if not(haveSupMode()) | ||
| then menvcfg[LPE] == 0b1 | ||
| else senvcfg[LPE] == 0b1 | ||
| } | ||
| /* extension to jalr */ | ||
| function zicfilp_update_elp(rs1_reg : regidx) -> unit = { | ||
| /* | ||
| * An indirect branch using JALR, C.JALR, or C.JR with rs1 as x7 is termed | ||
| * a software guarded branch. Such branches do not need to land on a LPAD | ||
| * instruction and thus do not set ELP to LP_EXPECTED. JALR/C.JR/C.JALR | ||
| * using x1/x5 as source are returns; they do not set ELP to LP_EXPECTED. | ||
| * | ||
| * is_lp_expected = ( (JALR || C.JR || C.JALR) && | ||
| * (rs1 != x1) && (rs1 != x5) && (rs1 != x7) ) ? 1 : 0; | ||
| */ | ||
| let is_lp_expected : bool = ((rs1_reg != 0b00001) & (rs1_reg != 0b00101) & | ||
| (rs1_reg != 0b00111)); | ||
| if is_lp_expected == true & zicfilp_xLPE() | ||
| then elp = ElpState_to_bits(LP_EXPECTED); | ||
|
|
||
| print("jalr: elp= " ^ BitStr(elp) ^ " is_lp_expected=" ^ BitStr(bool_to_bits(is_lp_expected))); | ||
| } | ||
| /* AUIPC with rd=x0 is a lpad instruction when zicfilp is active else a no-op */ | ||
| function clause execute zicfilp_lpad( lpl ) = { | ||
| /* expected label is in x7 bits 31:12 */ | ||
| let exp_lbl : bits(20) = x7[31..12]; | ||
|
|
||
| print("lpad:elp= " ^ BitStr(elp) ^ " lpl= " ^ BitStr(lpl) ^ " x7_31_12= " ^ BitStr(exp_lbl)); | ||
|
|
||
| if zicfilp_xLPE() & (elp == ElpState_to_bits(LP_EXPECTED)) then { | ||
| if ( (lpl != exp_lbl) & (lpl != 0b00000000000000000000) ) | ||
| then { handle_sw_check_exception(LANDING_PAD_FAULT); RETIRE_FAIL } | ||
| else { elp = ElpState_to_bits(NO_LP_EXPECTED); RETIRE_SUCCESS }; | ||
| } else { | ||
| RETIRE_SUCCESS | ||
| } | ||
| } | ||
| /* trap delivery extension */ | ||
| function zicfilp_preserve_elp(del_priv : Privilege) -> unit = { | ||
| /* When a trap is taken into privilege mode x, the xPELP is set | ||
| to ELP and ELP is set to NO_LP_EXPECTED. */ | ||
| /* Sail does not have support for Debug mode - this needs to be | ||
| updated when Debug mode support is added */ | ||
| if haveZicfilp() then { | ||
| match (del_priv, sizeof(xlen)) { | ||
| (Machine, 32 ) => {mstatush = update_MPELP(mstatush, elp)}, | ||
| (Machine, _ ) => {mstatus = update_mstatus_MPELP(mstatus, elp)}, | ||
| ( _, _ ) => {mstatus = update_SPELP(mstatus, elp)}, | ||
| }; | ||
| elp = ElpState_to_bits(NO_LP_EXPECTED); | ||
| } | ||
| } | ||
| /* extension to MRET */ | ||
| function zicfilp_set_elp_to_mpelp() -> unit = { | ||
| /* An MRET or SRET instruction is used to return from a trap in M-mode | ||
| * or S-mode, respectively. When executing an xRET instruction, if xPP | ||
| * holds the value y, then ELP is set to the value of xPELP if yLPE is | ||
| * 1; otherwise, it is set to NO_LP_EXPECTED; xPELP is set to | ||
| * NO_LP_EXPECTED. | ||
| */ | ||
| if haveZicfilp() then { | ||
| match zicfilp_xLPE() { | ||
| true => { elp = get_MPELP() }, | ||
| false => { elp = ElpState_to_bits(NO_LP_EXPECTED) } | ||
| }; | ||
| match (sizeof(xlen)) { | ||
| 32 => {mstatush = update_MPELP(mstatush, ElpState_to_bits(NO_LP_EXPECTED))}, | ||
| _ => {mstatus = update_mstatus_MPELP(mstatus, ElpState_to_bits(NO_LP_EXPECTED))} | ||
| }; | ||
| } | ||
| } | ||
| /* extension to SRET */ | ||
| function zicfilp_set_elp_to_spelp() -> unit = { | ||
| /* An MRET or SRET instruction is used to return from a trap in M-mode | ||
| * or S-mode, respectively. When executing an xRET instruction, if xPP | ||
| * holds the value y, then ELP is set to the value of xPELP if yLPE is | ||
| * 1; otherwise, it is set to NO_LP_EXPECTED; xPELP is set to | ||
| * NO_LP_EXPECTED. | ||
| */ | ||
| if haveZicfilp() then { | ||
| match zicfilp_xLPE() { | ||
| true => { elp = mstatus.SPELP() }, | ||
| false => { elp = ElpState_to_bits(NO_LP_EXPECTED) } | ||
| }; | ||
| mstatus = update_SPELP(mstatus, ElpState_to_bits(NO_LP_EXPECTED)); | ||
| } | ||
| } | ||
| /* Check if fetch violates ELP */ | ||
| function zicfilp_is_elp_violated() -> bool = { | ||
| /* landing pad is a AUIPC with rd=x0 */ | ||
| /* When ELP is set to LP_EXPECTED, if the next instruction in | ||
| * the instruction stream is not 4-byte aligned, or is not LPAD, or | ||
| * if the landing pad label encoded in LPAD is not zero and does not | ||
| * match the expected landing pad label in bits 31:12 of the x7 | ||
| * register, then a software-check exception (cause=18) with xtval | ||
| * set to "landing pad fault (code=2)" is raised else the ELP is | ||
| * updated to NO_LP_EXPECTED. The label check is performed in | ||
| * riscv_insts_zicfilp:zicfilp_lpad | ||
| */ | ||
| if not(zicfilp_xLPE()) | ||
| then false | ||
| else if elp != ElpState_to_bits(LP_EXPECTED) | ||
| then false | ||
| else if ( (PC[1 .. 0] != 0b00) | (instbits[6..0] != 0b0010111) | (instbits[11..7] != 0b00000) ) | ||
| then true | ||
| else false | ||
| } | ||
|
|
||
| /* helper to update MPELP in mstatus */ | ||
| function update_mstatus_MPELP(o : Mstatus, e : elp_state) -> Mstatus = | ||
| if sizeof(xlen) == 64 | ||
| then Mk_Mstatus([o.bits() with 41 .. 41 = e]) | ||
| else o | ||
|
|
||
| /* helpers to get MPELP from mstatus/mstatush */ | ||
| function get_MPELP() -> elp_state = | ||
| if sizeof(xlen) == 64 | ||
| then mstatus.bits()[41..41] | ||
| else mstatush.MPELP() |
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