target/riscv: implement zicfiss instructions

zicfiss has following instructions
 - sspopchk: pops a value from shadow stack and compares with x1/x5.
   If they dont match, reports a sw check exception with tval = 3.
 - sspush: pushes value in x1/x5 on shadow stack
 - ssrdp: reads current shadow stack
 - ssamoswap: swaps contents of shadow stack atomically

sspopchk/sspush/ssrdp default to zimop if zimop implemented and SSE=0

If SSE=0, ssamoswap is illegal instruction exception.

This patch implements shadow stack operations for qemu-user and shadow
stack is not protected.

Signed-off-by: Deepak Gupta <debug@rivosinc.com>
Co-developed-by: Jim Shu <jim.shu@sifive.com>
Co-developed-by: Andy Chiu <andy.chiu@sifive.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Message-ID: <20241008225010.1861630-17-debug@rivosinc.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>

target/riscv/cpu_bits.h

@@ -697,6 +697,8 @@ typedef enum RISCVException {
 
 /* zicfilp defines lp violation results in sw check with tval = 2*/
 #define RISCV_EXCP_SW_CHECK_FCFI_TVAL      2
+/* zicfiss defines ss violation results in sw check with tval = 3*/
+#define RISCV_EXCP_SW_CHECK_BCFI_TVAL      3
 
 #define RISCV_EXCP_INT_FLAG                0x80000000
 #define RISCV_EXCP_INT_MASK                0x7fffffff

target/riscv/insn32.decode

@@ -246,6 +246,7 @@ remud    0000001 .....  ..... 111 ..... 1111011 @r
 lr_w       00010 . . 00000 ..... 010 ..... 0101111 @atom_ld
 sc_w       00011 . . ..... ..... 010 ..... 0101111 @atom_st
 amoswap_w  00001 . . ..... ..... 010 ..... 0101111 @atom_st
+ssamoswap_w 01001 . . ..... ..... 010 ..... 0101111 @atom_st
 amoadd_w   00000 . . ..... ..... 010 ..... 0101111 @atom_st
 amoxor_w   00100 . . ..... ..... 010 ..... 0101111 @atom_st
 amoand_w   01100 . . ..... ..... 010 ..... 0101111 @atom_st
@@ -259,6 +260,7 @@ amomaxu_w  11100 . . ..... ..... 010 ..... 0101111 @atom_st
 lr_d       00010 . . 00000 ..... 011 ..... 0101111 @atom_ld
 sc_d       00011 . . ..... ..... 011 ..... 0101111 @atom_st
 amoswap_d  00001 . . ..... ..... 011 ..... 0101111 @atom_st
+ssamoswap_d 01001 . . ..... ..... 011 ..... 0101111 @atom_st
 amoadd_d   00000 . . ..... ..... 011 ..... 0101111 @atom_st
 amoxor_d   00100 . . ..... ..... 011 ..... 0101111 @atom_st
 amoand_d   01100 . . ..... ..... 011 ..... 0101111 @atom_st
@@ -1022,8 +1024,23 @@ amocas_d    00101 . . ..... ..... 011 ..... 0101111 @atom_st
 amocas_q    00101 . . ..... ..... 100 ..... 0101111 @atom_st
 
 # *** Zimop may-be-operation extension ***
-mop_r_n     1 . 00 .. 0111 .. ..... 100 ..... 1110011 @mop5
+{
-mop_rr_n    1 . 00 .. 1 ..... ..... 100 ..... 1110011 @mop3
+  # zicfiss instructions carved out of mop.r
+  [
+    ssrdp     1100110 11100 00000 100 rd:5  1110011
+    sspopchk  1100110 11100 00001 100 00000 1110011 &r2 rs1=1 rd=0
+    sspopchk  1100110 11100 00101 100 00000 1110011 &r2 rs1=5 rd=0
+  ]
+  mop_r_n    1 . 00 .. 0111 .. ..... 100 ..... 1110011 @mop5
+}
+{
+  # zicfiss instruction carved out of mop.rr
+  [
+    sspush    1100111 00001  00000 100 00000 1110011 &r2_s rs2=1 rs1=0
+    sspush    1100111 00101  00000 100 00000 1110011 &r2_s rs2=5 rs1=0
+  ]
+  mop_rr_n   1 . 00 .. 1 ..... ..... 100 ..... 1110011 @mop3
+}
 
 # *** Zabhb Standard Extension ***
 amoswap_b  00001 . . ..... ..... 000 ..... 0101111 @atom_st

target/riscv/insn_trans/trans_rvzicfiss.c.inc

@@ -0,0 +1,114 @@
+/*
+ * RISC-V translation routines for the Control-Flow Integrity Extension
+ *
+ * Copyright (c) 2024 Rivos Inc.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2 or later, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+static bool trans_sspopchk(DisasContext *ctx, arg_sspopchk *a)
+{
+    if (!ctx->bcfi_enabled) {
+        return false;
+    }
+
+    TCGv addr = tcg_temp_new();
+    TCGLabel *skip = gen_new_label();
+    uint32_t tmp = (get_xl(ctx) == MXL_RV64) ? 8 : 4;
+    TCGv data = tcg_temp_new();
+    tcg_gen_ld_tl(addr, tcg_env, offsetof(CPURISCVState, ssp));
+    decode_save_opc(ctx, RISCV_UW2_ALWAYS_STORE_AMO);
+    tcg_gen_qemu_ld_tl(data, addr, SS_MMU_INDEX(ctx),
+                       mxl_memop(ctx) | MO_ALIGN);
+    TCGv rs1 = get_gpr(ctx, a->rs1, EXT_NONE);
+    tcg_gen_brcond_tl(TCG_COND_EQ, data, rs1, skip);
+    tcg_gen_st_tl(tcg_constant_tl(RISCV_EXCP_SW_CHECK_BCFI_TVAL),
+                  tcg_env, offsetof(CPURISCVState, sw_check_code));
+    gen_helper_raise_exception(tcg_env,
+                  tcg_constant_i32(RISCV_EXCP_SW_CHECK));
+    gen_set_label(skip);
+    tcg_gen_addi_tl(addr, addr, tmp);
+    tcg_gen_st_tl(addr, tcg_env, offsetof(CPURISCVState, ssp));
+
+    return true;
+}
+
+static bool trans_sspush(DisasContext *ctx, arg_sspush *a)
+{
+    if (!ctx->bcfi_enabled) {
+        return false;
+    }
+
+    TCGv addr = tcg_temp_new();
+    int tmp = (get_xl(ctx) == MXL_RV64) ? -8 : -4;
+    TCGv data = get_gpr(ctx, a->rs2, EXT_NONE);
+    decode_save_opc(ctx, RISCV_UW2_ALWAYS_STORE_AMO);
+    tcg_gen_ld_tl(addr, tcg_env, offsetof(CPURISCVState, ssp));
+    tcg_gen_addi_tl(addr, addr, tmp);
+    tcg_gen_qemu_st_tl(data, addr, SS_MMU_INDEX(ctx),
+                       mxl_memop(ctx) | MO_ALIGN);
+    tcg_gen_st_tl(addr, tcg_env, offsetof(CPURISCVState, ssp));
+
+    return true;
+}
+
+static bool trans_ssrdp(DisasContext *ctx, arg_ssrdp *a)
+{
+    if (!ctx->bcfi_enabled || a->rd == 0) {
+        return false;
+    }
+
+    TCGv dest = dest_gpr(ctx, a->rd);
+    tcg_gen_ld_tl(dest, tcg_env, offsetof(CPURISCVState, ssp));
+    gen_set_gpr(ctx, a->rd, dest);
+
+    return true;
+}
+
+static bool trans_ssamoswap_w(DisasContext *ctx, arg_amoswap_w *a)
+{
+    REQUIRE_A_OR_ZAAMO(ctx);
+    if (!ctx->bcfi_enabled) {
+        return false;
+    }
+
+    TCGv dest = dest_gpr(ctx, a->rd);
+    TCGv src1, src2 = get_gpr(ctx, a->rs2, EXT_NONE);
+
+    decode_save_opc(ctx, RISCV_UW2_ALWAYS_STORE_AMO);
+    src1 = get_address(ctx, a->rs1, 0);
+
+    tcg_gen_atomic_xchg_tl(dest, src1, src2, SS_MMU_INDEX(ctx),
+                           (MO_ALIGN | MO_TESL));
+    gen_set_gpr(ctx, a->rd, dest);
+    return true;
+}
+
+static bool trans_ssamoswap_d(DisasContext *ctx, arg_amoswap_w *a)
+{
+    REQUIRE_64BIT(ctx);
+    REQUIRE_A_OR_ZAAMO(ctx);
+    if (!ctx->bcfi_enabled) {
+        return false;
+    }
+
+    TCGv dest = dest_gpr(ctx, a->rd);
+    TCGv src1, src2 = get_gpr(ctx, a->rs2, EXT_NONE);
+
+    decode_save_opc(ctx, RISCV_UW2_ALWAYS_STORE_AMO);
+    src1 = get_address(ctx, a->rs1, 0);
+
+    tcg_gen_atomic_xchg_tl(dest, src1, src2, SS_MMU_INDEX(ctx),
+                           (MO_ALIGN | MO_TESQ));
+    gen_set_gpr(ctx, a->rd, dest);
+    return true;
+}

target/riscv/translate.c

@@ -144,6 +144,8 @@ static inline bool has_ext(DisasContext *ctx, uint32_t ext)
 #define get_address_xl(ctx)    ((ctx)->address_xl)
 #endif
 
+#define mxl_memop(ctx) ((get_xl(ctx) + 1) | MO_TE)
+
 /* The word size for this machine mode. */
 static inline int __attribute__((unused)) get_xlen(DisasContext *ctx)
 {
@@ -1127,6 +1129,8 @@ static uint32_t opcode_at(DisasContextBase *dcbase, target_ulong pc)
     return translator_ldl(env, &ctx->base, pc);
 }
 
+#define SS_MMU_INDEX(ctx) (ctx->mem_idx | MMU_IDX_SS_WRITE)
+
 /* Include insn module translation function */
 #include "insn_trans/trans_rvi.c.inc"
 #include "insn_trans/trans_rvm.c.inc"
@@ -1157,6 +1161,7 @@ static uint32_t opcode_at(DisasContextBase *dcbase, target_ulong pc)
 #include "decode-insn16.c.inc"
 #include "insn_trans/trans_rvzce.c.inc"
 #include "insn_trans/trans_rvzcmop.c.inc"
+#include "insn_trans/trans_rvzicfiss.c.inc"
 
 /* Include decoders for factored-out extensions */
 #include "decode-XVentanaCondOps.c.inc"