Implements setting lp expected when `jalr` is encountered and implements `lpad` instruction of zicfilp. `lpad` instruction is taken out of auipc x0, <imm_20>. This is an existing HINTNOP space. If `lpad` is target of an indirect branch, cpu checks for 20 bit value in x7 upper with 20 bit value embedded in `lpad`. If they don't match, cpu raises a sw check exception with tval = 2.
Signed-off-by: Deepak Gupta <de...@rivosinc.com> Co-developed-by: Jim Shu <jim....@sifive.com> Co-developed-by: Andy Chiu <andy.c...@sifive.com> --- target/riscv/cpu_user.h | 1 + target/riscv/helper.h | 4 ++ target/riscv/insn32.decode | 6 ++- target/riscv/insn_trans/trans_rvi.c.inc | 51 +++++++++++++++++++++++++ target/riscv/op_helper.c | 32 ++++++++++++++++ 5 files changed, 93 insertions(+), 1 deletion(-) diff --git a/target/riscv/cpu_user.h b/target/riscv/cpu_user.h index 02afad608b..e6927ff847 100644 --- a/target/riscv/cpu_user.h +++ b/target/riscv/cpu_user.h @@ -15,5 +15,6 @@ #define xA6 16 #define xA7 17 /* syscall number for RVI ABI */ #define xT0 5 /* syscall number for RVE ABI */ +#define xT2 7 #endif diff --git a/target/riscv/helper.h b/target/riscv/helper.h index 451261ce5a..ab55bbbf73 100644 --- a/target/riscv/helper.h +++ b/target/riscv/helper.h @@ -121,6 +121,10 @@ DEF_HELPER_2(cbo_clean_flush, void, env, tl) DEF_HELPER_2(cbo_inval, void, env, tl) DEF_HELPER_2(cbo_zero, void, env, tl) +/* Forward CFI label checking */ +DEF_HELPER_2(cfi_jalr, void, env, int) +DEF_HELPER_2(cfi_check_landing_pad, void, env, int) + /* Special functions */ DEF_HELPER_2(csrr, tl, env, int) DEF_HELPER_3(csrw, void, env, int, tl) diff --git a/target/riscv/insn32.decode b/target/riscv/insn32.decode index c45b8fa1d8..c963c59c8e 100644 --- a/target/riscv/insn32.decode +++ b/target/riscv/insn32.decode @@ -40,6 +40,7 @@ %imm_z6 26:1 15:5 %imm_mop5 30:1 26:2 20:2 %imm_mop3 30:1 26:2 +%imm_cfi20 12:20 # Argument sets: &empty @@ -123,7 +124,10 @@ sfence_vm 0001000 00100 ..... 000 00000 1110011 @sfence_vm # *** RV32I Base Instruction Set *** lui .................... ..... 0110111 @u -auipc .................... ..... 0010111 @u +{ + lpad .................... 00000 0010111 %imm_cfi20 + auipc .................... ..... 0010111 @u +} jal .................... ..... 1101111 @j jalr ............ ..... 000 ..... 1100111 @i beq ....... ..... ..... 000 ..... 1100011 @b diff --git a/target/riscv/insn_trans/trans_rvi.c.inc b/target/riscv/insn_trans/trans_rvi.c.inc index 98e3806d5e..ee868c5fcb 100644 --- a/target/riscv/insn_trans/trans_rvi.c.inc +++ b/target/riscv/insn_trans/trans_rvi.c.inc @@ -36,6 +36,44 @@ static bool trans_lui(DisasContext *ctx, arg_lui *a) return true; } +static bool trans_lpad(DisasContext *ctx, arg_lpad *a) +{ + /* zicfilp only supported on 32bit and 64bit */ + if (get_xl(ctx) != MXL_RV32 && get_xl(ctx) != MXL_RV64) { + return false; + } + + /* forward cfi not enabled, return false */ + if (!ctx->fcfi_enabled) { + return false; + } + + /* + * If this is the first instruction of the TB, let the translator + * know the landing pad requirement was satisfied. No need to bother + * checking for CFI feature or enablement. + */ + + if (ctx->base.pc_next == ctx->base.pc_first) { + ctx->fcfi_lp_expected = false; + /* PC must be 4 byte aligned */ + if (ctx->fcfi_enabled && ((ctx->base.pc_next) & 0x3)) { + /* + * misaligned, according to spec we should raise sw check exception + */ + tcg_gen_st_tl( + tcg_constant_tl(RISCV_EXCP_SW_CHECK_FCFI_TVAL), + tcg_env, offsetof(CPURISCVState, sw_check_code)); + generate_exception(ctx, RISCV_EXCP_SW_CHECK); + return true; + } + } + + /* use helper to do label check */ + gen_helper_cfi_check_landing_pad(tcg_env, tcg_constant_i32(a->imm_cfi20)); + return true; +} + static bool trans_auipc(DisasContext *ctx, arg_auipc *a) { TCGv target_pc = dest_gpr(ctx, a->rd); @@ -75,6 +113,19 @@ static bool trans_jalr(DisasContext *ctx, arg_jalr *a) gen_set_gpr(ctx, a->rd, succ_pc); tcg_gen_mov_tl(cpu_pc, target_pc); + if (ctx->cfg_ptr->ext_zicfilp) { + /* + * Rely on a helper to check the forward CFI enable for the + * current process mode. The alternatives would be (1) include + * "fcfi enabled" in the cflags or (2) maintain a "fcfi + * currently enabled" in tcg_env and emit TCG code to access + * and test it. + */ + if (a->rs1 != xRA && a->rs1 != xT0 && a->rs1 != xT2) { + gen_helper_cfi_jalr(tcg_env, tcg_constant_i32(LP_EXPECTED)); + } + } + lookup_and_goto_ptr(ctx); if (misaligned) { diff --git a/target/riscv/op_helper.c b/target/riscv/op_helper.c index 488116cc2e..2d152f0a00 100644 --- a/target/riscv/op_helper.c +++ b/target/riscv/op_helper.c @@ -259,6 +259,38 @@ void helper_cbo_inval(CPURISCVState *env, target_ulong address) /* We don't emulate the cache-hierarchy, so we're done. */ } +void helper_cfi_jalr(CPURISCVState *env, int elp) +{ + /* + * The translation routine doesn't know if forward CFI is enabled + * in the current processor mode or not. It's not worth burning a + * cflags bit to encode this, or tracking the current-mode-fcfi + * enable in a dedicated member of 'env'. Just come out to a helper + * for jump/call on a core with CFI. + */ + if (cpu_get_fcfien(env)) { + env->elp = elp; + } +} + +void helper_cfi_check_landing_pad(CPURISCVState *env, int lbl) +{ + if ((env->elp == LP_EXPECTED) && cpu_get_fcfien(env)) { + /* + * Check for the 20bit label match. We already checked 4 byte + * alignment in tcg + * High 20bits (b31:12) in x7/t2 hold label. We need drop bits + * greater than 31 and then shift 12 right + */ + if (lbl && (lbl != ((env->gpr[xT2] & 0xFFFFFFFF) >> 12))) { + env->sw_check_code = RISCV_EXCP_SW_CHECK_FCFI_TVAL; + riscv_raise_exception(env, RISCV_EXCP_SW_CHECK, GETPC()); + } + + env->elp = NO_LP_EXPECTED; + } +} + #ifndef CONFIG_USER_ONLY target_ulong helper_sret(CPURISCVState *env) -- 2.44.0