| Message ID | 20240807000652.1417776-7-debug@rivosinc.com |
|---|---|
| State | New |
| Headers | show |
| Series | riscv support for control flow integrity extensions | expand |
On 8/7/24 10:06, Deepak Gupta wrote: > diff --git a/target/riscv/cpu_helper.c b/target/riscv/cpu_helper.c > index 364f3ee212..c7af430f38 100644 > --- a/target/riscv/cpu_helper.c > +++ b/target/riscv/cpu_helper.c > @@ -134,6 +134,19 @@ void cpu_get_tb_cpu_state(CPURISCVState *env, vaddr *pc, > flags = FIELD_DP32(flags, TB_FLAGS, VILL, 1); > } > > + if (cpu_get_fcfien(env)) { > + /* > + * For Forward CFI, only the expectation of a lpcll at > + * the start of the block is tracked (which can only happen > + * when FCFI is enabled for the current processor mode). A jump > + * or call at the end of the previous TB will have updated > + * env->elp to indicate the expectation. > + */ > + flags = FIELD_DP32(flags, TB_FLAGS, FCFI_LP_EXPECTED, > + env->elp != NO_LP_EXPECTED); A good example why it's better to store this as bool in the first place. > static void riscv_tr_tb_start(DisasContextBase *db, CPUState *cpu) > { > + DisasContext *ctx = container_of(db, DisasContext, base); > + > + if (ctx->fcfi_lp_expected) { > + /* > + * Since we can't look ahead to confirm that the first > + * instruction is a legal landing pad instruction, emit > + * compare-and-branch sequence that will be fixed-up in > + * riscv_tr_tb_stop() to either statically hit or skip an > + * illegal instruction exception depending on whether the > + * flag was lowered by translation of a CJLP or JLP as > + * the first instruction in the block. > + */ > + TCGv_i32 immediate; > + TCGLabel *l; > + l = gen_new_label(); > + immediate = tcg_temp_new_i32(); > + tcg_gen_movi_i32(immediate, 0); > + cfi_lp_check = tcg_last_op(); > + tcg_gen_brcondi_i32(TCG_COND_EQ, immediate, 0, l); > + gen_helper_raise_sw_check_excep(tcg_env, > + tcg_constant_tl(RISCV_EXCP_SW_CHECK_FCFI_TVAL), > + tcg_constant_tl(MISSING_LPAD), tcg_constant_tl(0)); > + gen_set_label(l); > + /* > + * Despite the use of gen_exception_illegal(), the rest of > + * the TB needs to be generated. The TCG optimizer will > + * clean things up depending on which path ends up being > + * active. > + */ > + ctx->base.is_jmp = DISAS_NEXT; > + } > } Again, don't do this here. There is a reason why only DISAS_NEXT is legal: plugins. You *must* do this in riscv_tr_translate_insn, like ARM. r~
On Wed, Aug 07, 2024 at 11:23:00AM +1000, Richard Henderson wrote: >On 8/7/24 10:06, Deepak Gupta wrote: >>diff --git a/target/riscv/cpu_helper.c b/target/riscv/cpu_helper.c >>index 364f3ee212..c7af430f38 100644 >>--- a/target/riscv/cpu_helper.c >>+++ b/target/riscv/cpu_helper.c >>@@ -134,6 +134,19 @@ void cpu_get_tb_cpu_state(CPURISCVState *env, vaddr *pc, >> flags = FIELD_DP32(flags, TB_FLAGS, VILL, 1); >> } >>+ if (cpu_get_fcfien(env)) { >>+ /* >>+ * For Forward CFI, only the expectation of a lpcll at >>+ * the start of the block is tracked (which can only happen >>+ * when FCFI is enabled for the current processor mode). A jump >>+ * or call at the end of the previous TB will have updated >>+ * env->elp to indicate the expectation. >>+ */ >>+ flags = FIELD_DP32(flags, TB_FLAGS, FCFI_LP_EXPECTED, >>+ env->elp != NO_LP_EXPECTED); > >A good example why it's better to store this as bool in the first place. > >> static void riscv_tr_tb_start(DisasContextBase *db, CPUState *cpu) >> { >>+ DisasContext *ctx = container_of(db, DisasContext, base); >>+ >>+ if (ctx->fcfi_lp_expected) { >>+ /* >>+ * Since we can't look ahead to confirm that the first >>+ * instruction is a legal landing pad instruction, emit >>+ * compare-and-branch sequence that will be fixed-up in >>+ * riscv_tr_tb_stop() to either statically hit or skip an >>+ * illegal instruction exception depending on whether the >>+ * flag was lowered by translation of a CJLP or JLP as >>+ * the first instruction in the block. >>+ */ >>+ TCGv_i32 immediate; >>+ TCGLabel *l; >>+ l = gen_new_label(); >>+ immediate = tcg_temp_new_i32(); >>+ tcg_gen_movi_i32(immediate, 0); >>+ cfi_lp_check = tcg_last_op(); >>+ tcg_gen_brcondi_i32(TCG_COND_EQ, immediate, 0, l); >>+ gen_helper_raise_sw_check_excep(tcg_env, >>+ tcg_constant_tl(RISCV_EXCP_SW_CHECK_FCFI_TVAL), >>+ tcg_constant_tl(MISSING_LPAD), tcg_constant_tl(0)); >>+ gen_set_label(l); >>+ /* >>+ * Despite the use of gen_exception_illegal(), the rest of >>+ * the TB needs to be generated. The TCG optimizer will >>+ * clean things up depending on which path ends up being >>+ * active. >>+ */ >>+ ctx->base.is_jmp = DISAS_NEXT; >>+ } >> } > >Again, don't do this here. >There is a reason why only DISAS_NEXT is legal: plugins. >You *must* do this in riscv_tr_translate_insn, like ARM. Sorry missed this. I remember you gave same feedack in last version. > > >r~
diff --git a/target/riscv/cpu.h b/target/riscv/cpu.h index 12334f9540..b77481428f 100644 --- a/target/riscv/cpu.h +++ b/target/riscv/cpu.h @@ -606,6 +606,9 @@ FIELD(TB_FLAGS, ITRIGGER, 22, 1) FIELD(TB_FLAGS, VIRT_ENABLED, 23, 1) FIELD(TB_FLAGS, PRIV, 24, 2) FIELD(TB_FLAGS, AXL, 26, 2) +/* zicfilp needs a TB flag to track indirect branches */ +FIELD(TB_FLAGS, FCFI_ENABLED, 28, 1) +FIELD(TB_FLAGS, FCFI_LP_EXPECTED, 29, 1) #ifdef TARGET_RISCV32 #define riscv_cpu_mxl(env) ((void)(env), MXL_RV32) diff --git a/target/riscv/cpu_bits.h b/target/riscv/cpu_bits.h index 127f2179dc..1709564b32 100644 --- a/target/riscv/cpu_bits.h +++ b/target/riscv/cpu_bits.h @@ -590,6 +590,10 @@ typedef enum { LP_EXPECTED = 1, } cfi_elp; +typedef enum { + MISSING_LPAD = 0, +} cfi_violation_cause; + /* hstatus CSR bits */ #define HSTATUS_VSBE 0x00000020 #define HSTATUS_GVA 0x00000040 @@ -691,6 +695,9 @@ typedef enum RISCVException { RISCV_EXCP_SEMIHOST = 0x3f, } RISCVException; +/* zicfilp defines lp violation results in sw check with tval = 2*/ +#define RISCV_EXCP_SW_CHECK_FCFI_TVAL 2 + #define RISCV_EXCP_INT_FLAG 0x80000000 #define RISCV_EXCP_INT_MASK 0x7fffffff diff --git a/target/riscv/cpu_helper.c b/target/riscv/cpu_helper.c index 364f3ee212..c7af430f38 100644 --- a/target/riscv/cpu_helper.c +++ b/target/riscv/cpu_helper.c @@ -134,6 +134,19 @@ void cpu_get_tb_cpu_state(CPURISCVState *env, vaddr *pc, flags = FIELD_DP32(flags, TB_FLAGS, VILL, 1); } + if (cpu_get_fcfien(env)) { + /* + * For Forward CFI, only the expectation of a lpcll at + * the start of the block is tracked (which can only happen + * when FCFI is enabled for the current processor mode). A jump + * or call at the end of the previous TB will have updated + * env->elp to indicate the expectation. + */ + flags = FIELD_DP32(flags, TB_FLAGS, FCFI_LP_EXPECTED, + env->elp != NO_LP_EXPECTED); + flags = FIELD_DP32(flags, TB_FLAGS, FCFI_ENABLED, 1); + } + #ifdef CONFIG_USER_ONLY fs = EXT_STATUS_DIRTY; vs = EXT_STATUS_DIRTY; diff --git a/target/riscv/helper.h b/target/riscv/helper.h index 451261ce5a..fc4c41db5e 100644 --- a/target/riscv/helper.h +++ b/target/riscv/helper.h @@ -121,6 +121,9 @@ 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) +/* helper for raising sw check exception */ +DEF_HELPER_4(raise_sw_check_excep, void, env, tl, tl, tl) + /* Special functions */ DEF_HELPER_2(csrr, tl, env, int) DEF_HELPER_3(csrw, void, env, int, tl) diff --git a/target/riscv/op_helper.c b/target/riscv/op_helper.c index 488116cc2e..3b47fb34ea 100644 --- a/target/riscv/op_helper.c +++ b/target/riscv/op_helper.c @@ -259,6 +259,13 @@ void helper_cbo_inval(CPURISCVState *env, target_ulong address) /* We don't emulate the cache-hierarchy, so we're done. */ } +void helper_raise_sw_check_excep(CPURISCVState *env, target_ulong swcheck_code, + target_ulong arg1, target_ulong arg2) +{ + env->sw_check_code = swcheck_code; + riscv_raise_exception(env, RISCV_EXCP_SW_CHECK, GETPC()); +} + #ifndef CONFIG_USER_ONLY target_ulong helper_sret(CPURISCVState *env) diff --git a/target/riscv/translate.c b/target/riscv/translate.c index acba90f170..fbca3b8a06 100644 --- a/target/riscv/translate.c +++ b/target/riscv/translate.c @@ -44,6 +44,7 @@ static TCGv load_val; /* globals for PM CSRs */ static TCGv pm_mask; static TCGv pm_base; +static TCGOp *cfi_lp_check; /* * If an operation is being performed on less than TARGET_LONG_BITS, @@ -116,6 +117,9 @@ typedef struct DisasContext { bool frm_valid; bool insn_start_updated; const GPtrArray *decoders; + /* zicfilp extension. fcfi_enabled, lp expected or not */ + bool fcfi_enabled; + bool fcfi_lp_expected; } DisasContext; static inline bool has_ext(DisasContext *ctx, uint32_t ext) @@ -1238,6 +1242,8 @@ static void riscv_tr_init_disas_context(DisasContextBase *dcbase, CPUState *cs) ctx->pm_base_enabled = FIELD_EX32(tb_flags, TB_FLAGS, PM_BASE_ENABLED); ctx->ztso = cpu->cfg.ext_ztso; ctx->itrigger = FIELD_EX32(tb_flags, TB_FLAGS, ITRIGGER); + ctx->fcfi_lp_expected = FIELD_EX32(tb_flags, TB_FLAGS, FCFI_LP_EXPECTED); + ctx->fcfi_enabled = FIELD_EX32(tb_flags, TB_FLAGS, FCFI_ENABLED); ctx->zero = tcg_constant_tl(0); ctx->virt_inst_excp = false; ctx->decoders = cpu->decoders; @@ -1245,6 +1251,37 @@ static void riscv_tr_init_disas_context(DisasContextBase *dcbase, CPUState *cs) static void riscv_tr_tb_start(DisasContextBase *db, CPUState *cpu) { + DisasContext *ctx = container_of(db, DisasContext, base); + + if (ctx->fcfi_lp_expected) { + /* + * Since we can't look ahead to confirm that the first + * instruction is a legal landing pad instruction, emit + * compare-and-branch sequence that will be fixed-up in + * riscv_tr_tb_stop() to either statically hit or skip an + * illegal instruction exception depending on whether the + * flag was lowered by translation of a CJLP or JLP as + * the first instruction in the block. + */ + TCGv_i32 immediate; + TCGLabel *l; + l = gen_new_label(); + immediate = tcg_temp_new_i32(); + tcg_gen_movi_i32(immediate, 0); + cfi_lp_check = tcg_last_op(); + tcg_gen_brcondi_i32(TCG_COND_EQ, immediate, 0, l); + gen_helper_raise_sw_check_excep(tcg_env, + tcg_constant_tl(RISCV_EXCP_SW_CHECK_FCFI_TVAL), + tcg_constant_tl(MISSING_LPAD), tcg_constant_tl(0)); + gen_set_label(l); + /* + * Despite the use of gen_exception_illegal(), the rest of + * the TB needs to be generated. The TCG optimizer will + * clean things up depending on which path ends up being + * active. + */ + ctx->base.is_jmp = DISAS_NEXT; + } } static void riscv_tr_insn_start(DisasContextBase *dcbase, CPUState *cpu) @@ -1303,6 +1340,14 @@ static void riscv_tr_tb_stop(DisasContextBase *dcbase, CPUState *cpu) default: g_assert_not_reached(); } + + if (ctx->fcfi_lp_expected) { + /* + * If the "lp expected" flag is still up, the block needs to take an + * illegal instruction exception. + */ + tcg_set_insn_param(cfi_lp_check, 1, tcgv_i32_arg(tcg_constant_i32(1))); + } } static const TranslatorOps riscv_tr_ops = {
zicfilp protects forward control flow (if enabled) by enforcing all indirect call and jmp must land on a landing pad instruction `lpad`. If target of an indirect call or jmp is not `lpad` then cpu/hart must raise a sw check exception with tval = 2. This patch implements the mechanism using TCG. Target architecture branch instruction must define the end of a TB. Using this property, during translation of branch instruction, TB flag = FCFI_LP_EXPECTED can be set. Translation of target TB can check if FCFI_LP_EXPECTED flag is set and a flag (fcfi_lp_expected) can be set in DisasContext. If `lpad` gets translated, fcfi_lp_expected flag in DisasContext can be cleared. Else it'll fault. 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> --- target/riscv/cpu.h | 3 +++ target/riscv/cpu_bits.h | 7 ++++++ target/riscv/cpu_helper.c | 13 +++++++++++ target/riscv/helper.h | 3 +++ target/riscv/op_helper.c | 7 ++++++ target/riscv/translate.c | 45 +++++++++++++++++++++++++++++++++++++++ 6 files changed, 78 insertions(+)