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Mon, 13 Oct 2025 14:56:29 -0700 (PDT) From: Deepak Gupta Date: Mon, 13 Oct 2025 14:56:06 -0700 Subject: [PATCH v20 14/28] riscv: Implements arch agnostic indirect branch tracking prctls MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20251013-v5_user_cfi_series-v20-14-b9de4be9912e@rivosinc.com> References: <20251013-v5_user_cfi_series-v20-0-b9de4be9912e@rivosinc.com> In-Reply-To: <20251013-v5_user_cfi_series-v20-0-b9de4be9912e@rivosinc.com> To: Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , Andrew Morton , "Liam R. Howlett" , Vlastimil Babka , Lorenzo Stoakes , Paul Walmsley , Palmer Dabbelt , Albert Ou , Conor Dooley , Rob Herring , Krzysztof Kozlowski , Arnd Bergmann , Christian Brauner , Peter Zijlstra , Oleg Nesterov , Eric Biederman , Kees Cook , Jonathan Corbet , Shuah Khan , Jann Horn , Conor Dooley , Miguel Ojeda , Alex Gaynor , Boqun Feng , Gary Guo , =?utf-8?q?Bj=C3=B6rn_Roy_Baron?= , Andreas Hindborg , Alice Ryhl , Trevor Gross , Benno Lossin Cc: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-riscv@lists.infradead.org, devicetree@vger.kernel.org, linux-arch@vger.kernel.org, linux-doc@vger.kernel.org, linux-kselftest@vger.kernel.org, alistair.francis@wdc.com, richard.henderson@linaro.org, jim.shu@sifive.com, andybnac@gmail.com, kito.cheng@sifive.com, charlie@rivosinc.com, atishp@rivosinc.com, evan@rivosinc.com, cleger@rivosinc.com, alexghiti@rivosinc.com, samitolvanen@google.com, broonie@kernel.org, rick.p.edgecombe@intel.com, rust-for-linux@vger.kernel.org, Zong Li , Deepak Gupta X-Mailer: b4 0.13.0 X-Stat-Signature: wsm5w8o68ucyigraj9kywxzw8ggh9c4u X-Rspamd-Queue-Id: 8C41420008 X-Rspamd-Server: rspam06 X-Rspam-User: X-HE-Tag: 1760392591-581987 X-HE-Meta: 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 ZdB07EOS Kj+XFYDwSVTivWy6Sf8nTe63udJ3S/eDyHttCBEkS1rKxK3LxnO0eE7GWcLLFp27Irk0QAhZkAjgmNSwCNYychsPSMZ91T+ZbFhuJVKG8vFdr9U4mbgFn+K+zI+Ge2ZeSVoEDKnsY7od6DvL3daWk2XGjZ3yD0qmnqURM/pA61J889pW4s6woN1Gimo0SQIsAIvdDpoO3wUAOaOH79q+ktuqmW783tO92pi0F89jSGNwA+chAm4afD1ZHytfuuGi8/ouHl739VsAaLbFW+vNh6aJL6+T+3kyCzRRS3TAllctGTNwkfIRXKpA2MrvFA2+LRXQS3JtzwQGGqT3kFSuWWSX7nmCnCWJuGCMxSIQYC7INP74RsrcMntYjTl5BaEsirbGrYVe1fjSmqthk4e1tbAYJwIOarYpFEziaIChuP+lJUWVghbNQciWfjA== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: prctls implemented are: PR_SET_INDIR_BR_LP_STATUS, PR_GET_INDIR_BR_LP_STATUS and PR_LOCK_INDIR_BR_LP_STATUS Reviewed-by: Zong Li Signed-off-by: Deepak Gupta --- arch/riscv/include/asm/usercfi.h | 14 +++++++ arch/riscv/kernel/entry.S | 4 ++ arch/riscv/kernel/process.c | 5 +++ arch/riscv/kernel/usercfi.c | 79 ++++++++++++++++++++++++++++++++++++++++ 4 files changed, 102 insertions(+) diff --git a/arch/riscv/include/asm/usercfi.h b/arch/riscv/include/asm/usercfi.h index d71093f414df..4501d741a609 100644 --- a/arch/riscv/include/asm/usercfi.h +++ b/arch/riscv/include/asm/usercfi.h @@ -16,6 +16,8 @@ struct kernel_clone_args; struct cfi_state { unsigned long ubcfi_en : 1; /* Enable for backward cfi. */ unsigned long ubcfi_locked : 1; + unsigned long ufcfi_en : 1; /* Enable for forward cfi. Note that ELP goes in sstatus */ + unsigned long ufcfi_locked : 1; unsigned long user_shdw_stk; /* Current user shadow stack pointer */ unsigned long shdw_stk_base; /* Base address of shadow stack */ unsigned long shdw_stk_size; /* size of shadow stack */ @@ -32,6 +34,10 @@ bool is_shstk_locked(struct task_struct *task); bool is_shstk_allocated(struct task_struct *task); void set_shstk_lock(struct task_struct *task); void set_shstk_status(struct task_struct *task, bool enable); +bool is_indir_lp_enabled(struct task_struct *task); +bool is_indir_lp_locked(struct task_struct *task); +void set_indir_lp_status(struct task_struct *task, bool enable); +void set_indir_lp_lock(struct task_struct *task); #define PR_SHADOW_STACK_SUPPORTED_STATUS_MASK (PR_SHADOW_STACK_ENABLE) @@ -57,6 +63,14 @@ void set_shstk_status(struct task_struct *task, bool enable); #define set_shstk_status(task, enable) do {} while (0) +#define is_indir_lp_enabled(task) false + +#define is_indir_lp_locked(task) false + +#define set_indir_lp_status(task, enable) do {} while (0) + +#define set_indir_lp_lock(task) do {} while (0) + #endif /* CONFIG_RISCV_USER_CFI */ #endif /* __ASSEMBLER__ */ diff --git a/arch/riscv/kernel/entry.S b/arch/riscv/kernel/entry.S index 8410850953d6..036a6ca7641f 100644 --- a/arch/riscv/kernel/entry.S +++ b/arch/riscv/kernel/entry.S @@ -174,6 +174,10 @@ SYM_CODE_START(handle_exception) * or vector in kernel space. */ li t0, SR_SUM | SR_FS_VS +#ifdef CONFIG_64BIT + li t1, SR_ELP + or t0, t0, t1 +#endif REG_L s0, TASK_TI_USER_SP(tp) csrrc s1, CSR_STATUS, t0 diff --git a/arch/riscv/kernel/process.c b/arch/riscv/kernel/process.c index a137d3483646..49f527e3acfd 100644 --- a/arch/riscv/kernel/process.c +++ b/arch/riscv/kernel/process.c @@ -163,6 +163,11 @@ void start_thread(struct pt_regs *regs, unsigned long pc, set_shstk_status(current, false); set_shstk_base(current, 0, 0); set_active_shstk(current, 0); + /* + * disable indirect branch tracking on exec. + * libc will enable it later via prctl. + */ + set_indir_lp_status(current, false); #ifdef CONFIG_64BIT regs->status &= ~SR_UXL; diff --git a/arch/riscv/kernel/usercfi.c b/arch/riscv/kernel/usercfi.c index 08620bdae696..2ebe789caa6b 100644 --- a/arch/riscv/kernel/usercfi.c +++ b/arch/riscv/kernel/usercfi.c @@ -72,6 +72,35 @@ void set_shstk_lock(struct task_struct *task) task->thread_info.user_cfi_state.ubcfi_locked = 1; } +bool is_indir_lp_enabled(struct task_struct *task) +{ + return task->thread_info.user_cfi_state.ufcfi_en; +} + +bool is_indir_lp_locked(struct task_struct *task) +{ + return task->thread_info.user_cfi_state.ufcfi_locked; +} + +void set_indir_lp_status(struct task_struct *task, bool enable) +{ + if (!cpu_supports_indirect_br_lp_instr()) + return; + + task->thread_info.user_cfi_state.ufcfi_en = enable ? 1 : 0; + + if (enable) + task->thread.envcfg |= ENVCFG_LPE; + else + task->thread.envcfg &= ~ENVCFG_LPE; + + csr_write(CSR_ENVCFG, task->thread.envcfg); +} + +void set_indir_lp_lock(struct task_struct *task) +{ + task->thread_info.user_cfi_state.ufcfi_locked = 1; +} /* * If size is 0, then to be compatible with regular stack we want it to be as big as * regular stack. Else PAGE_ALIGN it and return back @@ -371,3 +400,53 @@ int arch_lock_shadow_stack_status(struct task_struct *task, return 0; } + +int arch_get_indir_br_lp_status(struct task_struct *t, unsigned long __user *status) +{ + unsigned long fcfi_status = 0; + + if (!cpu_supports_indirect_br_lp_instr()) + return -EINVAL; + + /* indirect branch tracking is enabled on the task or not */ + fcfi_status |= (is_indir_lp_enabled(t) ? PR_INDIR_BR_LP_ENABLE : 0); + + return copy_to_user(status, &fcfi_status, sizeof(fcfi_status)) ? -EFAULT : 0; +} + +int arch_set_indir_br_lp_status(struct task_struct *t, unsigned long status) +{ + bool enable_indir_lp = false; + + if (!cpu_supports_indirect_br_lp_instr()) + return -EINVAL; + + /* indirect branch tracking is locked and further can't be modified by user */ + if (is_indir_lp_locked(t)) + return -EINVAL; + + /* Reject unknown flags */ + if (status & ~PR_INDIR_BR_LP_ENABLE) + return -EINVAL; + + enable_indir_lp = (status & PR_INDIR_BR_LP_ENABLE); + set_indir_lp_status(t, enable_indir_lp); + + return 0; +} + +int arch_lock_indir_br_lp_status(struct task_struct *task, + unsigned long arg) +{ + /* + * If indirect branch tracking is not supported or not enabled on task, + * nothing to lock here + */ + if (!cpu_supports_indirect_br_lp_instr() || + !is_indir_lp_enabled(task) || arg != 0) + return -EINVAL; + + set_indir_lp_lock(task); + + return 0; +} -- 2.43.0