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Fri, 14 Mar 2025 14:40:03 -0700 (PDT) From: Deepak Gupta Date: Fri, 14 Mar 2025 14:39:33 -0700 Subject: [PATCH v12 14/28] riscv: Implements arch agnostic indirect branch tracking prctls MIME-Version: 1.0 Message-Id: <20250314-v5_user_cfi_series-v12-14-e51202b53138@rivosinc.com> References: <20250314-v5_user_cfi_series-v12-0-e51202b53138@rivosinc.com> In-Reply-To: <20250314-v5_user_cfi_series-v12-0-e51202b53138@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 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, Deepak Gupta X-Mailer: b4 0.14.0 X-Stat-Signature: fkozr6jztfem9rj6z7cirhzsdzp5gdkb X-Rspamd-Queue-Id: D3833A000A X-Rspam-User: X-Rspamd-Server: rspam09 X-HE-Tag: 1741988404-681713 X-HE-Meta: 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 tRm679EV eLAz5YKt8ZGfNK7eA41UjaBJzbGZI9jz7E3uTWlGcEZ0I/yfpCc14TqbmWJnBeZzjm6KgeFnimizW30ZKTL6AfF70GvqiGhHGUa30WyCj5IiYnQc= 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 Signed-off-by: Deepak Gupta --- arch/riscv/include/asm/usercfi.h | 16 +++++++- arch/riscv/kernel/entry.S | 2 +- arch/riscv/kernel/process.c | 5 +++ arch/riscv/kernel/usercfi.c | 79 ++++++++++++++++++++++++++++++++++++++++ 4 files changed, 100 insertions(+), 2 deletions(-) diff --git a/arch/riscv/include/asm/usercfi.h b/arch/riscv/include/asm/usercfi.h index c4dcd256f19a..a8cec7c14d1d 100644 --- a/arch/riscv/include/asm/usercfi.h +++ b/arch/riscv/include/asm/usercfi.h @@ -16,7 +16,9 @@ struct kernel_clone_args; struct cfi_status { unsigned long ubcfi_en : 1; /* Enable for backward cfi. */ unsigned long ubcfi_locked : 1; - unsigned long rsvd : ((sizeof(unsigned long) * 8) - 2); + unsigned long ufcfi_en : 1; /* Enable for forward cfi. Note that ELP goes in sstatus */ + unsigned long ufcfi_locked : 1; + unsigned long rsvd : ((sizeof(unsigned long) * 8) - 4); 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 */ @@ -33,6 +35,10 @@ 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) @@ -58,6 +64,14 @@ void set_shstk_status(struct task_struct *task, bool enable); #define set_shstk_status(task, enable) +#define is_indir_lp_enabled(task) false + +#define is_indir_lp_locked(task) false + +#define set_indir_lp_status(task, enable) + +#define set_indir_lp_lock(task) + #endif /* CONFIG_RISCV_USER_CFI */ #endif /* __ASSEMBLY__ */ diff --git a/arch/riscv/kernel/entry.S b/arch/riscv/kernel/entry.S index 68c99124ea55..00494b54ff4a 100644 --- a/arch/riscv/kernel/entry.S +++ b/arch/riscv/kernel/entry.S @@ -143,7 +143,7 @@ SYM_CODE_START(handle_exception) * Disable the FPU/Vector to detect illegal usage of floating point * or vector in kernel space. */ - li t0, SR_SUM | SR_FS_VS + li t0, SR_SUM | SR_FS_VS | SR_ELP 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 cd11667593fe..4587201dd81d 100644 --- a/arch/riscv/kernel/process.c +++ b/arch/riscv/kernel/process.c @@ -160,6 +160,11 @@ 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 b93b324eed26..7937bcef9271 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 ? true : false; +} + +bool is_indir_lp_locked(struct task_struct *task) +{ + return task->thread_info.user_cfi_state.ufcfi_locked ? true : false; +} + +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 @@ -372,3 +401,53 @@ 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) ? true : false; + 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; +}