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Mon, 11 Nov 2024 12:54:37 -0800 (PST) From: Deepak Gupta Date: Mon, 11 Nov 2024 12:54:01 -0800 Subject: [PATCH v8 16/29] riscv: Implements arch agnostic indirect branch tracking prctls MIME-Version: 1.0 Message-Id: <20241111-v5_user_cfi_series-v8-16-dce14aa30207@rivosinc.com> References: <20241111-v5_user_cfi_series-v8-0-dce14aa30207@rivosinc.com> In-Reply-To: <20241111-v5_user_cfi_series-v8-0-dce14aa30207@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 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-Rspam-User: X-Rspamd-Queue-Id: A24EA40017 X-Rspamd-Server: rspam01 X-Stat-Signature: wbqthoe19hfsrpey47onwcnxydsup49w X-HE-Tag: 1731358421-799734 X-HE-Meta: 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 DS6iyTkG Di5DfgARUbvxUumObgYHgGrAB9qqxVH/X6JF3uy05wpyaeSUNSlHJmKRiXNvjw/LU+PTpUG/290yoH4uUPeKuJ+gZ2SbE9qnEQOq1LiICZf9b58xpyE6Xhf15jcKqd2/fpqykZsp+d4VCy36Q3+qcI51VbLe0XFP7tBIzJGpc8uFjyC7suP87HAeEnvlVik31q96PFdvbQnNkE0TkW/5/Qidbe7ep8j3wouu3r/3vZGHNDF5BSliMSUjTi+2wMstE+GBnjN9YLxb6zxubVocHoVXvxnLnt5BtFB1hlGWFe6sWyWsFu3Rb1OB5q6QUIyRVN6Wqp4mPNvpHifHGSkjC+caZCir2vfPiDT9vgTgKFiFEhlYgpCt9yPBttR+wN/lEnmIK1P9l4197/fRHhEFMfgvTmEFPT3AV+ry/XQHWEyA9JMll0E4OJgj9vYudA5EEOz2b9E4OLV9dKkuieIJlOwyr5A== 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. On trap entry, ELP state is recorded in sstatus image on stack and SR_ELP in CSR_STATUS is cleared. 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 | 76 ++++++++++++++++++++++++++++++++++++++++ 4 files changed, 97 insertions(+), 2 deletions(-) diff --git a/arch/riscv/include/asm/usercfi.h b/arch/riscv/include/asm/usercfi.h index 0b3aff008c85..19ee8e7e23ee 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 8f7f477517e3..a1f258fd7bbc 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 d75721b243af..226054db6c42 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 141ef70b08a3..c5fa90711089 100644 --- a/arch/riscv/kernel/usercfi.c +++ b/arch/riscv/kernel/usercfi.c @@ -69,6 +69,32 @@ 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) +{ + 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 +397,53 @@ 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; +}