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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-Rspamd-Queue-Id: 15C4EA001A X-Stat-Signature: uccismq5hf1hdddh9jqutjws9ypfmx88 X-Rspamd-Server: rspam09 X-Rspam-User: X-HE-Tag: 1730245483-487854 X-HE-Meta: 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 JBtwvGva /rsLlpEArHH8ohV4D9TCWb5l2bPghZzohP7MRUxl6gIKbVDj9BoA9fX/fV6m3tS3/TV6VxzWGJLKLStKnXxH7QRcDmpckajQC5pYGgbtaJREoM/Yu/IOaEhPO8iWbjMh6XECEfFp3BhGO1kO1QazgKXv2c0uQ0ypsinM968zJmcZgDnw3XYgulvICTou6y5S6ZJWBjZhWGu6Cjd3Cfn9LY1E4gD+Ew37tOOrKyZrd2pIfsts1iUYMWCzqXHEPYRTZyNAs5tvegTSWyVxSfmpw1OoJSo7OAtGLF/RdFKgbJlQwE4I3ZL45WR3Rc1McBz7h9LKmh5thUbHlSTH/GpUFy6IZEUXpdKcZDFvMsEMx1jaO19QpN4itFwbd8I9cQI8nPNkgZTfTQC3qvUwfPjOLyuhlaNCq/mWMxyh0QLHSzP6QkY7g6CC75cJJCxJQJvr/d6Das80RE2my94VJtiFqRos/k5doUeZyAt5ppyEuT0ZifXA= 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: Three architectures (x86, aarch64, riscv) have support for indirect branch tracking feature in a very similar fashion. On a very high level, indirect branch tracking is a CPU feature where CPU tracks branches which uses memory operand to perform control transfer in program. As part of this tracking on indirect branches, CPU goes in a state where it expects a landing pad instr on target and if not found then CPU raises some fault (architecture dependent) x86 landing pad instr - `ENDBRANCH` aarch64 landing pad instr - `BTI` riscv landing instr - `lpad` Given that three major arches have support for indirect branch tracking, This patch makes `prctl` for indirect branch tracking arch agnostic. To allow userspace to enable this feature for itself, following prtcls are defined: - PR_GET_INDIR_BR_LP_STATUS: Gets current configured status for indirect branch tracking. - PR_SET_INDIR_BR_LP_STATUS: Sets a configuration for indirect branch tracking. Following status options are allowed - PR_INDIR_BR_LP_ENABLE: Enables indirect branch tracking on user thread. - PR_INDIR_BR_LP_DISABLE; Disables indirect branch tracking on user thread. - PR_LOCK_INDIR_BR_LP_STATUS: Locks configured status for indirect branch tracking for user thread. Signed-off-by: Deepak Gupta Reviewed-by: Mark Brown --- include/linux/cpu.h | 4 ++++ include/uapi/linux/prctl.h | 27 +++++++++++++++++++++++++++ kernel/sys.c | 30 ++++++++++++++++++++++++++++++ 3 files changed, 61 insertions(+) diff --git a/include/linux/cpu.h b/include/linux/cpu.h index bdcec1732445..eff56aae05d7 100644 --- a/include/linux/cpu.h +++ b/include/linux/cpu.h @@ -203,4 +203,8 @@ static inline bool cpu_mitigations_auto_nosmt(void) } #endif +int arch_get_indir_br_lp_status(struct task_struct *t, unsigned long __user *status); +int arch_set_indir_br_lp_status(struct task_struct *t, unsigned long status); +int arch_lock_indir_br_lp_status(struct task_struct *t, unsigned long status); + #endif /* _LINUX_CPU_H_ */ diff --git a/include/uapi/linux/prctl.h b/include/uapi/linux/prctl.h index b8d7b6361754..41ffb53490a4 100644 --- a/include/uapi/linux/prctl.h +++ b/include/uapi/linux/prctl.h @@ -349,4 +349,31 @@ struct prctl_mm_map { */ #define PR_LOCK_SHADOW_STACK_STATUS 76 +/* + * Get the current indirect branch tracking configuration for the current + * thread, this will be the value configured via PR_SET_INDIR_BR_LP_STATUS. + */ +#define PR_GET_INDIR_BR_LP_STATUS 77 + +/* + * Set the indirect branch tracking configuration. PR_INDIR_BR_LP_ENABLE will + * enable cpu feature for user thread, to track all indirect branches and ensure + * they land on arch defined landing pad instruction. + * x86 - If enabled, an indirect branch must land on `ENDBRANCH` instruction. + * arch64 - If enabled, an indirect branch must land on `BTI` instruction. + * riscv - If enabled, an indirect branch must land on `lpad` instruction. + * PR_INDIR_BR_LP_DISABLE will disable feature for user thread and indirect + * branches will no more be tracked by cpu to land on arch defined landing pad + * instruction. + */ +#define PR_SET_INDIR_BR_LP_STATUS 78 +# define PR_INDIR_BR_LP_ENABLE (1UL << 0) + +/* + * Prevent further changes to the specified indirect branch tracking + * configuration. All bits may be locked via this call, including + * undefined bits. + */ +#define PR_LOCK_INDIR_BR_LP_STATUS 79 + #endif /* _LINUX_PRCTL_H */ diff --git a/kernel/sys.c b/kernel/sys.c index 3d38a9c7c5c9..dafa31485584 100644 --- a/kernel/sys.c +++ b/kernel/sys.c @@ -2339,6 +2339,21 @@ int __weak arch_lock_shadow_stack_status(struct task_struct *t, unsigned long st return -EINVAL; } +int __weak arch_get_indir_br_lp_status(struct task_struct *t, unsigned long __user *status) +{ + return -EINVAL; +} + +int __weak arch_set_indir_br_lp_status(struct task_struct *t, unsigned long status) +{ + return -EINVAL; +} + +int __weak arch_lock_indir_br_lp_status(struct task_struct *t, unsigned long status) +{ + return -EINVAL; +} + #define PR_IO_FLUSHER (PF_MEMALLOC_NOIO | PF_LOCAL_THROTTLE) #ifdef CONFIG_ANON_VMA_NAME @@ -2814,6 +2829,21 @@ SYSCALL_DEFINE5(prctl, int, option, unsigned long, arg2, unsigned long, arg3, return -EINVAL; error = arch_lock_shadow_stack_status(me, arg2); break; + case PR_GET_INDIR_BR_LP_STATUS: + if (arg3 || arg4 || arg5) + return -EINVAL; + error = arch_get_indir_br_lp_status(me, (unsigned long __user *) arg2); + break; + case PR_SET_INDIR_BR_LP_STATUS: + if (arg3 || arg4 || arg5) + return -EINVAL; + error = arch_set_indir_br_lp_status(me, arg2); + break; + case PR_LOCK_INDIR_BR_LP_STATUS: + if (arg3 || arg4 || arg5) + return -EINVAL; + error = arch_lock_indir_br_lp_status(me, arg2); + break; default: error = -EINVAL; break;