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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-Server: rspam03 X-Rspam-User: X-Rspamd-Queue-Id: A9AD44000B X-Stat-Signature: tz7oma8smtazomxa8qzb6oti4iym6pz7 X-HE-Tag: 1727798869-296583 X-HE-Meta: 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 vLEzQxXf I1OPTgMpUo0iZucU25r51DJZZSsNBEW6zHgtRjat4F77HlioZUDmGPT4che27GADiN0Fhw5Uox7SYqZkD9T9VORAWFf60WT16XIHN0Af/bEPEXg9DwuxQv5suWwlZmS21/z3OAWaPlXonkOWulYwQH5eLWT7W/Pmi4eeUYv/Kk6vieenZLz3J53YmpI/RlH0bzz+ANUoZT7aTjZkM7tBy57qRQWH4dxeLpyP1hVBqFwnyGlptpxi/sW1t1VCdXr1A7o3lLvi94oSnNcgJ7bf6/4n0l9ILAYeW0AVjszziergx/IFbW8TmVcIDzv2GRMcoOM8ZOJZbI3gPXsIMIcSNtljyTCkz0EzNyrzRdVBKLPC46uVjdKOLW0c/LTvHi/YkgTV64H3J4sKfRWXAKpm6YywZd9LqQr5xvT+lD64zhuFqbsxxvNkETqG5UW3JM9G41vSMRdbPuFo/4ih/ov2Mrp4wyQ== 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 --- 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;