diff mbox series

[v12,13/28] prctl: arch-agnostic prctl for indirect branch tracking

Message ID 20250314-v5_user_cfi_series-v12-13-e51202b53138@rivosinc.com (mailing list archive)
State New
Headers show
Series riscv control-flow integrity for usermode | expand

Commit Message

Deepak Gupta March 14, 2025, 9:39 p.m. UTC 
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`
arch64 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 <debug@rivosinc.com>
Reviewed-by: Mark Brown <broonie@kernel.org>
---
 include/linux/cpu.h        |  4 ++++
 include/uapi/linux/prctl.h | 27 +++++++++++++++++++++++++++
 kernel/sys.c               | 30 ++++++++++++++++++++++++++++++
 3 files changed, 61 insertions(+)

Comments

Zong Li March 17, 2025, 1:29 a.m. UTC | #1 
On Sat, Mar 15, 2025 at 6:51 AM Deepak Gupta <debug@rivosinc.com> wrote:
>
> 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`
> arch64 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 <debug@rivosinc.com>
> Reviewed-by: Mark Brown <broonie@kernel.org>
> ---
>  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 6a0a8f1c7c90..fb0c394430c6 100644
> --- a/include/linux/cpu.h
> +++ b/include/linux/cpu.h
> @@ -204,4 +204,8 @@ 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 5c6080680cb2..6cd90460cbad 100644
> --- a/include/uapi/linux/prctl.h
> +++ b/include/uapi/linux/prctl.h
> @@ -353,4 +353,31 @@ 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 cb366ff8703a..f347f3518d0b 100644
> --- a/kernel/sys.c
> +++ b/kernel/sys.c
> @@ -2336,6 +2336,21 @@ 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
> @@ -2811,6 +2826,21 @@ 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:
>                 trace_task_prctl_unknown(option, arg2, arg3, arg4, arg5);
>                 error = -EINVAL;
>

LGTM

Reviewed-by: Zong Li <zong.li@sifive.com>

> --
> 2.34.1
>
>
> _______________________________________________
> linux-riscv mailing list
> linux-riscv@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-riscv
diff mbox series

Patch

diff --git a/include/linux/cpu.h b/include/linux/cpu.h
index 6a0a8f1c7c90..fb0c394430c6 100644
--- a/include/linux/cpu.h
+++ b/include/linux/cpu.h
@@ -204,4 +204,8 @@  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 5c6080680cb2..6cd90460cbad 100644
--- a/include/uapi/linux/prctl.h
+++ b/include/uapi/linux/prctl.h
@@ -353,4 +353,31 @@  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 cb366ff8703a..f347f3518d0b 100644
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -2336,6 +2336,21 @@  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
@@ -2811,6 +2826,21 @@  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:
 		trace_task_prctl_unknown(option, arg2, arg3, arg4, arg5);
 		error = -EINVAL;