[PATCH v1 RFC Zisslpcfi 16/20] riscv: Implements sslp prctls

Deepak Gupta
2023-02-13T04:55:07Z

New prctls are PR_GET_SHADOW_STACK_STATUS/PR_SET_SHADOW_STACK_STATUS and
PR_GET_INDIRECT_BR_LP_STATUS/PR_SET_INDIRECT_BR_LP_STATUS are implemented
on riscv in this patch.

Signed-off-by: Deepak Gupta <debug@rivosinc.com>
---
arch/riscv/include/asm/processor.h | 4 +-
arch/riscv/kernel/process.c | 88 +++++++++++++++++++++++++++++-
2 files changed, 90 insertions(+), 2 deletions(-)

diff --git a/arch/riscv/include/asm/processor.h b/arch/riscv/include/asm/processor.h
index 39c36f739ebb..c088584580b4 100644
--- a/arch/riscv/include/asm/processor.h
+++ b/arch/riscv/include/asm/processor.h
@@ -46,7 +46,9 @@ struct cfi_status {
unsigned int ufcfi_en : 1; /* Enable for forward cfi. Note that ELP goes in sstatus */
unsigned int ubcfi_en : 1; /* Enable for backward cfi. */
unsigned int audit_mode : 1;
- unsigned int rsvd1 : 29;
+ unsigned int ufcfi_locked : 1;
+ unsigned int ubcfi_locked : 1;
+ unsigned int rsvd1 : 27;
unsigned int lp_label; /* saved label value (25bit) */
long user_shdw_stk; /* Current user shadow stack pointer */
long shdw_stk_base; /* Base address of shadow stack */
diff --git a/arch/riscv/kernel/process.c b/arch/riscv/kernel/process.c
index bfd8511914d9..1218ed4fd29f 100644
--- a/arch/riscv/kernel/process.c
+++ b/arch/riscv/kernel/process.c
@@ -257,4 +257,90 @@ int arch_elf_setup_cfi_state(const struct arch_elf_state *state)

return ret;
}
-#endif
\ No newline at end of file
+#endif
+
+#ifdef CONFIG_USER_SHADOW_STACK
+int arch_get_shadow_stack_status(struct task_struct *t, unsigned long __user *status)
+{
+ unsigned long bcfi_status = 0;
+ struct thread_info *info = NULL;
+
+ if (!arch_supports_shadow_stack())
+ return -EINVAL;
+
+ info = current_thread_info();
+ bcfi_status |= info->user_cfi_state.ubcfi_locked ? (1UL << 0) : 0;
+ bcfi_status |= info->user_cfi_state.ubcfi_en ? ((1UL << 1) |
+ (info->user_cfi_state.user_shdw_stk)) : 0;
+
+ return copy_to_user(status, &bcfi_status, sizeof(bcfi_status)) ? -EFAULT : 0;
+}
+
+int arch_set_shadow_stack_status(struct task_struct *t, unsigned long __user *status)
+{
+ unsigned long bcfi_status = 0;
+ struct thread_info *info = NULL;
+ unsigned long shdw_stk = 0;
+
+ if (!arch_supports_shadow_stack())
+ return -EINVAL;
+
+ info = current_thread_info();
+ /* bcfi status is locked and further can't be modified by user */
+ if (info->user_cfi_state.ubcfi_locked)
+ return -EINVAL;
+
+ if (copy_from_user(&bcfi_status, status, sizeof(bcfi_status)))
+ return -EFAULT;
+ /* clear two least significant bits. Always assume min 4 byte alignment */
+ shdw_stk = (long) (bcfi_status & (~3));
+
+ if (shdw_stk >= TASK_SIZE)
+ return -EINVAL;
+
+ info->user_cfi_state.ubcfi_en = (bcfi_status & (1UL << 1)) ? 1 : 0;
+ info->user_cfi_state.ubcfi_locked = (bcfi_status & (1UL << 0)) ? 1 : 0;
+ info->user_cfi_state.user_shdw_stk = (long) shdw_stk;
+
+ return 0;
+}
+#endif
+
+#ifdef CONFIG_USER_INDIRECT_BR_LP
+int arch_get_indir_br_lp_status(struct task_struct *t, unsigned long __user *status)
+{
+ unsigned long fcfi_status = 0;
+ struct thread_info *info = NULL;
+
+ if (!arch_supports_indirect_br_lp_instr())
+ return -EINVAL;
+
+ info = current_thread_info();
+ fcfi_status |= info->user_cfi_state.ufcfi_locked ? (1UL << 0) : 0;
+ fcfi_status |= info->user_cfi_state.ufcfi_en ? (1UL << 1) : 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 __user *status)
+{
+ unsigned long fcfi_status = 0;
+ struct thread_info *info = NULL;
+
+ if (!arch_supports_indirect_br_lp_instr())
+ return -EINVAL;
+
+ info = current_thread_info();
+ /* bcfi status is locked and further can't be modified by user */
+ if (info->user_cfi_state.ufcfi_locked)
+ return -EINVAL;
+
+ if (copy_from_user(&fcfi_status, status, sizeof(fcfi_status)))
+ return -EFAULT;
+
+ info->user_cfi_state.ufcfi_en = (fcfi_status & (1UL << 1)) ? 1 : 0;
+ info->user_cfi_state.ufcfi_locked = (fcfi_status & (1UL << 0)) ? 1 : 0;
+
+ return 0;
+}
+#endif