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 <debug@xxxxxxxxxxxx>
---
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 52850a2c79cf..099204d0cd4a 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 f7dec532657f..5207f018415c 100644
--- a/arch/riscv/kernel/process.c
+++ b/arch/riscv/kernel/process.c
@@ -159,6 +159,11 @@ 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 c77abe552c88..8da509afdbe9 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_info.envcfg |= ENVCFG_LPE;
+ else
+ task->thread_info.envcfg &= ~ENVCFG_LPE;
+
+ csr_write(CSR_ENVCFG, task->thread_info.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))
+ return -EINVAL;
+
+ set_indir_lp_lock(task);
+
+ return 0;
+}
--
2.45.0
