arch: riscv: reset global pointer on exception

Reset the gp on exception entry from u-mode to protect the kernel against a possible rogue user thread. Signed-off-by: Yong Cong Sin <[email protected]> Signed-off-by: Yong Cong Sin <[email protected]>
zephyrproject-rtos · Nov 14, 2024 · e30db2d · e30db2d
1 parent de3a845
commit e30db2d
Showing 1 changed file with 8 additions and 0 deletions.
diff --git a/arch/riscv/core/isr.S b/arch/riscv/core/isr.S
@@ -163,6 +163,14 @@ SECTION_FUNC(exception.entry, _isr_wrapper)
 	lr t0, ___cpu_t_current_OFFSET(s0)
 	lr tp, _thread_offset_to_tls(t0)
 
+	/* Make sure global pointer is sane */
+#ifdef CONFIG_RISCV_GP
+	.option push
+	.option norelax
+	la gp, __global_pointer$
+	.option pop
+#endif /* CONFIG_RISCV_GP */
+
 	/* Clear our per-thread usermode flag */
 	lui t0, %tprel_hi(is_user_mode)
 	add t0, t0, tp, %tprel_add(is_user_mode)