[PATCH V3] riscv: set trap vector earlier

[yang.zhang]

From: "yang.zhang" <yang.zhang at hexintek.com>

The exception vector of the booting hart is not set before enabling
the mmu and then still points to the value of the previous firmware,
typically _start. That makes it hard to debug setup_vm() when bad
things happen. So fix that by setting the exception vector earlier.

Reviewed-by: Alexandre Ghiti <alexghiti at rivosinc.com>
Signed-off-by: yang.zhang <yang.zhang at hexintek.com>

---
V2 -> v3:
- Fix commit message

v1 -> v2:
- As Alex commented, remove the patch for supporting hugesize kernek image
- Add the omissive logic of set trap vector earlier
https://lore.kernel.org/lkml/20240506022239.6817-1-gaoshanliukou@163.com
---
 arch/riscv/kernel/head.S | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/riscv/kernel/head.S b/arch/riscv/kernel/head.S
index 4236a69c35cb..03dc440e643e 100644
--- a/arch/riscv/kernel/head.S
+++ b/arch/riscv/kernel/head.S
@@ -300,6 +300,9 @@ SYM_CODE_START(_start_kernel)
 #else
 	mv a0, a1
 #endif /* CONFIG_BUILTIN_DTB */
+	/* Set trap vector to spin forever to help debug */
+	la a3, .Lsecondary_park
+	csrw CSR_TVEC, a3
 	call setup_vm
 #ifdef CONFIG_MMU
 	la a0, early_pg_dir
-- 
2.25.1