Re: [PATCH fixes] riscv/purgatory: 4B align purgatory_start

From: Alexandre Ghiti
Date: Fri Mar 28 2025 - 08:54:31 EST


Hi Björn,

On 28/03/2025 09:53, Björn Töpel wrote:
From: Björn Töpel <bjorn@xxxxxxxxxxxx>

When a crashkernel is launched on RISC-V, the entry to purgatory is
done by trapping via the stvec CSR. From riscv_kexec_norelocate():

| ...
| /*
| * Switch to physical addressing
| * This will also trigger a jump to CSR_STVEC
| * which in this case is the address of the new
| * kernel.
| */
| csrw CSR_STVEC, a2
| csrw CSR_SATP, zero

stvec requires that the address is 4B aligned, which was not the case,
e.g.:

| Loaded purgatory at 0xffffc000
| kexec_file: kexec_file_load: type:1, start:0xffffd232 head:0x4 flags:0x6

The address 0xffffd232 not 4B aligned.

Correct by adding proper function alignment.

With this change, crashkernels loaded with kexec-file will be able to
properly enter the purgatory.

Fixes: 736e30af583fb ("RISC-V: Add purgatory")
Signed-off-by: Björn Töpel <bjorn@xxxxxxxxxxxx>
---
arch/riscv/purgatory/entry.S | 1 +
1 file changed, 1 insertion(+)

diff --git a/arch/riscv/purgatory/entry.S b/arch/riscv/purgatory/entry.S
index 0e6ca6d5ae4b..c5db2f072c34 100644
--- a/arch/riscv/purgatory/entry.S
+++ b/arch/riscv/purgatory/entry.S
@@ -12,6 +12,7 @@
.text
+.align 2
SYM_CODE_START(purgatory_start)
lla sp, .Lstack

base-commit: acb4f33713b9f6cadb6143f211714c343465411c


Reviewed-by: Alexandre Ghiti <alexghiti@xxxxxxxxxxxx>

Thanks,

Alex