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

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

[Björn Töpel]

From: Björn Töpel <bjorn@rivosinc.com>

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@rivosinc.com>
---
 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
-- 
2.45.2

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

[Alexandre Ghiti]

Hi Björn,

On 28/03/2025 09:53, Björn Töpel wrote:
> From: Björn Töpel <bjorn@rivosinc.com>
>
> 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@rivosinc.com>
> ---
>   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@rivosinc.com>

Thanks,

Alex

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

[patchwork-bot+linux-riscv]

Hello:

This patch was applied to riscv/linux.git (for-next)
by Alexandre Ghiti <alexghiti@rivosinc.com>:

On Fri, 28 Mar 2025 09:53:11 +0100 you wrote:
> From: Björn Töpel <bjorn@rivosinc.com>
> 
> 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
> 
> [...]

Here is the summary with links:
  - [fixes] riscv/purgatory: 4B align purgatory_start
    https://git.kernel.org/riscv/c/3f7023171df4

You are awesome, thank you!
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