[PATCH v2] riscv/purgatory: align riscv_kernel_entry

[PATCH v2] riscv/purgatory: align riscv_kernel_entry

[Daniel Maslowski]

When alignment handling is delegated to the kernel, everything must be
word-aligned in purgatory, since the trap handler is then set to the
kexec one. Without the alignment, hitting the exception would
ultimately crash. On other occasions, the kernel's handler would take
care of exceptions.
This has been tested on a JH7110 SoC with oreboot and its SBI delegating
unaligned access exceptions and the kernel configured to handle them.

Fixes: 736e30af583fb6e0e2b8211b894ff99dea0f1ee7
Signed-off-by: Daniel Maslowski <cyrevolt@gmail.com>
---
 arch/riscv/purgatory/entry.S | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/riscv/purgatory/entry.S b/arch/riscv/purgatory/entry.S
index 5bcf3af903da..0e6ca6d5ae4b 100644
--- a/arch/riscv/purgatory/entry.S
+++ b/arch/riscv/purgatory/entry.S
@@ -7,6 +7,7 @@
  * Author: Li Zhengyu (lizhengyu3@huawei.com)
  *
  */
+#include <asm/asm.h>
 #include <linux/linkage.h>
 
 .text
@@ -34,6 +35,7 @@ SYM_CODE_END(purgatory_start)
 
 .data
 
+.align LGREG
 SYM_DATA(riscv_kernel_entry, .quad 0)
 
 .end
-- 
2.45.2


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Re: [PATCH v2] riscv/purgatory: align riscv_kernel_entry

[Jessica Clarke]

On 16 Jul 2024, at 21:40, Daniel Maslowski <cyrevolt@googlemail.com> wrote:
> 
> When alignment handling is delegated to the kernel, everything must be
> word-aligned in purgatory, since the trap handler is then set to the
> kexec one. Without the alignment, hitting the exception would
> ultimately crash. On other occasions, the kernel's handler would take
> care of exceptions.
> This has been tested on a JH7110 SoC with oreboot and its SBI delegating
> unaligned access exceptions and the kernel configured to handle them.
> 
> Fixes: 736e30af583fb6e0e2b8211b894ff99dea0f1ee7
> Signed-off-by: Daniel Maslowski <cyrevolt@gmail.com>
> ---
> arch/riscv/purgatory/entry.S | 2 ++
> 1 file changed, 2 insertions(+)
> 
> diff --git a/arch/riscv/purgatory/entry.S b/arch/riscv/purgatory/entry.S
> index 5bcf3af903da..0e6ca6d5ae4b 100644
> --- a/arch/riscv/purgatory/entry.S
> +++ b/arch/riscv/purgatory/entry.S
> @@ -7,6 +7,7 @@
>  * Author: Li Zhengyu (lizhengyu3@huawei.com)
>  *
>  */
> +#include <asm/asm.h>
> #include <linux/linkage.h>
> 
> .text
> @@ -34,6 +35,7 @@ SYM_CODE_END(purgatory_start)
> 
> .data
> 
> +.align LGREG
> SYM_DATA(riscv_kernel_entry, .quad 0)

It’s a bit weird to use LGREG for a .quad. The file is RV64-only
already, anyway.

Jess


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Re: [PATCH v2] riscv/purgatory: align riscv_kernel_entry

[Andreas Schwab]

On Jul 16 2024, Daniel Maslowski wrote:

> This has been tested on a JH7110 SoC with oreboot and its SBI delegating

coreboot?

-- 
Andreas Schwab, schwab@linux-m68k.org
GPG Key fingerprint = 7578 EB47 D4E5 4D69 2510  2552 DF73 E780 A9DA AEC1
"And now for something completely different."

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Re: [PATCH v2] riscv/purgatory: align riscv_kernel_entry

[Conor Dooley]

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On Tue, Jul 16, 2024 at 11:22:01PM +0200, Andreas Schwab wrote:
> On Jul 16 2024, Daniel Maslowski wrote:
> 
> > This has been tested on a JH7110 SoC with oreboot and its SBI delegating
> 
> coreboot?

oreboot is coreboot without the c :)

https://github.com/oreboot/oreboot

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Re: [PATCH v2] riscv/purgatory: align riscv_kernel_entry

[Geert Uytterhoeven]

Hi Conor,

On Tue, Jul 16, 2024 at 11:38 PM Conor Dooley <conor@kernel.org> wrote:
> On Tue, Jul 16, 2024 at 11:22:01PM +0200, Andreas Schwab wrote:
> > On Jul 16 2024, Daniel Maslowski wrote:
> >
> > > This has been tested on a JH7110 SoC with oreboot and its SBI delegating
> >
> > coreboot?
>
> oreboot is coreboot without the c :)

At first I thought this was just a joke about a typo...

> https://github.com/oreboot/oreboot

Given it's mainly written in Rust, perhaps it should have been called
roreboot? Or roarboot? ;-)

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds

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Re: [PATCH v2] riscv/purgatory: align riscv_kernel_entry

[Matthias Brugger]

On Tue, Jul 16, 2024 at 10:40:47PM +0200, Daniel Maslowski wrote:
> When alignment handling is delegated to the kernel, everything must be
> word-aligned in purgatory, since the trap handler is then set to the
> kexec one. Without the alignment, hitting the exception would
> ultimately crash. On other occasions, the kernel's handler would take
> care of exceptions.
> This has been tested on a JH7110 SoC with oreboot and its SBI delegating
> unaligned access exceptions and the kernel configured to handle them.
> 
> Fixes: 736e30af583fb6e0e2b8211b894ff99dea0f1ee7
Should be:

Fixes: 736e30af583fb ("RISC-V: Add purgatory")

Regards,
Matthias

> Signed-off-by: Daniel Maslowski <cyrevolt@gmail.com>
> ---
>  arch/riscv/purgatory/entry.S | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/arch/riscv/purgatory/entry.S b/arch/riscv/purgatory/entry.S
> index 5bcf3af903da..0e6ca6d5ae4b 100644
> --- a/arch/riscv/purgatory/entry.S
> +++ b/arch/riscv/purgatory/entry.S
> @@ -7,6 +7,7 @@
>   * Author: Li Zhengyu (lizhengyu3@huawei.com)
>   *
>   */
> +#include <asm/asm.h>
>  #include <linux/linkage.h>
>  
>  .text
> @@ -34,6 +35,7 @@ SYM_CODE_END(purgatory_start)
>  
>  .data
>  
> +.align LGREG
>  SYM_DATA(riscv_kernel_entry, .quad 0)
>  
>  .end
> -- 
> 2.45.2
> 
> 
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Re: [PATCH v2] riscv/purgatory: align riscv_kernel_entry

[Alexandre Ghiti]

Hi Daniel,

On 16/07/2024 22:40, Daniel Maslowski wrote:
> When alignment handling is delegated to the kernel, everything must be
> word-aligned in purgatory, since the trap handler is then set to the
> kexec one. Without the alignment, hitting the exception would
> ultimately crash. On other occasions, the kernel's handler would take
> care of exceptions.
> This has been tested on a JH7110 SoC with oreboot and its SBI delegating
> unaligned access exceptions and the kernel configured to handle them.
>
> Fixes: 736e30af583fb6e0e2b8211b894ff99dea0f1ee7
> Signed-off-by: Daniel Maslowski <cyrevolt@gmail.com>
> ---
>   arch/riscv/purgatory/entry.S | 2 ++
>   1 file changed, 2 insertions(+)
>
> diff --git a/arch/riscv/purgatory/entry.S b/arch/riscv/purgatory/entry.S
> index 5bcf3af903da..0e6ca6d5ae4b 100644
> --- a/arch/riscv/purgatory/entry.S
> +++ b/arch/riscv/purgatory/entry.S
> @@ -7,6 +7,7 @@
>    * Author: Li Zhengyu (lizhengyu3@huawei.com)
>    *
>    */
> +#include <asm/asm.h>
>   #include <linux/linkage.h>
>   
>   .text
> @@ -34,6 +35,7 @@ SYM_CODE_END(purgatory_start)
>   
>   .data
>   
> +.align LGREG
>   SYM_DATA(riscv_kernel_entry, .quad 0)
>   
>   .end


With the Fixes tag fixed like Matthias suggested, you can add:

Reviewed-by: Alexandre Ghiti <alexghiti@rivosinc.com>

Thanks,

Alex


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