The compressed payload is not necesarily 4-byte aligned, at least when
compiling with Clang. In that case, the 4-byte value appended to the
compressed payload that corresponds to the uncompressed kernel image
size must be read using get_unaligned_le().
This fixes Clang-built kernels not booting on MIPS (tested on a Ingenic
JZ4770 board).
Fixes: b8f54f2cde78 ("MIPS: ZBOOT: copy appended dtb to the end of the kernel")
Cc: <[email protected]> # v4.7
Signed-off-by: Paul Cercueil <[email protected]>
---
arch/mips/boot/compressed/decompress.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/mips/boot/compressed/decompress.c b/arch/mips/boot/compressed/decompress.c
index c61c641674e6..47c07990432b 100644
--- a/arch/mips/boot/compressed/decompress.c
+++ b/arch/mips/boot/compressed/decompress.c
@@ -117,7 +117,7 @@ void decompress_kernel(unsigned long boot_heap_start)
dtb_size = fdt_totalsize((void *)&__appended_dtb);
/* last four bytes is always image size in little endian */
- image_size = le32_to_cpup((void *)&__image_end - 4);
+ image_size = get_unaligned_le32((void *)&__image_end - 4);
/* copy dtb to where the booted kernel will expect it */
memcpy((void *)VMLINUX_LOAD_ADDRESS_ULL + image_size,
--
2.29.2
On Wed, Dec 16, 2020 at 3:40 PM Paul Cercueil <[email protected]> wrote:
>
> The compressed payload is not necesarily 4-byte aligned, at least when
> compiling with Clang. In that case, the 4-byte value appended to the
> compressed payload that corresponds to the uncompressed kernel image
> size must be read using get_unaligned_le().
Should it be get_unaligned_le32()?
>
> This fixes Clang-built kernels not booting on MIPS (tested on a Ingenic
> JZ4770 board).
>
> Fixes: b8f54f2cde78 ("MIPS: ZBOOT: copy appended dtb to the end of the kernel")
> Cc: <[email protected]> # v4.7
> Signed-off-by: Paul Cercueil <[email protected]>
Hi Paul, thanks for the patch (and for testing with Clang)!
Alternatively, we could re-align __image_end to the next 4B multiple
via:
diff --git a/arch/mips/boot/compressed/ld.script
b/arch/mips/boot/compressed/ld.script
index 0ebb667274d6..349919eff5fb 100644
--- a/arch/mips/boot/compressed/ld.script
+++ b/arch/mips/boot/compressed/ld.script
@@ -27,6 +27,7 @@ SECTIONS
/* Put the compressed image here */
__image_begin = .;
*(.image)
+ . = ALIGN(4);
__image_end = .;
CONSTRUCTORS
. = ALIGN(16);
The tradeoff being up to 3 wasted bytes of padding in the compressed
image, vs fetching one value slower (assuming unaligned loads are
slower than aligned loads MIPS, IDK). I doubt decompress_kernel is
called repeatedly, so let's take the byte saving approach of yours by
using unaligned loads!
Reviewed-by: Nick Desaulniers <[email protected]>
> ---
> arch/mips/boot/compressed/decompress.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/mips/boot/compressed/decompress.c b/arch/mips/boot/compressed/decompress.c
> index c61c641674e6..47c07990432b 100644
> --- a/arch/mips/boot/compressed/decompress.c
> +++ b/arch/mips/boot/compressed/decompress.c
> @@ -117,7 +117,7 @@ void decompress_kernel(unsigned long boot_heap_start)
> dtb_size = fdt_totalsize((void *)&__appended_dtb);
>
> /* last four bytes is always image size in little endian */
> - image_size = le32_to_cpup((void *)&__image_end - 4);
> + image_size = get_unaligned_le32((void *)&__image_end - 4);
>
> /* copy dtb to where the booted kernel will expect it */
> memcpy((void *)VMLINUX_LOAD_ADDRESS_ULL + image_size,
> --
> 2.29.2
>
--
Thanks,
~Nick Desaulniers
Hi Nick,
Le mer. 16 d?c. 2020 ? 18:08, Nick Desaulniers
<[email protected]> a ?crit :
> On Wed, Dec 16, 2020 at 3:40 PM Paul Cercueil <[email protected]>
> wrote:
>>
>> The compressed payload is not necesarily 4-byte aligned, at least
>> when
>> compiling with Clang. In that case, the 4-byte value appended to the
>> compressed payload that corresponds to the uncompressed kernel image
>> size must be read using get_unaligned_le().
>
> Should it be get_unaligned_le32()?
Indeed.
>>
>> This fixes Clang-built kernels not booting on MIPS (tested on a
>> Ingenic
>> JZ4770 board).
>>
>> Fixes: b8f54f2cde78 ("MIPS: ZBOOT: copy appended dtb to the end of
>> the kernel")
>> Cc: <[email protected]> # v4.7
>> Signed-off-by: Paul Cercueil <[email protected]>
>
> Hi Paul, thanks for the patch (and for testing with Clang)!
> Alternatively, we could re-align __image_end to the next 4B multiple
> via:
>
> diff --git a/arch/mips/boot/compressed/ld.script
> b/arch/mips/boot/compressed/ld.script
> index 0ebb667274d6..349919eff5fb 100644
> --- a/arch/mips/boot/compressed/ld.script
> +++ b/arch/mips/boot/compressed/ld.script
> @@ -27,6 +27,7 @@ SECTIONS
> /* Put the compressed image here */
> __image_begin = .;
> *(.image)
> + . = ALIGN(4);
> __image_end = .;
> CONSTRUCTORS
> . = ALIGN(16);
Actually that would not work (I did try that), since the 4-byte size
appended to the compressed payload is inside the *(.image) section. The
code that appends it (in scripts/Makefile.lib, I think) doesn't seem to
take care about aligning it to a 4-byte offset. I have no idea why it
does with GCC and doesn't with Clang, and I have no idea why the
compressed payload's size isn't aligned either.
> The tradeoff being up to 3 wasted bytes of padding in the compressed
> image, vs fetching one value slower (assuming unaligned loads are
> slower than aligned loads MIPS, IDK). I doubt decompress_kernel is
> called repeatedly, so let's take the byte saving approach of yours by
> using unaligned loads!
>
> Reviewed-by: Nick Desaulniers <[email protected]>
Thanks.
Cheers,
-Paul
>> ---
>> arch/mips/boot/compressed/decompress.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/arch/mips/boot/compressed/decompress.c
>> b/arch/mips/boot/compressed/decompress.c
>> index c61c641674e6..47c07990432b 100644
>> --- a/arch/mips/boot/compressed/decompress.c
>> +++ b/arch/mips/boot/compressed/decompress.c
>> @@ -117,7 +117,7 @@ void decompress_kernel(unsigned long
>> boot_heap_start)
>> dtb_size = fdt_totalsize((void *)&__appended_dtb);
>>
>> /* last four bytes is always image size in little
>> endian */
>> - image_size = le32_to_cpup((void *)&__image_end - 4);
>> + image_size = get_unaligned_le32((void
>> *)&__image_end - 4);
>>
>> /* copy dtb to where the booted kernel will expect
>> it */
>> memcpy((void *)VMLINUX_LOAD_ADDRESS_ULL +
>> image_size,
>> --
>> 2.29.2
>>
>
>
> --
> Thanks,
> ~Nick Desaulniers
On Thu, Dec 17, 2020 at 12:41 AM Paul Cercueil <[email protected]> wrote:
>
> The compressed payload is not necesarily 4-byte aligned, at least when
> compiling with Clang. In that case, the 4-byte value appended to the
> compressed payload that corresponds to the uncompressed kernel image
> size must be read using get_unaligned_le().
>
> This fixes Clang-built kernels not booting on MIPS (tested on a Ingenic
> JZ4770 board).
>
> Fixes: b8f54f2cde78 ("MIPS: ZBOOT: copy appended dtb to the end of the kernel")
> Cc: <[email protected]> # v4.7
> Signed-off-by: Paul Cercueil <[email protected]>
> ---
> arch/mips/boot/compressed/decompress.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
Reviewed-by: Philippe Mathieu-Daudé <[email protected]>
On Wed, Dec 16, 2020 at 11:39:56PM +0000, Paul Cercueil wrote:
> The compressed payload is not necesarily 4-byte aligned, at least when
> compiling with Clang. In that case, the 4-byte value appended to the
> compressed payload that corresponds to the uncompressed kernel image
> size must be read using get_unaligned_le().
>
> This fixes Clang-built kernels not booting on MIPS (tested on a Ingenic
> JZ4770 board).
>
> Fixes: b8f54f2cde78 ("MIPS: ZBOOT: copy appended dtb to the end of the kernel")
> Cc: <[email protected]> # v4.7
> Signed-off-by: Paul Cercueil <[email protected]>
> ---
> arch/mips/boot/compressed/decompress.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/mips/boot/compressed/decompress.c b/arch/mips/boot/compressed/decompress.c
> index c61c641674e6..47c07990432b 100644
> --- a/arch/mips/boot/compressed/decompress.c
> +++ b/arch/mips/boot/compressed/decompress.c
> @@ -117,7 +117,7 @@ void decompress_kernel(unsigned long boot_heap_start)
> dtb_size = fdt_totalsize((void *)&__appended_dtb);
>
> /* last four bytes is always image size in little endian */
> - image_size = le32_to_cpup((void *)&__image_end - 4);
> + image_size = get_unaligned_le32((void *)&__image_end - 4);
gives me following error
arch/mips/boot/compressed/decompress.c:120:16: error: implicit declaration of function ‘get_unaligned_le32’ [-Werror=implicit-function-declaration]
image_size = get_unaligned_le32((void *)&__image_end - 4);
I've added
#include <asm/unaligned.h>
which fixes the compile error, but I'm wondering why the patch compiled
for you ?
Thomas.
--
Crap can work. Given enough thrust pigs will fly, but it's not necessarily a
good idea. [ RFC1925, 2.3 ]