This series try to address a long lasting problem with legacy device
that require an appended DTB and the use of AUTO_ZRELADDR.
With these device AUTO_ZRELADDR is not possible if for some reason at
the start of the RAM it's needed to reserve some space. (example qcom SoC
that allocate reserved space for SMEM)
In the current implementation with appended DTB and AUTO_ZRELADDR,
the memory start is only derived from the PC register and it can't be
changed by declaring additional info in the DTS.
In a normal setup, we have an intentional undocumented chosen property
to handle this and the memory node to declare the start of the memory.
With this applied and ARM_ATAG_DTB_COMPAT_IGNORE_MEM enabled (more
info in the related patch) ipq806x can boot right away with AUTO_ZRELADDR
enabled and a correct memory node defined in DTS.
It's needed to ignore MEM ATAGs as most of the time the values from the
bootloader are hardcoded and OEM didn't care to actually provide them
resulting in funny situation where a Netgear R7800 with 512Mb of RAM
have Uboot passing 1.7GB of RAM with ATAGS.
While MEM ATAG may be broken, other ATAG like serial number or bootargs
might still be useful for partition declaration (cmdlinepart) or other
info hence DTB_COMPAT is still needed in these case and can't be
disabled.
I'm open to any suggestion on how this can be improved and I would love
some additional testing on other legacy platform but I assume this will
permit many legacy device to be correctly supported without having to
hardcode address.
Changes v2:
- Add Review and Ack Tags
- Use IS_ENABLED instead of global variable
Christian Marangi (2):
ARM: decompressor: support memory start validation for appended DTB
ARM: decompressor: add option to ignore MEM ATAGs
arch/arm/Kconfig | 12 ++++++++++++
arch/arm/boot/compressed/atags_to_fdt.c | 4 ++++
arch/arm/boot/compressed/head.S | 22 ++++++++++++++++++++++
3 files changed, 38 insertions(+)
--
2.43.0
There is currently a problem with a very specific sets of kernel config
and AUTO_ZRELADDR.
For the most common case AUTO_ZRELADDR check the PC register and
calculate the start of the physical memory. Then fdt_check_mem_start is
called to make sure the detected value makes sense by comparing it with
what is present in DTB in the memory nodes and if additional fixup are
required with the use of linux,usable-memory-range in the chosen node to
hardcode usable memory range in case some reserved space needs to be
addressed. With the help of this function the right address is
calculated and the kernel correctly decompress and loads.
Things starts to become problematic when in the mix,
CONFIG_ARM_APPENDED_DTB is used. This is a particular kernel config is
used when legacy systems doesn't support passing a DTB directly and a
DTB is appended at the end of the image.
In such case, fdt_check_mem_start is skipped in AUTO_ZRELADDR iteration
as the appended DTB can be augumented later with ATAGS passed from the
bootloader (if CONFIG_ARM_ATAG_DTB_COMPAT is enabled).
The main problem and what this patch address is the fact that
fdt_check_mem_start is never called later when the appended DTB is
augumented, hence any fixup and validation is not done making AUTO_ZRELADDR
detection inconsistent and most of the time wrong.
Add support in head.S for this by checking if AUTO_ZRELADDR is enabled
and calling fdt_check_mem_start with the appended DTB and the augumented
values permitting legacy device to provide info in DTB instead of
disabling AUTO_ZRELADDR and hardcoding the physical address offsets.
Signed-off-by: Christian Marangi <[email protected]>
Reviewed-by: Geert Uytterhoeven <[email protected]>
Reviewed-by: Linus Walleij <[email protected]>
---
arch/arm/boot/compressed/head.S | 22 ++++++++++++++++++++++
1 file changed, 22 insertions(+)
diff --git a/arch/arm/boot/compressed/head.S b/arch/arm/boot/compressed/head.S
index 9f406e9c0ea6..2ff38a8df1f0 100644
--- a/arch/arm/boot/compressed/head.S
+++ b/arch/arm/boot/compressed/head.S
@@ -443,6 +443,28 @@ restart: adr r0, LC1
add r6, r6, r5
add r10, r10, r5
add sp, sp, r5
+
+#ifdef CONFIG_AUTO_ZRELADDR
+ /*
+ * Validate calculated start of physical memory with appended DTB.
+ * In the first iteration for physical memory start calculation,
+ * we skipped validating it as it could have been augumented by
+ * ATAGs stored at an offset from the same start of physical memory.
+ *
+ * We now have parsed them and augumented the appended DTB if asked
+ * so we can finally validate the start of physical memory.
+ *
+ * This is needed to apply additional fixup with
+ * linux,usable-memory-range or to make sure AUTO_ZRELADDR detected
+ * the correct value.
+ */
+ sub r0, r4, #TEXT_OFFSET @ revert to base address
+ mov r1, r8 @ use appended DTB
+ bl fdt_check_mem_start
+
+ /* Determine final kernel image address. */
+ add r4, r0, #TEXT_OFFSET
+#endif
dtb_check_done:
#endif
--
2.43.0
Some bootloaders can pass broken MEM ATAGs that provide hardcoded
information about mounted RAM size and physical location.
Example booloader provide RAM of size 1.7Gb but actual mounted RAM
size is 512Mb causing kernel panic.
Add option CONFIG_ARM_ATAG_DTB_COMPAT_IGNORE_MEM to ignore these ATAG
and not augument appended DTB memory node.
Signed-off-by: Christian Marangi <[email protected]>
Acked-by: Linus Walleij <[email protected]>
---
arch/arm/Kconfig | 12 ++++++++++++
arch/arm/boot/compressed/atags_to_fdt.c | 4 ++++
2 files changed, 16 insertions(+)
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index b2ab8db63c4b..6bb5c6b28106 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -1549,6 +1549,18 @@ config ARM_ATAG_DTB_COMPAT
bootloaders, this option allows zImage to extract the information
from the ATAG list and store it at run time into the appended DTB.
+config ARM_ATAG_DTB_COMPAT_IGNORE_MEM
+ bool "Ignore MEM ATAG information from bootloader"
+ depends on ARM_ATAG_DTB_COMPAT
+ help
+ Some bootloaders can pass broken MEM ATAGs that provide hardcoded
+ information about mounted RAM size and physical location.
+ Example booloader provide RAM of size 1.7Gb but actual mounted RAM
+ size is 512Mb causing kernel panic.
+
+ Enable this option if MEM ATAGs should be ignored and the memory
+ node in the appended DTB should NOT be augumented.
+
choice
prompt "Kernel command line type" if ARM_ATAG_DTB_COMPAT
default ARM_ATAG_DTB_COMPAT_CMDLINE_FROM_BOOTLOADER
diff --git a/arch/arm/boot/compressed/atags_to_fdt.c b/arch/arm/boot/compressed/atags_to_fdt.c
index 627752f18661..b5bce4dad321 100644
--- a/arch/arm/boot/compressed/atags_to_fdt.c
+++ b/arch/arm/boot/compressed/atags_to_fdt.c
@@ -170,6 +170,10 @@ int atags_to_fdt(void *atag_list, void *fdt, int total_space)
setprop_string(fdt, "/chosen", "bootargs",
atag->u.cmdline.cmdline);
} else if (atag->hdr.tag == ATAG_MEM) {
+ /* Bootloader MEM ATAG are broken and should be ignored */
+ if (IS_ENABLED(CONFIG_ARM_ATAG_DTB_COMPAT_IGNORE_MEM))
+ continue;
+
if (memcount >= sizeof(mem_reg_property)/4)
continue;
if (!atag->u.mem.size)
--
2.43.0
On Sun, Jan 21, 2024 at 09:29:32PM +0100, Christian Marangi wrote:
> This series try to address a long lasting problem with legacy device
> that require an appended DTB and the use of AUTO_ZRELADDR.
>
> With these device AUTO_ZRELADDR is not possible if for some reason at
> the start of the RAM it's needed to reserve some space. (example qcom SoC
> that allocate reserved space for SMEM)
>
> In the current implementation with appended DTB and AUTO_ZRELADDR,
> the memory start is only derived from the PC register and it can't be
> changed by declaring additional info in the DTS.
>
> In a normal setup, we have an intentional undocumented chosen property
> to handle this and the memory node to declare the start of the memory.
>
> With this applied and ARM_ATAG_DTB_COMPAT_IGNORE_MEM enabled (more
> info in the related patch) ipq806x can boot right away with AUTO_ZRELADDR
> enabled and a correct memory node defined in DTS.
>
> It's needed to ignore MEM ATAGs as most of the time the values from the
> bootloader are hardcoded and OEM didn't care to actually provide them
> resulting in funny situation where a Netgear R7800 with 512Mb of RAM
> have Uboot passing 1.7GB of RAM with ATAGS.
>
> While MEM ATAG may be broken, other ATAG like serial number or bootargs
> might still be useful for partition declaration (cmdlinepart) or other
> info hence DTB_COMPAT is still needed in these case and can't be
> disabled.
>
> I'm open to any suggestion on how this can be improved and I would love
> some additional testing on other legacy platform but I assume this will
> permit many legacy device to be correctly supported without having to
> hardcode address.
>
> Changes v2:
> - Add Review and Ack Tags
> - Use IS_ENABLED instead of global variable
>
> Christian Marangi (2):
> ARM: decompressor: support memory start validation for appended DTB
> ARM: decompressor: add option to ignore MEM ATAGs
>
> arch/arm/Kconfig | 12 ++++++++++++
> arch/arm/boot/compressed/atags_to_fdt.c | 4 ++++
> arch/arm/boot/compressed/head.S | 22 ++++++++++++++++++++++
> 3 files changed, 38 insertions(+)
>
>
Any news for this?
--
Ansuel
On Wed, Feb 21, 2024 at 5:57 PM Christian Marangi <ansuelsmth@gmailcom> wrote:
> Any news for this?
Can you please put the patches into Russell's patch tracker so he can
apply them?
https://www.arm.linux.org.uk/developer/patches/
If you run into any problems, ping me on IRC and I'll help out.
Yours,
Linus Walleij
On Thu, Feb 22, 2024 at 01:07:56PM +0100, Linus Walleij wrote:
> On Wed, Feb 21, 2024 at 5:57 PM Christian Marangi <[email protected]> wrote:
>
> > Any news for this?
>
> Can you please put the patches into Russell's patch tracker so he can
> apply them?
> https://www.arm.linux.org.uk/developer/patches/
>
> If you run into any problems, ping me on IRC and I'll help out.
>
God I totally missed this email where I had to put the 2 patch in the
tracking system. Just did now... my bad!
--
Ansuel