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- From 2f86b9b71a11f86e3d850214ab781ebb17d7260e Mon Sep 17 00:00:00 2001
- From: Christian Marangi <[email protected]>
- Date: Fri, 19 Jan 2024 19:48:30 +0100
- Subject: [PATCH v2 1/2] ARM: decompressor: support memory start validation for
- appended DTB
- 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(+)
- --- 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
-
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