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76 lines
3.1 KiB
Diff
76 lines
3.1 KiB
Diff
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From 2f86b9b71a11f86e3d850214ab781ebb17d7260e Mon Sep 17 00:00:00 2001
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From: Christian Marangi <ansuelsmth@gmail.com>
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Date: Fri, 19 Jan 2024 19:48:30 +0100
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Subject: [PATCH v2 1/2] ARM: decompressor: support memory start validation for
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appended DTB
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There is currently a problem with a very specific sets of kernel config
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and AUTO_ZRELADDR.
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For the most common case AUTO_ZRELADDR check the PC register and
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calculate the start of the physical memory. Then fdt_check_mem_start is
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called to make sure the detected value makes sense by comparing it with
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what is present in DTB in the memory nodes and if additional fixup are
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required with the use of linux,usable-memory-range in the chosen node to
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hardcode usable memory range in case some reserved space needs to be
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addressed. With the help of this function the right address is
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calculated and the kernel correctly decompress and loads.
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Things starts to become problematic when in the mix,
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CONFIG_ARM_APPENDED_DTB is used. This is a particular kernel config is
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used when legacy systems doesn't support passing a DTB directly and a
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DTB is appended at the end of the image.
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In such case, fdt_check_mem_start is skipped in AUTO_ZRELADDR iteration
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as the appended DTB can be augumented later with ATAGS passed from the
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bootloader (if CONFIG_ARM_ATAG_DTB_COMPAT is enabled).
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The main problem and what this patch address is the fact that
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fdt_check_mem_start is never called later when the appended DTB is
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augumented, hence any fixup and validation is not done making AUTO_ZRELADDR
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detection inconsistent and most of the time wrong.
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Add support in head.S for this by checking if AUTO_ZRELADDR is enabled
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and calling fdt_check_mem_start with the appended DTB and the augumented
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values permitting legacy device to provide info in DTB instead of
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disabling AUTO_ZRELADDR and hardcoding the physical address offsets.
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Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>
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Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
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Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
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---
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arch/arm/boot/compressed/head.S | 22 ++++++++++++++++++++++
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1 file changed, 22 insertions(+)
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--- a/arch/arm/boot/compressed/head.S
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+++ b/arch/arm/boot/compressed/head.S
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@@ -443,6 +443,28 @@ restart: adr r0, LC1
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add r6, r6, r5
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add r10, r10, r5
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add sp, sp, r5
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+
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+#ifdef CONFIG_AUTO_ZRELADDR
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+ /*
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+ * Validate calculated start of physical memory with appended DTB.
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+ * In the first iteration for physical memory start calculation,
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+ * we skipped validating it as it could have been augumented by
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+ * ATAGS stored at an offset from the same start of physical memory.
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+ *
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+ * We now have parsed them and augumented the appended DTB if asked
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+ * so we can finally validate the start of physical memory.
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+ *
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+ * This is needed to apply additional fixup with
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+ * linux,usable-memory-range or to make sure AUTO_ZRELADDR detected
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+ * the correct value.
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+ */
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+ sub r0, r4, #TEXT_OFFSET @ revert to base address
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+ mov r1, r8 @ use appended DTB
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+ bl fdt_check_mem_start
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+
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+ /* Determine final kernel image address. */
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+ add r4, r0, #TEXT_OFFSET
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+#endif
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dtb_check_done:
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#endif
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