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d05f3b1908
Reverse commit 75317a0 since this is a special case.
Eliminate the real reason for the inability to boot the kernel.
Linux kernel hangs in early boot on 32-bit ARM platform,
when ftrace 4-byte "mcount" function call location for
"_raw_spin_unlock_irqrestore" function straddles icache lines.
The problem is present for (cross-compiler) GCC 10, 11, 12.
It does not happen when the kernel is compiled with GCC 9,
even when condition (1) is satisfied.
Detailed description:
https://forum.armbian.com/topic/41339-linux-image-legacy-sunxi2451-kernel-6192-is-broken-stuck-at-starting-kernel/?do=findComment&comment=196528
53 lines
1.8 KiB
Diff
53 lines
1.8 KiB
Diff
From 3d499ba2dce4ac8716f2c9bb07f66f45d0555a19 Mon Sep 17 00:00:00 2001
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From: The-going <48602507+The-going@users.noreply.github.com>
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Date: Fri, 12 Jul 2024 14:20:15 +0300
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Subject: arm: patch: call 'patch_unmap' after flushing dcache and icache
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Problem: Linux kernel hangs in early boot on 32-bit ARM platform,
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when ftrace 4-byte "mcount" function call location for
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"_raw_spin_unlock_irqrestore" function straddles icache lines.
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1. The ftrace location for "_raw_spin_unlock_irqrestore" is NOT
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4-byte aligned and 4 bytes at this location straddle the instruction
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cache line (0x20) boundaries.
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The problem is present for (cross-compiler) GCC 10, 11, 12.
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It does not happen when the kernel is compiled with GCC 9,
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even when condition (1) is satisfied.
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Detailed description:
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https://forum.armbian.com/topic/41339-linux-image-legacy-sunxi2451-kernel-6192-is-broken-stuck-at-starting-kernel/?do=findComment&comment=196528
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Author: @mikhailai
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---
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arch/arm/kernel/patch.c | 9 ++++++++-
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1 file changed, 8 insertions(+), 1 deletion(-)
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diff --git a/arch/arm/kernel/patch.c b/arch/arm/kernel/patch.c
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index e9e828b6bb30..ce0fd3aeb575 100644
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--- a/arch/arm/kernel/patch.c
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+++ b/arch/arm/kernel/patch.c
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@@ -101,11 +101,18 @@ void __kprobes __patch_text_real(void *addr, unsigned int insn, bool remap)
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if (waddr != addr) {
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flush_kernel_vmap_range(waddr, twopage ? size / 2 : size);
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- patch_unmap(FIX_TEXT_POKE0, &flags);
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}
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flush_icache_range((uintptr_t)(addr),
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(uintptr_t)(addr) + size);
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+
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+ /* Can only call 'patch_unmap' after flushing dcache and icache,
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+ * because it calls 'raw_spin_unlock_irqrestore', but that may
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+ * happen to be the very function we're currently patching
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+ * (as it happens during the ftrace init).
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+ */
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+ if (waddr != addr)
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+ patch_unmap(FIX_TEXT_POKE0, &flags);
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}
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static int __kprobes patch_text_stop_machine(void *data)
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--
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2.35.3
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