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see http://lists.infradead.org/pipermail/linux-rpi-kernel/2017-August/006884.html Signed-off-by: Matthias Reichl <hias@horus.com>
58 lines
1.4 KiB
Diff
58 lines
1.4 KiB
Diff
On Wed, 23 Aug 2017 17:42:14 +0200
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Matthias Reichl <hias@horus.com> wrote:
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> I haven't verified it myself but Phil Elwells first analysis here
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> sounds plausible
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>
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> https://github.com/raspberrypi/linux/issues/2166#issuecomment-323355145
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I noticed this comment:
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"What makes this interesting (and is the reason this doesn't fail
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normally) is that these functions are all called within kernel_init, so
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the __ro_after_init attribute shouldn't have caused the variable to be
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read-only yet."
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When ftrace starts, it needs to set the kernel text to write, and when
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it finishes it sets it back to readonly. But the kernel is not set to
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readonly at boot up.
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Can you test this patch? (Warning, I didn't even compile test it)
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-- Steve
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diff --git a/arch/arm/mm/init.c b/arch/arm/mm/init.c
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index ad80548..fd75f38 100644
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--- a/arch/arm/mm/init.c
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+++ b/arch/arm/mm/init.c
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@@ -745,19 +745,29 @@ static int __mark_rodata_ro(void *unused)
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return 0;
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}
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+static int kernel_set_to_readonly;
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+
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void mark_rodata_ro(void)
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{
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+ kernel_set_to_readonly = 1;
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+
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stop_machine(__mark_rodata_ro, NULL, NULL);
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}
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void set_kernel_text_rw(void)
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{
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+ if (!kernel_set_to_readonly)
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+ return;
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+
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set_section_perms(ro_perms, ARRAY_SIZE(ro_perms), false,
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current->active_mm);
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}
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void set_kernel_text_ro(void)
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{
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+ if (!kernel_set_to_readonly)
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+ return;
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+
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set_section_perms(ro_perms, ARRAY_SIZE(ro_perms), true,
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current->active_mm);
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}
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