4ec5542679
Greg Ungerer fixed recently a bug in the Linux kernel, which allows to use one memory region again. Signed-off-by: Waldemar Brodkorb <wbx@openadk.org> Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
46 lines
2.0 KiB
Diff
46 lines
2.0 KiB
Diff
m68knommu: fix user a5 register being overwritten
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On no-MMU systems the application a5 register can be overwitten with the
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address of the process data segment when processing application signals.
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For flat format applications compiled with full absolute relocation this
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effectively corrupts the a5 register on signal processing - and this very
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quickly leads to process crash and often takes out the whole system with
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a panic as well.
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This has no effect on flat format applications compiled with the more
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common PIC methods (such as -msep-data). These format applications reserve
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a5 for the pointer to the data segment anyway - so it doesn't change it.
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A long time ago the a5 register was used in the code packed into the user
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stack to enable signal return processing. And so it had to be restored on
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end of signal cleanup processing back to the original a5 user value. This
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was historically done by saving away a5 in the sigcontext structure. At
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some point (a long time back it seems) the a5 restore process was changed
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and it was hard coded to put the user data segment address directly into a5.
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Which is ok for the common PIC compiled application case, but breaks the
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full relocation application code.
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We no longer use this type of signal handling mechanism and so we don't
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need to do anything special to save and restore a5 at all now. So remove the
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code that hard codes a5 to the address of the user data segment.
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Signed-off-by: Greg Ungerer <gerg@linux-m68k.org>
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---
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arch/m68k/kernel/signal.c | 1 -
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1 file changed, 1 deletion(-)
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diff --git a/arch/m68k/kernel/signal.c b/arch/m68k/kernel/signal.c
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index 2dcee3a..9202f82 100644
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--- a/arch/m68k/kernel/signal.c
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+++ b/arch/m68k/kernel/signal.c
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@@ -213,7 +213,6 @@ static inline int frame_extra_sizes(int f)
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static inline void adjustformat(struct pt_regs *regs)
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{
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- ((struct switch_stack *)regs - 1)->a5 = current->mm->start_data;
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/*
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* set format byte to make stack appear modulo 4, which it will
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* be when doing the rte
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--
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1.9.1
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