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From 7ae1f5508d9a33fd58ed3059bd2d569961e3b8bd Mon Sep 17 00:00:00 2001 |
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From: Helge Deller <deller@gmx.de> |
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Date: Sat, 20 Aug 2022 17:59:17 +0200 |
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Subject: parisc: Fix exception handler for fldw and fstw instructions |
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From: Helge Deller <deller@gmx.de> |
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commit 7ae1f5508d9a33fd58ed3059bd2d569961e3b8bd upstream. |
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The exception handler is broken for unaligned memory acceses with fldw |
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and fstw instructions, because it trashes or uses randomly some other |
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floating point register than the one specified in the instruction word |
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on loads and stores. |
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The instruction "fldw 0(addr),%fr22L" (and the other fldw/fstw |
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instructions) encode the target register (%fr22) in the rightmost 5 bits |
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of the instruction word. The 7th rightmost bit of the instruction word |
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defines if the left or right half of %fr22 should be used. |
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While processing unaligned address accesses, the FR3() define is used to |
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extract the offset into the local floating-point register set. But the |
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calculation in FR3() was buggy, so that for example instead of %fr22, |
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register %fr12 [((22 * 2) & 0x1f) = 12] was used. |
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This bug has been since forever in the parisc kernel and I wonder why it |
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wasn't detected earlier. Interestingly I noticed this bug just because |
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the libime debian package failed to build on *native* hardware, while it |
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successfully built in qemu. |
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This patch corrects the bitshift and masking calculation in FR3(). |
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Signed-off-by: Helge Deller <deller@gmx.de> |
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Cc: <stable@vger.kernel.org> |
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Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
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--- |
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arch/parisc/kernel/unaligned.c | 2 +- |
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1 file changed, 1 insertion(+), 1 deletion(-) |
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--- a/arch/parisc/kernel/unaligned.c |
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+++ b/arch/parisc/kernel/unaligned.c |
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@@ -93,7 +93,7 @@ |
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#define R1(i) (((i)>>21)&0x1f) |
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#define R2(i) (((i)>>16)&0x1f) |
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#define R3(i) ((i)&0x1f) |
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-#define FR3(i) ((((i)<<1)&0x1f)|(((i)>>6)&1)) |
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+#define FR3(i) ((((i)&0x1f)<<1)|(((i)>>6)&1)) |
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#define IM(i,n) (((i)>>1&((1<<(n-1))-1))|((i)&1?((0-1L)<<(n-1)):0)) |
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#define IM5_2(i) IM((i)>>16,5) |
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#define IM5_3(i) IM((i),5) |
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