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https://github.com/torvalds/linux
synced 2024-11-05 18:23:50 +00:00
aeb3987683
This is based upon a report from Chris Torek and his initial patch.
From Chris's report:
--------------------
This came up in testing kgdb, using the built-in tests -- turn
on CONFIG_KGDB_TESTS, then
echo V1 > /sys/module/kgdbts/parameters/kgdbts
-- but it would affect using kgdb if you were debugging and looking
at bad pointers.
--------------------
When we get a copy_{from,to}_user() request and the %asi is set to
something other than ASI_AIUS (which is userspace) then we branch off
to a routine called memcpy_user_stub(). It just does a straight
memcpy since we are copying from kernel to kernel in this case.
The logic was that since source and destination are both kernel
pointers we don't need to have exception checks.
But for what probe_kernel_{read,write}() is trying to do, we have to
have the checks, otherwise things like kgdb bad kernel pointer
accesses don't do the right thing.
Signed-off-by: David S. Miller <davem@davemloft.net>
92 lines
1.6 KiB
ArmAsm
92 lines
1.6 KiB
ArmAsm
/* copy_in_user.S: Copy from userspace to userspace.
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*
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* Copyright (C) 1999, 2000, 2004 David S. Miller (davem@redhat.com)
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*/
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#include <linux/linkage.h>
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#include <asm/asi.h>
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#define XCC xcc
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#define EX(x,y) \
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98: x,y; \
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.section __ex_table,"a";\
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.align 4; \
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.word 98b, __retl_one; \
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.text; \
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.align 4;
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.register %g2,#scratch
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.register %g3,#scratch
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.text
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.align 32
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/* Don't try to get too fancy here, just nice and
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* simple. This is predominantly used for well aligned
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* small copies in the compat layer. It is also used
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* to copy register windows around during thread cloning.
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*/
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ENTRY(___copy_in_user) /* %o0=dst, %o1=src, %o2=len */
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cmp %o2, 0
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be,pn %XCC, 85f
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or %o0, %o1, %o3
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cmp %o2, 16
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bleu,a,pn %XCC, 80f
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or %o3, %o2, %o3
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/* 16 < len <= 64 */
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andcc %o3, 0x7, %g0
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bne,pn %XCC, 90f
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nop
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andn %o2, 0x7, %o4
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and %o2, 0x7, %o2
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1: subcc %o4, 0x8, %o4
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EX(ldxa [%o1] %asi, %o5)
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EX(stxa %o5, [%o0] %asi)
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add %o1, 0x8, %o1
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bgu,pt %XCC, 1b
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add %o0, 0x8, %o0
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andcc %o2, 0x4, %g0
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be,pt %XCC, 1f
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nop
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sub %o2, 0x4, %o2
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EX(lduwa [%o1] %asi, %o5)
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EX(stwa %o5, [%o0] %asi)
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add %o1, 0x4, %o1
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add %o0, 0x4, %o0
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1: cmp %o2, 0
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be,pt %XCC, 85f
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nop
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ba,pt %xcc, 90f
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nop
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80: /* 0 < len <= 16 */
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andcc %o3, 0x3, %g0
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bne,pn %XCC, 90f
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nop
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82:
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subcc %o2, 4, %o2
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EX(lduwa [%o1] %asi, %g1)
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EX(stwa %g1, [%o0] %asi)
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add %o1, 4, %o1
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bgu,pt %XCC, 82b
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add %o0, 4, %o0
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85: retl
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clr %o0
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.align 32
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90:
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subcc %o2, 1, %o2
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EX(lduba [%o1] %asi, %g1)
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EX(stba %g1, [%o0] %asi)
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add %o1, 1, %o1
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bgu,pt %XCC, 90b
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add %o0, 1, %o0
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retl
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clr %o0
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ENDPROC(___copy_in_user)
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