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sh: __copy_user function can corrupt the stack in case of exception

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The __copy_user function can corrupt the stack in the case of a
non-trivial length of data, and either of the first two move instructions
cause an exception. This is because the fixup for these two instructions
is mapped to the no_pop case, but these instructions execute after the
stack is pushed.

This change creates an explicit NO_POP exception mapping macro, and uses
it for the two instructions executed in the trivial case where no stack
pushes occur.

More information at ST Linux bugzilla:

	https://bugzilla.stlinux.com/show_bug.cgi?id=4824

Signed-off-by: Dylan Reid <dylan_reid@bose.com>
Signed-off-by: Stuart Menefy <stuart.menefy@st.com>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>
This commit is contained in:
Stuart MENEFY 2008-10-10 19:49:30 +01:00 committed by Paul Mundt
parent 2cd0ebc83d
commit 5d52013cbb
1 changed files with 8 additions and 3 deletions
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11
arch/sh/lib/copy_page.S
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@ -80,6 +80,11 @@ ENTRY(copy_page)
.section __ex_table, "a"; \
.long 9999b, 6000f ; \
.previous
#define EX_NO_POP(...) \
9999: __VA_ARGS__ ; \
.section __ex_table, "a"; \
.long 9999b, 6005f ; \
.previous
ENTRY(__copy_user)
! Check if small number of bytes
mov #11,r0
@ -139,9 +144,9 @@ EX( mov.b r1,@r4 )
bt 1f
2:
EX( mov.b @r5+,r0 )
EX_NO_POP( mov.b @r5+,r0 )
dt r6
EX( mov.b r0,@r4 )
EX_NO_POP( mov.b r0,@r4 )
bf/s 2b
add #1,r4
@ -150,7 +155,7 @@ EX( mov.b r0,@r4 )
# Exception handler:
.section .fixup, "ax"
6000:
6005:
mov.l 8000f,r1
mov r3,r0
jmp @r1