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https://github.com/AuxXxilium/linux_dsm_epyc7002.git
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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>
36 lines
752 B
ArmAsm
36 lines
752 B
ArmAsm
/* NGcopy_to_user.S: Niagara optimized copy to userspace.
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*
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* Copyright (C) 2006, 2007 David S. Miller (davem@davemloft.net)
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*/
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#define EX_ST(x) \
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98: x; \
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.section __ex_table,"a";\
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.align 4; \
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.word 98b, __ret_one_asi;\
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.text; \
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.align 4;
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#ifndef ASI_AIUS
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#define ASI_AIUS 0x11
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#endif
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#define FUNC_NAME NGcopy_to_user
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#define STORE(type,src,addr) type##a src, [addr] ASI_AIUS
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#define STORE_ASI ASI_BLK_INIT_QUAD_LDD_AIUS
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#define EX_RETVAL(x) %g0
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#ifdef __KERNEL__
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/* Writing to %asi is _expensive_ so we hardcode it.
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* Reading %asi to check for KERNEL_DS is comparatively
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* cheap.
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*/
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#define PREAMBLE \
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rd %asi, %g1; \
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cmp %g1, ASI_AIUS; \
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bne,pn %icc, ___copy_in_user; \
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nop
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#endif
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#include "NGmemcpy.S"
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