2020-05-03 06:03:54 -06:00
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/* SPDX-License-Identifier: GPL-2.0-only */
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#ifndef __ASM_UACCESS_ASM_H__
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#define __ASM_UACCESS_ASM_H__
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#include <asm/asm-offsets.h>
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#include <asm/domain.h>
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#include <asm/memory.h>
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#include <asm/thread_info.h>
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.macro csdb
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#ifdef CONFIG_THUMB2_KERNEL
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.inst.w 0xf3af8014
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#else
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.inst 0xe320f014
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#endif
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.endm
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.macro check_uaccess, addr:req, size:req, limit:req, tmp:req, bad:req
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#ifndef CONFIG_CPU_USE_DOMAINS
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adds \tmp, \addr, #\size - 1
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sbcscc \tmp, \tmp, \limit
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bcs \bad
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#ifdef CONFIG_CPU_SPECTRE
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movcs \addr, #0
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csdb
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#endif
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#endif
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.endm
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.macro uaccess_mask_range_ptr, addr:req, size:req, limit:req, tmp:req
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#ifdef CONFIG_CPU_SPECTRE
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sub \tmp, \limit, #1
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subs \tmp, \tmp, \addr @ tmp = limit - 1 - addr
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addhs \tmp, \tmp, #1 @ if (tmp >= 0) {
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subshs \tmp, \tmp, \size @ tmp = limit - (addr + size) }
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movlo \addr, #0 @ if (tmp < 0) addr = NULL
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csdb
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#endif
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.endm
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.macro uaccess_disable, tmp, isb=1
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#ifdef CONFIG_CPU_SW_DOMAIN_PAN
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/*
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* Whenever we re-enter userspace, the domains should always be
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* set appropriately.
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*/
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mov \tmp, #DACR_UACCESS_DISABLE
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mcr p15, 0, \tmp, c3, c0, 0 @ Set domain register
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.if \isb
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instr_sync
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.endif
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#endif
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.endm
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.macro uaccess_enable, tmp, isb=1
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#ifdef CONFIG_CPU_SW_DOMAIN_PAN
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/*
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* Whenever we re-enter userspace, the domains should always be
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* set appropriately.
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*/
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mov \tmp, #DACR_UACCESS_ENABLE
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mcr p15, 0, \tmp, c3, c0, 0
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.if \isb
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instr_sync
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.endif
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#endif
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.endm
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ARM: uaccess: fix DACR mismatch with nested exceptions
[ Upstream commit 71f8af1110101facfad68989ff91f88f8e2c3e22 ]
Tomas Paukrt reports that his SAM9X60 based system (ARM926, ARMv5TJ)
fails to fix up alignment faults, eventually resulting in a kernel
oops.
The problem occurs when using CONFIG_CPU_USE_DOMAINS with commit
e6978e4bf181 ("ARM: save and reset the address limit when entering an
exception"). This is because the address limit is set back to
TASK_SIZE on exception entry, and, although it is restored on exception
exit, the domain register is not.
Hence, this sequence can occur:
interrupt
pt_regs->addr_limit = addr_limit // USER_DS
addr_limit = USER_DS
alignment exception
__probe_kernel_read()
old_fs = get_fs() // USER_DS
set_fs(KERNEL_DS)
addr_limit = KERNEL_DS
dacr.kernel = DOMAIN_MANAGER
interrupt
pt_regs->addr_limit = addr_limit // KERNEL_DS
addr_limit = USER_DS
alignment exception
__probe_kernel_read()
old_fs = get_fs() // USER_DS
set_fs(KERNEL_DS)
addr_limit = KERNEL_DS
dacr.kernel = DOMAIN_MANAGER
...
set_fs(old_fs)
addr_limit = USER_DS
dacr.kernel = DOMAIN_CLIENT
...
addr_limit = pt_regs->addr_limit // KERNEL_DS
interrupt returns
At this point, addr_limit is correctly restored to KERNEL_DS for
__probe_kernel_read() to continue execution, but dacr.kernel is not,
it has been reset by the set_fs(old_fs) to DOMAIN_CLIENT.
This would not have happened prior to the mentioned commit, because
addr_limit would remain KERNEL_DS, so get_fs() would have returned
KERNEL_DS, and so would correctly nest.
This commit fixes the problem by also saving the DACR on exception
entry if either CONFIG_CPU_SW_DOMAIN_PAN or CONFIG_CPU_USE_DOMAINS are
enabled, and resetting the DACR appropriately on exception entry to
match addr_limit and PAN settings.
Fixes: e6978e4bf181 ("ARM: save and reset the address limit when entering an exception")
Reported-by: Tomas Paukrt <tomas.paukrt@advantech.cz>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
2020-05-03 06:24:07 -06:00
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#if defined(CONFIG_CPU_SW_DOMAIN_PAN) || defined(CONFIG_CPU_USE_DOMAINS)
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2020-05-03 06:14:09 -06:00
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#define DACR(x...) x
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#else
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#define DACR(x...)
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2020-05-03 06:03:54 -06:00
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#endif
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/*
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ARM: uaccess: fix DACR mismatch with nested exceptions
[ Upstream commit 71f8af1110101facfad68989ff91f88f8e2c3e22 ]
Tomas Paukrt reports that his SAM9X60 based system (ARM926, ARMv5TJ)
fails to fix up alignment faults, eventually resulting in a kernel
oops.
The problem occurs when using CONFIG_CPU_USE_DOMAINS with commit
e6978e4bf181 ("ARM: save and reset the address limit when entering an
exception"). This is because the address limit is set back to
TASK_SIZE on exception entry, and, although it is restored on exception
exit, the domain register is not.
Hence, this sequence can occur:
interrupt
pt_regs->addr_limit = addr_limit // USER_DS
addr_limit = USER_DS
alignment exception
__probe_kernel_read()
old_fs = get_fs() // USER_DS
set_fs(KERNEL_DS)
addr_limit = KERNEL_DS
dacr.kernel = DOMAIN_MANAGER
interrupt
pt_regs->addr_limit = addr_limit // KERNEL_DS
addr_limit = USER_DS
alignment exception
__probe_kernel_read()
old_fs = get_fs() // USER_DS
set_fs(KERNEL_DS)
addr_limit = KERNEL_DS
dacr.kernel = DOMAIN_MANAGER
...
set_fs(old_fs)
addr_limit = USER_DS
dacr.kernel = DOMAIN_CLIENT
...
addr_limit = pt_regs->addr_limit // KERNEL_DS
interrupt returns
At this point, addr_limit is correctly restored to KERNEL_DS for
__probe_kernel_read() to continue execution, but dacr.kernel is not,
it has been reset by the set_fs(old_fs) to DOMAIN_CLIENT.
This would not have happened prior to the mentioned commit, because
addr_limit would remain KERNEL_DS, so get_fs() would have returned
KERNEL_DS, and so would correctly nest.
This commit fixes the problem by also saving the DACR on exception
entry if either CONFIG_CPU_SW_DOMAIN_PAN or CONFIG_CPU_USE_DOMAINS are
enabled, and resetting the DACR appropriately on exception entry to
match addr_limit and PAN settings.
Fixes: e6978e4bf181 ("ARM: save and reset the address limit when entering an exception")
Reported-by: Tomas Paukrt <tomas.paukrt@advantech.cz>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
2020-05-03 06:24:07 -06:00
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* Save the address limit on entry to a privileged exception.
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*
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* If we are using the DACR for kernel access by the user accessors
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* (CONFIG_CPU_USE_DOMAINS=y), always reset the DACR kernel domain
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* back to client mode, whether or not \disable is set.
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*
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* If we are using SW PAN, set the DACR user domain to no access
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* if \disable is set.
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2020-05-03 06:03:54 -06:00
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*/
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.macro uaccess_entry, tsk, tmp0, tmp1, tmp2, disable
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2020-05-03 06:14:09 -06:00
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ldr \tmp1, [\tsk, #TI_ADDR_LIMIT]
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mov \tmp2, #TASK_SIZE
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str \tmp2, [\tsk, #TI_ADDR_LIMIT]
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DACR( mrc p15, 0, \tmp0, c3, c0, 0)
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DACR( str \tmp0, [sp, #SVC_DACR])
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str \tmp1, [sp, #SVC_ADDR_LIMIT]
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ARM: uaccess: fix DACR mismatch with nested exceptions
[ Upstream commit 71f8af1110101facfad68989ff91f88f8e2c3e22 ]
Tomas Paukrt reports that his SAM9X60 based system (ARM926, ARMv5TJ)
fails to fix up alignment faults, eventually resulting in a kernel
oops.
The problem occurs when using CONFIG_CPU_USE_DOMAINS with commit
e6978e4bf181 ("ARM: save and reset the address limit when entering an
exception"). This is because the address limit is set back to
TASK_SIZE on exception entry, and, although it is restored on exception
exit, the domain register is not.
Hence, this sequence can occur:
interrupt
pt_regs->addr_limit = addr_limit // USER_DS
addr_limit = USER_DS
alignment exception
__probe_kernel_read()
old_fs = get_fs() // USER_DS
set_fs(KERNEL_DS)
addr_limit = KERNEL_DS
dacr.kernel = DOMAIN_MANAGER
interrupt
pt_regs->addr_limit = addr_limit // KERNEL_DS
addr_limit = USER_DS
alignment exception
__probe_kernel_read()
old_fs = get_fs() // USER_DS
set_fs(KERNEL_DS)
addr_limit = KERNEL_DS
dacr.kernel = DOMAIN_MANAGER
...
set_fs(old_fs)
addr_limit = USER_DS
dacr.kernel = DOMAIN_CLIENT
...
addr_limit = pt_regs->addr_limit // KERNEL_DS
interrupt returns
At this point, addr_limit is correctly restored to KERNEL_DS for
__probe_kernel_read() to continue execution, but dacr.kernel is not,
it has been reset by the set_fs(old_fs) to DOMAIN_CLIENT.
This would not have happened prior to the mentioned commit, because
addr_limit would remain KERNEL_DS, so get_fs() would have returned
KERNEL_DS, and so would correctly nest.
This commit fixes the problem by also saving the DACR on exception
entry if either CONFIG_CPU_SW_DOMAIN_PAN or CONFIG_CPU_USE_DOMAINS are
enabled, and resetting the DACR appropriately on exception entry to
match addr_limit and PAN settings.
Fixes: e6978e4bf181 ("ARM: save and reset the address limit when entering an exception")
Reported-by: Tomas Paukrt <tomas.paukrt@advantech.cz>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
2020-05-03 06:24:07 -06:00
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.if \disable && IS_ENABLED(CONFIG_CPU_SW_DOMAIN_PAN)
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/* kernel=client, user=no access */
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mov \tmp2, #DACR_UACCESS_DISABLE
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mcr p15, 0, \tmp2, c3, c0, 0
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instr_sync
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.elseif IS_ENABLED(CONFIG_CPU_USE_DOMAINS)
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/* kernel=client */
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bic \tmp2, \tmp0, #domain_mask(DOMAIN_KERNEL)
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orr \tmp2, \tmp2, #domain_val(DOMAIN_KERNEL, DOMAIN_CLIENT)
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mcr p15, 0, \tmp2, c3, c0, 0
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instr_sync
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2020-05-03 06:03:54 -06:00
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.endif
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.endm
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/* Restore the user access state previously saved by uaccess_entry */
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.macro uaccess_exit, tsk, tmp0, tmp1
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ldr \tmp1, [sp, #SVC_ADDR_LIMIT]
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2020-05-03 06:14:09 -06:00
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DACR( ldr \tmp0, [sp, #SVC_DACR])
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2020-05-03 06:03:54 -06:00
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str \tmp1, [\tsk, #TI_ADDR_LIMIT]
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2020-05-03 06:14:09 -06:00
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DACR( mcr p15, 0, \tmp0, c3, c0, 0)
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2020-05-03 06:03:54 -06:00
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.endm
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2020-05-03 06:14:09 -06:00
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#undef DACR
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2020-05-03 06:03:54 -06:00
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#endif /* __ASM_UACCESS_ASM_H__ */
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