We need to have memory dependencies on get_domain/set_domain to avoid
the compiler over-optimising these inline assembly instructions.
Loads/stores must not be reordered across a set_domain(), so introduce
a compiler barrier for that assembly.
The value of get_domain() must not be cached across a set_domain(), but
we still want to allow the compiler to optimise it away. Introduce a
dependency on current_thread_info()->cpu_domain to avoid this; the new
memory clobber in set_domain() should therefore cause the compiler to
re-load this. The other advantage of using this is we should have its
address in the register set already, or very soon after at most call
sites.
Tested-by: Robert Jarzmik <robert.jarzmik@free.fr>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Provide a software-based implementation of the priviledged no access
support found in ARMv8.1.
Userspace pages are mapped using a different domain number from the
kernel and IO mappings. If we switch the user domain to "no access"
when we enter the kernel, we can prevent the kernel from touching
userspace.
However, the kernel needs to be able to access userspace via the
various user accessor functions. With the wrapping in the previous
patch, we can temporarily enable access when the kernel needs user
access, and re-disable it afterwards.
This allows us to trap non-intended accesses to userspace, eg, caused
by an inadvertent dereference of the LIST_POISON* values, which, with
appropriate user mappings setup, can be made to succeed. This in turn
can allow use-after-free bugs to be further exploited than would
otherwise be possible.
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
DOMAIN_TABLE is not used; in any case, it aliases to the kernel domain.
Remove this definition.
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Keep the machine vectors in its own domain to avoid software based
user access control from making the vector code inaccessible, and
thereby deadlocking the machine.
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Since we switched to early trap initialisation in 94e5a85b3b
("ARM: earlier initialization of vectors page") we haven't been writing
directly to the vectors page, and so there's no need for this domain
to be in manager mode. Switch it to client mode.
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Provide a macro to generate the mask for a domain, rather than using
domain_val(, DOMAIN_MANAGER) which won't work when CPU_USE_DOMAINS
is turned off.
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Rather than modifying both the domain access control register and our
per-thread copy, modify only the domain access control register, and
use the per-thread copy to save and restore the register over context
switches. We can also avoid the explicit initialisation of the
init thread_info structure.
This allows us to avoid needing to gain access to the thread information
at the uaccess control sites.
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Avoid polluting drivers with a set_domain() macro, which interferes with
structure member names:
drivers/net/wireless/ath/ath9k/dfs_pattern_detector.c:294:33: error: macro "set_domain" passed 2 arguments, but takes just 1
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Disintegrate asm/system.h for ARM.
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Russell King <linux@arm.linux.org.uk>
cc: linux-arm-kernel@lists.infradead.org
This macro is used to generate unprivileged accesses (LDRT/STRT) to user
space.
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Nicolas Pitre <nico@linaro.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
This patch removes the domain switching functionality via the set_fs and
__switch_to functions on cores that have a TLS register.
Currently, the ioremap and vmalloc areas share the same level 1 page
tables and therefore have the same domain (DOMAIN_KERNEL). When the
kernel domain is modified from Client to Manager (via the __set_fs or in
the __switch_to function), the XN (eXecute Never) bit is overridden and
newer CPUs can speculatively prefetch the ioremap'ed memory.
Linux performs the kernel domain switching to allow user-specific
functions (copy_to/from_user, get/put_user etc.) to access kernel
memory. In order for these functions to work with the kernel domain set
to Client, the patch modifies the LDRT/STRT and related instructions to
the LDR/STR ones.
The user pages access rights are also modified for kernel read-only
access rather than read/write so that the copy-on-write mechanism still
works. CPU_USE_DOMAINS gets disabled only if the hardware has a TLS register
(CPU_32v6K is defined) since writing the TLS value to the high vectors page
isn't possible.
The user addresses passed to the kernel are checked by the access_ok()
function so that they do not point to the kernel space.
Tested-by: Anton Vorontsov <cbouatmailru@gmail.com>
Cc: Tony Lindgren <tony@atomide.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Move platform independent header files to arch/arm/include/asm, leaving
those in asm/arch* and asm/plat* alone.
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Russell King