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authorJames Morse <james.morse@arm.com>2015-07-22 19:05:54 +0100
committerWill Deacon <will.deacon@arm.com>2015-07-27 11:08:41 +0100
commit338d4f49d6f7114a017d294ccf7374df4f998edc (patch)
treeaf0b5cedc6e042623346d4e82be24eda190626a1 /arch/arm64/lib/clear_user.S
parentarm64: Generalise msr_s/mrs_s operations (diff)
downloadlinux-dev-338d4f49d6f7114a017d294ccf7374df4f998edc.tar.xz
linux-dev-338d4f49d6f7114a017d294ccf7374df4f998edc.zip
arm64: kernel: Add support for Privileged Access Never
'Privileged Access Never' is a new arm8.1 feature which prevents privileged code from accessing any virtual address where read or write access is also permitted at EL0. This patch enables the PAN feature on all CPUs, and modifies {get,put}_user helpers temporarily to permit access. This will catch kernel bugs where user memory is accessed directly. 'Unprivileged loads and stores' using ldtrb et al are unaffected by PAN. Reviewed-by: Catalin Marinas <catalin.marinas@arm.com> Signed-off-by: James Morse <james.morse@arm.com> [will: use ALTERNATIVE in asm and tidy up pan_enable check] Signed-off-by: Will Deacon <will.deacon@arm.com>
Diffstat (limited to '')
-rw-r--r--arch/arm64/lib/clear_user.S8
1 files changed, 8 insertions, 0 deletions
diff --git a/arch/arm64/lib/clear_user.S b/arch/arm64/lib/clear_user.S
index c17967fdf5f6..a9723c71c52b 100644
--- a/arch/arm64/lib/clear_user.S
+++ b/arch/arm64/lib/clear_user.S
@@ -16,7 +16,11 @@
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#include <linux/linkage.h>
+
+#include <asm/alternative.h>
#include <asm/assembler.h>
+#include <asm/cpufeature.h>
+#include <asm/sysreg.h>
.text
@@ -29,6 +33,8 @@
* Alignment fixed up by hardware.
*/
ENTRY(__clear_user)
+ALTERNATIVE("nop", __stringify(SET_PSTATE_PAN(0)), ARM64_HAS_PAN, \
+ CONFIG_ARM64_PAN)
mov x2, x1 // save the size for fixup return
subs x1, x1, #8
b.mi 2f
@@ -48,6 +54,8 @@ USER(9f, strh wzr, [x0], #2 )
b.mi 5f
USER(9f, strb wzr, [x0] )
5: mov x0, #0
+ALTERNATIVE("nop", __stringify(SET_PSTATE_PAN(1)), ARM64_HAS_PAN, \
+ CONFIG_ARM64_PAN)
ret
ENDPROC(__clear_user)