From 338d4f49d6f7114a017d294ccf7374df4f998edc Mon Sep 17 00:00:00 2001 From: James Morse Date: Wed, 22 Jul 2015 19:05:54 +0100 Subject: 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 Signed-off-by: James Morse [will: use ALTERNATIVE in asm and tidy up pan_enable check] Signed-off-by: Will Deacon --- arch/arm64/lib/clear_user.S | 8 ++++++++ 1 file changed, 8 insertions(+) (limited to 'arch/arm64/lib/clear_user.S') 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 . */ #include + +#include #include +#include +#include .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) -- cgit v1.2.3-59-g8ed1b