We can zero GPRs x0 - x29 upon entry from EL0 to make it harder for userspace to control values consumed by speculative gadgets.
We don't blat x30, since this is stashed much later, and we'll blat it before invoking C code. Signed-off-by: Mark Rutland <[email protected]> Cc: Catalin Marinas <[email protected]> Cc: Will Deacon <[email protected]> --- arch/arm64/kernel/entry.S | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S index 22c58e7dfc0f..39440c2ee66d 100644 --- a/arch/arm64/kernel/entry.S +++ b/arch/arm64/kernel/entry.S @@ -63,6 +63,12 @@ #endif .endm + .macro clear_gp_regs + .irp n,0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29 + mov x\n, xzr + .endr + .endm + /* * Bad Abort numbers *----------------- @@ -179,6 +185,7 @@ skip_apply_ssbd\@: stp x28, x29, [sp, #16 * 14] .if \el == 0 + clear_gp_regs mrs x21, sp_el0 ldr_this_cpu tsk, __entry_task, x20 // Ensure MDSCR_EL1.SS is clear, ldr x19, [tsk, #TSK_TI_FLAGS] // since we can unmask debug @@ -186,7 +193,6 @@ skip_apply_ssbd\@: apply_ssbd 1, x22, x23 - mov x29, xzr // fp pointed to user-space .else add x21, sp, #S_FRAME_SIZE get_thread_info tsk -- 2.11.0
