Commit 49003a8d authored by James Morse's avatar James Morse Committed by Will Deacon

arm64: don't call C code with el0's fp register

On entry from el0, we save all the registers on the kernel stack, and
restore them before returning. x29 remains unchanged when we call out
to C code, which will store x29 as the frame-pointer on the stack.

Instead, write 0 into x29 after entry from el0, to avoid any risk of
tracing into user space.
Signed-off-by: default avatarJames Morse <james.morse@arm.com>
Signed-off-by: default avatarWill Deacon <will.deacon@arm.com>
parent 1ffe199b
...@@ -93,6 +93,8 @@ ...@@ -93,6 +93,8 @@
and tsk, tsk, #~(THREAD_SIZE - 1) // Ensure MDSCR_EL1.SS is clear, and tsk, tsk, #~(THREAD_SIZE - 1) // Ensure MDSCR_EL1.SS is clear,
ldr x19, [tsk, #TI_FLAGS] // since we can unmask debug ldr x19, [tsk, #TI_FLAGS] // since we can unmask debug
disable_step_tsk x19, x20 // exceptions when scheduling. disable_step_tsk x19, x20 // exceptions when scheduling.
mov x29, xzr // fp pointed to user-space
.else .else
add x21, sp, #S_FRAME_SIZE add x21, sp, #S_FRAME_SIZE
.endif .endif
......
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