From: James Morse james.morse@arm.com
commit 6c5bf79b69f911560fbf82214c0971af6e58e682 upstream.
Systems using kpti enter and exit the kernel through a trampoline mapping that is always mapped, even when the kernel is not. tramp_valias is a macro to find the address of a symbol in the trampoline mapping.
Adding extra sets of vectors will expand the size of the entry.tramp.text section to beyond 4K. tramp_valias will be unable to generate addresses for symbols beyond 4K as it uses the 12 bit immediate of the add instruction.
As there are now two registers available when tramp_alias is called, use the extra register to avoid the 4K limit of the 12 bit immediate.
Reviewed-by: Russell King (Oracle) rmk+kernel@armlinux.org.uk Reviewed-by: Catalin Marinas catalin.marinas@arm.com [ Removed SDEI for backport ] Signed-off-by: James Morse james.morse@arm.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/arm64/kernel/entry.S | 11 +++++++---- 1 file changed, 7 insertions(+), 4 deletions(-)
--- a/arch/arm64/kernel/entry.S +++ b/arch/arm64/kernel/entry.S @@ -97,9 +97,12 @@ .org .Lventry_start@ + 128 // Did we overflow the ventry slot? .endm
- .macro tramp_alias, dst, sym + .macro tramp_alias, dst, sym, tmp mov_q \dst, TRAMP_VALIAS - add \dst, \dst, #(\sym - .entry.tramp.text) + adr_l \tmp, \sym + add \dst, \dst, \tmp + adr_l \tmp, .entry.tramp.text + sub \dst, \dst, \tmp .endm
// This macro corrupts x0-x3. It is the caller's duty @@ -254,10 +257,10 @@ alternative_else_nop_endif #ifdef CONFIG_UNMAP_KERNEL_AT_EL0 bne 4f msr far_el1, x29 - tramp_alias x30, tramp_exit_native + tramp_alias x30, tramp_exit_native, x29 br x30 4: - tramp_alias x30, tramp_exit_compat + tramp_alias x30, tramp_exit_compat, x29 br x30 #endif .else