arm64: entry.S: Add ventry overflow sanity checks

commit 4330e2c5c04c27bebf89d34e0bc14e6943413067 upstream.

Subsequent patches add even more code to the ventry slots.
Ensure kernels that overflow a ventry slot don't get built.

Reviewed-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: James Morse <james.morse@arm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
index bc6d5a9..4ddccc5 100644 (file)
--- a/arch/arm64/kernel/entry.S
+++ b/arch/arm64/kernel/entry.S
@@ -37,6 +37,7 @@
 
        .macro kernel_ventry, el:req, ht:req, regsize:req, label:req
        .align 7
+.Lventry_start\@:
 #ifdef CONFIG_UNMAP_KERNEL_AT_EL0
        .if     \el == 0
 alternative_if ARM64_UNMAP_KERNEL_AT_EL0
@@ -95,6 +96,7 @@ alternative_else_nop_endif
        mrs     x0, tpidrro_el0
 #endif
        b       el\el\ht\()_\regsize\()_\label
+.org .Lventry_start\@ + 128    // Did we overflow the ventry slot?
        .endm
 
        .macro tramp_alias, dst, sym
@@ -662,6 +664,7 @@ alternative_else_nop_endif
        add     x30, x30, #(1b - tramp_vectors)
        isb
        ret
+.org 1b + 128  // Did we overflow the ventry slot?
        .endm
 
        .macro tramp_exit, regsize = 64