scs: add CONFIG_MMU dependency for vfree_atomic()

The shadow call stack implementation fails to build without CONFIG_MMU:

  ld.lld: error: undefined symbol: vfree_atomic
  >>> referenced by scs.c
  >>>               kernel/scs.o:(scs_free) in archive vmlinux.a

Link: https://lkml.kernel.org/r/20240122175204.2371009-1-samuel.holland@sifive.com
Fixes: a2abe7cbd8fe ("scs: switch to vmapped shadow stacks")
Signed-off-by: Samuel Holland <samuel.holland@sifive.com>
Reviewed-by: Sami Tolvanen <samitolvanen@google.com>
Cc: Will Deacon <will@kernel.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/arch/Kconfig b/arch/Kconfig
index c91917b508736d1fa0d37d5bf3b1e4bf5550e211..a5af0edd3eb8f3b64e6e51bffb2ac491cb31bc26 100644 (file)
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -673,6 +673,7 @@ config SHADOW_CALL_STACK
        bool "Shadow Call Stack"
        depends on ARCH_SUPPORTS_SHADOW_CALL_STACK
        depends on DYNAMIC_FTRACE_WITH_ARGS || DYNAMIC_FTRACE_WITH_REGS || !FUNCTION_GRAPH_TRACER
+       depends on MMU
        help
          This option enables the compiler's Shadow Call Stack, which
          uses a shadow stack to protect function return addresses from