gcc-plugins/stackleak: Avoid .head.text section

The .head.text section carries the startup code that runs with the MMU
off or with a translation of memory that deviates from the ordinary one.
So avoid instrumentation with the stackleak plugin, which already avoids
.init.text and .noinstr.text entirely.

Fixes: 48204ab ("x86/sme: Move early SME kernel encryption handling into .head.text")
Reported-by: kernel test robot <oliver.sang@intel.com>
Closes: https://lore.kernel.org/oe-lkp/202403221630.2692c998-oliver.sang@intel.com
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Link: https://lore.kernel.org/r/20240328064256.2358634-2-ardb+git@google.com
Signed-off-by: Kees Cook <keescook@chromium.org>

Author: ardbiesheuvel

scripts/gcc-plugins/stackleak_plugin.c

@@ -467,6 +467,8 @@ static bool stackleak_gate(void)
 			return false;
 		if (STRING_EQUAL(section, ".entry.text"))
 			return false;
+		if (STRING_EQUAL(section, ".head.text"))
+			return false;
 	}
 
 	return track_frame_size >= 0;