can't remove -ffreestanding from i386

[nickdesaulniers]

@kees was looking to use an old patch of mine to get FORTIFY_SOURCE working for ARCH=i386 LLVM=1 builds. We got a report that this caused kernel panics. I traced this to a bug in LLVM, reported upstream.

[nickdesaulniers]

https://lore.kernel.org/lkml/164934565464.389.2546833245037255032.tip-bot2@tip-bot2/
Look's like meat's back on the menu, boys.

[nickdesaulniers]

Note to self:
-mregparm=3 ends up:

1. setting the inreg parameter attribute, and
2. setting the !{i32 1, !"NumRegisterParameters", i32 3 module attribute.

[nickdesaulniers]

https://reviews.llvm.org/D125285

[nickdesaulniers]

Waiting on backport in llvm/llvm-project#53645 (comment).

I tested this quickly:

diff --git a/arch/x86/Makefile b/arch/x86/Makefile
index 63d50f65b828..8da13220afa0 100644
--- a/arch/x86/Makefile
+++ b/arch/x86/Makefile
@@ -101,7 +101,7 @@ ifeq ($(CONFIG_X86_32),y)
         KBUILD_CFLAGS += $(cflags-y)
 
         # temporary until string.h is fixed
-        KBUILD_CFLAGS += -ffreestanding
+        #KBUILD_CFLAGS += -ffreestanding
 
        ifeq ($(CONFIG_STACKPROTECTOR),y)
                ifeq ($(CONFIG_SMP),y)
diff --git a/security/Kconfig b/security/Kconfig
index 9b2c4925585a..a916640970f7 100644
--- a/security/Kconfig
+++ b/security/Kconfig
@@ -179,8 +179,6 @@ config FORTIFY_SOURCE
        depends on ARCH_HAS_FORTIFY_SOURCE
        # https://bugs.llvm.org/show_bug.cgi?id=41459
        depends on !CC_IS_CLANG || CLANG_VERSION >= 120001
-       # https://github.com/llvm/llvm-project/issues/53645
-       depends on !CC_IS_CLANG || !X86_32
        help
          Detect overflows of buffers in common string and memory functions
          where the compiler can determine and validate the buffer sizes.

with ARCH=i386 make LLVM=1 -j72 and thinLTO. I should do version checks for these instead in a more formal kernel patch (but not today 😴 )

clang-15 it is.