--- /dev/null
+From ee2ab467bddfb2d7f68d996dbab94d7b88f8eaf7 Mon Sep 17 00:00:00 2001
+From: Nathan Chancellor <nathan@kernel.org>
+Date: Tue, 21 Jan 2025 18:11:33 -0700
+Subject: x86/boot: Use '-std=gnu11' to fix build with GCC 15
+MIME-Version: 1.0
+Content-Type: text/plain; charset=UTF-8
+Content-Transfer-Encoding: 8bit
+
+From: Nathan Chancellor <nathan@kernel.org>
+
+commit ee2ab467bddfb2d7f68d996dbab94d7b88f8eaf7 upstream.
+
+GCC 15 changed the default C standard version to C23, which should not
+have impacted the kernel because it requests the gnu11 standard via
+'-std=' in the main Makefile. However, the x86 compressed boot Makefile
+uses its own set of KBUILD_CFLAGS without a '-std=' value (i.e., using
+the default), resulting in errors from the kernel's definitions of bool,
+true, and false in stddef.h, which are reserved keywords under C23.
+
+ ./include/linux/stddef.h:11:9: error: expected identifier before ‘false’
+ 11 | false = 0,
+ ./include/linux/types.h:35:33: error: two or more data types in declaration specifiers
+ 35 | typedef _Bool bool;
+
+Set '-std=gnu11' in the x86 compressed boot Makefile to resolve the
+error and consistently use the same C standard version for the entire
+kernel.
+
+Closes: https://lore.kernel.org/4OAhbllK7x4QJGpZjkYjtBYNLd_2whHx9oFiuZcGwtVR4hIzvduultkgfAIRZI3vQpZylu7Gl929HaYFRGeMEalWCpeMzCIIhLxxRhq4U-Y=@protonmail.com/
+Closes: https://lore.kernel.org/Z4467umXR2PZ0M1H@tucnak/
+Reported-by: Kostadin Shishmanov <kostadinshishmanov@protonmail.com>
+Reported-by: Jakub Jelinek <jakub@redhat.com>
+Signed-off-by: Nathan Chancellor <nathan@kernel.org>
+Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
+Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
+Cc:stable@vger.kernel.org
+Link: https://lore.kernel.org/all/20250121-x86-use-std-consistently-gcc-15-v1-1-8ab0acf645cb%40kernel.org
+Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+---
+ arch/x86/boot/compressed/Makefile | 1 +
+ 1 file changed, 1 insertion(+)
+
+--- a/arch/x86/boot/compressed/Makefile
++++ b/arch/x86/boot/compressed/Makefile
+@@ -33,6 +33,7 @@ targets := vmlinux vmlinux.bin vmlinux.b
+ # avoid errors with '-march=i386', and future flags may depend on the target to
+ # be valid.
+ KBUILD_CFLAGS := -m$(BITS) -O2 $(CLANG_FLAGS)
++KBUILD_CFLAGS += -std=gnu11
+ KBUILD_CFLAGS += -fno-strict-aliasing -fPIE
+ KBUILD_CFLAGS += -DDISABLE_BRANCH_PROFILING
+ cflags-$(CONFIG_X86_32) := -march=i386