Linux kernel build for qemu runtime to source code review.

linux-kernel-build-for-gdb-in-qemu.sh

make clean
make defconfig
sed -i 's/-O2/-Og/g' Makefile
make -j $(nproc)
make -j8 cscope tags

<< 'MULTILINE-COMMENT'
~/linux$ git diff
diff --git a/Makefile b/Makefile
index 18b4cebe5564..cd61d89aebfb 100644
--- a/Makefile
+++ b/Makefile
@@ -401,10 +401,10 @@ else
 HOSTCC = gcc
 HOSTCXX        = g++
 endif
-KBUILD_HOSTCFLAGS   := -Wall -Wmissing-prototypes -Wstrict-prototypes -O2 \
+KBUILD_HOSTCFLAGS   := -Wall -Wmissing-prototypes -Wstrict-prototypes -Og \
                -fomit-frame-pointer -std=gnu89 $(HOST_LFS_CFLAGS) \
                $(HOSTCFLAGS)
-KBUILD_HOSTCXXFLAGS := -O2 $(HOST_LFS_CFLAGS) $(HOSTCXXFLAGS)
+KBUILD_HOSTCXXFLAGS := -Og $(HOST_LFS_CFLAGS) $(HOSTCXXFLAGS)
 KBUILD_HOSTLDFLAGS  := $(HOST_LFS_LDFLAGS) $(HOSTLDFLAGS)
 KBUILD_HOSTLDLIBS   := $(HOST_LFS_LIBS) $(HOSTLDLIBS)

@@ -719,7 +719,7 @@ KBUILD_CFLAGS       += $(call cc-disable-warning, format-overflow)
 KBUILD_CFLAGS  += $(call cc-disable-warning, address-of-packed-member)

 ifdef CONFIG_CC_OPTIMIZE_FOR_PERFORMANCE
-KBUILD_CFLAGS += -O2
+KBUILD_CFLAGS += -Og
 else ifdef CONFIG_CC_OPTIMIZE_FOR_PERFORMANCE_O3
 KBUILD_CFLAGS += -O3
 else ifdef CONFIG_CC_OPTIMIZE_FOR_SIZE
diff --git a/include/linux/thread_info.h b/include/linux/thread_info.h
index f3040b0b4b23..2cd2681480aa 100644
--- a/include/linux/thread_info.h
+++ b/include/linux/thread_info.h
@@ -151,7 +151,7 @@ static __always_inline __must_check bool
 check_copy_size(const void *addr, size_t bytes, bool is_source)
 {
        int sz = __compiletime_object_size(addr);
-       if (unlikely(sz >= 0 && sz < bytes)) {
+       if (false && unlikely(sz >= 0 && sz < bytes)) {
                if (!__builtin_constant_p(bytes))
                        copy_overflow(sz, bytes);
                else if (is_source)
MULTILINE-COMMENT