# git rev-parse -q --verify a180bd1d7e16173d965b263c5a536aa40afa2a2a^{commit} a180bd1d7e16173d965b263c5a536aa40afa2a2a already have revision, skipping fetch # git checkout -q -f -B kisskb a180bd1d7e16173d965b263c5a536aa40afa2a2a # git clean -qxdf # < git log -1 # commit a180bd1d7e16173d965b263c5a536aa40afa2a2a # Author: Linus Torvalds # Date: Sun Jul 4 16:12:42 2021 -0700 # # iov_iter: remove uaccess_kernel() warning from iov_iter_init() # # This warning was there to catch any architectures that still use # CONFIG_SET_FS, and that would mis-use iov_iter_init() for anything that # wasn't a proper user space pointer. So that # # WARN_ON_ONCE(uaccess_kernel()); # # makes perfect conceptual sense: you really shouldn't use a kernel # pointer with set_fs(KERNEL_DS) and then pass it to iov_iter_init(). # # HOWEVER. # # Guenter Roeck reports that this warning actually triggers in no-mmu # configurations of both ARM and m68k. And the reason isn't that they # pass in a kernel pointer under set_fs(KERNEL_DS) at all: the reason is # that in those configurations, "uaccess_kernel()" is simply not reliable. # # Those no-mmu setups set USER_DS and KERNEL_DS to the same values, so you # can't test for the difference. # # In particular, the no-mmu case for ARM does # # #define USER_DS KERNEL_DS # #define uaccess_kernel() (true) # # so USER_DS and KERNEL_DS have the same value, and uaccess_kernel() is # always trivially true. # # The m68k case is slightly different and not quite as obvious. It does # (spread out over multiple header files just to be extra exciting: # asm/processor.h, asm/segment.h and asm-generic/uaccess.h): # # #define TASK_SIZE (0xFFFFFFFFUL) # #define USER_DS MAKE_MM_SEG(TASK_SIZE) # #define KERNEL_DS MAKE_MM_SEG(~0UL) # #define get_fs() (current_thread_info()->addr_limit) # #define uaccess_kernel() (get_fs().seg == KERNEL_DS.seg) # # but the end result is the same: uaccess_kernel() will always be true, # because USER_DS and KERNEL_DS end up having the same value, even if that # value is defined differently. # # This is very arguably a misfeature in those implementations, but in the # end we don't really care. All modern architectures have gotten rid of # set_fs() already, and generic kernel code never uses it. And while the # sanity check was a nice idea, an architecture would have to go the extra # mile to actually break this. # # So this well-intentioned warning isn't really all that likely to find # anything but these known false positives, and as such just isn't worth # maintaining. # # Reported-by: Guenter Roeck # Fixes: 8cd54c1c8480 ("iov_iter: separate direction from flavour") # Cc: Matthew Wilcox # Cc: Al Viro # Signed-off-by: Linus Torvalds # < /opt/cross/kisskb/korg/gcc-4.9.4-nolibc/arm-linux-gnueabi/bin/arm-linux-gnueabi-gcc --version # < /opt/cross/kisskb/korg/gcc-4.9.4-nolibc/arm-linux-gnueabi/bin/arm-linux-gnueabi-ld --version # < git log --format=%s --max-count=1 a180bd1d7e16173d965b263c5a536aa40afa2a2a # < make -s -j 10 ARCH=arm O=/kisskb/build/linus_imx_v6_v7_defconfig_arm-gcc4.9 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-4.9.4-nolibc/arm-linux-gnueabi/bin/arm-linux-gnueabi- imx_v6_v7_defconfig # < make -s -j 10 ARCH=arm O=/kisskb/build/linus_imx_v6_v7_defconfig_arm-gcc4.9 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-4.9.4-nolibc/arm-linux-gnueabi/bin/arm-linux-gnueabi- help # make -s -j 10 ARCH=arm O=/kisskb/build/linus_imx_v6_v7_defconfig_arm-gcc4.9 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-4.9.4-nolibc/arm-linux-gnueabi/bin/arm-linux-gnueabi- olddefconfig # make -s -j 10 ARCH=arm O=/kisskb/build/linus_imx_v6_v7_defconfig_arm-gcc4.9 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-4.9.4-nolibc/arm-linux-gnueabi/bin/arm-linux-gnueabi- In file included from /opt/cross/kisskb/korg/gcc-4.9.4-nolibc/arm-linux-gnueabi/bin/../lib/gcc/arm-linux-gnueabi/4.9.4/plugin/include/tm.h:23, from /kisskb/src/scripts/gcc-plugins/gcc-common.h:15, from /kisskb/src/scripts/gcc-plugins/arm_ssp_per_task_plugin.c:3: /opt/cross/kisskb/korg/gcc-4.9.4-nolibc/arm-linux-gnueabi/bin/../lib/gcc/arm-linux-gnueabi/4.9.4/plugin/include/config/elfos.h:102:21: warning: invalid suffix on literal; C++11 requires a space between literal and string macro [-Wliteral-suffix] fprintf ((FILE), "%s"HOST_WIDE_INT_PRINT_UNSIGNED"\n",\ ^ /opt/cross/kisskb/korg/gcc-4.9.4-nolibc/arm-linux-gnueabi/bin/../lib/gcc/arm-linux-gnueabi/4.9.4/plugin/include/config/elfos.h:170:24: warning: invalid suffix on literal; C++11 requires a space between literal and string macro [-Wliteral-suffix] fprintf ((FILE), ","HOST_WIDE_INT_PRINT_UNSIGNED",%u\n", \ ^ In file included from /opt/cross/kisskb/korg/gcc-4.9.4-nolibc/arm-linux-gnueabi/bin/../lib/gcc/arm-linux-gnueabi/4.9.4/plugin/include/tm.h:44, from /kisskb/src/scripts/gcc-plugins/gcc-common.h:15, from /kisskb/src/scripts/gcc-plugins/arm_ssp_per_task_plugin.c:3: /opt/cross/kisskb/korg/gcc-4.9.4-nolibc/arm-linux-gnueabi/bin/../lib/gcc/arm-linux-gnueabi/4.9.4/plugin/include/defaults.h:126:24: warning: invalid suffix on literal; C++11 requires a space between literal and string macro [-Wliteral-suffix] fprintf ((FILE), ","HOST_WIDE_INT_PRINT_UNSIGNED",%u\n", \ ^ cc1plus: warning: unrecognized command line option '-Wno-format-diag' /kisskb/src/net/sched/sch_frag.c: In function 'sch_fragment': /kisskb/src/net/sched/sch_frag.c:93:10: warning: missing braces around initializer [-Wmissing-braces] struct rtable sch_frag_rt = { 0 }; ^ /kisskb/src/net/sched/sch_frag.c:93:10: warning: (near initialization for 'sch_frag_rt.dst') [-Wmissing-braces] Completed OK # rm -rf /kisskb/build/linus_imx_v6_v7_defconfig_arm-gcc4.9 # Build took: 0:06:23.382273