# git rev-parse -q --verify 382d4cd1847517ffcb1800fd462b625db7b2ebea^{commit} # git fetch -q -n -f git://fs.ozlabs.ibm.com/kernel/linus master warning: The last gc run reported the following. Please correct the root cause and remove .git/gc.log. Automatic cleanup will not be performed until the file is removed. warning: There are too many unreachable loose objects; run 'git prune' to remove them. # git rev-parse -q --verify 382d4cd1847517ffcb1800fd462b625db7b2ebea^{commit} 382d4cd1847517ffcb1800fd462b625db7b2ebea # git checkout -q -f -B kisskb 382d4cd1847517ffcb1800fd462b625db7b2ebea # git clean -qxdf # < git log -1 # commit 382d4cd1847517ffcb1800fd462b625db7b2ebea # Author: Helge Deller # Date: Fri Aug 25 21:50:33 2023 +0200 # # lib/clz_ctz.c: Fix __clzdi2() and __ctzdi2() for 32-bit kernels # # The gcc compiler translates on some architectures the 64-bit # __builtin_clzll() function to a call to the libgcc function __clzdi2(), # which should take a 64-bit parameter on 32- and 64-bit platforms. # # But in the current kernel code, the built-in __clzdi2() function is # defined to operate (wrongly) on 32-bit parameters if BITS_PER_LONG == # 32, thus the return values on 32-bit kernels are in the range from # [0..31] instead of the expected [0..63] range. # # This patch fixes the in-kernel functions __clzdi2() and __ctzdi2() to # take a 64-bit parameter on 32-bit kernels as well, thus it makes the # functions identical for 32- and 64-bit kernels. # # This bug went unnoticed since kernel 3.11 for over 10 years, and here # are some possible reasons for that: # # a) Some architectures have assembly instructions to count the bits and # which are used instead of calling __clzdi2(), e.g. on x86 the bsr # instruction and on ppc cntlz is used. On such architectures the # wrong __clzdi2() implementation isn't used and as such the bug has # no effect and won't be noticed. # # b) Some architectures link to libgcc.a, and the in-kernel weak # functions get replaced by the correct 64-bit variants from libgcc.a. # # c) __builtin_clzll() and __clzdi2() doesn't seem to be used in many # places in the kernel, and most likely only in uncritical functions, # e.g. when printing hex values via seq_put_hex_ll(). The wrong return # value will still print the correct number, but just in a wrong # formatting (e.g. with too many leading zeroes). # # d) 32-bit kernels aren't used that much any longer, so they are less # tested. # # A trivial testcase to verify if the currently running 32-bit kernel is # affected by the bug is to look at the output of /proc/self/maps: # # Here the kernel uses a correct implementation of __clzdi2(): # # root@debian:~# cat /proc/self/maps # 00010000-00019000 r-xp 00000000 08:05 787324 /usr/bin/cat # 00019000-0001a000 rwxp 00009000 08:05 787324 /usr/bin/cat # 0001a000-0003b000 rwxp 00000000 00:00 0 [heap] # f7551000-f770d000 r-xp 00000000 08:05 794765 /usr/lib/hppa-linux-gnu/libc.so.6 # ... # # and this kernel uses the broken implementation of __clzdi2(): # # root@debian:~# cat /proc/self/maps # 0000000010000-0000000019000 r-xp 00000000 000000008:000000005 787324 /usr/bin/cat # 0000000019000-000000001a000 rwxp 000000009000 000000008:000000005 787324 /usr/bin/cat # 000000001a000-000000003b000 rwxp 00000000 00:00 0 [heap] # 00000000f73d1000-00000000f758d000 r-xp 00000000 000000008:000000005 794765 /usr/lib/hppa-linux-gnu/libc.so.6 # ... # # Signed-off-by: Helge Deller # Fixes: 4df87bb7b6a22 ("lib: add weak clz/ctz functions") # Cc: Chanho Min # Cc: Geert Uytterhoeven # Cc: stable@vger.kernel.org # v3.11+ # Signed-off-by: Linus Torvalds # < /opt/cross/kisskb/korg/gcc-12.2.0-nolibc/mips-linux/bin/mips-linux-gcc --version # < /opt/cross/kisskb/korg/gcc-12.2.0-nolibc/mips-linux/bin/mips-linux-ld --version # < git log --format=%s --max-count=1 382d4cd1847517ffcb1800fd462b625db7b2ebea # make -s -j 160 ARCH=mips O=/kisskb/build/linus-rand_allmodconfig_mips-gcc12 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-12.2.0-nolibc/mips-linux/bin/mips-linux- allmodconfig # Added to kconfig CONFIG_BUILD_DOCSRC=n # Added to kconfig CONFIG_MODULE_SIG=n # Added to kconfig CONFIG_SAMPLES=n # Added to kconfig CONFIG_MIPS_CPS_NS16550_BASE=0x1b0003f8 # Added to kconfig CONFIG_MIPS_CPS_NS16550_SHIFT=0 # Added to kconfig CONFIG_GCC_PLUGINS=n # Added to kconfig # < make -s -j 160 ARCH=mips O=/kisskb/build/linus-rand_allmodconfig_mips-gcc12 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-12.2.0-nolibc/mips-linux/bin/mips-linux- help # make -s -j 160 ARCH=mips O=/kisskb/build/linus-rand_allmodconfig_mips-gcc12 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-12.2.0-nolibc/mips-linux/bin/mips-linux- olddefconfig .config:14503:warning: override: reassigning to symbol MIPS_CPS_NS16550_SHIFT # make -s -j 160 ARCH=mips O=/kisskb/build/linus-rand_allmodconfig_mips-gcc12 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-12.2.0-nolibc/mips-linux/bin/mips-linux- Completed OK # rm -rf /kisskb/build/linus-rand_allmodconfig_mips-gcc12 # Build took: 0:10:06.766550