# git rev-parse -q --verify 574823bfab82d9d8fa47f422778043fbb4b4f50e^{commit} 574823bfab82d9d8fa47f422778043fbb4b4f50e already have revision, skipping fetch # git checkout -q -f -B kisskb 574823bfab82d9d8fa47f422778043fbb4b4f50e # git clean -qxdf # < git log -1 # commit 574823bfab82d9d8fa47f422778043fbb4b4f50e # Author: Linus Torvalds # Date: Sat Jan 5 17:50:59 2019 -0800 # # Change mincore() to count "mapped" pages rather than "cached" pages # # The semantics of what "in core" means for the mincore() system call are # somewhat unclear, but Linux has always (since 2.3.52, which is when # mincore() was initially done) treated it as "page is available in page # cache" rather than "page is mapped in the mapping". # # The problem with that traditional semantic is that it exposes a lot of # system cache state that it really probably shouldn't, and that users # shouldn't really even care about. # # So let's try to avoid that information leak by simply changing the # semantics to be that mincore() counts actual mapped pages, not pages # that might be cheaply mapped if they were faulted (note the "might be" # part of the old semantics: being in the cache doesn't actually guarantee # that you can access them without IO anyway, since things like network # filesystems may have to revalidate the cache before use). # # In many ways the old semantics were somewhat insane even aside from the # information leak issue. From the very beginning (and that beginning is # a long time ago: 2.3.52 was released in March 2000, I think), the code # had a comment saying # # Later we can get more picky about what "in core" means precisely. # # and this is that "later". Admittedly it is much later than is really # comfortable. # # NOTE! This is a real semantic change, and it is for example known to # change the output of "fincore", since that program literally does a # mmmap without populating it, and then doing "mincore()" on that mapping # that doesn't actually have any pages in it. # # I'm hoping that nobody actually has any workflow that cares, and the # info leak is real. # # We may have to do something different if it turns out that people have # valid reasons to want the old semantics, and if we can limit the # information leak sanely. # # Cc: Kevin Easton # Cc: Jiri Kosina # Cc: Masatake YAMATO # Cc: Andrew Morton # Cc: Greg KH # Cc: Peter Zijlstra # Cc: Michal Hocko # Signed-off-by: Linus Torvalds # < /opt/cross/kisskb/korg/gcc-8.1.0-nolibc/aarch64-linux/bin/aarch64-linux-gcc --version # < /opt/cross/kisskb/korg/gcc-8.1.0-nolibc/aarch64-linux/bin/aarch64-linux-ld --version # < git log --format=%s --max-count=1 574823bfab82d9d8fa47f422778043fbb4b4f50e # < make -s -j 10 ARCH=arm64 O=/kisskb/build/linus_arm64-allmodconfig_arm64-gcc8 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-8.1.0-nolibc/aarch64-linux/bin/aarch64-linux- allmodconfig # make -s -j 10 ARCH=arm64 O=/kisskb/build/linus_arm64-allmodconfig_arm64-gcc8 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-8.1.0-nolibc/aarch64-linux/bin/aarch64-linux- /kisskb/src/arch/arm64/boot/dts/rockchip/rk3399-gru-bob.dts:25.9-29.5: Warning (graph_port): /edp-panel/ports: graph port node name should be 'port' /kisskb/src/arch/arm64/boot/dts/rockchip/rk3399-gru-kevin.dts:46.9-50.5: Warning (graph_port): /edp-panel/ports: graph port node name should be 'port' /kisskb/src/arch/arm64/boot/dts/rockchip/rk3399-sapphire-excavator.dts:94.9-98.5: Warning (graph_port): /edp-panel/ports: graph port node name should be 'port' In file included from /kisskb/src/include/asm-generic/bug.h:18, from /kisskb/src/arch/arm64/include/asm/bug.h:37, from /kisskb/src/include/linux/bug.h:5, from /kisskb/src/include/linux/mmdebug.h:5, from /kisskb/src/include/linux/mm.h:9, from /kisskb/src/drivers/dma/imx-dma.c:14: /kisskb/src/drivers/dma/imx-dma.c: In function 'imxdma_sg_next': /kisskb/src/include/linux/kernel.h:846:29: warning: comparison of distinct pointer types lacks a cast (!!(sizeof((typeof(x) *)1 == (typeof(y) *)1))) ^~ /kisskb/src/include/linux/kernel.h:860:4: note: in expansion of macro '__typecheck' (__typecheck(x, y) && __no_side_effects(x, y)) ^~~~~~~~~~~ /kisskb/src/include/linux/kernel.h:870:24: note: in expansion of macro '__safe_cmp' __builtin_choose_expr(__safe_cmp(x, y), \ ^~~~~~~~~~ /kisskb/src/include/linux/kernel.h:879:19: note: in expansion of macro '__careful_cmp' #define min(x, y) __careful_cmp(x, y, <) ^~~~~~~~~~~~~ /kisskb/src/drivers/dma/imx-dma.c:288:8: note: in expansion of macro 'min' now = min(d->len, sg_dma_len(sg)); ^~~ Completed OK # rm -rf /kisskb/build/linus_arm64-allmodconfig_arm64-gcc8 # Build took: 0:40:39.689882