On March 4, 2017 3:46:44 PM PST, Logan Gunthorpe <log...@deltatee.com> wrote: >Hi Borislav, > >Thanks for the help. > >On 04/03/17 03:43 PM, Borislav Petkov wrote: >> You can boot with "debug-alternative" and look for those strings >where > >Here's the symbols for memcpy and the corresponding apply_alternatives >lines: > >ffffffff8122df90 T __memcpy >ffffffff8122df90 W memcpy >ffffffff8122dfb0 T memcpy_erms >ffffffff8122dfc0 T memcpy_orig > >[ 0.076018] apply_alternatives: feat: 3*32+16, old: >(ffffffff8122df90, len: 5), repl: (ffffffff819d7ac5, len: 0), pad: 0 >[ 0.076019] ffffffff8122df90: old_insn: e9 2b 00 00 00 >[ 0.076021] ffffffff8122df90: final_insn: 66 66 90 66 90 > >So it looks like it's patching in a NOP as it is supposed to. > > >> Also, do >> >> make <path-to-file>.s >> >> of the file where it does memcpy_fromio() and attach it here. I'd >like to see >> what the compiler generates. > >I've attached the whole file but this is the code in question: > > .loc 5 219 0 > movq 936(%rbp), %rdx # stdev_3(D)->mmio_mrpc, tmp127 > leaq 48(%rbx), %rax #, tmp113 > movq 40(%rbx), %rcx # MEM[(struct switchtec_user *)__mptr_7 + >-56B].read_len, MEM[(struct switchtec_user *)__mptr_7 + -56B].read_len > movq %rax, %rdi # tmp113, tmp118 > leaq 1024(%rdx), %rsi #, tmp114 > rep movsb > >Strangely, it decided to inline a memcpy with rep movsb. Any idea why >the compiler would do that? Is this just gcc being stupid? My gcc >version is below. > >Thanks, > >Logan > > >Using built-in specs. >COLLECT_GCC=gcc >COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-linux-gnu/4.9/lto-wrapper >Target: x86_64-linux-gnu >Configured with: ../src/configure -v --with-pkgversion='Debian >4.9.2-10' >--with-bugurl=file:///usr/share/doc/gcc-4.9/README.Bugs >--enable-languages=c,c++,java,go,d,fortran,objc,obj-c++ --prefix=/usr >--program-suffix=-4.9 --enable-shared --enable-linker-build-id >--libexecdir=/usr/lib --without-included-gettext --enable-threads=posix >--with-gxx-include-dir=/usr/include/c++/4.9 --libdir=/usr/lib >--enable-nls --with-sysroot=/ --enable-clocale=gnu >--enable-libstdcxx-debug --enable-libstdcxx-time=yes >--enable-gnu-unique-object --disable-vtable-verify --enable-plugin >--with-system-zlib --disable-browser-plugin --enable-java-awt=gtk >--enable-gtk-cairo >--with-java-home=/usr/lib/jvm/java-1.5.0-gcj-4.9-amd64/jre >--enable-java-home >--with-jvm-root-dir=/usr/lib/jvm/java-1.5.0-gcj-4.9-amd64 >--with-jvm-jar-dir=/usr/lib/jvm-exports/java-1.5.0-gcj-4.9-amd64 >--with-arch-directory=amd64 >--with-ecj-jar=/usr/share/java/eclipse-ecj.jar --enable-objc-gc >--enable-multiarch --with-arch-32=i586 --with-abi=m64 >--with-multilib-list=m32,m64,mx32 --enable-multilib --with-tune=generic >--enable-checking=release --build=x86_64-linux-gnu >--host=x86_64-linux-gnu --target=x86_64-linux-gnu >Thread model: posix >gcc version 4.9.2 (Debian 4.9.2-10)
For newer processors, as determined by -mtune=, it is actually the best option for an arbitrary copy. -- Sent from my Android device with K-9 Mail. Please excuse my brevity.
