On Thu, May 27, 2021 at 01:47:41PM -0300, Arnaldo Carvalho de Melo wrote: > Em Thu, May 27, 2021 at 12:38:38PM -0300, Arnaldo Carvalho de Melo escreveu: > > Em Thu, May 27, 2021 at 05:27:58PM +0200, Michal Suchánek escreveu: > > > Hello, > > > > > > On Thu, May 27, 2021 at 11:58:24AM -0300, Arnaldo Carvalho de Melo wrote: > > > > Em Thu, May 27, 2021 at 11:55:10AM -0300, Arnaldo Carvalho de Melo escreveu: > > > > > Em Mon, May 24, 2021 at 04:42:22PM -0700, Andrii Nakryiko escreveu: > > > > > > btf_encoder is ignoring zero-sized per-CPU ELF symbols, but the same has to be > > > > > > done for DWARF variables when matching them with ELF symbols. This is due to > > > > > > zero-sized DWARF variables matching unrelated (non-zero-sized) variable that > > > > > > happens to be allocated at the exact same address, leading to a lot of > > > > > > confusion in BTF. > > > > > > > > > > > See [0] for when this causes big problems. > > > > > > > > > > > [0] https://lore.kernel.org/bpf/CAEf4BzZ0-sihSL-UAm21JcaCCY92CqfNxycHRZYXcoj8OYb=wA@xxxxxxxxxxxxxx/ > > > > > > > > I also added this: > > > > > > > > Reported-by: Michal Suchánek <msuchanek@xxxxxxx> > > > > > > > > Michal, so you tested this patch and verified it fixed the problem? If > > > > so please let me know so that I also add: > > > > > > This is the first time I see this patch. > > > > > > Given that linux-next does not build for me at the moment > > > I don't think I will test it soon. > > > > Ok, I'm test building with torvalds/master, will try with linux-next > > afterwards, > > I build and booted torvalds/master, all seems to work, now moving to > linux-next. [ 9s] /usr/bin/qemu-kvm -nodefaults -no-reboot -nographic -vga none -cpu host -object rng-random,filename=/dev/random,id=rng0 -device virtio-rng-pci,rng=rng0 -runas qemu -net none -kernel /var/cache/obs/worker/root_2/.mount/boot/kernel -initrd /var/cache/obs/worker/root_2/.mount/boot/initrd -append root=/dev/disk/by-id/virtio-0 rootfstype=ext4 rootflags=noatime ext4.allow_unsupported=1 mitigations=off panic=1 quiet no-kvmclock elevator=noop nmi_watchdog=0 rw rd.driver.pre=binfmt_misc console=ttyS0 init=/.build/build -m 8192 -drive file=/var/cache/obs/worker/root_2/root,format=raw,if=none,id=disk,cache=unsafe -device virtio-blk-pci,drive=disk,serial=0 -drive file=/var/cache/obs/worker/root_2/swap,format=raw,if=none,id=swap,cache=unsafe -device virtio-blk-pci,drive=swap,serial=1 -serial stdio -chardev socket,id=monitor,server,nowait,path=/var/cache/obs/worker/root_2/root.qemu/monitor -mon chardev=monitor,mode=readline -smp 8 [ 9s] c[?7l[2J[0mSeaBIOS (version rel-1.14.0-0-g155821a-rebuilt.opensuse.org) [ 15s] Booting from ROM..c[?7l[2J### VM INTERACTION END ### [ 15s] 2nd stage started in virtual machine [ 15s] machine type: x86_64 [ 15s] Linux version: 5.13.0-rc3-next-2[ 5.210478] sysrq: Changing Loglevel [ 15s] 0210526-2.g3bd43[ 5.211566] sysrq: Loglevel set to 4 [ 15s] 9f-vanilla #1 SMP Thu May 27 18:27:17 UTC 2021 (3bd439f) [ 15s] Increasing log level from now on... [ 15s] Enable sysrq operations [ 15s] Setting up swapspace version 1, size = 2 GiB (2097147904 bytes) [ 15s] no label, UUID=6e22796c-6df5-4859-a291-24acde2e92e5 [ 15s] swapon: /dev/vdb: found signature [pagesize=4096, signature=swap] [ 15s] swapon: /dev/vdb: pagesize=4096, swapsize=2097152000, devsize=2097152000 [ 15s] swapon /dev/vdb [ 15s] WARNING: udev not running, creating extra device nodes [ 15s] logging output to //.build.log... next-20210527 does not build becuase of missing symbol but next-20210526 built with the patched pahole boots. Tested-by: Michal Suchánek <msuchanek@xxxxxxx> Thanks Michal > > > Thanks, > > > > - Arnaldo > > > > > Thanks > > > > > > Michal > > > > > > > > > > > Tested-by: Michal Suchánek <msuchanek@xxxxxxx> > > > > > > > > Thanks, > > > > > > > > - Arnaldo > > > > > > > > > > +++ b/btf_encoder.c > > > > > > @@ -550,6 +551,7 @@ int cu__encode_btf(struct cu *cu, int verbose, bool force, > > > > > > > > > > > > /* addr has to be recorded before we follow spec */ > > > > > > addr = var->ip.addr; > > > > > > + dwarf_name = variable__name(var, cu); > > > > > > > > > > > > /* DWARF takes into account .data..percpu section offset > > > > > > * within its segment, which for vmlinux is 0, but for kernel > > > > > > @@ -582,11 +584,9 @@ int cu__encode_btf(struct cu *cu, int verbose, bool force, > > > > > > * modules per-CPU data section has non-zero offset so all > > > > > > * per-CPU symbols have non-zero values. > > > > > > */ > > > > > > - if (var->ip.addr == 0) { > > > > > > - dwarf_name = variable__name(var, cu); > > > > > > + if (var->ip.addr == 0) > > > > > > if (!dwarf_name || strcmp(dwarf_name, name)) > > > > > > continue; > > > > > > - } > > > > > > > > > > > > if (var->spec) > > > > > > var = var->spec; > > > > > > @@ -600,6 +600,13 @@ int cu__encode_btf(struct cu *cu, int verbose, bool force, > > > > > > > > > > I just changed the above hunk to be: > > > > > > > > > > @@ -583,7 +585,6 @@ int cu__encode_btf(struct cu *cu, int verbose, bool force, > > > > > * per-CPU symbols have non-zero values. > > > > > */ > > > > > if (var->ip.addr == 0) { > > > > > - dwarf_name = variable__name(var, cu); > > > > > if (!dwarf_name || strcmp(dwarf_name, name)) > > > > > continue; > > > > > } > > > > > > > > > > > > > > > Which is shorter and keeps the {} around a multi line if block, ok? > > > > > > > > > > Thanks, applied! > > > > > > > > > > - Arnaldo > > > > > > > > -- > > > > > > > > - Arnaldo > > > > -- > > > > - Arnaldo > > -- > > - Arnaldo
