On Thu, Jan 21, 2021 at 3:03 AM Sedat Dilek <sedat.dilek@xxxxxxxxx> wrote: > > On Mon, Jan 18, 2021 at 10:56 PM Bill Wendling <morbo@xxxxxxxxxx> wrote: > > > > On Mon, Jan 18, 2021 at 9:26 AM Sedat Dilek <sedat.dilek@xxxxxxxxx> wrote: > > > > > > On Mon, Jan 18, 2021 at 1:39 PM Sedat Dilek <sedat.dilek@xxxxxxxxx> wrote: > > > > > > > > On Mon, Jan 18, 2021 at 3:32 AM Bill Wendling <morbo@xxxxxxxxxx> wrote: > > > > > > > > > > On Sun, Jan 17, 2021 at 4:27 PM Sedat Dilek <sedat.dilek@xxxxxxxxx> wrote: > > > > > > > > > > > > [ big snip ] > > > > > > > > > > [More snippage.] > > > > > > > > > > > [ CC Fangrui ] > > > > > > > > > > > > With the attached... > > > > > > > > > > > > [PATCH v3] module: Ignore _GLOBAL_OFFSET_TABLE_ when warning for > > > > > > undefined symbols > > > > > > > > > > > > ...I was finally able to boot into a rebuild PGO-optimized Linux-kernel. > > > > > > For details see ClangBuiltLinux issue #1250 "Unknown symbol > > > > > > _GLOBAL_OFFSET_TABLE_ loading kernel modules". > > > > > > > > > > > Thanks for confirming that this works with the above patch. > > > > > > > > > > > @ Bill Nick Sami Nathan > > > > > > > > > > > > 1, Can you say something of the impact passing "LLVM_IAS=1" to make? > > > > > > > > > > The integrated assembler and this option are more-or-less orthogonal > > > > > to each other. One can still use the GNU assembler with PGO. If you're > > > > > having an issue, it may be related to ClangBuiltLinux issue #1250. > > > > > > > > > > > 2. Can you please try Nick's DWARF v5 support patchset v5 and > > > > > > CONFIG_DEBUG_INFO_DWARF5=y (see attachments)? > > > > > > > > > > > I know Nick did several tests with PGO. He may have looked into it > > > > > already, but we can check. > > > > > > > > > > > > > Reproducible. > > > > > > > > LLVM_IAS=1 + DWARF5 = Not bootable > > > > > > > > I will try: > > > > > > > > LLVM_IAS=1 + DWARF4 > > > > > > > > > > I was not able to boot into such a built Linux-kernel. > > > > > PGO will have no effect on debugging data. If this is an issue with > > DWARF, then it's likely orthogonal to the PGO patch. > > > > > For me worked: DWARF2 and LLVM_IAS=1 *not* set. > > > > > > Of course, this could be an issue with my system's LLVM/Clang. > > > > > > Debian clang version > > > 12.0.0-++20210115111113+45ef053bd709-1~exp1~20210115101809.3724 > > > > > Please use the official clang 11.0.1 release > > (https://releases.llvm.org/download.html), modifying the > > kernel/pgo/Kconfig as I suggested above. The reason we specify clang > > 12 for the minimal version is because of an issue that was recently > > fixed. > > > > I downgraded to clang-11.1.0-rc1. > ( See attachment. ) > > Doing the first build with PGO enabled plus DWARF5 and LLVM_IAS=1 works. > > But again after generating vmlinux.profdata and doing the PGO-rebuild > - the resulting Linux-kernel does NOT boot in QEMU or on bare metal. > With GNU/as I can boot. > > So this is independent of DWARF v4 or DWARF v5 (LLVM_IAS=1 and DWARF > v2 is not allowed). > There is something wrong (here) with passing LLVM_IAS=1 to make when > doing the PGO-rebuild. > > Can someone please verify and confirm that the PGO-rebuild with > LLVM_IAS=1 boots or boots not? > > Thanks. > > - Sedat - > > > > Can you give me a LLVM commit-id where you had success with LLVM_IAS=1 > > > and especially CONFIG_DEBUG_INFO_DWARF5=y? > > > Success means I was able to boot in QEMU and/or bare metal. > > > > > The DWARF5 patch isn't in yet, so I don't want to rely upon it too much. > > I passed LLVM_IAS=1 with KAFLAGS=-fprofile-use=vmlinux.profdata: /usr/bin/perf_5.10 stat make V=1 -j4 HOSTCC=clang HOSTCXX=clang++ HOSTLD=ld.lld CC=clang LD=ld.lld PAHOLE=/opt/paho le/bin/pahole LOCALVERSION=-2-amd64-clang11-pgo KBUILD_VERBOSE=1 KBUILD_BUILD_HOST=iniza KBUILD_BUILD_USER=sedat.dilek@xxxxxxxxx KBUILD_BUILD_TIMESTAMP=2021-01-21 bind eb-pkg KDEB_PKGVERSION=5.11.0~rc4-2~bullseye+dileks1 LLVM=1 KCFLAGS=-fprofile-use=vmlinux.profdata LLVM_IAS=1 KAFLAGS=-fprofile-use=vmlinux.profdata The resulting Linux-kernel does not boot. But I see in the build-log these warnings: warning: arch/x86/platform/efi/quirks.c: Function control flow change detected (hash mismatch) efi_arch_mem_reserve Hash = 73770966985 [-Wbackend-plugin] warning: arch/x86/platform/efi/efi.c: Function control flow change detected (hash mismatch) efi_attr_is_visible Hash = 57959232386 [-Wbackend-plugin] warning: arch/x86/boot/compressed/string.c: Function control flow change detected (hash mismatch) memcmp Hash = 12884901887 [-Wbackend-plugin] warning: arch/x86/boot/compressed/string.c: Function control flow change detected (hash mismatch) bcmp Hash = 12884901887 [-Wbackend-plugin] warning: arch/x86/boot/compressed/string.c: Function control flow change detected (hash mismatch) strcmp Hash = 44149752232 [-Wbackend-plugin] warning: arch/x86/boot/compressed/string.c: Function control flow change detected (hash mismatch) strnlen Hash = 29212902728 [-Wbackend-plugin] warning: arch/x86/boot/compressed/string.c: Function control flow change detected (hash mismatch) simple_strtoull Hash = 288230479369728480 [-Wbackend-plugin] warning: arch/x86/boot/compressed/string.c: Function control flow change detected (hash mismatch) strstr Hash = 76464046323 [-Wbackend-plugin] warning: arch/x86/boot/compressed/string.c: Function control flow change detected (hash mismatch) strchr Hash = 30948479515 [-Wbackend-plugin] warning: arch/x86/boot/compressed/string.c: Function control flow change detected (hash mismatch) kstrtoull Hash = 288230543187488006 [-Wbackend-plugin] What does "Function control flow change detected (hash mismatch)" mean? Related with my boot problems? - Sedat -
