On Tue, Feb 2, 2021 at 10:38 PM Khem Raj <[email protected]> wrote: > > I am not looking at 5.4 since the issue is x86 specific and all x86 > BSPs on master are already on 5.10 perhaps we wont need to backport it > immediately
Yah. And I just tried to port the patches, x86-entry-Emit-a-symbol-for-register-restoring-thunk.patch was bad enough, but I was manually able to do a reject resolution that looks minimally sane .. but objtool-Fix-seg-fault-with-Clang-non-section-symbols.patch rejects in every single file in the patch and they look non trivial to fix. I'll keep watching for something on 5.4 -stable, but it will be tricky to do it ourselves. Bruce > > On Tue, Feb 2, 2021 at 7:29 PM Bruce Ashfield <[email protected]> > wrote: > > > > On Tue, Feb 2, 2021 at 10:26 PM Khem Raj <[email protected]> wrote: > > > > > > ah I see your patch series, does this include above two patches ? > > > > It does yes. > > > > My local build worked, and since you confirmed they were good for the > > binutils fix, I cherry picked them on that basis. > > > > I did notice that they failed to cherry-pick to v5.4 though, so if > > want that to work with the new binutils, we have work to do, or wait > > for -stable. Let me know if you are looking at it, otherwise, I'll see > > what needs to be done tonight/tomorrow. > > > > Bruce > > > > > > > > On Tue, Feb 2, 2021 at 7:18 PM Khem Raj <[email protected]> wrote: > > > > > > > > Hi Bruce > > > > > > > > Yeah :) it was my local series and as mentioned temp hack. I think we > > > > will wait for your SRCREV bumps for final fix. but perhaps this can > > > > help to temporarily testing master-next a bit. > > > > > > > > On Tue, Feb 2, 2021 at 7:12 PM Bruce Ashfield > > > > <[email protected]> wrote: > > > > > > > > > > Richard, > > > > > > > > > > Obviously ignore this patch. > > > > > > > > > > It'll fail to apply as soon as my SRCREVs are bumped, and honestly, > > > > > it's a hassle to have to wonder if this has been applied, have a > > > > > failure, sent a revert, etc. > > > > > > > > > > I'm not even sure why it was sent. > > > > > > > > > > Bruce > > > > > > > > > > On Tue, Feb 2, 2021 at 8:36 PM Khem Raj <[email protected]> wrote: > > > > > > > > > > > > This is for master-next testing only !! > > > > > > > > > > > > Signed-off-by: Khem Raj <[email protected]> > > > > > > --- > > > > > > ...fault-with-Clang-non-section-symbols.patch | 150 > > > > > > ++++++++++++++++++ > > > > > > ...-symbol-for-register-restoring-thunk.patch | 125 +++++++++++++++ > > > > > > meta/recipes-kernel/linux/linux-yocto_5.10.bb | 5 + > > > > > > 3 files changed, 280 insertions(+) > > > > > > create mode 100644 > > > > > > meta/recipes-kernel/linux/files/0001-objtool-Fix-seg-fault-with-Clang-non-section-symbols.patch > > > > > > create mode 100644 > > > > > > meta/recipes-kernel/linux/files/0001-x86-entry-Emit-a-symbol-for-register-restoring-thunk.patch > > > > > > > > > > > > diff --git > > > > > > a/meta/recipes-kernel/linux/files/0001-objtool-Fix-seg-fault-with-Clang-non-section-symbols.patch > > > > > > > > > > > > b/meta/recipes-kernel/linux/files/0001-objtool-Fix-seg-fault-with-Clang-non-section-symbols.patch > > > > > > new file mode 100644 > > > > > > index 0000000000..f606e3ee6d > > > > > > --- /dev/null > > > > > > +++ > > > > > > b/meta/recipes-kernel/linux/files/0001-objtool-Fix-seg-fault-with-Clang-non-section-symbols.patch > > > > > > @@ -0,0 +1,150 @@ > > > > > > +From 44f6a7c0755d8dd453c70557e11687bb080a6f21 Mon Sep 17 00:00:00 > > > > > > 2001 > > > > > > +From: Josh Poimboeuf <[email protected]> > > > > > > +Date: Mon, 14 Dec 2020 16:04:20 -0600 > > > > > > +Subject: [PATCH] objtool: Fix seg fault with Clang non-section > > > > > > symbols > > > > > > + > > > > > > +The Clang assembler likes to strip section symbols, which means > > > > > > objtool > > > > > > +can't reference some text code by its section. This confuses > > > > > > objtool > > > > > > +greatly, causing it to seg fault. > > > > > > + > > > > > > +The fix is similar to what was done before, for ORC reloc > > > > > > generation: > > > > > > + > > > > > > + e81e07244325 ("objtool: Support Clang non-section symbols in ORC > > > > > > generation") > > > > > > + > > > > > > +Factor out that code into a common helper and use it for static > > > > > > call > > > > > > +reloc generation as well. > > > > > > + > > > > > > +Reported-by: Arnd Bergmann <[email protected]> > > > > > > +Signed-off-by: Josh Poimboeuf <[email protected]> > > > > > > +Signed-off-by: Peter Zijlstra (Intel) <[email protected]> > > > > > > +Reviewed-by: Nick Desaulniers <[email protected]> > > > > > > +Reviewed-by: Miroslav Benes <[email protected]> > > > > > > +Link: https://github.com/ClangBuiltLinux/linux/issues/1207 > > > > > > +Link: > > > > > > https://lkml.kernel.org/r/ba6b6c0f0dd5acbba66e403955a967d9fdd1726a.1607983452.git.jpoim...@redhat.com > > > > > > +--- > > > > > > + tools/objtool/check.c | 11 +++++++++-- > > > > > > + tools/objtool/elf.c | 26 ++++++++++++++++++++++++++ > > > > > > + tools/objtool/elf.h | 2 ++ > > > > > > + tools/objtool/orc_gen.c | 29 +++++------------------------ > > > > > > + 4 files changed, 42 insertions(+), 26 deletions(-) > > > > > > + > > > > > > +diff --git a/tools/objtool/check.c b/tools/objtool/check.c > > > > > > +index c6ab44543c92..5f8d3eed78a1 100644 > > > > > > +--- a/tools/objtool/check.c > > > > > > ++++ b/tools/objtool/check.c > > > > > > +@@ -467,13 +467,20 @@ static int > > > > > > create_static_call_sections(struct objtool_file *file) > > > > > > + > > > > > > + /* populate reloc for 'addr' */ > > > > > > + reloc = malloc(sizeof(*reloc)); > > > > > > ++ > > > > > > + if (!reloc) { > > > > > > + perror("malloc"); > > > > > > + return -1; > > > > > > + } > > > > > > + memset(reloc, 0, sizeof(*reloc)); > > > > > > +- reloc->sym = insn->sec->sym; > > > > > > +- reloc->addend = insn->offset; > > > > > > ++ > > > > > > ++ insn_to_reloc_sym_addend(insn->sec, insn->offset, > > > > > > reloc); > > > > > > ++ if (!reloc->sym) { > > > > > > ++ WARN_FUNC("static call tramp: missing > > > > > > containing symbol", > > > > > > ++ insn->sec, insn->offset); > > > > > > ++ return -1; > > > > > > ++ } > > > > > > ++ > > > > > > + reloc->type = R_X86_64_PC32; > > > > > > + reloc->offset = idx * sizeof(struct > > > > > > static_call_site); > > > > > > + reloc->sec = reloc_sec; > > > > > > +diff --git a/tools/objtool/elf.c b/tools/objtool/elf.c > > > > > > +index 4e1d7460574b..be89c741ba9a 100644 > > > > > > +--- a/tools/objtool/elf.c > > > > > > ++++ b/tools/objtool/elf.c > > > > > > +@@ -262,6 +262,32 @@ struct reloc *find_reloc_by_dest(const struct > > > > > > elf *elf, struct section *sec, uns > > > > > > + return find_reloc_by_dest_range(elf, sec, offset, 1); > > > > > > + } > > > > > > + > > > > > > ++void insn_to_reloc_sym_addend(struct section *sec, unsigned long > > > > > > offset, > > > > > > ++ struct reloc *reloc) > > > > > > ++{ > > > > > > ++ if (sec->sym) { > > > > > > ++ reloc->sym = sec->sym; > > > > > > ++ reloc->addend = offset; > > > > > > ++ return; > > > > > > ++ } > > > > > > ++ > > > > > > ++ /* > > > > > > ++ * The Clang assembler strips section symbols, so we have > > > > > > to reference > > > > > > ++ * the function symbol instead: > > > > > > ++ */ > > > > > > ++ reloc->sym = find_symbol_containing(sec, offset); > > > > > > ++ if (!reloc->sym) { > > > > > > ++ /* > > > > > > ++ * Hack alert. This happens when we need to > > > > > > reference the NOP > > > > > > ++ * pad insn immediately after the function. > > > > > > ++ */ > > > > > > ++ reloc->sym = find_symbol_containing(sec, offset - > > > > > > 1); > > > > > > ++ } > > > > > > ++ > > > > > > ++ if (reloc->sym) > > > > > > ++ reloc->addend = offset - reloc->sym->offset; > > > > > > ++} > > > > > > ++ > > > > > > + static int read_sections(struct elf *elf) > > > > > > + { > > > > > > + Elf_Scn *s = NULL; > > > > > > +diff --git a/tools/objtool/elf.h b/tools/objtool/elf.h > > > > > > +index 807f8c670097..e6890cc70a25 100644 > > > > > > +--- a/tools/objtool/elf.h > > > > > > ++++ b/tools/objtool/elf.h > > > > > > +@@ -140,6 +140,8 @@ struct reloc *find_reloc_by_dest(const struct > > > > > > elf *elf, struct section *sec, uns > > > > > > + struct reloc *find_reloc_by_dest_range(const struct elf *elf, > > > > > > struct section *sec, > > > > > > + unsigned long offset, unsigned > > > > > > int len); > > > > > > + struct symbol *find_func_containing(struct section *sec, unsigned > > > > > > long offset); > > > > > > ++void insn_to_reloc_sym_addend(struct section *sec, unsigned long > > > > > > offset, > > > > > > ++ struct reloc *reloc); > > > > > > + int elf_rebuild_reloc_section(struct elf *elf, struct section > > > > > > *sec); > > > > > > + > > > > > > + #define for_each_sec(file, sec) > > > > > > \ > > > > > > +diff --git a/tools/objtool/orc_gen.c b/tools/objtool/orc_gen.c > > > > > > +index 235663b96adc..9ce68b385a1b 100644 > > > > > > +--- a/tools/objtool/orc_gen.c > > > > > > ++++ b/tools/objtool/orc_gen.c > > > > > > +@@ -105,30 +105,11 @@ static int create_orc_entry(struct elf *elf, > > > > > > struct section *u_sec, struct secti > > > > > > + } > > > > > > + memset(reloc, 0, sizeof(*reloc)); > > > > > > + > > > > > > +- if (insn_sec->sym) { > > > > > > +- reloc->sym = insn_sec->sym; > > > > > > +- reloc->addend = insn_off; > > > > > > +- } else { > > > > > > +- /* > > > > > > +- * The Clang assembler doesn't produce section > > > > > > symbols, so we > > > > > > +- * have to reference the function symbol instead: > > > > > > +- */ > > > > > > +- reloc->sym = find_symbol_containing(insn_sec, > > > > > > insn_off); > > > > > > +- if (!reloc->sym) { > > > > > > +- /* > > > > > > +- * Hack alert. This happens when we need > > > > > > to reference > > > > > > +- * the NOP pad insn immediately after the > > > > > > function. > > > > > > +- */ > > > > > > +- reloc->sym = > > > > > > find_symbol_containing(insn_sec, > > > > > > +- insn_off > > > > > > - 1); > > > > > > +- } > > > > > > +- if (!reloc->sym) { > > > > > > +- WARN("missing symbol for insn at offset > > > > > > 0x%lx\n", > > > > > > +- insn_off); > > > > > > +- return -1; > > > > > > +- } > > > > > > +- > > > > > > +- reloc->addend = insn_off - reloc->sym->offset; > > > > > > ++ insn_to_reloc_sym_addend(insn_sec, insn_off, reloc); > > > > > > ++ if (!reloc->sym) { > > > > > > ++ WARN("missing symbol for insn at offset 0x%lx", > > > > > > ++ insn_off); > > > > > > ++ return -1; > > > > > > + } > > > > > > + > > > > > > + reloc->type = R_X86_64_PC32; > > > > > > +-- > > > > > > +2.30.0 > > > > > > + > > > > > > diff --git > > > > > > a/meta/recipes-kernel/linux/files/0001-x86-entry-Emit-a-symbol-for-register-restoring-thunk.patch > > > > > > > > > > > > b/meta/recipes-kernel/linux/files/0001-x86-entry-Emit-a-symbol-for-register-restoring-thunk.patch > > > > > > new file mode 100644 > > > > > > index 0000000000..320d7e929c > > > > > > --- /dev/null > > > > > > +++ > > > > > > b/meta/recipes-kernel/linux/files/0001-x86-entry-Emit-a-symbol-for-register-restoring-thunk.patch > > > > > > @@ -0,0 +1,125 @@ > > > > > > +From de98d14b7f4511380a9d9b784a12507c790d8a54 Mon Sep 17 00:00:00 > > > > > > 2001 > > > > > > +From: Nick Desaulniers <[email protected]> > > > > > > +Date: Tue, 12 Jan 2021 11:46:24 -0800 > > > > > > +Subject: [PATCH] x86/entry: Emit a symbol for register restoring > > > > > > thunk > > > > > > + > > > > > > +Arnd found a randconfig that produces the warning: > > > > > > + > > > > > > + arch/x86/entry/thunk_64.o: warning: objtool: missing symbol for > > > > > > insn at > > > > > > + offset 0x3e > > > > > > + > > > > > > +when building with LLVM_IAS=1 (Clang's integrated assembler). Josh > > > > > > +notes: > > > > > > + > > > > > > + With the LLVM assembler not generating section symbols, objtool > > > > > > has no > > > > > > + way to reference this code when it generates ORC unwinder > > > > > > entries, > > > > > > + because this code is outside of any ELF function. > > > > > > + > > > > > > + The limitation now being imposed by objtool is that all code > > > > > > must be > > > > > > + contained in an ELF symbol. And .L symbols don't create such > > > > > > symbols. > > > > > > + > > > > > > + So basically, you can use an .L symbol *inside* a function or a > > > > > > code > > > > > > + segment, you just can't use the .L symbol to contain the code > > > > > > using a > > > > > > + SYM_*_START/END annotation pair. > > > > > > + > > > > > > +Fangrui notes that this optimization is helpful for reducing image > > > > > > size > > > > > > +when compiling with -ffunction-sections and -fdata-sections. I have > > > > > > +observed on the order of tens of thousands of symbols for the > > > > > > kernel > > > > > > +images built with those flags. > > > > > > + > > > > > > +A patch has been authored against GNU binutils to match this > > > > > > behavior > > > > > > +of not generating unused section symbols ([1]), so this will > > > > > > +also become a problem for users of GNU binutils once they upgrade > > > > > > to 2.36. > > > > > > + > > > > > > +Omit the .L prefix on a label so that the assembler will emit an > > > > > > entry > > > > > > +into the symbol table for the label, with STB_LOCAL binding. This > > > > > > +enables objtool to generate proper unwind info here with > > > > > > LLVM_IAS=1 or > > > > > > +GNU binutils 2.36+. > > > > > > + > > > > > > + [ bp: Massage commit message. ] > > > > > > + > > > > > > +Reported-by: Arnd Bergmann <[email protected]> > > > > > > +Suggested-by: Josh Poimboeuf <[email protected]> > > > > > > +Suggested-by: Borislav Petkov <[email protected]> > > > > > > +Suggested-by: Mark Brown <[email protected]> > > > > > > +Signed-off-by: Nick Desaulniers <[email protected]> > > > > > > +Signed-off-by: Borislav Petkov <[email protected]> > > > > > > +Acked-by: Peter Zijlstra (Intel) <[email protected]> > > > > > > +Acked-by: Josh Poimboeuf <[email protected]> > > > > > > +Link: > > > > > > https://lkml.kernel.org/r/[email protected] > > > > > > +Link: https://github.com/ClangBuiltLinux/linux/issues/1209 > > > > > > +Link: https://reviews.llvm.org/D93783 > > > > > > +Link: https://sourceware.org/binutils/docs/as/Symbol-Names.html > > > > > > +Link: > > > > > > https://sourceware.org/git/?p=binutils-gdb.git;a=commit;h=d1bcae833b32f1408485ce69f844dcd7ded093a8 > > > > > > [1] > > > > > > +--- > > > > > > + Documentation/asm-annotations.rst | 5 +++++ > > > > > > + arch/x86/entry/thunk_64.S | 8 ++++---- > > > > > > + include/linux/linkage.h | 5 +++++ > > > > > > + 3 files changed, 14 insertions(+), 4 deletions(-) > > > > > > + > > > > > > +diff --git a/Documentation/asm-annotations.rst > > > > > > b/Documentation/asm-annotations.rst > > > > > > +index 32ea57483378..76424e0431f4 100644 > > > > > > +--- a/Documentation/asm-annotations.rst > > > > > > ++++ b/Documentation/asm-annotations.rst > > > > > > +@@ -100,6 +100,11 @@ Instruction Macros > > > > > > + ~~~~~~~~~~~~~~~~~~ > > > > > > + This section covers ``SYM_FUNC_*`` and ``SYM_CODE_*`` enumerated > > > > > > above. > > > > > > + > > > > > > ++``objtool`` requires that all code must be contained in an ELF > > > > > > symbol. Symbol > > > > > > ++names that have a ``.L`` prefix do not emit symbol table entries. > > > > > > ``.L`` > > > > > > ++prefixed symbols can be used within a code region, but should be > > > > > > avoided for > > > > > > ++denoting a range of code via ``SYM_*_START/END`` annotations. > > > > > > ++ > > > > > > + * ``SYM_FUNC_START`` and ``SYM_FUNC_START_LOCAL`` are supposed to > > > > > > be **the > > > > > > + most frequent markings**. They are used for functions with > > > > > > standard calling > > > > > > + conventions -- global and local. Like in C, they both align the > > > > > > functions to > > > > > > +diff --git a/arch/x86/entry/thunk_64.S b/arch/x86/entry/thunk_64.S > > > > > > +index ccd32877a3c4..c9a9fbf1655f 100644 > > > > > > +--- a/arch/x86/entry/thunk_64.S > > > > > > ++++ b/arch/x86/entry/thunk_64.S > > > > > > +@@ -31,7 +31,7 @@ SYM_FUNC_START_NOALIGN(\name) > > > > > > + .endif > > > > > > + > > > > > > + call \func > > > > > > +- jmp .L_restore > > > > > > ++ jmp __thunk_restore > > > > > > + SYM_FUNC_END(\name) > > > > > > + _ASM_NOKPROBE(\name) > > > > > > + .endm > > > > > > +@@ -44,7 +44,7 @@ SYM_FUNC_END(\name) > > > > > > + #endif > > > > > > + > > > > > > + #ifdef CONFIG_PREEMPTION > > > > > > +-SYM_CODE_START_LOCAL_NOALIGN(.L_restore) > > > > > > ++SYM_CODE_START_LOCAL_NOALIGN(__thunk_restore) > > > > > > + popq %r11 > > > > > > + popq %r10 > > > > > > + popq %r9 > > > > > > +@@ -56,6 +56,6 @@ SYM_CODE_START_LOCAL_NOALIGN(.L_restore) > > > > > > + popq %rdi > > > > > > + popq %rbp > > > > > > + ret > > > > > > +- _ASM_NOKPROBE(.L_restore) > > > > > > +-SYM_CODE_END(.L_restore) > > > > > > ++ _ASM_NOKPROBE(__thunk_restore) > > > > > > ++SYM_CODE_END(__thunk_restore) > > > > > > + #endif > > > > > > +diff --git a/include/linux/linkage.h b/include/linux/linkage.h > > > > > > +index 5bcfbd972e97..dbf8506decca 100644 > > > > > > +--- a/include/linux/linkage.h > > > > > > ++++ b/include/linux/linkage.h > > > > > > +@@ -178,6 +178,11 @@ > > > > > > + * Objtool generates debug info for both FUNC & CODE, but needs > > > > > > special > > > > > > + * annotations for each CODE's start (to describe the actual > > > > > > stack frame). > > > > > > + * > > > > > > ++ * Objtool requires that all code must be contained in an ELF > > > > > > symbol. Symbol > > > > > > ++ * names that have a .L prefix do not emit symbol table entries. > > > > > > .L > > > > > > ++ * prefixed symbols can be used within a code region, but should > > > > > > be avoided for > > > > > > ++ * denoting a range of code via ``SYM_*_START/END`` annotations. > > > > > > ++ * > > > > > > + * ALIAS -- does not generate debug info -- the aliased function > > > > > > will > > > > > > + */ > > > > > > + > > > > > > +-- > > > > > > +2.30.0 > > > > > > + > > > > > > diff --git a/meta/recipes-kernel/linux/linux-yocto_5.10.bb > > > > > > b/meta/recipes-kernel/linux/linux-yocto_5.10.bb > > > > > > index 7e570b04f5..aa328aff52 100644 > > > > > > --- a/meta/recipes-kernel/linux/linux-yocto_5.10.bb > > > > > > +++ b/meta/recipes-kernel/linux/linux-yocto_5.10.bb > > > > > > @@ -29,6 +29,11 @@ SRCREV_meta ?= > > > > > > "47c7a3148a4d7653cec536ba202b25148d1952ad" > > > > > > SRC_URI = > > > > > > "git://git.yoctoproject.org/linux-yocto.git;name=machine;branch=${KBRANCH}; > > > > > > \ > > > > > > > > > > > > git://git.yoctoproject.org/yocto-kernel-cache;type=kmeta;name=meta;branch=yocto-5.10;destsuffix=${KMETA}" > > > > > > > > > > > > +SRC_URI += "\ > > > > > > + > > > > > > file://0001-objtool-Fix-seg-fault-with-Clang-non-section-symbols.patch > > > > > > \ > > > > > > + > > > > > > file://0001-x86-entry-Emit-a-symbol-for-register-restoring-thunk.patch > > > > > > \ > > > > > > +" > > > > > > + > > > > > > LIC_FILES_CHKSUM = > > > > > > "file://COPYING;md5=6bc538ed5bd9a7fc9398086aedcd7e46" > > > > > > LINUX_VERSION ?= "5.10.5" > > > > > > > > > > > > -- > > > > > > 2.30.0 > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > -- > > > > > - Thou shalt not follow the NULL pointer, for chaos and madness await > > > > > thee at its end > > > > > - "Use the force Harry" - Gandalf, Star Trek II > > > > > > > > -- > > - Thou shalt not follow the NULL pointer, for chaos and madness await > > thee at its end > > - "Use the force Harry" - Gandalf, Star Trek II -- - Thou shalt not follow the NULL pointer, for chaos and madness await thee at its end - "Use the force Harry" - Gandalf, Star Trek II
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