From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-ej1-f46.google.com (mail-ej1-f46.google.com [209.85.218.46]) by mx.groups.io with SMTP id smtpd.web10.4121.1612321966917884656 for ; Tue, 02 Feb 2021 19:12:47 -0800 Authentication-Results: mx.groups.io; dkim=pass header.i=@gmail.com header.s=20161025 header.b=Dnj0WVX2; spf=pass (domain: gmail.com, ip: 209.85.218.46, mailfrom: bruce.ashfield@gmail.com) Received: by mail-ej1-f46.google.com with SMTP id b9so13706308ejy.12 for ; Tue, 02 Feb 2021 19:12:46 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=mT3hItcKDGh+TwyzpAI+i3bdR6AQap++AnDVUAh1J/Y=; b=Dnj0WVX2HnOT3ky4Bp5uH9YFHkLBTYlTQ/1wBoIuKy8BT7/vZHuS5YGKjYThAtSSAb TgiMG4/kmuuFeVIzBCme/aeOIeFU5HNx9ttuTev5dRmHjKtWertZx0L/6UUb5bYJDBcY ZHRe/F/pz0sneF6aurO8YhWShFmlTNSItejubOc1wApIjjGrh/oKr/qf5wHsGTW4F8wt jiVH8P7pBZFWP3wWL9kFgHNzTh2mjcxaXY3uhTq8ty1tvAafihh/RsFoX5CdHTubdWjt +P9I3XWQI+xIoCuqYbabOx2Vg8wzjkppkC8NUFgldJ5uEkR1E7TsQXN/WOtlD2IfODmB Q0Fg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=mT3hItcKDGh+TwyzpAI+i3bdR6AQap++AnDVUAh1J/Y=; b=NL+bzGrThN9BAv+d5zx7tFJeYlTexEvgNfQ133O8TEwig93VqJBul5PRvaWK1wFoYA GJ0ZaFjqqPE5XoJpwsPXxtO2neF7h/mCk/fz58BiyO6bZgSK1354cFiY0kfDEBBK02ss QBrVBvuh8dfQs9aOF2Oi5ILOXaNxDeAppS/cpWB3G4LrSeMw7HHabEaK9oqJzkgAnH7G 6t7GtYEK99LsxC4YjrbFK6iupY/7Gdoa/MtQHXBXQjP9npIFZ0BQkj8NToYmzXn64JHK AiMmLfRXxMDHWMGuRu8D7+jlhjPxCRP+/0Di9q9nMBDnGz+czOkZDyT4z32okSIf+Q3a Xejw== X-Gm-Message-State: AOAM532EVtsvpzpyKg6HeU0EqiF7zpXefgzmg4FxhjrcOET8LgOHme3M 8mdpIxiBPoVhB6upCtv/saF1/r0fikPlxz/k3ws= X-Google-Smtp-Source: ABdhPJwYmnAnj06y5ur4mOmZIxoBGx9lgMdMTIefIzq/pGg0+ZvGqe5awrJRuUswXIjaW/g8Xo3oMC0rCX8K0ZST4zw= X-Received: by 2002:a17:907:2d9e:: with SMTP id gt30mr1082656ejc.357.1612321965303; Tue, 02 Feb 2021 19:12:45 -0800 (PST) MIME-Version: 1.0 References: <20210203013635.2512741-1-raj.khem@gmail.com> <20210203013635.2512741-5-raj.khem@gmail.com> In-Reply-To: <20210203013635.2512741-5-raj.khem@gmail.com> From: "Bruce Ashfield" Date: Tue, 2 Feb 2021 22:12:34 -0500 Message-ID: Subject: Re: [OE-core] [v2 5/5] linux-yocto-5.10: Backport couple of patches for binutils 2.36 upgrade To: Khem Raj Cc: Patches and discussions about the oe-core layer Content-Type: text/plain; charset="UTF-8" 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 wrote: > > This is for master-next testing only !! > > Signed-off-by: Khem Raj > --- > ...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 > +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 > +Signed-off-by: Josh Poimboeuf > +Signed-off-by: Peter Zijlstra (Intel) > +Reviewed-by: Nick Desaulniers > +Reviewed-by: Miroslav Benes > +Link: https://github.com/ClangBuiltLinux/linux/issues/1207 > +Link: https://lkml.kernel.org/r/ba6b6c0f0dd5acbba66e403955a967d9fdd1726a.1607983452.git.jpoimboe@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 > +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 > +Suggested-by: Josh Poimboeuf > +Suggested-by: Borislav Petkov > +Suggested-by: Mark Brown > +Signed-off-by: Nick Desaulniers > +Signed-off-by: Borislav Petkov > +Acked-by: Peter Zijlstra (Intel) > +Acked-by: Josh Poimboeuf > +Link: https://lkml.kernel.org/r/20210112194625.4181814-1-ndesaulniers@google.com > +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