Re: [OE-core] [v2 5/5] linux-yocto-5.10: Backport couple of patches for binutils 2.36 upgrade

["Khem Raj" <raj.khem@gmail.com>]

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

On Tue, Feb 2, 2021 at 7:29 PM Bruce Ashfield <bruce.ashfield@gmail.com> wrote:
>
> On Tue, Feb 2, 2021 at 10:26 PM Khem Raj <raj.khem@gmail.com> 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 <raj.khem@gmail.com> 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 <bruce.ashfield@gmail.com> 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 <raj.khem@gmail.com> wrote:
> > > > >
> > > > > This is for master-next testing only !!
> > > > >
> > > > > Signed-off-by: Khem Raj <raj.khem@gmail.com>
> > > > > ---
> > > > >  ...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 <jpoimboe@redhat.com>
> > > > > +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 <arnd@kernel.org>
> > > > > +Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
> > > > > +Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
> > > > > +Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
> > > > > +Reviewed-by: Miroslav Benes <mbenes@suse.cz>
> > > > > +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 <ndesaulniers@google.com>
> > > > > +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 <arnd@arndb.de>
> > > > > +Suggested-by: Josh Poimboeuf <jpoimboe@redhat.com>
> > > > > +Suggested-by: Borislav Petkov <bp@alien8.de>
> > > > > +Suggested-by: Mark Brown <broonie@kernel.org>
> > > > > +Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
> > > > > +Signed-off-by: Borislav Petkov <bp@suse.de>
> > > > > +Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
> > > > > +Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
> > > > > +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
>
>
>
> --
> - Thou shalt not follow the NULL pointer, for chaos and madness await
> thee at its end
> - "Use the force Harry" - Gandalf, Star Trek II