Hi all,
The latest GNU assembler (binutils-2.36.1) is removing unused section symbols
like Clang [1]. So linux-5.10.15 can't be built with binutils-2.36.1 now. It
has been reported as https://bugzilla.kernel.org/show_bug.cgi?id=211693.
I can confirm this commit fixes the issue. It should be cherry-picked into
stable branches, so the following stable releases will be able to built with
latest GNU toolchain.
[1]: https://sourceware.org/pipermail/binutils/2020-December/114671.html
At last, happy new lunar year guys :).
On 2020-12-16 13:49 +0000, tip-bot2 for Josh Poimboeuf wrote:
> The following commit has been merged into the objtool/urgent branch of tip:
>
> Commit-ID: 44f6a7c0755d8dd453c70557e11687bb080a6f21
> Gitweb:
> https://git.kernel.org/tip/44f6a7c0755d8dd453c70557e11687bb080a6f21
> Author: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
> AuthorDate: Mon, 14 Dec 2020 16:04:20 -06:00
> Committer: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> CommitterDate: Wed, 16 Dec 2020 14:35:46 +01:00
>
> 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@xxxxxxxxxx>
> Signed-off-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
> Reviewed-by: Nick Desaulniers <ndesaulniers@xxxxxxxxxx>
> Reviewed-by: Miroslav Benes <mbenes@xxxxxxx>
> Link: https://github.com/ClangBuiltLinux/linux/issues/1207
> Link:
> https://lkml.kernel.org/r/ba6b6c0f0dd5acbba66e403955a967d9fdd1726a.1607983452.git.jpoimboe@xxxxxxxxxx
> ---
> 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 c6ab445..5f8d3ee 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 4e1d746..be89c74 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 807f8c6..e6890cc 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 235663b..9ce68b3 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;
--
Xi Ruoyao <xry111@xxxxxxxxxxxxxxxx>
School of Aerospace Science and Technology, Xidian University
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