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linux-intel/5.10: fix build with binutils 2.36

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Backport a couple of patches to fix builds with binutils v2.36. These
should not be required once these are made available in LTS branches.

Signed-off-by: Anuj Mittal <anuj.mittal@intel.com>
This commit is contained in:
Anuj Mittal 2021-02-03 10:31:30 +08:00
parent 2de1d83580
commit 9ca88f0ea5
4 changed files with 282 additions and 2 deletions
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4
recipes-kernel/linux/linux-intel-rt_5.10.bb
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@ -11,7 +11,9 @@ python () {
LIC_FILES_CHKSUM = "file://COPYING;md5=6bc538ed5bd9a7fc9398086aedcd7e46" LIC_FILES_CHKSUM = "file://COPYING;md5=6bc538ed5bd9a7fc9398086aedcd7e46"
SRC_URI_append = " file://0001-menuconfig-mconf-cfg-Allow-specification-of-ncurses-.patch \ SRC_URI_append = " file://0001-menuconfig-mconf-cfg-Allow-specification-of-ncurses-.patch \
" file://objtool-fix-segfault-with-clang.patch \
file://x86-entry-Emit-a-symbol-for-register-restoring-thunk.patch \
"
KBRANCH = "5.10/preempt-rt" KBRANCH = "5.10/preempt-rt"
KMETA_BRANCH = "yocto-5.10" KMETA_BRANCH = "yocto-5.10"

150
recipes-kernel/linux/linux-intel/objtool-fix-segfault-with-clang.patch Normal file
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@ -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
Upstream-Status: Backport
Signed-off-by: Anuj Mittal <anuj.mittal@intel.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 c6ab44543c92a..5f8d3eed78a18 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 4e1d7460574b4..be89c741ba9a0 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 807f8c6700974..e6890cc70a25b 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 235663b96adc7..9ce68b385a1b8 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;

125
recipes-kernel/linux/linux-intel/x86-entry-Emit-a-symbol-for-register-restoring-thunk.patch Normal file
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@ -0,0 +1,125 @@
From 5e6dca82bcaa49348f9e5fcb48df4881f6d6c4ae 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]
Upstream-Status: Backport
Signed-off-by: Anuj Mittal <anuj.mittal@intel.com>
---
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 32ea57483378d..76424e0431f4b 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 ccd32877a3c41..c9a9fbf1655f3 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 5bcfbd972e970..dbf8506decca0 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
*/

5
recipes-kernel/linux/linux-intel_5.10.bb
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@ -5,7 +5,10 @@ KMETA_BRANCH = "yocto-5.10"
LIC_FILES_CHKSUM = "file://COPYING;md5=6bc538ed5bd9a7fc9398086aedcd7e46" LIC_FILES_CHKSUM = "file://COPYING;md5=6bc538ed5bd9a7fc9398086aedcd7e46"
SRC_URI_append = " file://0001-menuconfig-mconf-cfg-Allow-specification-of-ncurses-.patch" SRC_URI_append = " file://0001-menuconfig-mconf-cfg-Allow-specification-of-ncurses-.patch \
file://objtool-fix-segfault-with-clang.patch \
file://x86-entry-Emit-a-symbol-for-register-restoring-thunk.patch \
"
DEPENDS += "elfutils-native openssl-native util-linux-native" DEPENDS += "elfutils-native openssl-native util-linux-native"