linux-intel/5.10: fix build with binutils 2.36

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>

4 files changed, 282 insertions, 2 deletions

diff --git a/recipes-kernel/linux/linux-intel-rt_5.10.bb b/recipes-kernel/linux/linux-intel-rt_5.10.bb
index b1a32c1a..ae0f45f2 100644
--- a/recipes-kernel/linux/linux-intel-rt_5.10.bb
+++ b/recipes-kernel/linux/linux-intel-rt_5.10.bb
@@ -11,7 +11,9 @@ python () {
 
 LIC_FILES_CHKSUM = "file://COPYING;md5=6bc538ed5bd9a7fc9398086aedcd7e46"
 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"
 KMETA_BRANCH = "yocto-5.10"
diff --git a/recipes-kernel/linux/linux-intel/objtool-fix-segfault-with-clang.patch b/recipes-kernel/linux/linux-intel/objtool-fix-segfault-with-clang.patch
new file mode 100644
index 00000000..f4b1374f
--- /dev/null
+++ b/recipes-kernel/linux/linux-intel/objtool-fix-segfault-with-clang.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
+
+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;
diff --git a/recipes-kernel/linux/linux-intel/x86-entry-Emit-a-symbol-for-register-restoring-thunk.patch b/recipes-kernel/linux/linux-intel/x86-entry-Emit-a-symbol-for-register-restoring-thunk.patch
new file mode 100644
index 00000000..3cd07c0a
--- /dev/null
+++ b/recipes-kernel/linux/linux-intel/x86-entry-Emit-a-symbol-for-register-restoring-thunk.patch
@@ -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
+  */
+ 
diff --git a/recipes-kernel/linux/linux-intel_5.10.bb b/recipes-kernel/linux/linux-intel_5.10.bb
index caf2c899..585dea49 100644
--- a/recipes-kernel/linux/linux-intel_5.10.bb
+++ b/recipes-kernel/linux/linux-intel_5.10.bb
@@ -5,7 +5,10 @@ KMETA_BRANCH = "yocto-5.10"
 
 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"