[ Upstream commit 5141d3a06b2da1731ac82091298b766a1f95d3d8 ]

elf_update_symbol fails to preserve the special st_shndx values
between [SHN_LORESERVE, SHN_HIRESERVE], which results in it
converting SHN_ABS entries into SHN_UNDEF, for example. Explicitly
check for the special indexes and ensure these symbols are not
marked undefined.

Fixes: ead165fa1042 ("objtool: Fix symbol creation")
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20220908215504.3686827-17-samitolvanen@google.com
Signed-off-by: Sasha Levin <sashal@kernel.org>

commit 46c7405df7de8deb97229eacebcee96d61415f3f upstream.

Currently x86 cross-compilation fails on big endian system with:

  x86_64-cross-ld: init/main.o: invalid string offset 488112128 >= 6229 for section `.strtab'

Mark new ELF data in elf_create_undef_symbol() as symbol, so that libelf
does endianness handling correctly.

Fixes: 2f2f7e47f052 ("objtool: Add elf_create_undef_symbol()")
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: https://lore.kernel.org/r/patch-1.thread-6c9df9.git-d39264656387.your-ad-here.call-01620841104-ext-2554@work.hours
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

commit 22682a07acc308ef78681572e19502ce8893c4d4 upstream.

Commit c087c6e7b551 ("objtool: Fix type of reloc::addend") failed to
appreciate cross building from ILP32 hosts, where 'int' == 'long' and
the issue persists.

As such, use s64/int64_t/Elf64_Sxword for this field and suffer the
pain that is ISO C99 printf formats for it.

Fixes: c087c6e7b551 ("objtool: Fix type of reloc::addend")
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
[peterz: reword changelog, s/long long/s64/]
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: <stable@vger.kernel.org>
Link: https://lkml.kernel.org/r/alpine.LRH.2.02.2205161041260.11556@file01.intranet.prod.int.rdu2.redhat.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

commit ead165fa1042247b033afad7be4be9b815d04ade upstream.

Nathan reported objtool failing with the following messages:

  warning: objtool: no non-local symbols !?
  warning: objtool: gelf_update_symshndx: invalid section index

The problem is due to commit 4abff6d48dbc ("objtool: Fix code relocs
vs weak symbols") failing to consider the case where an object would
have no non-local symbols.

The problem that commit tries to address is adding a STB_LOCAL symbol
to the symbol table in light of the ELF spec's requirement that:

  In each symbol table, all symbols with STB_LOCAL binding preced the
  weak and global symbols.  As ``Sections'' above describes, a symbol
  table section's sh_info section header member holds the symbol table
  index for the first non-local symbol.

The approach taken is to find this first non-local symbol, move that
to the end and then re-use the freed spot to insert a new local symbol
and increment sh_info.

Except it never considered the case of object files without global
symbols and got a whole bunch of details wrong -- so many in fact that
it is a wonder it ever worked :/

Specifically:

 - It failed to re-hash the symbol on the new index, so a subsequent
   find_symbol_by_index() would not find it at the new location and a
   query for the old location would now return a non-deterministic
   choice between the old and new symbol.

 - It failed to appreciate that the GElf wrappers are not a valid disk
   format (it works because GElf is basically Elf64 and we only
   support x86_64 atm.)

 - It failed to fully appreciate how horrible the libelf API really is
   and got the gelf_update_symshndx() call pretty much completely
   wrong; with the direct consequence that if inserting a second
   STB_LOCAL symbol would require moving the same STB_GLOBAL symbol
   again it would completely come unstuck.

Write a new elf_update_symbol() function that wraps all the magic
required to update or create a new symbol at a given index.

Specifically, gelf_update_sym*() require an @ndx argument that is
relative to the @data argument; this means you have to manually
iterate the section data descriptor list and update @ndx.

Fixes: 4abff6d48dbc ("objtool: Fix code relocs vs weak symbols")
Reported-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Acked-by: Josh Poimboeuf <jpoimboe@kernel.org>
Tested-by: Nathan Chancellor <nathan@kernel.org>
Cc: <stable@vger.kernel.org>
Link: https://lkml.kernel.org/r/YoPCTEYjoPqE4ZxB@hirez.programming.kicks-ass.net
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
[bwh: Backported to 5.10: elf_hash_add() takes a hash table pointer,
 not just a name]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

commit c087c6e7b551b7f208c0b852304f044954cf2bb3 upstream.

Elf{32,64}_Rela::r_addend is of type: Elf{32,64}_Sword, that means
that our reloc::addend needs to be long or face tuncation issues when
we do elf_rebuild_reloc_section():

  - 107:  48 b8 00 00 00 00 00 00 00 00   movabs $0x0,%rax        109: R_X86_64_64        level4_kernel_pgt+0x80000067
  + 107:  48 b8 00 00 00 00 00 00 00 00   movabs $0x0,%rax        109: R_X86_64_64        level4_kernel_pgt-0x7fffff99

Fixes: 627fce14809b ("objtool: Add ORC unwind table generation")
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
Link: https://lkml.kernel.org/r/20220419203807.596871927@infradead.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

commit 4abff6d48dbcea8200c7ea35ba70c242d128ebf3 upstream.

Occasionally objtool driven code patching (think .static_call_sites
.retpoline_sites etc..) goes sideways and it tries to patch an
instruction that doesn't match.

Much head-scatching and cursing later the problem is as outlined below
and affects every section that objtool generates for us, very much
including the ORC data. The below uses .static_call_sites because it's
convenient for demonstration purposes, but as mentioned the ORC
sections, .retpoline_sites and __mount_loc are all similarly affected.

Consider:

foo-weak.c:

  extern void __SCT__foo(void);

  __attribute__((weak)) void foo(void)
  {
	  return __SCT__foo();
  }

foo.c:

  extern void __SCT__foo(void);
  extern void my_foo(void);

  void foo(void)
  {
	  my_foo();
	  return __SCT__foo();
  }

These generate the obvious code
(gcc -O2 -fcf-protection=none -fno-asynchronous-unwind-tables -c foo*.c):

foo-weak.o:
0000000000000000 <foo>:
   0:   e9 00 00 00 00          jmpq   5 <foo+0x5>      1: R_X86_64_PLT32       __SCT__foo-0x4

foo.o:
0000000000000000 <foo>:
   0:   48 83 ec 08             sub    $0x8,%rsp
   4:   e8 00 00 00 00          callq  9 <foo+0x9>      5: R_X86_64_PLT32       my_foo-0x4
   9:   48 83 c4 08             add    $0x8,%rsp
   d:   e9 00 00 00 00          jmpq   12 <foo+0x12>    e: R_X86_64_PLT32       __SCT__foo-0x4

Now, when we link these two files together, you get something like
(ld -r -o foos.o foo-weak.o foo.o):

foos.o:
0000000000000000 <foo-0x10>:
   0:   e9 00 00 00 00          jmpq   5 <foo-0xb>      1: R_X86_64_PLT32       __SCT__foo-0x4
   5:   66 2e 0f 1f 84 00 00 00 00 00   nopw   %cs:0x0(%rax,%rax,1)
   f:   90                      nop

0000000000000010 <foo>:
  10:   48 83 ec 08             sub    $0x8,%rsp
  14:   e8 00 00 00 00          callq  19 <foo+0x9>     15: R_X86_64_PLT32      my_foo-0x4
  19:   48 83 c4 08             add    $0x8,%rsp
  1d:   e9 00 00 00 00          jmpq   22 <foo+0x12>    1e: R_X86_64_PLT32      __SCT__foo-0x4

Noting that ld preserves the weak function text, but strips the symbol
off of it (hence objdump doing that funny negative offset thing). This
does lead to 'interesting' unused code issues with objtool when ran on
linked objects, but that seems to be working (fingers crossed).

So far so good.. Now lets consider the objtool static_call output
section (readelf output, old binutils):

foo-weak.o:

Relocation section '.rela.static_call_sites' at offset 0x2c8 contains 1 entry:
    Offset             Info             Type               Symbol's Value  Symbol's Name + Addend
0000000000000000  0000000200000002 R_X86_64_PC32          0000000000000000 .text + 0
0000000000000004  0000000d00000002 R_X86_64_PC32          0000000000000000 __SCT__foo + 1

foo.o:

Relocation section '.rela.static_call_sites' at offset 0x310 contains 2 entries:
    Offset             Info             Type               Symbol's Value  Symbol's Name + Addend
0000000000000000  0000000200000002 R_X86_64_PC32          0000000000000000 .text + d
0000000000000004  0000000d00000002 R_X86_64_PC32          0000000000000000 __SCT__foo + 1

foos.o:

Relocation section '.rela.static_call_sites' at offset 0x430 contains 4 entries:
    Offset             Info             Type               Symbol's Value  Symbol's Name + Addend
0000000000000000  0000000100000002 R_X86_64_PC32          0000000000000000 .text + 0
0000000000000004  0000000d00000002 R_X86_64_PC32          0000000000000000 __SCT__foo + 1
0000000000000008  0000000100000002 R_X86_64_PC32          0000000000000000 .text + 1d
000000000000000c  0000000d00000002 R_X86_64_PC32          0000000000000000 __SCT__foo + 1

So we have two patch sites, one in the dead code of the weak foo and one
in the real foo. All is well.

*HOWEVER*, when the toolchain strips unused section symbols it
generates things like this (using new enough binutils):

foo-weak.o:

Relocation section '.rela.static_call_sites' at offset 0x2c8 contains 1 entry:
    Offset             Info             Type               Symbol's Value  Symbol's Name + Addend
0000000000000000  0000000200000002 R_X86_64_PC32          0000000000000000 foo + 0
0000000000000004  0000000d00000002 R_X86_64_PC32          0000000000000000 __SCT__foo + 1

foo.o:

Relocation section '.rela.static_call_sites' at offset 0x310 contains 2 entries:
    Offset             Info             Type               Symbol's Value  Symbol's Name + Addend
0000000000000000  0000000200000002 R_X86_64_PC32          0000000000000000 foo + d
0000000000000004  0000000d00000002 R_X86_64_PC32          0000000000000000 __SCT__foo + 1

foos.o:

Relocation section '.rela.static_call_sites' at offset 0x430 contains 4 entries:
    Offset             Info             Type               Symbol's Value  Symbol's Name + Addend
0000000000000000  0000000100000002 R_X86_64_PC32          0000000000000000 foo + 0
0000000000000004  0000000d00000002 R_X86_64_PC32          0000000000000000 __SCT__foo + 1
0000000000000008  0000000100000002 R_X86_64_PC32          0000000000000000 foo + d
000000000000000c  0000000d00000002 R_X86_64_PC32          0000000000000000 __SCT__foo + 1

And now we can see how that foos.o .static_call_sites goes side-ways, we
now have _two_ patch sites in foo. One for the weak symbol at foo+0
(which is no longer a static_call site!) and one at foo+d which is in
fact the right location.

This seems to happen when objtool cannot find a section symbol, in which
case it falls back to any other symbol to key off of, however in this
case that goes terribly wrong!

As such, teach objtool to create a section symbol when there isn't
one.

Fixes: 44f6a7c0755d ("objtool: Fix seg fault with Clang non-section symbols")
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
Link: https://lkml.kernel.org/r/20220419203807.655552918@infradead.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

commit 134ab5bd1883312d7a4b3033b05c6b5a1bb8889b upstream.

Instead of writing complete alternatives, simply provide a list of all
the retpoline thunk calls. Then the kernel is free to do with them as
it pleases. Simpler code all-round.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Borislav Petkov <bp@suse.de>
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
Tested-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/r/20211026120309.850007165@infradead.org
[cascardo: fixed conflict because of missing
 8b946cc38e063f0f7bb67789478c38f6d7d457c9]
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>
[bwh: Backported to 5.10: deleted functions had slightly different code]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

commit 584fd3b31889852d0d6f3dd1e3d8e9619b660d2c upstream.

When an ELF object uses extended symbol section indexes (IOW it has a
.symtab_shndx section), these must be kept in sync with the regular
symbol table (.symtab).

So for every new symbol we emit, make sure to also emit a
.symtab_shndx value to keep the arrays of equal size.

Note: since we're writing an UNDEF symbol, most GElf_Sym fields will
be 0 and we can repurpose one (st_size) to host the 0 for the xshndx
value.

Fixes: 2f2f7e47f052 ("objtool: Add elf_create_undef_symbol()")
Reported-by: Nick Desaulniers <ndesaulniers@google.com>
Suggested-by: Fangrui Song <maskray@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Nick Desaulniers <ndesaulniers@google.com>
Link: https://lkml.kernel.org/r/YL3q1qFO9QIRL/BA@hirez.programming.kicks-ass.net
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

commit 2f2f7e47f0525cbaad5dd9675fd9d8aa8da12046 upstream.

Allow objtool to create undefined symbols; this allows creating
relocations to symbols not currently in the symbol table.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Miroslav Benes <mbenes@suse.cz>
Link: https://lkml.kernel.org/r/20210326151300.064743095@infradead.org
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

commit 9a7827b7789c630c1efdb121daa42c6e77dce97f upstream.

Create a common helper to add symbols.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Miroslav Benes <mbenes@suse.cz>
Link: https://lkml.kernel.org/r/20210326151300.003468981@infradead.org
[bwh: Backported to 5.10: rb_add() parameter order is different]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>