linux-stable.git/tools/objtool, branch v5.15.26

objtool: Handle __sanitize_cov*() tail calls

2021-11-18T18:16:23+00:00

[ Upstream commit f56dae88a81fded66adf2bea9922d1d98d1da14f ]

Turns out the compilers also generate tail calls to __sanitize_cov*(),
make sure to also patch those out in noinstr code.

Fixes: 0f1441b44e82 ("objtool: Fix noinstr vs KCOV")
Signed-off-by: Peter Zijlstra (Intel) 
Acked-by: Marco Elver 
Link: https://lore.kernel.org/r/20210624095147.818783799@infradead.org
Signed-off-by: Sasha Levin

x86/xen: Mark cpu_bringup_and_idle() as dead_end_function

2021-11-18T18:16:23+00:00

[ Upstream commit 9af9dcf11bda3e2c0e24c1acaacb8685ad974e93 ]

The asm_cpu_bringup_and_idle() function is required to push the return
value on the stack in order to make ORC happy, but the only reason
objtool doesn't complain is because of a happy accident.

The thing is that asm_cpu_bringup_and_idle() doesn't return, so
validate_branch() never terminates and falls through to the next
function, which in the normal case is the hypercall_page. And that, as
it happens, is 4095 NOPs and a RET.

Make asm_cpu_bringup_and_idle() terminate on it's own, by making the
function it calls as a dead-end. This way we no longer rely on what
code happens to come after.

Fixes: c3881eb58d56 ("x86/xen: Make the secondary CPU idle tasks reliable")
Signed-off-by: Peter Zijlstra (Intel) 
Reviewed-by: Juergen Gross 
Reviewed-by: Miroslav Benes 
Link: https://lore.kernel.org/r/20210624095147.693801717@infradead.org
Signed-off-by: Sasha Levin

objtool: Update section header before relocations

2021-10-07T03:11:57+00:00

The libelf implementation from elftoolchain has a safety check in
gelf_update_rel[a] to check that the data corresponds to a section
that has type SHT_REL[A] [0]. If the relocation is updated before
the section header is updated with the proper type, this check
fails.

To fix this, update the section header first, before the relocations.
Previously, the section size was calculated in elf_rebuild_reloc_section
by counting the number of entries in the reloc_list. However, we
now need the size during elf_write so instead keep a running total
and add to it for every new relocation.

[0] https://sourceforge.net/p/elftoolchain/mailman/elftoolchain-developers/thread/CAGw6cBtkZro-8wZMD2ULkwJ39J+tHtTtAWXufMjnd3cQ7XG54g@mail.gmail.com/

Signed-off-by: Michael Forney 
Reviewed-by: Miroslav Benes 
Signed-off-by: Josh Poimboeuf 
Link: https://lore.kernel.org/r/20210509000103.11008-2-mforney@mforney.org

objtool: Check for gelf_update_rel[a] failures

2021-10-07T03:11:53+00:00

Otherwise, if these fail we end up with garbage data in the
.rela.orc_unwind_ip section, leading to errors like

  ld: fs/squashfs/namei.o: bad reloc symbol index (0x7f16 >= 0x12) for offset 0x7f16d5c82cc8 in section `.orc_unwind_ip'

Signed-off-by: Michael Forney 
Reviewed-by: Miroslav Benes 
Signed-off-by: Josh Poimboeuf 
Link: https://lore.kernel.org/r/20210509000103.11008-1-mforney@mforney.org

objtool: Remove redundant 'len' field from struct section

2021-10-05T19:03:21+00:00

The section structure already contains sh_size, so just remove the extra
'len' member that requires extra mirroring and potential confusion.

Suggested-by: Josh Poimboeuf 
Signed-off-by: Joe Lawrence 
Reviewed-by: Miroslav Benes 
Signed-off-by: Josh Poimboeuf 
Link: https://lore.kernel.org/r/20210822225037.54620-3-joe.lawrence@redhat.com
Cc: Andy Lavr 
Cc: Peter Zijlstra 
Cc: x86@kernel.org
Cc: linux-kernel@vger.kernel.org

objtool: Make .altinstructions section entry size consistent

2021-10-05T19:03:20+00:00

Commit e31694e0a7a7 ("objtool: Don't make .altinstructions writable")
aligned objtool-created and kernel-created .altinstructions section
flags, but there remains a minor discrepency in their use of a section
entry size: objtool sets one while the kernel build does not.

While sh_entsize of sizeof(struct alt_instr) seems intuitive, this small
deviation can cause failures with external tooling (kpatch-build).

Fix this by creating new .altinstructions sections with sh_entsize of 0
and then later updating sec->sh_size as alternatives are added to the
section.  An added benefit is avoiding the data descriptor and buffer
created by elf_create_section(), but previously unused by
elf_add_alternative().

Fixes: 9bc0bb50727c ("objtool/x86: Rewrite retpoline thunk calls")
Signed-off-by: Joe Lawrence 
Reviewed-by: Miroslav Benes 
Signed-off-by: Josh Poimboeuf 
Link: https://lore.kernel.org/r/20210822225037.54620-2-joe.lawrence@redhat.com
Cc: Andy Lavr 
Cc: Peter Zijlstra 
Cc: x86@kernel.org
Cc: linux-kernel@vger.kernel.org

objtool: Remove reloc symbol type checks in get_alt_entry()

2021-10-05T19:03:20+00:00

Converting a special section's relocation reference to a symbol is
straightforward.  No need for objtool to complain that it doesn't know
how to handle it.  Just handle it.

This fixes the following warning:

  arch/x86/kvm/emulate.o: warning: objtool: __ex_table+0x4: don't know how to handle reloc symbol type: kvm_fastop_exception

Fixes: 24ff65257375 ("objtool: Teach get_alt_entry() about more relocation types")
Reported-by: Linus Torvalds 
Signed-off-by: Josh Poimboeuf 
Link: https://lore.kernel.org/r/feadbc3dfb3440d973580fad8d3db873cbfe1694.1633367242.git.jpoimboe@redhat.com
Cc: Peter Zijlstra 
Cc: x86@kernel.org
Cc: Miroslav Benes 
Cc: linux-kernel@vger.kernel.org

objtool: print out the symbol type when complaining about it

2021-10-03T20:45:48+00:00

The objtool warning that the kvm instruction emulation code triggered
wasn't very useful:

    arch/x86/kvm/emulate.o: warning: objtool: __ex_table+0x4: don't know how to handle reloc symbol type: kvm_fastop_exception

in that it helpfully tells you which symbol name it had trouble figuring
out the relocation for, but it doesn't actually say what the unknown
symbol type was that triggered it all.

In this case it was because of missing type information (type 0, aka
STT_NOTYPE), but on the whole it really should just have printed that
out as part of the message.

Because if this warning triggers, that's very much the first thing you
want to know - why did reloc2sec_off() return failure for that symbol?

So rather than just saying you can't handle some type of symbol without
saying what the type _was_, just print out the type number too.

Fixes: 24ff65257375 ("objtool: Teach get_alt_entry() about more relocation types")
Link: https://lore.kernel.org/lkml/CAHk-=wiZwq-0LknKhXN4M+T8jbxn_2i9mcKpO+OaBSSq_Eh7tg@mail.gmail.com/
Signed-off-by: Linus Torvalds

objtool: Teach get_alt_entry() about more relocation types

2021-10-01T11:57:47+00:00

Occasionally objtool encounters symbol (as opposed to section)
relocations in .altinstructions. Typically they are the alternatives
written by elf_add_alternative() as encountered on a noinstr
validation run on vmlinux after having already ran objtool on the
individual .o files.

Basically this is the counterpart of commit 44f6a7c0755d ("objtool:
Fix seg fault with Clang non-section symbols"), because when these new
assemblers (binutils now also does this) strip the section symbols,
elf_add_reloc_to_insn() is forced to emit symbol based relocations.

As such, teach get_alt_entry() about different relocation types.

Fixes: 9bc0bb50727c ("objtool/x86: Rewrite retpoline thunk calls")
Reported-by: Stephen Rothwell 
Reported-by: Borislav Petkov 
Signed-off-by: Peter Zijlstra (Intel) 
Acked-by: Josh Poimboeuf 
Tested-by: Nathan Chancellor 
Link: https://lore.kernel.org/r/YVWUvknIEVNkPvnP@hirez.programming.kicks-ass.net

Merge tags 'objtool-urgent-2021-06-28' and 'objtool-core-2021-06-28' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2021-06-28T18:35:55+00:00

Pull objtool fix and updates from Ingo Molnar:
 "An ELF format fix for a section flags mismatch bug that breaks kernel
  tooling such as kpatch-build.

  The biggest change in this cycle is the new code to handle and rewrite
  variable sized jump labels - which results in slightly tighter code
  generation in hot paths, through the use of short(er) NOPs.

  Also a number of cleanups and fixes, and a change to the generic
  include/linux/compiler.h to handle a s390 GCC quirk"

* tag 'objtool-urgent-2021-06-28' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  objtool: Don't make .altinstructions writable

* tag 'objtool-core-2021-06-28' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  objtool: Improve reloc hash size guestimate
  instrumentation.h: Avoid using inline asm operand modifiers
  compiler.h: Avoid using inline asm operand modifiers
  kbuild: Fix objtool dependency for 'OBJECT_FILES_NON_STANDARD_ := n'
  objtool: Reflow handle_jump_alt()
  jump_label/x86: Remove unused JUMP_LABEL_NOP_SIZE
  jump_label, x86: Allow short NOPs
  objtool: Provide stats for jump_labels
  objtool: Rewrite jump_label instructions
  objtool: Decode jump_entry::key addend
  jump_label, x86: Emit short JMP
  jump_label: Free jump_entry::key bit1 for build use
  jump_label, x86: Add variable length patching support
  jump_label, x86: Introduce jump_entry_size()
  jump_label, x86: Improve error when we fail expected text
  jump_label, x86: Factor out the __jump_table generation
  jump_label, x86: Strip ASM jump_label support
  x86, objtool: Dont exclude arch/x86/realmode/
  objtool: Rewrite hashtable sizing