linux.git/tools/objtool/arch, branch v5.18

objtool: Add IBT/ENDBR decoding

2022-03-15T09:32:46+00:00

Intel IBT requires the target of any indirect CALL or JMP instruction
to be the ENDBR instruction; optionally it allows those two
instructions to have a NOTRACK prefix in order to avoid this
requirement.

The kernel will not enable the use of NOTRACK, as such any occurence
of it in compiler generated code should be flagged.

Teach objtool to Decode ENDBR instructions and WARN about NOTRACK
prefixes.

Signed-off-by: Peter Zijlstra (Intel) 
Acked-by: Josh Poimboeuf 
Link: https://lore.kernel.org/r/20220308154319.645963517@infradead.org

tools/objtool: Check for use of the ENQCMD instruction in the kernel

2022-03-15T09:32:30+00:00

The ENQCMD instruction implicitly accesses the PASID_MSR to fill in the
pasid field of the descriptor being submitted to an accelerator. But
there is no precise (and stable across kernel changes) point at which
the PASID_MSR is updated from the value for one task to the next.

Kernel code that uses accelerators must always use the ENQCMDS instruction
which does not access the PASID_MSR.

Check for use of the ENQCMD instruction in the kernel and warn on its
usage.

Signed-off-by: Fenghua Yu 
Signed-off-by: Borislav Petkov 
Reviewed-by: Tony Luck 
Acked-by: Josh Poimboeuf 
Link: https://lore.kernel.org/r/20220207230254.3342514-11-fenghua.yu@intel.com
Signed-off-by: Peter Zijlstra

objtool: Add straight-line-speculation validation

2021-12-08T18:26:50+00:00

Teach objtool to validate the straight-line-speculation constraints:

 - speculation trap after indirect calls
 - speculation trap after RET

Notable: when an instruction is annotated RETPOLINE_SAFE, indicating
  speculation isn't a problem, also don't care about sls for that
  instruction.

Signed-off-by: Peter Zijlstra (Intel) 
Signed-off-by: Borislav Petkov 
Link: https://lore.kernel.org/r/20211204134908.023037659@infradead.org

objtool,x86: Replace alternatives with .retpoline_sites

2021-10-28T21:25:25+00:00

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) 
Reviewed-by: Borislav Petkov 
Acked-by: Josh Poimboeuf 
Tested-by: Alexei Starovoitov 
Link: https://lore.kernel.org/r/20211026120309.850007165@infradead.org

Merge branch 'objtool/urgent'

2021-10-06T22:40:17+00:00

Fixup conflicts.

# Conflicts:
#	tools/objtool/check.c

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: Support pv_opsindirect calls for noinstr

2021-09-17T11:20:26+00:00

Normally objtool will now follow indirect calls; there is no need.

However, this becomes a problem with noinstr validation; if there's an
indirect call from noinstr code, we very much need to know it is to
another noinstr function. Luckily there aren't many indirect calls in
entry code with the obvious exception of paravirt. As such, noinstr
validation didn't work with paravirt kernels.

In order to track pv_ops[] call targets, objtool reads the static
pv_ops[] tables as well as direct assignments to the pv_ops[] array,
provided the compiler makes them a single instruction like:

  bf87:       48 c7 05 00 00 00 00 00 00 00 00        movq   $0x0,0x0(%rip)
    bf92 
    bf8a: R_X86_64_PC32     pv_ops+0x268

There are, as of yet, no warnings for when this goes wrong :/

Using the functions found with the above means, all pv_ops[] calls are
now subject to noinstr validation.

Signed-off-by: Peter Zijlstra (Intel) 
Link: https://lore.kernel.org/r/20210624095149.118815755@infradead.org

objtool: Handle __sanitize_cov*() tail calls

2021-09-15T13:51:45+00:00

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

objtool: Introduce CFI hash

2021-09-15T13:51:45+00:00

Andi reported that objtool on vmlinux.o consumes more memory than his
system has, leading to horrific performance.

This is in part because we keep a struct instruction for every
instruction in the file in-memory. Shrink struct instruction by
removing the CFI state (which includes full register state) from it
and demand allocating it.

Given most instructions don't actually change CFI state, there's lots
of repetition there, so add a hash table to find previous CFI
instances.

Reduces memory consumption (and runtime) for processing an
x86_64-allyesconfig:

  pre:  4:40.84 real,   143.99 user,    44.18 sys,      30624988 mem
  post: 2:14.61 real,   108.58 user,    25.04 sys,      16396184 mem

Suggested-by: Andi Kleen 
Signed-off-by: Peter Zijlstra (Intel) 
Link: https://lore.kernel.org/r/20210624095147.756759107@infradead.org

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