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  1. 05 Apr, 2022 2 commits
    • Peter Zijlstra's avatar
      objtool: Fix IBT tail-call detection · d139bca4
      Peter Zijlstra authored 
      Objtool reports:

  arch/x86/crypto/poly1305-x86_64.o: warning: objtool: poly1305_blocks_avx() falls through to next function poly1305_blocks_x86_64()
  arch/x86/crypto/poly1305-x86_64.o: warning: objtool: poly1305_emit_avx() falls through to next function poly1305_emit_x86_64()
  arch/x86/crypto/poly1305-x86_64.o: warning: objtool: poly1305_blocks_avx2() falls through to next function poly1305_blocks_x86_64()

Which reads like:

0000000000000040 <poly1305_blocks_x86_64>:
	 40:       f3 0f 1e fa             endbr64
	...

0000000000000400 <poly1305_blocks_avx>:
	400:       f3 0f 1e fa             endbr64
	404:       44 8b 47 14             mov    0x14(%rdi),%r8d
	408:       48 81 fa 80 00 00 00    cmp    $0x80,%rdx
	40f:       73 09                   jae    41a <poly1305_blocks_avx+0x1a>
	411:       45 85 c0                test   %r8d,%r8d
	414:       0f 84 2a fc ff ff       je     44 <poly1305_blocks_x86_64+0x4>
	...

These are simple conditional tail-calls and *should* be recognised as
such by objtool, however due to a mistake in commit 08f87a93
("objtool: Validate IBT assumptions") this is failing.

Specifically, the jump_dest is +4, this means the instruction pointed
at will not be ENDBR and as such it will fail the second clause of
is_first_func_insn() that was supposed to capture this exact case.

Instead, have is_first_func_insn() look at the previous instruction.

Fixes: 08f87a93 ("objtool: Validate IBT assumptions")
Reported-by: default avatarStephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20220322115125.811582125@infradead.org
      d139bca4
    • Vincent Mailhol's avatar
      x86/bug: Prevent shadowing in __WARN_FLAGS · 9ce02f0f
      Vincent Mailhol authored 
      The macro __WARN_FLAGS() uses a local variable named "f". This being a
common name, there is a risk of shadowing other variables.

For example, GCC would yield:

| In file included from ./include/linux/bug.h:5,
|                  from ./include/linux/cpumask.h:14,
|                  from ./arch/x86/include/asm/cpumask.h:5,
|                  from ./arch/x86/include/asm/msr.h:11,
|                  from ./arch/x86/include/asm/processor.h:22,
|                  from ./arch/x86/include/asm/timex.h:5,
|                  from ./include/linux/timex.h:65,
|                  from ./include/linux/time32.h:13,
|                  from ./include/linux/time.h:60,
|                  from ./include/linux/stat.h:19,
|                  from ./include/linux/module.h:13,
|                  from virt/lib/irqbypass.mod.c:1:
| ./include/linux/rcupdate.h: In function 'rcu_head_after_call_rcu':
| ./arch/x86/include/asm/bug.h:80:21: warning: declaration of 'f' shadows a parameter [-Wshadow]
|    80 |         __auto_type f = BUGFLAG_WARNING|(flags);                \
|       |                     ^
| ./include/asm-generic/bug.h:106:17: note: in expansion of macro '__WARN_FLAGS'
|   106 |                 __WARN_FLAGS(BUGFLAG_ONCE |                     \
|       |                 ^~~~~~~~~~~~
| ./include/linux/rcupdate.h:1007:9: note: in expansion of macro 'WARN_ON_ONCE'
|  1007 |         WARN_ON_ONCE(func != (rcu_callback_t)~0L);
|       |         ^~~~~~~~~~~~
| In file included from ./include/linux/rbtree.h:24,
|                  from ./include/linux/mm_types.h:11,
|                  from ./include/linux/buildid.h:5,
|                  from ./include/linux/module.h:14,
|                  from virt/lib/irqbypass.mod.c:1:
| ./include/linux/rcupdate.h:1001:62: note: shadowed declaration is here
|  1001 | rcu_head_after_call_rcu(struct rcu_head *rhp, rcu_callback_t f)
|       |                                               ~~~~~~~~~~~~~~~^

For reference, sparse also warns about it, c.f. [1].

This patch renames the variable from f to __flags (with two underscore
prefixes as suggested in the Linux kernel coding style [2]) in order
to prevent collisions.

[1] https://lore.kernel.org/all/CAFGhKbyifH1a+nAMCvWM88TK6fpNPdzFtUXPmRGnnQeePV+1sw@mail.gmail.com/

[2] Linux kernel coding style, section 12) Macros, Enums and RTL,
paragraph 5) namespace collisions when defining local variables in
macros resembling functions
https://www.kernel.org/doc/html/latest/process/coding-style.html#macros-enums-and-rtl

Fixes: bfb1a7c9 ("x86/bug: Merge annotate_reachable() into_BUG_FLAGS() asm")
Signed-off-by: default avatarVincent Mailhol <mailhol.vincent@wanadoo.fr>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: default avatarNick Desaulniers <ndesaulniers@google.com>
Acked-by: default avatarJosh Poimboeuf <jpoimboe@redhat.com>
Link: https://lkml.kernel.org/r/20220324023742.106546-1-mailhol.vincent@wanadoo.fr
      9ce02f0f
  3. 04 Apr, 2022 1 commit
  5. 03 Apr, 2022 8 commits
  7. 02 Apr, 2022 29 commits
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