1. 21 Feb, 2018 3 commits
  2. 15 Feb, 2018 1 commit
  3. 09 Feb, 2018 1 commit
  4. 30 Jan, 2018 2 commits
    • Josh Poimboeuf's avatar
      objtool: Add support for alternatives at the end of a section · 17bc3391
      Josh Poimboeuf authored
      
      
      Now that the previous patch gave objtool the ability to read retpoline
      alternatives, it shows a new warning:
      
        arch/x86/entry/entry_64.o: warning: objtool: .entry_trampoline: don't know how to handle alternatives at end of section
      
      This is due to the JMP_NOSPEC in entry_SYSCALL_64_trampoline().
      
      Previously, objtool ignored this situation because it wasn't needed, and
      it would have required a bit of extra code.  Now that this case exists,
      add proper support for it.
      Signed-off-by: default avatarJosh Poimboeuf <jpoimboe@redhat.com>
      Cc: Andy Lutomirski <luto@kernel.org>
      Cc: Borislav Petkov <bp@alien8.de>
      Cc: Dave Hansen <dave.hansen@linux.intel.com>
      Cc: David Woodhouse <dwmw2@infradead.org>
      Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
      Cc: Guenter Roeck <linux@roeck-us.net>
      Cc: H. Peter Anvin <hpa@zytor.com>
      Cc: Juergen Gross <jgross@suse.com>
      Cc: Linus Torvalds <torvalds@linux-foundation.org>
      Cc: Peter Zijlstra <peterz@infradead.org>
      Cc: Thomas Gleixner <tglx@linutronix.de>
      Link: http://lkml.kernel.org/r/2a30a3c2158af47d891a76e69bb1ef347e0443fd.1517284349.git.jpoimboe@redhat.com
      
      Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
      17bc3391
    • Josh Poimboeuf's avatar
      objtool: Improve retpoline alternative handling · a845c7cf
      Josh Poimboeuf authored
      
      
      Currently objtool requires all retpolines to be:
      
        a) patched in with alternatives; and
      
        b) annotated with ANNOTATE_NOSPEC_ALTERNATIVE.
      
      If you forget to do both of the above, objtool segfaults trying to
      dereference a NULL 'insn->call_dest' pointer.
      
      Avoid that situation and print a more helpful error message:
      
        quirks.o: warning: objtool: efi_delete_dummy_variable()+0x99: unsupported intra-function call
        quirks.o: warning: objtool: If this is a retpoline, please patch it in with alternatives and annotate it with ANNOTATE_NOSPEC_ALTERNATIVE.
      
      Future improvements can be made to make objtool smarter with respect to
      retpolines, but this is a good incremental improvement for now.
      Reported-and-tested-by: default avatarGuenter Roeck <linux@roeck-us.net>
      Signed-off-by: default avatarJosh Poimboeuf <jpoimboe@redhat.com>
      Cc: Andy Lutomirski <luto@kernel.org>
      Cc: Borislav Petkov <bp@alien8.de>
      Cc: Dave Hansen <dave.hansen@linux.intel.com>
      Cc: David Woodhouse <dwmw2@infradead.org>
      Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
      Cc: H. Peter Anvin <hpa@zytor.com>
      Cc: Juergen Gross <jgross@suse.com>
      Cc: Linus Torvalds <torvalds@linux-foundation.org>
      Cc: Peter Zijlstra <peterz@infradead.org>
      Cc: Thomas Gleixner <tglx@linutronix.de>
      Link: http://lkml.kernel.org/r/819e50b6d9c2e1a22e34c1a636c0b2057cc8c6e5.1517284349.git.jpoimboe@redhat.com
      
      Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
      a845c7cf
  5. 15 Jan, 2018 1 commit
    • Kees Cook's avatar
      usercopy: Enhance and rename report_usercopy() · b394d468
      Kees Cook authored
      
      
      In preparation for refactoring the usercopy checks to pass offset to
      the hardened usercopy report, this renames report_usercopy() to the
      more accurate usercopy_abort(), marks it as noreturn because it is,
      adds a hopefully helpful comment for anyone investigating such reports,
      makes the function available to the slab allocators, and adds new "detail"
      and "offset" arguments.
      Signed-off-by: default avatarKees Cook <keescook@chromium.org>
      b394d468
  6. 11 Jan, 2018 2 commits
    • Josh Poimboeuf's avatar
      objtool: Allow alternatives to be ignored · 258c7605
      Josh Poimboeuf authored
      
      
      Getting objtool to understand retpolines is going to be a bit of a
      challenge.  For now, take advantage of the fact that retpolines are
      patched in with alternatives.  Just read the original (sane)
      non-alternative instruction, and ignore the patched-in retpoline.
      
      This allows objtool to understand the control flow *around* the
      retpoline, even if it can't yet follow what's inside.  This means the
      ORC unwinder will fail to unwind from inside a retpoline, but will work
      fine otherwise.
      Signed-off-by: default avatarJosh Poimboeuf <jpoimboe@redhat.com>
      Signed-off-by: default avatarDavid Woodhouse <dwmw@amazon.co.uk>
      Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
      Cc: gnomes@lxorguk.ukuu.org.uk
      Cc: Rik van Riel <riel@redhat.com>
      Cc: Andi Kleen <ak@linux.intel.com>
      Cc: thomas.lendacky@amd.com
      Cc: Peter Zijlstra <peterz@infradead.org>
      Cc: Linus Torvalds <torvalds@linux-foundation.org>
      Cc: Jiri Kosina <jikos@kernel.org>
      Cc: Andy Lutomirski <luto@amacapital.net>
      Cc: Dave Hansen <dave.hansen@intel.com>
      Cc: Kees Cook <keescook@google.com>
      Cc: Tim Chen <tim.c.chen@linux.intel.com>
      Cc: Greg Kroah-Hartman <gregkh@linux-foundation.org>
      Cc: Paul Turner <pjt@google.com>
      Link: https://lkml.kernel.org/r/1515707194-20531-3-git-send-email-dwmw@amazon.co.uk
      258c7605
    • Josh Poimboeuf's avatar
      objtool: Detect jumps to retpoline thunks · 39b73533
      Josh Poimboeuf authored
      
      
      A direct jump to a retpoline thunk is really an indirect jump in
      disguise.  Change the objtool instruction type accordingly.
      
      Objtool needs to know where indirect branches are so it can detect
      switch statement jump tables.
      
      This fixes a bunch of warnings with CONFIG_RETPOLINE like:
      
        arch/x86/events/intel/uncore_nhmex.o: warning: objtool: nhmex_rbox_msr_enable_event()+0x44: sibling call from callable instruction with modified stack frame
        kernel/signal.o: warning: objtool: copy_siginfo_to_user()+0x91: sibling call from callable instruction with modified stack frame
        ...
      Signed-off-by: default avatarJosh Poimboeuf <jpoimboe@redhat.com>
      Signed-off-by: default avatarDavid Woodhouse <dwmw@amazon.co.uk>
      Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
      Cc: gnomes@lxorguk.ukuu.org.uk
      Cc: Rik van Riel <riel@redhat.com>
      Cc: Andi Kleen <ak@linux.intel.com>
      Cc: thomas.lendacky@amd.com
      Cc: Peter Zijlstra <peterz@infradead.org>
      Cc: Linus Torvalds <torvalds@linux-foundation.org>
      Cc: Jiri Kosina <jikos@kernel.org>
      Cc: Andy Lutomirski <luto@amacapital.net>
      Cc: Dave Hansen <dave.hansen@intel.com>
      Cc: Kees Cook <keescook@google.com>
      Cc: Tim Chen <tim.c.chen@linux.intel.com>
      Cc: Greg Kroah-Hartman <gregkh@linux-foundation.org>
      Cc: Paul Turner <pjt@google.com>
      Link: https://lkml.kernel.org/r/1515707194-20531-2-git-send-email-dwmw@amazon.co.uk
      39b73533
  7. 20 Oct, 2017 1 commit
  8. 28 Sep, 2017 1 commit
  9. 23 Sep, 2017 1 commit
    • Josh Poimboeuf's avatar
      objtool: Handle another GCC stack pointer adjustment bug · 0d0970ee
      Josh Poimboeuf authored
      The kbuild bot reported the following warning with GCC 4.4 and a
      randconfig:
      
        net/socket.o: warning: objtool: compat_sock_ioctl()+0x1083: stack state mismatch: cfa1=7+160 cfa2=-1+0
      
      This is caused by another GCC non-optimization, where it backs up and
      restores the stack pointer for no apparent reason:
      
          2f91:       48 89 e0                mov    %rsp,%rax
          2f94:       4c 89 e7                mov    %r12,%rdi
          2f97:       4c 89 f6                mov    %r14,%rsi
          2f9a:       ba 20 00 00 00          mov    $0x20,%edx
          2f9f:       48 89 c4                mov    %rax,%rsp
      
      This issue would have been happily ignored before the following commit:
      
        dd88a0a0
      
       ("objtool: Handle GCC stack pointer adjustment bug")
      
      But now that objtool is paying attention to such stack pointer writes
      to/from a register, it needs to understand them properly.  In this case
      that means recognizing that the "mov %rsp, %rax" instruction is
      potentially a backup of the stack pointer.
      Reported-by: default avatarkbuild test robot <fengguang.wu@intel.com>
      Signed-off-by: default avatarJosh Poimboeuf <jpoimboe@redhat.com>
      Cc: Alexander Potapenko <glider@google.com>
      Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
      Cc: Andy Lutomirski <luto@kernel.org>
      Cc: Arnd Bergmann <arnd@arndb.de>
      Cc: Dmitriy Vyukov <dvyukov@google.com>
      Cc: Linus Torvalds <torvalds@linux-foundation.org>
      Cc: Matthias Kaehlcke <mka@chromium.org>
      Cc: Miguel Bernal Marin <miguel.bernal.marin@linux.intel.com>
      Cc: Peter Zijlstra <peterz@infradead.org>
      Cc: Thomas Gleixner <tglx@linutronix.de>
      Fixes: dd88a0a0 ("objtool: Handle GCC stack pointer adjustment bug")
      Link: http://lkml.kernel.org/r/8c7aa8e9a36fbbb6655d9d8e7cea58958c912da8.1505942196.git.jpoimboe@redhat.com
      
      Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
      0d0970ee
  10. 30 Aug, 2017 1 commit
    • Josh Poimboeuf's avatar
      objtool: Handle GCC stack pointer adjustment bug · dd88a0a0
      Josh Poimboeuf authored
      Arnd Bergmann reported the following warning with GCC 7.1.1:
      
        fs/fs_pin.o: warning: objtool: pin_kill()+0x139: stack state mismatch: cfa1=7+88 cfa2=7+96
      
      And the kbuild robot reported the following warnings with GCC 5.4.1:
      
        fs/fs_pin.o: warning: objtool: pin_kill()+0x182: return with modified stack frame
        fs/quota/dquot.o: warning: objtool: dquot_alloc_inode()+0x140: stack state mismatch: cfa1=7+120 cfa2=7+128
        fs/quota/dquot.o: warning: objtool: dquot_free_inode()+0x11a: stack state mismatch: cfa1=7+112 cfa2=7+120
      
      Those warnings are caused by an unusual GCC non-optimization where it
      uses an intermediate register to adjust the stack pointer.  It does:
      
        lea    0x8(%rsp), %rcx
        ...
        mov    %rcx, %rsp
      
      Instead of the obvious:
      
        add    $0x8, %rsp
      
      It makes no sense to use an intermediate register, so I opened a GCC bug
      to track it:
      
        https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81813
      
      
      
      But it's not exactly a high-priority bug and it looks like we'll be
      stuck with this issue for a while.  So for now we have to track register
      values when they're loaded with stack pointer offsets.
      
      This is kind of a big workaround for a tiny problem, but c'est la vie.
      I hope to eventually create a GCC plugin to implement a big chunk of
      objtool's functionality.  Hopefully at that point we'll be able to
      remove of a lot of these GCC-isms from the objtool code.
      Reported-by: default avatarArnd Bergmann <arnd@arndb.de>
      Reported-by: default avatarkbuild test robot <fengguang.wu@intel.com>
      Signed-off-by: default avatarJosh Poimboeuf <jpoimboe@redhat.com>
      Cc: Linus Torvalds <torvalds@linux-foundation.org>
      Cc: Peter Zijlstra <peterz@infradead.org>
      Cc: Thomas Gleixner <tglx@linutronix.de>
      Link: http://lkml.kernel.org/r/6a41a96884c725e7f05413bb7df40cfe824b2444.1504028945.git.jpoimboe@redhat.com
      
      Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
      dd88a0a0
  11. 21 Aug, 2017 1 commit
    • Josh Poimboeuf's avatar
      objtool: Fix objtool fallthrough detection with function padding · ee97638b
      Josh Poimboeuf authored
      
      
      When GCC adds NOP padding between functions, those NOPs aren't
      associated with a function symbol, which breaks objtool's detection of a
      function falling through to another function.  Instead it shows
      confusing errors like:
      
        drivers/mtd/chips/cfi_util.o: warning: objtool: cfi_qry_mode_on()+0x8b: return with modified stack frame
        drivers/mtd/chips/cfi_util.o: warning: objtool: cfi_qry_mode_on()+0x0: stack state mismatch: cfa1=-4-32 cfa2=7+8
        drivers/mtd/chips/cfi_cmdset_0002.o: warning: objtool: fixup_use_fwh_lock()+0x8: unknown stack-related register move
        drivers/mtd/chips/cfi_cmdset_0002.o: warning: objtool: fixup_use_fwh_lock()+0x0: stack state mismatch: cfa1=6+16 cfa2=7+8
        drivers/mtd/chips/cfi_cmdset_0002.o: warning: objtool: do_otp_write()+0xa: unsupported stack pointer realignment
        drivers/mtd/chips/cfi_cmdset_0002.o: warning: objtool: do_otp_write()+0x0: stack state mismatch: cfa1=-4-40 cfa2=7+8
      Reported-by: default avatarkbuild test robot <fengguang.wu@intel.com>
      Signed-off-by: default avatarJosh Poimboeuf <jpoimboe@redhat.com>
      Cc: Linus Torvalds <torvalds@linux-foundation.org>
      Cc: Peter Zijlstra <peterz@infradead.org>
      Cc: Thomas Gleixner <tglx@linutronix.de>
      Link: http://lkml.kernel.org/r/43e7aae9a7a7710cd6df597fa9dc501da4ba0602.1502472193.git.jpoimboe@redhat.com
      
      Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
      ee97638b
  12. 11 Aug, 2017 2 commits
  13. 28 Jul, 2017 2 commits
    • Josh Poimboeuf's avatar
      objtool: Skip unreachable warnings for 'alt' instructions · 0e2bb2bc
      Josh Poimboeuf authored
      
      
      When a whitelisted function uses one of the ALTERNATIVE macros, it
      produces false positive warnings like:
      
        arch/x86/kvm/vmx.o: warning: objtool: .altinstr_replacement+0x0: unreachable instruction
        arch/x86/kvm/svm.o: warning: objtool: .altinstr_replacement+0x6e: unreachable instruction
      
      There's no easy way to whitelist alternative instructions, so instead
      just skip any 'unreachable' warnings associated with them.
      Reported-by: default avatarArnd Bergmann <arnd@arndb.de>
      Signed-off-by: default avatarJosh Poimboeuf <jpoimboe@redhat.com>
      Cc: Linus Torvalds <torvalds@linux-foundation.org>
      Cc: Peter Zijlstra <peterz@infradead.org>
      Cc: Thomas Gleixner <tglx@linutronix.de>
      Link: http://lkml.kernel.org/r/a5d0a8c60155f03b36a31fac871e12cf75f35fd0.1501188854.git.jpoimboe@redhat.com
      
      Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
      0e2bb2bc
    • Josh Poimboeuf's avatar
      objtool: Assume unannotated UD2 instructions are dead ends · 649ea4d5
      Josh Poimboeuf authored
      Arnd reported some false positive warnings with GCC 7:
      
        drivers/hid/wacom_wac.o: warning: objtool: wacom_bpt3_touch()+0x2a5: stack state mismatch: cfa1=7+8 cfa2=6+16
        drivers/iio/adc/vf610_adc.o: warning: objtool: vf610_adc_calculate_rates() falls through to next function vf610_adc_sample_set()
        drivers/pwm/pwm-hibvt.o: warning: objtool: hibvt_pwm_get_state() falls through to next function hibvt_pwm_remove()
        drivers/pwm/pwm-mediatek.o: warning: objtool: mtk_pwm_config() falls through to next function mtk_pwm_enable()
        drivers/spi/spi-bcm2835.o: warning: objtool: .text: unexpected end of section
        drivers/spi/spi-bcm2835aux.o: warning: objtool: .text: unexpected end of section
        drivers/watchdog/digicolor_wdt.o: warning: objtool: dc_wdt_get_timeleft() falls through to next function dc_wdt_restart()
      
      When GCC 7 detects a potential divide-by-zero condition, it sometimes
      inserts a UD2 instruction for the case where the divisor is zero,
      instead of letting the hardware trap on the divide instruction.
      
      Objtool doesn't consider UD2 to be fatal unless it's annotated with
      unreachable().  So it considers the GCC-generated UD2 to be non-fatal,
      and it tries to follow the control flow past the UD2 and gets
      confused.
      
      Previously, objtool *did* assume UD2 was always a dead end.  That
      changed with the following commit:
      
        d1091c7f ("objtool: Improve detection of BUG() and other dead ends")
      
      The motivation behind that change was that Peter was planning on using
      UD2 for __WARN(), which is *not* a dead end.  However, it turns out
      that some emulators rely on UD2 being fatal, so he ended up using
      'ud0' instead:
      
        9a93848f
      
       ("x86/debug: Implement __WARN() using UD0")
      
      For GCC 4.5+, it should be safe to go back to the previous assumption
      that UD2 is fatal, even when it's not annotated with unreachable().
      
      But for pre-4.5 versions of GCC, the unreachable() macro isn't
      supported, so such cases of UD2 need to be explicitly annotated as
      reachable.
      Reported-by: default avatarArnd Bergmann <arnd@arndb.de>
      Signed-off-by: default avatarJosh Poimboeuf <jpoimboe@redhat.com>
      Cc: Linus Torvalds <torvalds@linux-foundation.org>
      Cc: Peter Zijlstra <peterz@infradead.org>
      Cc: Thomas Gleixner <tglx@linutronix.de>
      Fixes: d1091c7f ("objtool: Improve detection of BUG() and other dead ends")
      Link: http://lkml.kernel.org/r/e57fa9dfede25f79487da8126ee9cdf7b856db65.1501188854.git.jpoimboe@redhat.com
      
      Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
      649ea4d5
  14. 25 Jul, 2017 1 commit
  15. 18 Jul, 2017 2 commits
    • Josh Poimboeuf's avatar
      objtool, x86: Add facility for asm code to provide unwind hints · 39358a03
      Josh Poimboeuf authored
      
      
      Some asm (and inline asm) code does special things to the stack which
      objtool can't understand.  (Nor can GCC or GNU assembler, for that
      matter.)  In such cases we need a facility for the code to provide
      annotations, so the unwinder can unwind through it.
      
      This provides such a facility, in the form of unwind hints.  They're
      similar to the GNU assembler .cfi* directives, but they give more
      information, and are needed in far fewer places, because objtool can
      fill in the blanks by following branches and adjusting the stack pointer
      for pushes and pops.
      Signed-off-by: default avatarJosh Poimboeuf <jpoimboe@redhat.com>
      Cc: Andy Lutomirski <luto@kernel.org>
      Cc: Borislav Petkov <bp@alien8.de>
      Cc: Brian Gerst <brgerst@gmail.com>
      Cc: Denys Vlasenko <dvlasenk@redhat.com>
      Cc: H. Peter Anvin <hpa@zytor.com>
      Cc: Jiri Slaby <jslaby@suse.cz>
      Cc: Linus Torvalds <torvalds@linux-foundation.org>
      Cc: Mike Galbraith <efault@gmx.de>
      Cc: Peter Zijlstra <peterz@infradead.org>
      Cc: Thomas Gleixner <tglx@linutronix.de>
      Cc: live-patching@vger.kernel.org
      Link: http://lkml.kernel.org/r/0f5f3c9104fca559ff4088bece1d14ae3bca52d5.1499786555.git.jpoimboe@redhat.com
      
      Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
      39358a03
    • Josh Poimboeuf's avatar
      objtool: Add ORC unwind table generation · 627fce14
      Josh Poimboeuf authored
      
      
      Now that objtool knows the states of all registers on the stack for each
      instruction, it's straightforward to generate debuginfo for an unwinder
      to use.
      
      Instead of generating DWARF, generate a new format called ORC, which is
      more suitable for an in-kernel unwinder.  See
      Documentation/x86/orc-unwinder.txt for a more detailed description of
      this new debuginfo format and why it's preferable to DWARF.
      Signed-off-by: default avatarJosh Poimboeuf <jpoimboe@redhat.com>
      Cc: Andy Lutomirski <luto@kernel.org>
      Cc: Borislav Petkov <bp@alien8.de>
      Cc: Brian Gerst <brgerst@gmail.com>
      Cc: Denys Vlasenko <dvlasenk@redhat.com>
      Cc: H. Peter Anvin <hpa@zytor.com>
      Cc: Jiri Slaby <jslaby@suse.cz>
      Cc: Linus Torvalds <torvalds@linux-foundation.org>
      Cc: Mike Galbraith <efault@gmx.de>
      Cc: Peter Zijlstra <peterz@infradead.org>
      Cc: Thomas Gleixner <tglx@linutronix.de>
      Cc: live-patching@vger.kernel.org
      Link: http://lkml.kernel.org/r/c9b9f01ba6c5ed2bdc9bb0957b78167fdbf9632e.1499786555.git.jpoimboe@redhat.com
      
      Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
      627fce14
  16. 08 Jul, 2017 1 commit
    • Josh Poimboeuf's avatar
      objtool: Fix sibling call detection logic · 4855022a
      Josh Poimboeuf authored
      
      
      With some configs, objtool reports the following warning:
      
        arch/x86/kernel/ftrace.o: warning: objtool: ftrace_modify_code_direct()+0x2d: sibling call from callable instruction with modified stack frame
      
      The instruction it's complaining about isn't actually a sibling call.
      It's just a normal jump to an address inside the function.  Objtool
      thought it was a sibling call because the instruction's jump_dest wasn't
      initialized because the function was supposed to be ignored due to its
      use of sync_core().
      
      Objtool ended up validating the function instead of ignoring it because
      it didn't properly recognize a sibling call to the function.  So fix the
      sibling call logic.  Also add a warning to catch ignored functions being
      validated so we'll get a more useful error message next time.
      Reported-by: default avatarMike Galbraith <efault@gmx.de>
      Signed-off-by: default avatarJosh Poimboeuf <jpoimboe@redhat.com>
      Cc: Linus Torvalds <torvalds@linux-foundation.org>
      Cc: Peter Zijlstra <peterz@infradead.org>
      Cc: Thomas Gleixner <tglx@linutronix.de>
      Link: http://lkml.kernel.org/r/96cc8ecbcdd8cb29ddd783817b4af918a6a171b0.1499437107.git.jpoimboe@redhat.com
      
      Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
      4855022a
  17. 30 Jun, 2017 3 commits
  18. 16 Jun, 2017 1 commit
  19. 19 Apr, 2017 1 commit
  20. 07 Mar, 2017 1 commit
    • Josh Poimboeuf's avatar
      objtool: Fix another GCC jump table detection issue · 5c51f4ae
      Josh Poimboeuf authored
      
      
      Arnd Bergmann reported a (false positive) objtool warning:
      
        drivers/infiniband/sw/rxe/rxe_resp.o: warning: objtool: rxe_responder()+0xfe: sibling call from callable instruction with changed frame pointer
      
      The issue is in find_switch_table().  It tries to find a switch
      statement's jump table by walking backwards from an indirect jump
      instruction, looking for a relocation to the .rodata section.  In this
      case it stopped walking prematurely: the first .rodata relocation it
      encountered was for a variable (resp_state_name) instead of a jump
      table, so it just assumed there wasn't a jump table.
      
      The fix is to ignore any .rodata relocation which refers to an ELF
      object symbol.  This works because the jump tables are anonymous and
      have no symbols associated with them.
      Reported-by: default avatarArnd Bergmann <arnd@arndb.de>
      Tested-by: default avatarArnd Bergmann <arnd@arndb.de>
      Signed-off-by: default avatarJosh Poimboeuf <jpoimboe@redhat.com>
      Cc: Denys Vlasenko <dvlasenk@redhat.com>
      Cc: Linus Torvalds <torvalds@linux-foundation.org>
      Cc: Peter Zijlstra <peterz@infradead.org>
      Cc: Thomas Gleixner <tglx@linutronix.de>
      Fixes: 3732710f ("objtool: Improve rare switch jump table pattern detection")
      Link: http://lkml.kernel.org/r/20170302225723.3ndbsnl4hkqbne7a@treble
      
      Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
      5c51f4ae
  21. 01 Mar, 2017 1 commit
  22. 24 Feb, 2017 1 commit
    • Josh Poimboeuf's avatar
      objtool: Improve detection of BUG() and other dead ends · d1091c7f
      Josh Poimboeuf authored
      
      
      The BUG() macro's use of __builtin_unreachable() via the unreachable()
      macro tells gcc that the instruction is a dead end, and that it's safe
      to assume the current code path will not execute past the previous
      instruction.
      
      On x86, the BUG() macro is implemented with the 'ud2' instruction.  When
      objtool's branch analysis sees that instruction, it knows the current
      code path has come to a dead end.
      
      Peter Zijlstra has been working on a patch to change the WARN macros to
      use 'ud2'.  That patch will break objtool's assumption that 'ud2' is
      always a dead end.
      
      Generally it's best for objtool to avoid making those kinds of
      assumptions anyway.  The more ignorant it is of kernel code internals,
      the better.
      
      So create a more generic way for objtool to detect dead ends by adding
      an annotation to the unreachable() macro.  The annotation stores a
      pointer to the end of the unreachable code path in an '__unreachable'
      section.  Objtool can read that section to find the dead ends.
      Tested-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
      Signed-off-by: default avatarJosh Poimboeuf <jpoimboe@redhat.com>
      Cc: Linus Torvalds <torvalds@linux-foundation.org>
      Cc: Peter Zijlstra <peterz@infradead.org>
      Cc: Thomas Gleixner <tglx@linutronix.de>
      Link: http://lkml.kernel.org/r/41a6d33971462ebd944a1c60ad4bf5be86c17b77.1487712920.git.jpoimboe@redhat.com
      
      Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
      d1091c7f
  23. 27 Oct, 2016 1 commit
  24. 16 Oct, 2016 2 commits
    • Josh Poimboeuf's avatar
      objtool: Skip all "unreachable instruction" warnings for gcov kernels · 9cfffb11
      Josh Poimboeuf authored
      
      
      Recently objtool has started reporting a few "unreachable instruction"
      warnings when CONFIG_GCOV is enabled for newer versions of GCC.  Usually
      this warning means there's some new control flow that objtool doesn't
      understand.  But in this case, objtool is correct and the instructions
      really are inaccessible.  It's an annoying quirk of gcov, but it's
      harmless, so it's ok to just silence the warnings.
      
      With older versions of GCC, it was relatively easy to detect
      gcov-specific instructions and to skip any unreachable warnings produced
      by them.  But GCC 6 has gotten craftier.
      
      Instead of continuing to play whack-a-mole with gcov, just use a bigger,
      more permanent hammer and disable unreachable warnings for the whole
      file when gcov is enabled.  This is fine to do because a) unreachable
      warnings are usually of questionable value; and b) gcov isn't used for
      production kernels and we can relax the checks a bit there.
      Reported-by: default avatarkbuild test robot <fengguang.wu@intel.com>
      Signed-off-by: default avatarJosh Poimboeuf <jpoimboe@redhat.com>
      Cc: Andy Lutomirski <luto@kernel.org>
      Cc: Arnd Bergmann <arnd@arndb.de>
      Cc: Borislav Petkov <bp@alien8.de>
      Cc: Brian Gerst <brgerst@gmail.com>
      Cc: Denys Vlasenko <dvlasenk@redhat.com>
      Cc: H. Peter Anvin <hpa@zytor.com>
      Cc: Linus Torvalds <torvalds@linux-foundation.org>
      Cc: Peter Zijlstra <peterz@infradead.org>
      Cc: Thomas Gleixner <tglx@linutronix.de>
      Link: http://lkml.kernel.org/r/38d5c87d61d9cd46486dd2c86f46603dff0df86f.1476393584.git.jpoimboe@redhat.com
      
      Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
      9cfffb11
    • Josh Poimboeuf's avatar
      objtool: Improve rare switch jump table pattern detection · 3732710f
      Josh Poimboeuf authored
      
      
      GCC 6 added a new switch statement jump table optimization which makes
      objtool's life harder.  It looks like:
      
        mov [rodata addr],%reg1
        ... some instructions ...
        jmpq *(%reg1,%reg2,8)
      
      The optimization is quite rare, but objtool still needs to be able to
      identify the pattern so that it can follow all possible control flow
      paths related to the switch statement.
      
      In order to detect the pattern, objtool starts from the indirect jump
      and scans backwards through the function until it finds the first
      instruction in the pattern.  If it encounters an unconditional jump
      along the way, it stops and considers the pattern to be not found.
      
      As it turns out, unconditional jumps can happen, as long as they are
      small forward jumps within the range being scanned.
      
      This fixes the following warnings:
      
        drivers/infiniband/sw/rxe/rxe_comp.o: warning: objtool: rxe_completer()+0x2f4: sibling call from callable instruction with changed frame pointer
        drivers/infiniband/sw/rxe/rxe_resp.o: warning: objtool: rxe_responder()+0x10f: sibling call from callable instruction with changed frame pointer
      Reported-by: default avatarArnd Bergmann <arnd@arndb.de>
      Signed-off-by: default avatarJosh Poimboeuf <jpoimboe@redhat.com>
      Cc: Andy Lutomirski <luto@kernel.org>
      Cc: Borislav Petkov <bp@alien8.de>
      Cc: Brian Gerst <brgerst@gmail.com>
      Cc: Denys Vlasenko <dvlasenk@redhat.com>
      Cc: H. Peter Anvin <hpa@zytor.com>
      Cc: Linus Torvalds <torvalds@linux-foundation.org>
      Cc: Peter Zijlstra <peterz@infradead.org>
      Cc: Thomas Gleixner <tglx@linutronix.de>
      Link: http://lkml.kernel.org/r/8a9ed68ae1780e8d3963e4ee13f2f257fe3a3c33.1476393584.git.jpoimboe@redhat.com
      
      Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
      3732710f
  25. 23 Sep, 2016 1 commit
  26. 29 Jul, 2016 1 commit
    • Josh Poimboeuf's avatar
      objtool: Support new GCC 6 switch jump table pattern · 6d01f28b
      Josh Poimboeuf authored
      
      
      This fixes some false positive objtool warnings seen with gcc 6.1.1:
      
        kernel/trace/ring_buffer.o: warning: objtool: ring_buffer_read_page()+0x36c: sibling call from callable instruction with changed frame pointer
        arch/x86/kernel/reboot.o: warning: objtool: native_machine_emergency_restart()+0x139: sibling call from callable instruction with changed frame pointer
        lib/xz/xz_dec_stream.o: warning: objtool: xz_dec_run()+0xc2: sibling call from callable instruction with changed frame pointer
      
      With GCC 6, a new code pattern is sometimes used to access a switch
      statement jump table in .rodata, which objtool doesn't yet recognize:
      
        mov [rodata addr],%reg1
        ... some instructions ...
        jmpq *(%reg1,%reg2,8)
      
      Add support for detecting that pattern.  The detection code is rather
      crude, but it's still effective at weeding out false positives and
      catching real warnings.  It can be refined later once objtool starts
      reading DWARF CFI.
      Reported-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
      Signed-off-by: default avatarJosh Poimboeuf <jpoimboe@redhat.com>
      Cc: Andy Lutomirski <luto@kernel.org>
      Cc: Borislav Petkov <bp@alien8.de>
      Cc: Brian Gerst <brgerst@gmail.com>
      Cc: Denys Vlasenko <dvlasenk@redhat.com>
      Cc: H. Peter Anvin <hpa@zytor.com>
      Cc: Peter Zijlstra <peterz@infradead.org>
      Cc: Thomas Gleixner <tglx@linutronix.de>
      Link: http://lkml.kernel.org/r/b8c9503b4ad8c8a827cc5400db4c1b40a3ea07bc.1469751119.git.jpoimboe@redhat.com
      
      Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
      6d01f28b
  27. 15 Jul, 2016 1 commit
    • Arnaldo Carvalho de Melo's avatar
      objtool: Initialize variable to silence old compiler · b49364f3
      Arnaldo Carvalho de Melo authored
      gcc version 4.1.2 20080704 (Red Hat 4.1.2-55) barfs with:
      
          CC       /tmp/build/objtool/builtin-check.o
        cc1: warnings being treated as errors
        builtin-check.c: In function 'cmd_check':
        builtin-check.c:667: warning: 'prev_rela' may be used uninitialized in this function
        mv: cannot stat `/tmp/build/objtool/.builtin-check.o.tmp': No such file or directory
        make[1]: *** [/tmp/build/objtool/builtin-check.o] Error 1
      
      Init it to NULL to silence it.
      
      Cc: Adrian Hunter <adrian.hunter@intel.com>
      Cc: David Ahern <dsahern@gmail.com>
      Cc: Jiri Olsa <jolsa@kernel.org>
      Cc: Josh Poimboeuf <jpoimboe@redhat.com>
      Cc: Namhyung Kim <namhyung@kernel.org>
      Cc: Wang Nan <wangnan0@huawei.com>
      Link: http://lkml.kernel.org/n/tip-qolo31rl2ojlwj1lj9dhemyz@git.kernel.org
      
      Signed-off-by: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
      b49364f3
  28. 12 Jul, 2016 1 commit
  29. 10 Jul, 2016 1 commit
  30. 16 Apr, 2016 1 commit
    • Josh Poimboeuf's avatar
      objtool: Detect falling through to the next function · b1547d31
      Josh Poimboeuf authored
      
      
      There are several cases in compiled C code where a function may not
      return at the end, and may instead fall through to the next function.
      
      That may indicate a bug in the code, or a gcc bug, or even an objtool
      bug.  But in each case, objtool reports an unhelpful warning, something
      like:
      
        drivers/scsi/qla2xxx/qla_attr.o: warning: objtool: qla2x00_get_fc_host_stats()+0x0: duplicate frame pointer save
        drivers/scsi/qla2xxx/qla_attr.o: warning: objtool: qla2x00_get_fc_host_stats()+0x0: frame pointer state mismatch
      
      Detect this situation and print a more useful error message:
      
        drivers/scsi/qla2xxx/qla_attr.o: warning: objtool: qla2x00_get_host_fabric_name() falls through to next function qla2x00_get_starget_node_name()
      
      Also add some information about this warning and its potential causes to
      the documentation.
      Reported-by: default avatarkbuild test robot <fengguang.wu@intel.com>
      Signed-off-by: default avatarJosh Poimboeuf <jpoimboe@redhat.com>
      Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
      Cc: Andy Lutomirski <luto@amacapital.net>
      Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
      Cc: Borislav Petkov <bp@alien8.de>
      Cc: Brian Gerst <brgerst@gmail.com>
      Cc: Denys Vlasenko <dvlasenk@redhat.com>
      Cc: H. Peter Anvin <hpa@zytor.com>
      Cc: Jiri Olsa <jolsa@redhat.com>
      Cc: Linus Torvalds <torvalds@linux-foundation.org>
      Cc: Peter Zijlstra <peterz@infradead.org>
      Cc: Thomas Gleixner <tglx@linutronix.de>
      Link: http://lkml.kernel.org/r/caa4ec6c687931db805e692d4e4bf06cd87d33e6.1460729697.git.jpoimboe@redhat.com
      
      Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
      b1547d31