17 May, 2019
1 commit
-
Pull core fixes from Ingo Molnar:
"A handful of objtool updates, plus a documentation addition for
__ab_c_size()"* 'core-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
objtool: Fix whitelist documentation typo
objtool: Fix function fallthrough detection
objtool: Don't use ignore flag for fake jumps
overflow.h: Add comment documenting __ab_c_size()
15 May, 2019
1 commit
-
The directive specified in the documentation to add an exception
for a single file in a Makefile was inverted.Signed-off-by: Raphael Gault
Signed-off-by: Josh Poimboeuf
Cc: Linus Torvalds
Cc: Peter Zijlstra
Cc: Thomas Gleixner
Link: http://lkml.kernel.org/r/522362a1b934ee39d0af0abb231f68e160ecf1a8.1557874043.git.jpoimboe@redhat.com
Signed-off-by: Ingo Molnar
14 May, 2019
2 commits
-
When a function falls through to the next function due to a compiler
bug, objtool prints some obscure warnings. For example:drivers/regulator/core.o: warning: objtool: regulator_count_voltages()+0x95: return with modified stack frame
drivers/regulator/core.o: warning: objtool: regulator_count_voltages()+0x0: stack state mismatch: cfa1=7+32 cfa2=7+8Instead it should be printing:
drivers/regulator/core.o: warning: objtool: regulator_supply_is_couple() falls through to next function regulator_count_voltages()
This used to work, but was broken by the following commit:
13810435b9a7 ("objtool: Support GCC 8's cold subfunctions")
The padding nops at the end of a function aren't actually part of the
function, as defined by the symbol table. So the 'func' variable in
validate_branch() is getting cleared to NULL when a padding nop is
encountered, breaking the fallthrough detection.If the current instruction doesn't have a function associated with it,
just consider it to be part of the previously detected function by not
overwriting the previous value of 'func'.Reported-by: kbuild test robot
Signed-off-by: Josh Poimboeuf
Cc: Linus Torvalds
Cc: Peter Zijlstra
Cc: Thomas Gleixner
Cc:
Fixes: 13810435b9a7 ("objtool: Support GCC 8's cold subfunctions")
Link: http://lkml.kernel.org/r/546d143820cd08a46624ae8440d093dd6c902cae.1557766718.git.jpoimboe@redhat.com
Signed-off-by: Ingo Molnar -
The ignore flag is set on fake jumps in order to keep
add_jump_destinations() from setting their jump_dest, since it already
got set when the fake jump was created.But using the ignore flag is a bit of a hack. It's normally used to
skip validation of an instruction, which doesn't really make sense for
fake jumps.Also, after the next patch, using the ignore flag for fake jumps can
trigger a false "why am I validating an ignored function?" warning.Instead just add an explicit check in add_jump_destinations() to skip
fake jumps.Signed-off-by: Josh Poimboeuf
Cc: Linus Torvalds
Cc: Peter Zijlstra
Cc: Thomas Gleixner
Link: http://lkml.kernel.org/r/71abc072ff48b2feccc197723a9c52859476c068.1557766718.git.jpoimboe@redhat.com
Signed-off-by: Ingo Molnar
09 May, 2019
1 commit
-
Pull documentation updates from Jonathan Corbet:
"A reasonably busy cycle for docs, including:- Lots of work on the Chinese and Italian translations
- Some license-rules clarifications from Christoph
- Various build-script fixes
- A new document on memory models
- RST conversion of the live-patching docs
- The usual collection of typo fixes and corrections"
* tag 'docs-5.2' of git://git.lwn.net/linux: (140 commits)
docs/livepatch: Unify style of livepatch documentation in the ReST format
docs: livepatch: convert docs to ReST and rename to *.rst
scripts/documentation-file-ref-check: detect broken :doc:`foo`
scripts/documentation-file-ref-check: don't parse Next/ dir
LICENSES: Rename other to deprecated
LICENSES: Clearly mark dual license only licenses
docs: Don't reference the ZLib license in license-rules.rst
docs/vm: Minor editorial changes in the THP and hugetlbfs
docs/vm: add documentation of memory models
doc:it_IT: translation alignment
doc: fix typo in PGP guide
dontdiff: update with Kconfig build artifacts
docs/zh_CN: fix typos in 1.Intro.rst file
docs/zh_CN: redirect CoC docs to Chinese version
doc: mm: migration doesn't use FOLL_SPLIT anymore
docs: doc-guide: remove the extension from .rst files
doc: kselftest: Fix KBUILD_OUTPUT usage instructions
docs: trace: fix some Sphinx warnings
docs: speculation.txt: mark example blocks as such
docs: ntb.txt: add blank lines to clean up some Sphinx warnings
...
08 May, 2019
1 commit
-
Convert livepatch documentation to ReST format. The changes
are mostly trivial, as the documents are already on a good
shape. Just a few markup changes are needed for Sphinx to
properly parse the docs.The conversion is actually:
- add blank lines and identation in order to identify paragraphs;
- fix tables markups;
- add some lists markups;
- mark literal blocks;
- The in-file TOC becomes a comment, in order to skip it from the
output, as Sphinx already generates an index there.
- adjust title markups.At its new index.rst, let's add a :orphan: while this is not linked to
the main index.rst file, in order to avoid build warnings.Signed-off-by: Mauro Carvalho Chehab
Signed-off-by: Petr Mladek
Acked-by: Miroslav Benes
Acked-by: Josh Poimboeuf
Acked-by: Joe Lawrence
Reviewed-by: Kamalesh Babulal
Signed-off-by: Jonathan Corbet
07 May, 2019
1 commit
-
Pull objtool updates from Ingo Molnar:
"This is a series from Peter Zijlstra that adds x86 build-time uaccess
validation of SMAP to objtool, which will detect and warn about the
following uaccess API usage bugs and weirdnesses:- call to %s() with UACCESS enabled
- return with UACCESS enabled
- return with UACCESS disabled from a UACCESS-safe function
- recursive UACCESS enable
- redundant UACCESS disable
- UACCESS-safe disables UACCESSAs it turns out not leaking uaccess permissions outside the intended
uaccess functionality is hard when the interfaces are complex and when
such bugs are mostly dormant.As a bonus we now also check the DF flag. We had at least one
high-profile bug in that area in the early days of Linux, and the
checking is fairly simple. The checks performed and warnings emitted
are:- call to %s() with DF set
- return with DF set
- return with modified stack frame
- recursive STD
- redundant CLDIt's all x86-only for now, but later on this can also be used for PAN
on ARM and objtool is fairly cross-platform in principle.While all warnings emitted by this new checking facility that got
reported to us were fixed, there might be GCC version dependent
warnings that were not reported yet - which we'll address, should they
trigger.The warnings are non-fatal build warnings"
* 'core-objtool-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (27 commits)
mm/uaccess: Use 'unsigned long' to placate UBSAN warnings on older GCC versions
x86/uaccess: Dont leak the AC flag into __put_user() argument evaluation
sched/x86_64: Don't save flags on context switch
objtool: Add Direction Flag validation
objtool: Add UACCESS validation
objtool: Fix sibling call detection
objtool: Rewrite alt->skip_orig
objtool: Add --backtrace support
objtool: Rewrite add_ignores()
objtool: Handle function aliases
objtool: Set insn->func for alternatives
x86/uaccess, kcov: Disable stack protector
x86/uaccess, ftrace: Fix ftrace_likely_update() vs. SMAP
x86/uaccess, ubsan: Fix UBSAN vs. SMAP
x86/uaccess, kasan: Fix KASAN vs SMAP
x86/smap: Ditch __stringify()
x86/uaccess: Introduce user_access_{save,restore}()
x86/uaccess, signal: Fix AC=1 bloat
x86/uaccess: Always inline user_access_begin()
x86/uaccess, xen: Suppress SMAP warnings
...
05 Apr, 2019
1 commit
-
This fixes the following warning seen on GCC 7.3:
arch/x86/kernel/dumpstack.o: warning: objtool: oops_end() falls through to next function show_regs()
Reported-by: kbuild test robot
Signed-off-by: Josh Poimboeuf
Signed-off-by: Thomas Gleixner
Cc: Peter Zijlstra
Link: https://lkml.kernel.org/r/3418ebf5a5a9f6ed7e80954c741c0b904b67b5dc.1554398240.git.jpoimboe@redhat.com
03 Apr, 2019
9 commits
-
Having DF escape is BAD(tm).
Linus; you suggested this one, but since DF really is only used from
ASM and the failure case is fairly obvious, do we really need this?OTOH the patch is fairly small and simple, so let's just do this
to demonstrate objtool's superior awesomeness.Suggested-by: Linus Torvalds
Signed-off-by: Peter Zijlstra (Intel)
Acked-by: Josh Poimboeuf
Cc: Borislav Petkov
Cc: Peter Zijlstra
Cc: Thomas Gleixner
Signed-off-by: Ingo Molnar -
It is important that UACCESS regions are as small as possible;
furthermore the UACCESS state is not scheduled, so doing anything that
might directly call into the scheduler will cause random code to be
ran with UACCESS enabled.Teach objtool too track UACCESS state and warn about any CALL made
while UACCESS is enabled. This very much includes the __fentry__()
and __preempt_schedule() calls.Note that exceptions _do_ save/restore the UACCESS state, and therefore
they can drive preemption. This also means that all exception handlers
must have an otherwise redundant UACCESS disable instruction;
therefore ignore this warning for !STT_FUNC code (exception handlers
are not normal functions).Signed-off-by: Peter Zijlstra (Intel)
Acked-by: Josh Poimboeuf
Cc: Borislav Petkov
Cc: Linus Torvalds
Cc: Peter Zijlstra
Cc: Thomas Gleixner
Signed-off-by: Ingo Molnar -
It turned out that we failed to detect some sibling calls;
specifically those without relocation records; like:$ ./objdump-func.sh defconfig-build/mm/kasan/generic.o __asan_loadN
0000 0000000000000840 :
0000 840: 48 8b 0c 24 mov (%rsp),%rcx
0004 844: 31 d2 xor %edx,%edx
0006 846: e9 45 fe ff ff jmpq 690So extend the cross-function jump to also consider those that are not
between known (or newly detected) parent/child functions, as
sibling-cals when they jump to the start of the function.The second part of that condition is to deal with random jumps to the
middle of other function, as can be found in
arch/x86/lib/copy_user_64.S for example.This then (with later patches applied) makes the above recognise the
sibling call:mm/kasan/generic.o: warning: objtool: __asan_loadN()+0x6: call to check_memory_region() with UACCESS enabled
Also make sure to set insn->call_dest for sibling calls so we can know
who we're calling. This is useful information when printing validation
warnings later.Signed-off-by: Peter Zijlstra (Intel)
Acked-by: Josh Poimboeuf
Cc: Borislav Petkov
Cc: Linus Torvalds
Cc: Peter Zijlstra
Cc: Thomas Gleixner
Signed-off-by: Ingo Molnar -
Really skip the original instruction flow, instead of letting it
continue with NOPs.Since the alternative code flow already continues after the original
instructions, only the alt-original is skipped.Signed-off-by: Peter Zijlstra (Intel)
Acked-by: Josh Poimboeuf
Cc: Borislav Petkov
Cc: Linus Torvalds
Cc: Peter Zijlstra
Cc: Thomas Gleixner
Signed-off-by: Ingo Molnar -
For when you want to know the path that reached your fail state:
$ ./objtool check --no-fp --backtrace arch/x86/lib/usercopy_64.o
arch/x86/lib/usercopy_64.o: warning: objtool: .altinstr_replacement+0x3: UACCESS disable without MEMOPs: __clear_user()
arch/x86/lib/usercopy_64.o: warning: objtool: __clear_user()+0x3a: (alt)
arch/x86/lib/usercopy_64.o: warning: objtool: __clear_user()+0x2e: (branch)
arch/x86/lib/usercopy_64.o: warning: objtool: __clear_user()+0x18: (branch)
arch/x86/lib/usercopy_64.o: warning: objtool: .altinstr_replacement+0xffffffffffffffff: (branch)
arch/x86/lib/usercopy_64.o: warning: objtool: __clear_user()+0x5: (alt)
arch/x86/lib/usercopy_64.o: warning: objtool: __clear_user()+0x0: :
0: e8 00 00 00 00 callq 5
1: R_X86_64_PLT32 __fentry__-0x4
5: 90 nop
6: 90 nop
7: 90 nop
8: 48 89 f0 mov %rsi,%rax
b: 48 c1 ee 03 shr $0x3,%rsi
f: 83 e0 07 and $0x7,%eax
12: 48 89 f1 mov %rsi,%rcx
15: 48 85 c9 test %rcx,%rcx
18: 74 0f je 29
1a: 48 c7 07 00 00 00 00 movq $0x0,(%rdi)
21: 48 83 c7 08 add $0x8,%rdi
25: ff c9 dec %ecx
27: 75 f1 jne 1a
29: 48 89 c1 mov %rax,%rcx
2c: 85 c9 test %ecx,%ecx
2e: 74 0a je 3a
30: c6 07 00 movb $0x0,(%rdi)
33: 48 ff c7 inc %rdi
36: ff c9 dec %ecx
38: 75 f6 jne 30
3a: 90 nop
3b: 90 nop
3c: 90 nop
3d: 48 89 c8 mov %rcx,%rax
40: c3 retqSigned-off-by: Peter Zijlstra (Intel)
Acked-by: Josh Poimboeuf
Cc: Borislav Petkov
Cc: Linus Torvalds
Cc: Peter Zijlstra
Cc: Thomas Gleixner
Signed-off-by: Ingo Molnar -
The whole add_ignores() thing was wildly weird; rewrite it according
to 'modern' ways.Signed-off-by: Peter Zijlstra (Intel)
Acked-by: Josh Poimboeuf
Cc: Borislav Petkov
Cc: Linus Torvalds
Cc: Peter Zijlstra
Cc: Thomas Gleixner
Signed-off-by: Ingo Molnar -
Function aliases result in different symbols for the same set of
instructions; track a canonical symbol so there is a unique point of
access.This again prepares the way for function attributes. And in particular
the need for aliases comes from how KASAN uses them.Signed-off-by: Peter Zijlstra (Intel)
Acked-by: Josh Poimboeuf
Cc: Borislav Petkov
Cc: Linus Torvalds
Cc: Peter Zijlstra
Cc: Thomas Gleixner
Signed-off-by: Ingo Molnar -
In preparation of function attributes, we need each instruction to
have a valid link back to its function.Therefore make sure we set the function association for alternative
instruction sequences; they are, after all, still part of the function.Signed-off-by: Peter Zijlstra (Intel)
Acked-by: Josh Poimboeuf
Cc: Borislav Petkov
Cc: Linus Torvalds
Cc: Peter Zijlstra
Cc: Thomas Gleixner
Signed-off-by: Ingo Molnar -
To facillitate other usage of ignoring alternatives; rename
ANNOTATE_NOSPEC_IGNORE to ANNOTATE_IGNORE_ALTERNATIVE.Signed-off-by: Peter Zijlstra (Intel)
Cc: Borislav Petkov
Cc: Josh Poimboeuf
Cc: Linus Torvalds
Cc: Peter Zijlstra
Cc: Thomas Gleixner
Signed-off-by: Ingo Molnar
28 Mar, 2019
1 commit
-
If it is not in the default location, compilation fails at several points.
Signed-off-by: Rolf Eike Beer
Signed-off-by: Josh Poimboeuf
Signed-off-by: Thomas Gleixner
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/91a25e992566a7968fedc89ec80e7f4c83ad0548.1553622500.git.jpoimboe@redhat.com
21 Mar, 2019
1 commit
-
Objtool uses over 512k of stack, thanks to the hash table embedded in
the objtool_file struct. This causes an unnecessarily large stack
allocation and breaks users with low stack limits.Move the struct off the stack.
Fixes: 042ba73fe7eb ("objtool: Add several performance improvements")
Reported-by: Vassili Karpov
Signed-off-by: Josh Poimboeuf
Signed-off-by: Thomas Gleixner
Cc: Peter Zijlstra
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/df92dcbc4b84b02ffa252f46876df125fb56e2d7.1552954176.git.jpoimboe@redhat.com
21 Nov, 2018
2 commits
-
Because find_symbol_by_name() traverses the same lists as
read_symbols(), changing sym->name in place without copying it affects
the result of find_symbol_by_name(). In the case where a ".cold"
function precedes its parent in sec->symbol_list, it can result in a
function being considered a parent of itself. This leads to function
length being set to 0 and other consequent side-effects including a
segfault in add_switch_table(). The effects of this bug are only
visible when building with -ffunction-sections in KCFLAGS.Fix by copying the search string instead of modifying it in place.
Signed-off-by: Artem Savkov
Signed-off-by: Josh Poimboeuf
Cc: Linus Torvalds
Cc: Peter Zijlstra
Cc: Thomas Gleixner
Fixes: 13810435b9a7 ("objtool: Support GCC 8's cold subfunctions")
Link: http://lkml.kernel.org/r/910abd6b5a4945130fd44f787c24e07b9e07c8da.1542736240.git.jpoimboe@redhat.com
Signed-off-by: Ingo Molnar -
If read_symbols() fails during second list traversal (the one dealing
with ".cold" subfunctions) it frees the symbol, but never deletes it
from the list/hash_table resulting in symbol being freed again in
elf_close(). Fix it by just returning an error, leaving cleanup to
elf_close().Signed-off-by: Artem Savkov
Signed-off-by: Josh Poimboeuf
Cc: Linus Torvalds
Cc: Peter Zijlstra
Cc: Thomas Gleixner
Fixes: 13810435b9a7 ("objtool: Support GCC 8's cold subfunctions")
Link: http://lkml.kernel.org/r/beac5a9b7da9e8be90223459dcbe07766ae437dd.1542736240.git.jpoimboe@redhat.com
Signed-off-by: Ingo Molnar
04 Nov, 2018
1 commit
-
Signed-off-by: Ingo Molnar
01 Nov, 2018
1 commit
-
Starting with GCC 8, a lot of unlikely code was moved out of line to
"cold" subfunctions in .text.unlikely.For example, the unlikely bits of:
irq_do_set_affinity()
are moved out to the following subfunction:
irq_do_set_affinity.cold.49()
Starting with GCC 9, the numbered suffix has been removed. So in the
above example, the cold subfunction is instead:irq_do_set_affinity.cold()
Tweak the objtool subfunction detection logic so that it detects both
GCC 8 and GCC 9 naming schemes.Reported-by: Peter Zijlstra (Intel)
Signed-off-by: Josh Poimboeuf
Signed-off-by: Thomas Gleixner
Tested-by: Peter Zijlstra (Intel)
Acked-by: Peter Zijlstra (Intel)
Link: https://lkml.kernel.org/r/015e9544b1f188d36a7f02fa31e9e95629aa5f50.1541040800.git.jpoimboe@redhat.com
29 Oct, 2018
1 commit
-
…rgent, to pick up simple topic branches
Signed-off-by: Ingo Molnar <mingo@kernel.org>
27 Sep, 2018
1 commit
-
Similar to the arm64 case, 64-bit x86 can benefit from using relative
references rather than absolute ones when emitting struct jump_entry
instances. Not only does this reduce the memory footprint of the entries
themselves by 33%, it also removes the need for carrying relocation
metadata on relocatable builds (i.e., for KASLR) which saves a fair
chunk of .init space as well (although the savings are not as dramatic
as on arm64)Signed-off-by: Ard Biesheuvel
Signed-off-by: Thomas Gleixner
Acked-by: Peter Zijlstra (Intel)
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-s390@vger.kernel.org
Cc: Arnd Bergmann
Cc: Heiko Carstens
Cc: Kees Cook
Cc: Will Deacon
Cc: Catalin Marinas
Cc: Steven Rostedt
Cc: Martin Schwidefsky
Cc: Jessica Yu
Link: https://lkml.kernel.org/r/20180919065144.25010-7-ard.biesheuvel@linaro.org
08 Sep, 2018
1 commit
-
Add support for processing switch jump tables in objects with multiple
.rodata sections, such as those created by '-ffunction-sections' and
'-fdata-sections'. Currently, objtool always looks in .rodata for jump
table information, which results in many "sibling call from callable
instruction with modified stack frame" warnings with objects compiled
using those flags.The fix is comprised of three parts:
1. Flagging all .rodata sections when importing ELF information for
easier checking later.2. Keeping a reference to the section each relocation is from in order
to get the list_head for the other relocations in that section.3. Finding jump tables by following relocations to .rodata sections,
rather than always referencing a single global .rodata section.The patch has been tested without data sections enabled and no
differences in the resulting orc unwind information were seen.Note that as objtool adds terminators to end of each .text section the
unwind information generated between a function+data sections build and
a normal build aren't directly comparable. Manual inspection suggests
that objtool is now generating the correct information, or at least
making more of an effort to do so than it did previously.Signed-off-by: Allan Xavier
Signed-off-by: Josh Poimboeuf
Signed-off-by: Thomas Gleixner
Link: https://lkml.kernel.org/r/099bdc375195c490dda04db777ee0b95d566ded1.1536325914.git.jpoimboe@redhat.com
16 Aug, 2018
1 commit
-
Pull Kbuild updates from Masahiro Yamada:
- verify depmod is installed before modules_install
- support build salt in case build ids must be unique between builds
- allow users to specify additional host compiler flags via HOST*FLAGS,
and rename internal variables to KBUILD_HOST*FLAGS- update buildtar script to drop vax support, add arm64 support
- update builddeb script for better debarch support
- document the pit-fall of if_changed usage
- fix parallel build of UML with O= option
- make 'samples' target depend on headers_install to fix build errors
- remove deprecated host-progs variable
- add a new coccinelle script for refcount_t vs atomic_t check
- improve double-test coccinelle script
- misc cleanups and fixes
* tag 'kbuild-v4.19' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild: (41 commits)
coccicheck: return proper error code on fail
Coccinelle: doubletest: reduce side effect false positives
kbuild: remove deprecated host-progs variable
kbuild: make samples really depend on headers_install
um: clean up archheaders recipe
kbuild: add %asm-generic to no-dot-config-targets
um: fix parallel building with O= option
scripts: Add Python 3 support to tracing/draw_functrace.py
builddeb: Add automatic support for sh{3,4}{,eb} architectures
builddeb: Add automatic support for riscv* architectures
builddeb: Add automatic support for m68k architecture
builddeb: Add automatic support for or1k architecture
builddeb: Add automatic support for sparc64 architecture
builddeb: Add automatic support for mips{,64}r6{,el} architectures
builddeb: Add automatic support for mips64el architecture
builddeb: Add automatic support for ppc64 and powerpcspe architectures
builddeb: Introduce functions to simplify kconfig tests in set_debarch
builddeb: Drop check for 32-bit s390
builddeb: Change architecture detection fallback to use dpkg-architecture
builddeb: Skip architecture detection when KBUILD_DEBARCH is set
...
14 Aug, 2018
1 commit
-
Pull x86 asm updates from Thomas Gleixner:
"The lowlevel and ASM code updates for x86:- Make stack trace unwinding more reliable
- ASM instruction updates for better code generation
- Various cleanups"
* 'x86-asm-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
x86/entry/64: Add two more instruction suffixes
x86/asm/64: Use 32-bit XOR to zero registers
x86/build/vdso: Simplify 'cmd_vdso2c'
x86/build/vdso: Remove unused vdso-syms.lds
x86/stacktrace: Enable HAVE_RELIABLE_STACKTRACE for the ORC unwinder
x86/unwind/orc: Detect the end of the stack
x86/stacktrace: Do not fail for ORC with regs on stack
x86/stacktrace: Clarify the reliable success paths
x86/stacktrace: Remove STACKTRACE_DUMP_ONCE
x86/stacktrace: Do not unwind after user regs
x86/asm: Use CC_SET/CC_OUT in percpu_cmpxchg8b_double() to micro-optimize code generation
18 Jul, 2018
2 commits
-
In preparation for enabling command line LDFLAGS, re-name HOSTLDFLAGS
to KBUILD_HOSTLDFLAGS as the internal use only flags. This should not
have any visible effects.Signed-off-by: Laura Abbott
Signed-off-by: Masahiro Yamada -
In preparation for enabling command line CFLAGS, re-name HOSTCFLAGS to
KBUILD_HOSTCFLAGS as the internal use only flags. This should not have
any visible effects.Signed-off-by: Laura Abbott
Signed-off-by: Masahiro Yamada
14 Jul, 2018
1 commit
-
Clang puts its section header names in the '.strtab' section instead of
'.shstrtab', which causes objtool to fail with a "can't find
.shstrtab section" warning when attempting to write ORC metadata to an
object file.If '.shstrtab' doesn't exist, use '.strtab' instead.
Signed-off-by: Simon Ser
Signed-off-by: Josh Poimboeuf
Cc: Linus Torvalds
Cc: Peter Zijlstra
Cc: Thomas Gleixner
Link: http://lkml.kernel.org/r/d1c1c3fe55872be433da7bc5e1860538506229ba.1531153015.git.jpoimboe@redhat.com
Signed-off-by: Ingo Molnar
02 Jul, 2018
1 commit
-
Since the following commit:
cd77849a69cf ("objtool: Fix GCC 8 cold subfunction detection for aliased functions")
... if the kernel is built with EXTRA_CFLAGS='-fno-reorder-functions',
objtool can get stuck in an infinite loop.That flag causes the new GCC 8 cold subfunctions to be placed in .text
instead of .text.unlikely. But it also has an unfortunate quirk: in the
symbol table, the subfunction (e.g., nmi_panic.cold.7) is nested inside
the parent (nmi_panic).That function overlap confuses objtool, and causes it to get into an
infinite loop in next_insn_same_func(). Here's Allan's description of
the loop:"Objtool iterates through the instructions in nmi_panic using
next_insn_same_func. Once it reaches the end of nmi_panic at 0x534 it
jumps to 0x528 as that's the start of nmi_panic.cold.7. However, since
the instructions starting at 0x528 are still associated with nmi_panic
objtool will get stuck in a loop, continually jumping back to 0x528
after reaching 0x534."Fix it by shortening the length of the parent function so that the
functions no longer overlap.Reported-and-analyzed-by: Allan Xavier
Signed-off-by: Josh Poimboeuf
Cc: Allan Xavier
Cc: Andy Lutomirski
Cc: Borislav Petkov
Cc: Brian Gerst
Cc: Denys Vlasenko
Cc: H. Peter Anvin
Cc: Linus Torvalds
Cc: Peter Zijlstra
Cc: Thomas Gleixner
Link: http://lkml.kernel.org/r/9e704c52bee651129b036be14feda317ae5606ae.1530136978.git.jpoimboe@redhat.com
Signed-off-by: Ingo Molnar
21 Jun, 2018
1 commit
-
The existing UNWIND_HINT_EMPTY annotations happen to be good indicators
of where entry code calls into C code for the first time. So also use
them to mark the end of the stack for the ORC unwinder.Use that information to set unwind->error if the ORC unwinder doesn't
unwind all the way to the end. This will be needed for enabling
HAVE_RELIABLE_STACKTRACE for the ORC unwinder so we can use it with the
livepatch consistency model.Thanks to Jiri Slaby for teaching the ORCs about the unwind hints.
Signed-off-by: Josh Poimboeuf
Signed-off-by: Jiri Slaby
Acked-by: Josh Poimboeuf
Cc: Andy Lutomirski
Cc: Borislav Petkov
Cc: Brian Gerst
Cc: Denys Vlasenko
Cc: H. Peter Anvin
Cc: Linus Torvalds
Cc: Peter Zijlstra
Cc: Thomas Gleixner
Link: https://lkml.kernel.org/lkml/20180518064713.26440-5-jslaby@suse.cz
Signed-off-by: Ingo Molnar
20 Jun, 2018
1 commit
-
machine_real_restart() is annotated as '__noreturn", so add it to the
objtool noreturn list. This fixes the following warning with clang and
CONFIG_CC_OPTIMIZE_FOR_SIZE=y:arch/x86/kernel/reboot.o: warning: objtool: native_machine_emergency_restart() falls through to next function machine_power_off()
Reported-by: Matthias Kaehlcke
Signed-off-by: Josh Poimboeuf
Signed-off-by: Thomas Gleixner
Tested-by: Matthias Kaehlcke
Reviewed-by: Matthias Kaehlcke
Link: https://lkml.kernel.org/r/791712792aa4431bdd55bf1beb33a169ddf3b4a2.1529423255.git.jpoimboe@redhat.com
06 Jun, 2018
1 commit
-
The kbuild test robot reported the following issue:
kernel/time/posix-stubs.o: warning: objtool: sys_ni_posix_timers.cold.1()+0x0: unreachable instruction
This file creates symbol aliases for the sys_ni_posix_timers() function.
So there are multiple ELF function symbols for the same function:23: 0000000000000150 26 FUNC GLOBAL DEFAULT 1 __x64_sys_timer_create
24: 0000000000000150 26 FUNC GLOBAL DEFAULT 1 sys_ni_posix_timers
25: 0000000000000150 26 FUNC GLOBAL DEFAULT 1 __ia32_sys_timer_create
26: 0000000000000150 26 FUNC GLOBAL DEFAULT 1 __x64_sys_timer_gettimeHere's the corresponding cold subfunction:
11: 0000000000000000 45 FUNC LOCAL DEFAULT 6 sys_ni_posix_timers.cold.1
When analyzing overlapping functions, objtool only looks at the first
one in the symbol list. The rest of the functions are basically ignored
because they point to instructions which have already been analyzed.So in this case it analyzes the __x64_sys_timer_create() function, but
then it fails to recognize that its cold subfunction is
sys_ni_posix_timers.cold.1(), because the names are different.Make the subfunction detection a little smarter by associating each
subfunction with the first function which jumps to it, since that's the
one which will be analyzed.Unfortunately we still have to leave the original subfunction detection
code in place, thanks to GCC switch tables. (See the comment for more
details.)Fixes: 13810435b9a7 ("objtool: Support GCC 8's cold subfunctions")
Reported-by: kbuild test robot
Signed-off-by: Josh Poimboeuf
Signed-off-by: Thomas Gleixner
Cc: Peter Zijlstra
Link: https://lkml.kernel.org/r/d3ba52662cbc8e3a64a3b64d44b4efc5674fd9ab.1527855808.git.jpoimboe@redhat.com
19 May, 2018
1 commit
-
With the following commit:
fd35c88b7417 ("objtool: Support GCC 8 switch tables")
I added a "can't find switch jump table" warning, to stop covering up
silent failures if add_switch_table() can't find anything.That warning found yet another bug in the objtool switch table detection
logic. For cases 1 and 2 (as described in the comments of
find_switch_table()), the find_symbol_containing() check doesn't adjust
the offset for RIP-relative switch jumps.Incidentally, this bug was already fixed for case 3 with:
6f5ec2993b1f ("objtool: Detect RIP-relative switch table references")
However, that commit missed the fix for cases 1 and 2.
The different cases are now starting to look more and more alike. So
fix the bug by consolidating them into a single case, by checking the
original dynamic jump instruction in the case 3 loop.This also simplifies the code and makes it more robust against future
switch table detection issues -- of which I'm sure there will be many...Switch table detection has been the most fragile area of objtool, by
far. I long for the day when we'll have a GCC plugin for annotating
switch tables. Linus asked me to delay such a plugin due to the
flakiness of the plugin infrastructure in older versions of GCC, so this
rickety code is what we're stuck with for now. At least the code is now
a little simpler than it was.Reported-by: kbuild test robot
Signed-off-by: Josh Poimboeuf
Cc: Linus Torvalds
Cc: Peter Zijlstra
Cc: Thomas Gleixner
Link: http://lkml.kernel.org/r/f400541613d45689086329432f3095119ffbc328.1526674218.git.jpoimboe@redhat.com
Signed-off-by: Ingo Molnar
15 May, 2018
1 commit
-
Typically a switch table can be found by detecting a .rodata access
followed an indirect jump:1969: 4a 8b 0c e5 00 00 00 mov 0x0(,%r12,8),%rcx
1970: 00
196d: R_X86_64_32S .rodata+0x438
1971: e9 00 00 00 00 jmpq 1976
1972: R_X86_64_PC32 __x86_indirect_thunk_rcx-0x4Randy Dunlap reported a case (seen with GCC 4.8) where the .rodata
access uses RIP-relative addressing:19bd: 48 8b 3d 00 00 00 00 mov 0x0(%rip),%rdi # 19c4
19c0: R_X86_64_PC32 .rodata+0x45c
19c4: e9 00 00 00 00 jmpq 19c9
19c5: R_X86_64_PC32 __x86_indirect_thunk_rdi-0x4In this case the relocation addend needs to be adjusted accordingly in
order to find the location of the switch table.The fix is for case 3 (as described in the comments), but also make the
existing case 1 & 2 checks more precise by only adjusting the addend for
R_X86_64_PC32 relocations.This fixes the following warnings:
drivers/video/fbdev/omap2/omapfb/dss/dispc.o: warning: objtool: dispc_runtime_suspend()+0xbb8: sibling call from callable instruction with modified stack frame
drivers/video/fbdev/omap2/omapfb/dss/dispc.o: warning: objtool: dispc_runtime_resume()+0xcc5: sibling call from callable instruction with modified stack frameReported-by: Randy Dunlap
Signed-off-by: Josh Poimboeuf
Cc: Linus Torvalds
Cc: Peter Zijlstra
Cc: Thomas Gleixner
Link: http://lkml.kernel.org/r/b6098294fd67afb69af8c47c9883d7a68bf0f8ea.1526305958.git.jpoimboe@redhat.com
Signed-off-by: Ingo Molnar
14 May, 2018
3 commits
-
With GCC 8, some issues were found with the objtool switch table
detection.1) In the .rodata section, immediately after the switch table, there can
be another object which contains a pointer to the function which had
the switch statement. In this case objtool wrongly considers the
function pointer to be part of the switch table. Fix it by:a) making sure there are no pointers to the beginning of the
function; andb) making sure there are no gaps in the switch table.
Only the former was needed, the latter adds additional protection for
future optimizations.2) In find_switch_table(), case 1 and case 2 are missing the check to
ensure that the .rodata switch table data is anonymous, i.e. that it
isn't already associated with an ELF symbol. Fix it by adding the
same find_symbol_containing() check which is used for case 3.This fixes the following warnings with GCC 8:
drivers/block/virtio_blk.o: warning: objtool: virtio_queue_rq()+0x0: stack state mismatch: cfa1=7+8 cfa2=7+72
net/ipv6/icmp.o: warning: objtool: icmpv6_rcv()+0x0: stack state mismatch: cfa1=7+8 cfa2=7+64
drivers/usb/core/quirks.o: warning: objtool: quirks_param_set()+0x0: stack state mismatch: cfa1=7+8 cfa2=7+48
drivers/mtd/nand/raw/nand_hynix.o: warning: objtool: hynix_nand_decode_id()+0x0: stack state mismatch: cfa1=7+8 cfa2=7+24
drivers/mtd/nand/raw/nand_samsung.o: warning: objtool: samsung_nand_decode_id()+0x0: stack state mismatch: cfa1=7+8 cfa2=7+32
drivers/gpu/drm/nouveau/nvkm/subdev/top/gk104.o: warning: objtool: gk104_top_oneinit()+0x0: stack state mismatch: cfa1=7+8 cfa2=7+64Reported-by: Arnd Bergmann
Reported-by: kbuild test robot
Signed-off-by: Josh Poimboeuf
Acked-by: Peter Zijlstra (Intel)
Cc: David Laight
Cc: Greg KH
Cc: Linus Torvalds
Cc: Peter Zijlstra
Cc: Randy Dunlap
Cc: Thomas Gleixner
Cc: damian
Link: http://lkml.kernel.org/r/20180510224849.xwi34d6tzheb5wgw@treble
Signed-off-by: Ingo Molnar -
GCC 8 moves a lot of unlikely code out of line to "cold" subfunctions in
.text.unlikely. Properly detect the new subfunctions and treat them as
extensions of the original functions.This fixes a bunch of warnings like:
kernel/cgroup/cgroup.o: warning: objtool: parse_cgroup_root_flags()+0x33: sibling call from callable instruction with modified stack frame
kernel/cgroup/cgroup.o: warning: objtool: cgroup_addrm_files()+0x290: sibling call from callable instruction with modified stack frame
kernel/cgroup/cgroup.o: warning: objtool: cgroup_apply_control_enable()+0x25b: sibling call from callable instruction with modified stack frame
kernel/cgroup/cgroup.o: warning: objtool: rebind_subsystems()+0x325: sibling call from callable instruction with modified stack frameReported-and-tested-by: damian
Reported-by: Arnd Bergmann
Signed-off-by: Josh Poimboeuf
Acked-by: Peter Zijlstra (Intel)
Cc: David Laight
Cc: Greg KH
Cc: Linus Torvalds
Cc: Peter Zijlstra
Cc: Randy Dunlap
Cc: Thomas Gleixner
Link: http://lkml.kernel.org/r/0965e7fcfc5f31a276f0c7f298ff770c19b68706.1525923412.git.jpoimboe@redhat.com
Signed-off-by: Ingo Molnar -
Objtool has some crude logic for detecting static "noreturn" functions
(aka "dead ends"). This is necessary for being able to correctly follow
GCC code flow when such functions are called.It's remotely possible for two functions to call each other via sibling
calls. If they don't have RET instructions, objtool's noreturn
detection logic goes into a recursive loop:drivers/char/ipmi/ipmi_ssif.o: warning: objtool: return_hosed_msg()+0x0: infinite recursion (objtool bug!)
drivers/char/ipmi/ipmi_ssif.o: warning: objtool: deliver_recv_msg()+0x0: infinite recursion (objtool bug!)Instead of reporting an error in this case, consider the functions to be
non-dead-ends.Reported-and-tested-by: Randy Dunlap
Signed-off-by: Josh Poimboeuf
Acked-by: Peter Zijlstra (Intel)
Cc: Arnd Bergmann
Cc: David Laight
Cc: Greg KH
Cc: Linus Torvalds
Cc: Peter Zijlstra
Cc: Thomas Gleixner
Cc: damian
Link: http://lkml.kernel.org/r/7cc156408c5781a1f62085d352ced1fe39fe2f91.1525923412.git.jpoimboe@redhat.com
Signed-off-by: Ingo Molnar