solved and the nightmare is complete, here's the next one: speculating
after RET instructions and leaking privileged information using the now
pretty much classical covert channels.
It is called RETBleed and the mitigation effort and controlling
functionality has been modelled similar to what already existing
mitigations provide.
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Merge tag 'x86_bugs_retbleed' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull x86 retbleed fixes from Borislav Petkov:
"Just when you thought that all the speculation bugs were addressed and
solved and the nightmare is complete, here's the next one: speculating
after RET instructions and leaking privileged information using the
now pretty much classical covert channels.
It is called RETBleed and the mitigation effort and controlling
functionality has been modelled similar to what already existing
mitigations provide"
* tag 'x86_bugs_retbleed' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (54 commits)
x86/speculation: Disable RRSBA behavior
x86/kexec: Disable RET on kexec
x86/bugs: Do not enable IBPB-on-entry when IBPB is not supported
x86/entry: Move PUSH_AND_CLEAR_REGS() back into error_entry
x86/bugs: Add Cannon lake to RETBleed affected CPU list
x86/retbleed: Add fine grained Kconfig knobs
x86/cpu/amd: Enumerate BTC_NO
x86/common: Stamp out the stepping madness
KVM: VMX: Prevent RSB underflow before vmenter
x86/speculation: Fill RSB on vmexit for IBRS
KVM: VMX: Fix IBRS handling after vmexit
KVM: VMX: Prevent guest RSB poisoning attacks with eIBRS
KVM: VMX: Convert launched argument to flags
KVM: VMX: Flatten __vmx_vcpu_run()
objtool: Re-add UNWIND_HINT_{SAVE_RESTORE}
x86/speculation: Remove x86_spec_ctrl_mask
x86/speculation: Use cached host SPEC_CTRL value for guest entry/exit
x86/speculation: Fix SPEC_CTRL write on SMT state change
x86/speculation: Fix firmware entry SPEC_CTRL handling
x86/speculation: Fix RSB filling with CONFIG_RETPOLINE=n
...
On Tue, Jun 28, 2022 at 04:28:58PM +0800, Pengfei Xu wrote:
> # ./ftracetest
> === Ftrace unit tests ===
> [1] Basic trace file check [PASS]
> [2] Basic test for tracers [PASS]
> [3] Basic trace clock test [PASS]
> [4] Basic event tracing check [PASS]
> [5] Change the ringbuffer size [PASS]
> [6] Snapshot and tracing setting [PASS]
> [7] trace_pipe and trace_marker [PASS]
> [8] Test ftrace direct functions against tracers [UNRESOLVED]
> [9] Test ftrace direct functions against kprobes [UNRESOLVED]
> [10] Generic dynamic event - add/remove eprobe events [FAIL]
> [11] Generic dynamic event - add/remove kprobe events
>
> It 100% reproduced in step 11 and then missing ENDBR BUG generated:
> "
> [ 9332.752836] mmiotrace: enabled CPU7.
> [ 9332.788612] mmiotrace: disabled.
> [ 9337.103426] traps: Missing ENDBR: syscall_regfunc+0x0/0xb0
It turns out that while syscall_regfunc() does have an ENDBR when
generated, it gets sealed by objtool's .ibt_endbr_seal list.
Since the only text references to this function:
$ git grep syscall_regfunc
include/linux/tracepoint.h:extern int syscall_regfunc(void);
include/trace/events/syscalls.h: syscall_regfunc, syscall_unregfunc
include/trace/events/syscalls.h: syscall_regfunc, syscall_unregfunc
kernel/tracepoint.c:int syscall_regfunc(void)
appear in the __tracepoint section which is excluded by objtool.
Fixes: 3c6f9f77e6 ("objtool: Rework ibt and extricate from stack validation")
Reported-by: Pengfei Xu <pengfei.xu@intel.com
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/Yrrepdaow4F5kqG0@hirez.programming.kicks-ass.net
Do fine-grained Kconfig for all the various retbleed parts.
NOTE: if your compiler doesn't support return thunks this will
silently 'upgrade' your mitigation to IBPB, you might not like this.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Commit
c536ed2fff ("objtool: Remove SAVE/RESTORE hints")
removed the save/restore unwind hints because they were no longer
needed. Now they're going to be needed again so re-add them.
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Since entry asm is tricky, add a validation pass that ensures the
retbleed mitigation has been done before the first actual RET
instruction.
Entry points are those that either have UNWIND_HINT_ENTRY, which acts
as UNWIND_HINT_EMPTY but marks the instruction as an entry point, or
those that have UWIND_HINT_IRET_REGS at +0.
This is basically a variant of validate_branch() that is
intra-function and it will simply follow all branches from marked
entry points and ensures that all paths lead to ANNOTATE_UNRET_END.
If a path hits RET or an indirection the path is a fail and will be
reported.
There are 3 ANNOTATE_UNRET_END instances:
- UNTRAIN_RET itself
- exception from-kernel; this path doesn't need UNTRAIN_RET
- all early exceptions; these also don't need UNTRAIN_RET
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Update retpoline validation with the new CONFIG_RETPOLINE requirement of
not having bare naked RET instructions.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Note: needs to be in a section distinct from Retpolines such that the
Retpoline RET substitution cannot possibly use immediate jumps.
ORC unwinding for zen_untrain_ret() and __x86_return_thunk() is a
little tricky but works due to the fact that zen_untrain_ret() doesn't
have any stack ops and as such will emit a single ORC entry at the
start (+0x3f).
Meanwhile, unwinding an IP, including the __x86_return_thunk() one
(+0x40) will search for the largest ORC entry smaller or equal to the
IP, these will find the one ORC entry (+0x3f) and all works.
[ Alexandre: SVM part. ]
[ bp: Build fix, massages. ]
Suggested-by: Andrew Cooper <Andrew.Cooper3@citrix.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Needed because zen_untrain_ret() will be called from noinstr code.
Also makes sense since the thunks MUST NOT contain instrumentation nor
be poked with dynamic instrumentation.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Find all the return-thunk sites and record them in a .return_sites
section such that the kernel can undo this.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
- Add HOSTPKG_CONFIG env variable to allow users to override pkg-config
- Support W=e as a shorthand for KCFLAGS=-Werror
- Fix CONFIG_IKHEADERS build to support toybox cpio
- Add scripts/dummy-tools/pahole to ease distro packagers' life
- Suppress false-positive warnings from checksyscalls.sh for W=2 build
- Factor out the common code of arch/*/boot/install.sh into
scripts/install.sh
- Support 'kernel-install' tool in scripts/prune-kernel
- Refactor module-versioning to link the symbol versions at the final
link of vmlinux and modules
- Remove CONFIG_MODULE_REL_CRCS because module-versioning now works in
an arch-agnostic way
- Refactor modpost, Makefiles
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Merge tag 'kbuild-v5.19' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild
Pull Kbuild updates from Masahiro Yamada:
- Add HOSTPKG_CONFIG env variable to allow users to override pkg-config
- Support W=e as a shorthand for KCFLAGS=-Werror
- Fix CONFIG_IKHEADERS build to support toybox cpio
- Add scripts/dummy-tools/pahole to ease distro packagers' life
- Suppress false-positive warnings from checksyscalls.sh for W=2 build
- Factor out the common code of arch/*/boot/install.sh into
scripts/install.sh
- Support 'kernel-install' tool in scripts/prune-kernel
- Refactor module-versioning to link the symbol versions at the final
link of vmlinux and modules
- Remove CONFIG_MODULE_REL_CRCS because module-versioning now works in
an arch-agnostic way
- Refactor modpost, Makefiles
* tag 'kbuild-v5.19' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild: (56 commits)
genksyms: adjust the output format to modpost
kbuild: stop merging *.symversions
kbuild: link symbol CRCs at final link, removing CONFIG_MODULE_REL_CRCS
modpost: extract symbol versions from *.cmd files
modpost: add sym_find_with_module() helper
modpost: change the license of EXPORT_SYMBOL to bool type
modpost: remove left-over cross_compile declaration
kbuild: record symbol versions in *.cmd files
kbuild: generate a list of objects in vmlinux
modpost: move *.mod.c generation to write_mod_c_files()
modpost: merge add_{intree_flag,retpoline,staging_flag} to add_header
scripts/prune-kernel: Use kernel-install if available
kbuild: factor out the common installation code into scripts/install.sh
modpost: split new_symbol() to symbol allocation and hash table addition
modpost: make sym_add_exported() always allocate a new symbol
modpost: make multiple export error
modpost: dump Module.symvers in the same order of modules.order
modpost: traverse the namespace_list in order
modpost: use doubly linked list for dump_lists
modpost: traverse unresolved symbols in order
...
Commit c087c6e7b5 ("objtool: Fix type of reloc::addend") failed to
appreciate cross building from ILP32 hosts, where 'int' == 'long' and
the issue persists.
As such, use s64/int64_t/Elf64_Sxword for this field and suffer the
pain that is ISO C99 printf formats for it.
Fixes: c087c6e7b5 ("objtool: Fix type of reloc::addend")
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
[peterz: reword changelog, s/long long/s64/]
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: <stable@vger.kernel.org>
Link: https://lkml.kernel.org/r/alpine.LRH.2.02.2205161041260.11556@file01.intranet.prod.int.rdu2.redhat.com
Nathan reported objtool failing with the following messages:
warning: objtool: no non-local symbols !?
warning: objtool: gelf_update_symshndx: invalid section index
The problem is due to commit 4abff6d48d ("objtool: Fix code relocs
vs weak symbols") failing to consider the case where an object would
have no non-local symbols.
The problem that commit tries to address is adding a STB_LOCAL symbol
to the symbol table in light of the ELF spec's requirement that:
In each symbol table, all symbols with STB_LOCAL binding preced the
weak and global symbols. As ``Sections'' above describes, a symbol
table section's sh_info section header member holds the symbol table
index for the first non-local symbol.
The approach taken is to find this first non-local symbol, move that
to the end and then re-use the freed spot to insert a new local symbol
and increment sh_info.
Except it never considered the case of object files without global
symbols and got a whole bunch of details wrong -- so many in fact that
it is a wonder it ever worked :/
Specifically:
- It failed to re-hash the symbol on the new index, so a subsequent
find_symbol_by_index() would not find it at the new location and a
query for the old location would now return a non-deterministic
choice between the old and new symbol.
- It failed to appreciate that the GElf wrappers are not a valid disk
format (it works because GElf is basically Elf64 and we only
support x86_64 atm.)
- It failed to fully appreciate how horrible the libelf API really is
and got the gelf_update_symshndx() call pretty much completely
wrong; with the direct consequence that if inserting a second
STB_LOCAL symbol would require moving the same STB_GLOBAL symbol
again it would completely come unstuck.
Write a new elf_update_symbol() function that wraps all the magic
required to update or create a new symbol at a given index.
Specifically, gelf_update_sym*() require an @ndx argument that is
relative to the @data argument; this means you have to manually
iterate the section data descriptor list and update @ndx.
Fixes: 4abff6d48d ("objtool: Fix code relocs vs weak symbols")
Reported-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Acked-by: Josh Poimboeuf <jpoimboe@kernel.org>
Tested-by: Nathan Chancellor <nathan@kernel.org>
Cc: <stable@vger.kernel.org>
Link: https://lkml.kernel.org/r/YoPCTEYjoPqE4ZxB@hirez.programming.kicks-ass.net
When build objtool on x86, the generated file inat-tables.c is in
arch/x86/lib instead of arch/x86, use the correct dir to remove it
when make clean.
$ cd tools/objtool
$ make
[...]
GEN arch/x86/lib/inat-tables.c
[...]
Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Link: https://lore.kernel.org/r/1652258270-6278-2-git-send-email-yangtiezhu@loongson.cn
The '--lto' option is a confusing way of telling objtool to do stack
validation despite it being a linked object. It's no longer needed now
that an explicit '--stackval' option exists. The '--vmlinux' option is
also redundant.
Remove both options in favor of a straightforward '--link' option which
identifies a linked object.
Also, implicitly set '--link' with a warning if the user forgets to do
so and we can tell that it's a linked object. This makes it easier for
manual vmlinux runs.
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Miroslav Benes <mbenes@suse.cz>
Link: https://lkml.kernel.org/r/dcd3ceffd15a54822c6183e5766d21ad06082b45.1650300597.git.jpoimboe@redhat.com
Objtool has some hacks in place to workaround toolchain limitations
which otherwise would break no-instrumentation rules. Make the hacks
explicit (and optional for other arches) by turning it into a cmdline
option and kernel config option.
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Miroslav Benes <mbenes@suse.cz>
Link: https://lkml.kernel.org/r/b326eeb9c33231b9dfbb925f194ed7ee40edcd7c.1650300597.git.jpoimboe@redhat.com
Objtool secretly does a jump label hack to overcome the limitations of
the toolchain. Make the hack explicit (and optional for other arches)
by turning it into a cmdline option and kernel config option.
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Miroslav Benes <mbenes@suse.cz>
Link: https://lkml.kernel.org/r/3bdcbfdd27ecb01ddec13c04bdf756a583b13d24.1650300597.git.jpoimboe@redhat.com
Now that CONFIG_STACK_VALIDATION is frame-pointer specific, do the same
for the '--stackval' option. Now the '--no-fp' option is redundant and
can be removed.
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Miroslav Benes <mbenes@suse.cz>
Link: https://lkml.kernel.org/r/f563fa064b3b63d528de250c72012d49e14742a3.1650300597.git.jpoimboe@redhat.com
Extricate ibt from validate_branch() so they can be executed (or ported)
independently from each other.
While shuffling code around, simplify and improve the ibt logic:
- Ignore an explicit list of known sections which reference functions
for reasons other than indirect branching to them. This helps prevent
unnnecesary sealing.
- Warn on missing !ENDBR for all other sections, not just .data and
.rodata. This finds additional warnings, because there are sections
other than .[ro]data which reference function pointers. For example,
the ksymtab sections which are used for exporting symbols.
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Miroslav Benes <mbenes@suse.cz>
Link: https://lkml.kernel.org/r/fd1435e46bb95f81031b8fb1fa360f5f787e4316.1650300597.git.jpoimboe@redhat.com
To help prevent objtool users from having to do math to convert function
addresses to section addresses, and to help out with finding data
addresses reported by IBT validation, add an option to print the section
address in addition to the function address.
Normal:
vmlinux.o: warning: objtool: fixup_exception()+0x2d1: unreachable instruction
With '--sec-address':
vmlinux.o: warning: objtool: fixup_exception()+0x2d1 (.text+0x76c51): unreachable instruction
Suggested-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Miroslav Benes <mbenes@suse.cz>
Link: https://lkml.kernel.org/r/2cea4d5299d53d1a4c09212a6ad7820aa46fda7a.1650300597.git.jpoimboe@redhat.com
The parentheses in the "func()+off" address output are inconsistent with
how the kernel prints function addresses, breaking Peter's scripts.
Remove them.
Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Miroslav Benes <mbenes@suse.cz>
Link: https://lkml.kernel.org/r/f2bec70312f62ef4f1ea21c134d9def627182ad3.1650300597.git.jpoimboe@redhat.com
Objtool has a fairly singular focus. It runs on object files and does
validations and transformations which can be combined in various ways.
The subcommand model has never been a good fit, making it awkward to
combine and remove options.
Remove the "check" and "orc" subcommands in favor of a more traditional
cmdline option model. This makes it much more flexible to use, and
easier to port individual features to other arches.
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Miroslav Benes <mbenes@suse.cz>
Link: https://lkml.kernel.org/r/5c61ebf805e90aefc5fa62bc63468ffae53b9df6.1650300597.git.jpoimboe@redhat.com
Split the existing options into two groups: actions, which actually do
something; and options, which modify the actions in some way.
Also there's no need to have short flags for all the non-action options.
Reserve short flags for the more important actions.
While at it:
- change a few of the short flags to be more intuitive
- make option descriptions more consistently descriptive
- sort options in the source like they are when printed
- move options to a global struct
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Miroslav Benes <mbenes@suse.cz>
Link: https://lkml.kernel.org/r/9dcaa752f83aca24b1b21f0b0eeb28a0c181c0b0.1650300597.git.jpoimboe@redhat.com
Occasionally objtool driven code patching (think .static_call_sites
.retpoline_sites etc..) goes sideways and it tries to patch an
instruction that doesn't match.
Much head-scatching and cursing later the problem is as outlined below
and affects every section that objtool generates for us, very much
including the ORC data. The below uses .static_call_sites because it's
convenient for demonstration purposes, but as mentioned the ORC
sections, .retpoline_sites and __mount_loc are all similarly affected.
Consider:
foo-weak.c:
extern void __SCT__foo(void);
__attribute__((weak)) void foo(void)
{
return __SCT__foo();
}
foo.c:
extern void __SCT__foo(void);
extern void my_foo(void);
void foo(void)
{
my_foo();
return __SCT__foo();
}
These generate the obvious code
(gcc -O2 -fcf-protection=none -fno-asynchronous-unwind-tables -c foo*.c):
foo-weak.o:
0000000000000000 <foo>:
0: e9 00 00 00 00 jmpq 5 <foo+0x5> 1: R_X86_64_PLT32 __SCT__foo-0x4
foo.o:
0000000000000000 <foo>:
0: 48 83 ec 08 sub $0x8,%rsp
4: e8 00 00 00 00 callq 9 <foo+0x9> 5: R_X86_64_PLT32 my_foo-0x4
9: 48 83 c4 08 add $0x8,%rsp
d: e9 00 00 00 00 jmpq 12 <foo+0x12> e: R_X86_64_PLT32 __SCT__foo-0x4
Now, when we link these two files together, you get something like
(ld -r -o foos.o foo-weak.o foo.o):
foos.o:
0000000000000000 <foo-0x10>:
0: e9 00 00 00 00 jmpq 5 <foo-0xb> 1: R_X86_64_PLT32 __SCT__foo-0x4
5: 66 2e 0f 1f 84 00 00 00 00 00 nopw %cs:0x0(%rax,%rax,1)
f: 90 nop
0000000000000010 <foo>:
10: 48 83 ec 08 sub $0x8,%rsp
14: e8 00 00 00 00 callq 19 <foo+0x9> 15: R_X86_64_PLT32 my_foo-0x4
19: 48 83 c4 08 add $0x8,%rsp
1d: e9 00 00 00 00 jmpq 22 <foo+0x12> 1e: R_X86_64_PLT32 __SCT__foo-0x4
Noting that ld preserves the weak function text, but strips the symbol
off of it (hence objdump doing that funny negative offset thing). This
does lead to 'interesting' unused code issues with objtool when ran on
linked objects, but that seems to be working (fingers crossed).
So far so good.. Now lets consider the objtool static_call output
section (readelf output, old binutils):
foo-weak.o:
Relocation section '.rela.static_call_sites' at offset 0x2c8 contains 1 entry:
Offset Info Type Symbol's Value Symbol's Name + Addend
0000000000000000 0000000200000002 R_X86_64_PC32 0000000000000000 .text + 0
0000000000000004 0000000d00000002 R_X86_64_PC32 0000000000000000 __SCT__foo + 1
foo.o:
Relocation section '.rela.static_call_sites' at offset 0x310 contains 2 entries:
Offset Info Type Symbol's Value Symbol's Name + Addend
0000000000000000 0000000200000002 R_X86_64_PC32 0000000000000000 .text + d
0000000000000004 0000000d00000002 R_X86_64_PC32 0000000000000000 __SCT__foo + 1
foos.o:
Relocation section '.rela.static_call_sites' at offset 0x430 contains 4 entries:
Offset Info Type Symbol's Value Symbol's Name + Addend
0000000000000000 0000000100000002 R_X86_64_PC32 0000000000000000 .text + 0
0000000000000004 0000000d00000002 R_X86_64_PC32 0000000000000000 __SCT__foo + 1
0000000000000008 0000000100000002 R_X86_64_PC32 0000000000000000 .text + 1d
000000000000000c 0000000d00000002 R_X86_64_PC32 0000000000000000 __SCT__foo + 1
So we have two patch sites, one in the dead code of the weak foo and one
in the real foo. All is well.
*HOWEVER*, when the toolchain strips unused section symbols it
generates things like this (using new enough binutils):
foo-weak.o:
Relocation section '.rela.static_call_sites' at offset 0x2c8 contains 1 entry:
Offset Info Type Symbol's Value Symbol's Name + Addend
0000000000000000 0000000200000002 R_X86_64_PC32 0000000000000000 foo + 0
0000000000000004 0000000d00000002 R_X86_64_PC32 0000000000000000 __SCT__foo + 1
foo.o:
Relocation section '.rela.static_call_sites' at offset 0x310 contains 2 entries:
Offset Info Type Symbol's Value Symbol's Name + Addend
0000000000000000 0000000200000002 R_X86_64_PC32 0000000000000000 foo + d
0000000000000004 0000000d00000002 R_X86_64_PC32 0000000000000000 __SCT__foo + 1
foos.o:
Relocation section '.rela.static_call_sites' at offset 0x430 contains 4 entries:
Offset Info Type Symbol's Value Symbol's Name + Addend
0000000000000000 0000000100000002 R_X86_64_PC32 0000000000000000 foo + 0
0000000000000004 0000000d00000002 R_X86_64_PC32 0000000000000000 __SCT__foo + 1
0000000000000008 0000000100000002 R_X86_64_PC32 0000000000000000 foo + d
000000000000000c 0000000d00000002 R_X86_64_PC32 0000000000000000 __SCT__foo + 1
And now we can see how that foos.o .static_call_sites goes side-ways, we
now have _two_ patch sites in foo. One for the weak symbol at foo+0
(which is no longer a static_call site!) and one at foo+d which is in
fact the right location.
This seems to happen when objtool cannot find a section symbol, in which
case it falls back to any other symbol to key off of, however in this
case that goes terribly wrong!
As such, teach objtool to create a section symbol when there isn't
one.
Fixes: 44f6a7c075 ("objtool: Fix seg fault with Clang non-section symbols")
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
Link: https://lkml.kernel.org/r/20220419203807.655552918@infradead.org
Objtool's function fallthrough detection only works on C objects.
The distinction between C and assembly objects no longer makes sense
with objtool running on vmlinux.o.
Now that copy_user_64.S has been fixed up, and an objtool sibling call
detection bug has been fixed, the asm code is in "compliance" and this
hack is no longer needed. Remove it.
Fixes: ed53a0d971 ("x86/alternative: Use .ibt_endbr_seal to seal indirect calls")
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/b434cff98eca3a60dcc64c620d7d5d405a0f441c.1649718562.git.jpoimboe@redhat.com
In add_jump_destinations(), sibling call detection requires 'insn->func'
to be valid. But alternative instructions get their 'func' set in
handle_group_alt(), which runs *after* add_jump_destinations(). So
sibling calls in alternatives code don't get properly detected.
Fix that by changing the initialization order: call
add_special_section_alts() *before* add_jump_destinations().
This also means the special case for a missing 'jump_dest' in
add_jump_destinations() can be removed, as it has already been dealt
with.
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/c02e0a0a2a4286b5f848d17c77fdcb7e0caf709c.1649718562.git.jpoimboe@redhat.com
For most sibling calls, 'jump_dest' is NULL because objtool treats the
jump like a call and sets 'call_dest'. But there are a few edge cases
where that's not true. Make it consistent to avoid unexpected behavior.
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/8737d6b9d1691831aed73375f444f0f42da3e2c9.1649718562.git.jpoimboe@redhat.com
When a "!ENDBR" warning is reported for a data section, objtool just
prints the text address of the relocation target twice, without giving
any clues about the location of the original data reference:
vmlinux.o: warning: objtool: dcbnl_netdevice_event()+0x0: .text+0xb64680: data relocation to !ENDBR: dcbnl_netdevice_event+0x0
Instead, print the address of the data reference, in addition to the
address of the relocation target.
vmlinux.o: warning: objtool: dcbnl_nb+0x0: .data..read_mostly+0xe260: data relocation to !ENDBR: dcbnl_netdevice_event+0x0
Fixes: 89bc853eae ("objtool: Find unused ENDBR instructions")
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/762e88d51300e8eaf0f933a5b0feae20ac033bea.1650300597.git.jpoimboe@redhat.com
GCC-8 isn't clever enough to figure out that cpu_start_entry() is a
noreturn while objtool is. This results in code after the call in
start_secondary(). Give GCC a hand so that they all agree on things.
vmlinux.o: warning: objtool: start_secondary()+0x10e: unreachable
Reported-by: Rick Edgecombe <rick.p.edgecombe@intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
Link: https://lore.kernel.org/r/20220408094718.383658532@infradead.org
Since not all compilers have a function attribute to disable KCOV
instrumentation, objtool can rewrite KCOV instrumentation in noinstr
functions as per commit:
f56dae88a8 ("objtool: Handle __sanitize_cov*() tail calls")
However, this has subtle interaction with the SLS validation from
commit:
1cc1e4c8aa ("objtool: Add straight-line-speculation validation")
In that when a tail-call instrucion is replaced with a RET an
additional INT3 instruction is also written, but is not represented in
the decoded instruction stream.
This then leads to false positive missing INT3 objtool warnings in
noinstr code.
Instead of adding additional struct instruction objects, mark the RET
instruction with retpoline_safe to suppress the warning (since we know
there really is an INT3).
Fixes: 1cc1e4c8aa ("objtool: Add straight-line-speculation validation")
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20220323230712.GA8939@worktop.programming.kicks-ass.net
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 08f87a93c8
("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: 08f87a93c8 ("objtool: Validate IBT assumptions")
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20220322115125.811582125@infradead.org
Add HOSTPKG_CONFIG to allow tooling that builds the kernel to override
what pkg-config and parameters are used.
Signed-off-by: Chun-Tse Shao <ctshao@google.com>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
- Add new environment variables, USERCFLAGS and USERLDFLAGS to allow
additional flags to be passed to user-space programs.
- Fix missing fflush() bugs in Kconfig and fixdep
- Fix a minor bug in the comment format of the .config file
- Make kallsyms ignore llvm's local labels, .L*
- Fix UAPI compile-test for cross-compiling with Clang
- Extend the LLVM= syntax to support LLVM=<suffix> form for using a
particular version of LLVm, and LLVM=<prefix> form for using custom
LLVM in a particular directory path.
- Clean up Makefiles
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Merge tag 'kbuild-v5.18-v2' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild
Pull Kbuild updates from Masahiro Yamada:
- Add new environment variables, USERCFLAGS and USERLDFLAGS to allow
additional flags to be passed to user-space programs.
- Fix missing fflush() bugs in Kconfig and fixdep
- Fix a minor bug in the comment format of the .config file
- Make kallsyms ignore llvm's local labels, .L*
- Fix UAPI compile-test for cross-compiling with Clang
- Extend the LLVM= syntax to support LLVM=<suffix> form for using a
particular version of LLVm, and LLVM=<prefix> form for using custom
LLVM in a particular directory path.
- Clean up Makefiles
* tag 'kbuild-v5.18-v2' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild:
kbuild: Make $(LLVM) more flexible
kbuild: add --target to correctly cross-compile UAPI headers with Clang
fixdep: use fflush() and ferror() to ensure successful write to files
arch: syscalls: simplify uapi/kapi directory creation
usr/include: replace extra-y with always-y
certs: simplify empty certs creation in certs/Makefile
certs: include certs/signing_key.x509 unconditionally
kallsyms: ignore all local labels prefixed by '.L'
kconfig: fix missing '# end of' for empty menu
kconfig: add fflush() before ferror() check
kbuild: replace $(if A,A,B) with $(or A,B)
kbuild: Add environment variables for userprogs flags
kbuild: unify cmd_copy and cmd_shipped
Find all ENDBR instructions which are never referenced and stick them
in a section such that the kernel can poison them, sealing the
functions from ever being an indirect call target.
This removes about 1-in-4 ENDBR instructions.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
Link: https://lore.kernel.org/r/20220308154319.763643193@infradead.org
Intel IBT requires that every indirect JMP/CALL targets an ENDBR
instructions, failing this #CP happens and we die. Similarly, all
exception entries should be ENDBR.
Find all code relocations and ensure they're either an ENDBR
instruction or ANNOTATE_NOENDBR. For the exceptions look for
UNWIND_HINT_IRET_REGS at sym+0 not being ENDBR.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
Link: https://lore.kernel.org/r/20220308154319.705110141@infradead.org
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) <peterz@infradead.org>
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
Link: https://lore.kernel.org/r/20220308154319.645963517@infradead.org
Read the new NOENDBR annotation. While there, attempt to not bloat
struct instruction.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
Link: https://lore.kernel.org/r/20220308154319.586815435@infradead.org
Currently ASM_REACHABLE only works for UD2 instructions; reorder
things to also allow over-riding dead_end_function().
To that end:
- Mark INSN_BUG instructions in decode_instructions(), this saves
having to iterate all instructions yet again.
- Have add_call_destinations() set insn->dead_end for
dead_end_function() calls.
- Move add_dead_ends() *after* add_call_destinations() such that
ASM_REACHABLE can clear the ->dead_end mark.
- have validate_branch() only check ->dead_end.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
Link: https://lore.kernel.org/r/20220308154319.410010807@infradead.org
