Pull x86 asm alternatives updates from Borislav Petkov:
- Teach the static_call patching infrastructure to handle conditional
tall calls properly which can be static calls too
- Add proper struct alt_instr.flags which controls different aspects of
insn patching behavior
* tag 'x86_alternatives_for_v6.3_rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
x86/static_call: Add support for Jcc tail-calls
x86/alternatives: Teach text_poke_bp() to patch Jcc.d32 instructions
x86/alternatives: Introduce int3_emulate_jcc()
x86/alternatives: Add alt_instr.flags
For mysterious raisins I listed the new __asan_mem*() functions as
being uaccess safe, this is giving objtool fails on KASAN builds
because these functions call out to the actual __mem*() functions
which are not marked uaccess safe.
Removing it doesn't make the robots unhappy.
Fixes: 69d4c0d321 ("entry, kasan, x86: Disallow overriding mem*() functions")
Reported-by: "Paul E. McKenney" <paulmck@kernel.org>
Bisected-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20230126182302.GA687063@paulmck-ThinkPad-P17-Gen-1
Hand-written asm often contains non-function symbols in executable
sections. _end symbols for finding the size of instruction blocks
for runtime processing is one such usage.
optprobe_template_end is one example that causes the warning:
objtool: optprobe_template_end(): can't find starting instruction
This is because the symbol happens to be at the end of the file (and
therefore end of a section in the object file).
So ignore end-of-section STT_NOTYPE symbols instead of bailing out
because an instruction can't be found. While we're here, add a more
descriptive warning for STT_FUNC symbols found at the end of a
section.
[ This also solves a PowerPC regression reported by Sathvika Vasireddy. ]
Reported-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Reported-by: Sathvika Vasireddy <sv@linux.ibm.com>
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Sathvika Vasireddy <sv@linux.ibm.com>
Link: https://lore.kernel.org/r/20221220101323.3119939-1-npiggin@gmail.com
Add a struct alt_instr.flags field which will contain different flags
controlling alternatives patching behavior.
The initial idea was to be able to specify it as a separate macro
parameter but that would mean touching all possible invocations of the
alternatives macros and thus a lot of churn.
What is more, as PeterZ suggested, being able to say ALT_NOT(feature) is
very readable and explains exactly what is meant.
So make the feature field a u32 where the patching flags are the upper
u16 part of the dword quantity while the lower u16 word is the feature.
The highest feature number currently is 0x26a (i.e., word 19) so there
is plenty of space. If that becomes insufficient, the field can be
extended to u64 which will then make struct alt_instr of the nice size
of 16 bytes (14 bytes currently).
There should be no functional changes resulting from this.
Suggested-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/Y6RCoJEtxxZWwotd@zn.tnic
Pull powerpc updates from Michael Ellerman:
- Add powerpc qspinlock implementation optimised for large system
scalability and paravirt. See the merge message for more details
- Enable objtool to be built on powerpc to generate mcount locations
- Use a temporary mm for code patching with the Radix MMU, so the
writable mapping is restricted to the patching CPU
- Add an option to build the 64-bit big-endian kernel with the ELFv2
ABI
- Sanitise user registers on interrupt entry on 64-bit Book3S
- Many other small features and fixes
Thanks to Aboorva Devarajan, Angel Iglesias, Benjamin Gray, Bjorn
Helgaas, Bo Liu, Chen Lifu, Christoph Hellwig, Christophe JAILLET,
Christophe Leroy, Christopher M. Riedl, Colin Ian King, Deming Wang,
Disha Goel, Dmitry Torokhov, Finn Thain, Geert Uytterhoeven, Gustavo A.
R. Silva, Haowen Bai, Joel Stanley, Jordan Niethe, Julia Lawall, Kajol
Jain, Laurent Dufour, Li zeming, Miaoqian Lin, Michael Jeanson, Nathan
Lynch, Naveen N. Rao, Nayna Jain, Nicholas Miehlbradt, Nicholas Piggin,
Pali Rohár, Randy Dunlap, Rohan McLure, Russell Currey, Sathvika
Vasireddy, Shaomin Deng, Stephen Kitt, Stephen Rothwell, Thomas
Weißschuh, Tiezhu Yang, Uwe Kleine-König, Xie Shaowen, Xiu Jianfeng,
XueBing Chen, Yang Yingliang, Zhang Jiaming, ruanjinjie, Jessica Yu,
and Wolfram Sang.
* tag 'powerpc-6.2-1' of git://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux: (181 commits)
powerpc/code-patching: Fix oops with DEBUG_VM enabled
powerpc/qspinlock: Fix 32-bit build
powerpc/prom: Fix 32-bit build
powerpc/rtas: mandate RTAS syscall filtering
powerpc/rtas: define pr_fmt and convert printk call sites
powerpc/rtas: clean up includes
powerpc/rtas: clean up rtas_error_log_max initialization
powerpc/pseries/eeh: use correct API for error log size
powerpc/rtas: avoid scheduling in rtas_os_term()
powerpc/rtas: avoid device tree lookups in rtas_os_term()
powerpc/rtasd: use correct OF API for event scan rate
powerpc/rtas: document rtas_call()
powerpc/pseries: unregister VPA when hot unplugging a CPU
powerpc/pseries: reset the RCU watchdogs after a LPM
powerpc: Take in account addition CPU node when building kexec FDT
powerpc: export the CPU node count
powerpc/cpuidle: Set CPUIDLE_FLAG_POLLING for snooze state
powerpc/dts/fsl: Fix pca954x i2c-mux node names
cxl: Remove unnecessary cxl_pci_window_alignment()
selftests/powerpc: Fix resource leaks
...
Pull x86 core updates from Borislav Petkov:
- Add the call depth tracking mitigation for Retbleed which has been
long in the making. It is a lighterweight software-only fix for
Skylake-based cores where enabling IBRS is a big hammer and causes a
significant performance impact.
What it basically does is, it aligns all kernel functions to 16 bytes
boundary and adds a 16-byte padding before the function, objtool
collects all functions' locations and when the mitigation gets
applied, it patches a call accounting thunk which is used to track
the call depth of the stack at any time.
When that call depth reaches a magical, microarchitecture-specific
value for the Return Stack Buffer, the code stuffs that RSB and
avoids its underflow which could otherwise lead to the Intel variant
of Retbleed.
This software-only solution brings a lot of the lost performance
back, as benchmarks suggest:
https://lore.kernel.org/all/20220915111039.092790446@infradead.org/
That page above also contains a lot more detailed explanation of the
whole mechanism
- Implement a new control flow integrity scheme called FineIBT which is
based on the software kCFI implementation and uses hardware IBT
support where present to annotate and track indirect branches using a
hash to validate them
- Other misc fixes and cleanups
* tag 'x86_core_for_v6.2' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (80 commits)
x86/paravirt: Use common macro for creating simple asm paravirt functions
x86/paravirt: Remove clobber bitmask from .parainstructions
x86/debug: Include percpu.h in debugreg.h to get DECLARE_PER_CPU() et al
x86/cpufeatures: Move X86_FEATURE_CALL_DEPTH from bit 18 to bit 19 of word 11, to leave space for WIP X86_FEATURE_SGX_EDECCSSA bit
x86/Kconfig: Enable kernel IBT by default
x86,pm: Force out-of-line memcpy()
objtool: Fix weak hole vs prefix symbol
objtool: Optimize elf_dirty_reloc_sym()
x86/cfi: Add boot time hash randomization
x86/cfi: Boot time selection of CFI scheme
x86/ibt: Implement FineIBT
objtool: Add --cfi to generate the .cfi_sites section
x86: Add prefix symbols for function padding
objtool: Add option to generate prefix symbols
objtool: Avoid O(bloody terrible) behaviour -- an ode to libelf
objtool: Slice up elf_create_section_symbol()
kallsyms: Revert "Take callthunks into account"
x86: Unconfuse CONFIG_ and X86_FEATURE_ namespaces
x86/retpoline: Fix crash printing warning
x86/paravirt: Fix a !PARAVIRT build warning
...
Provide an implementation for arch_pc_relative_reloc(). It is needed to
pass the build once 61c6065ef7 ("objtool: Allow !PC relative
relocations") is merged.
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Boris (and the robot) reported that objtool grew a new complaint about
unreachable instructions. Upon inspection it was immediately clear
the __weak zombie instructions struck again.
For the unweary, the linker will simply remove the symbol for
overriden __weak symbols but leave the instructions in place, creating
unreachable instructions -- and objtool likes to report these.
Commit 4adb236867 ("objtool: Ignore extra-symbol code") was supposed
to have dealt with that, but the new commit 9f2899fe36 ("objtool:
Add option to generate prefix symbols") subtly broke that logic by
created unvisited symbols.
Fixes: 9f2899fe36 ("objtool: Add option to generate prefix symbols")
Reported-by: Borislav Petkov <bp@alien8.de>
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
When moving a symbol in the symtab its index changes and any reloc
referring that symtol-table-index will need to be rewritten too.
In order to facilitate this, objtool simply marks the whole reloc
section 'changed' which will cause the whole section to be
re-generated.
However, finding the relocs that use any given symbol is implemented
rather crudely -- a fully iteration of all sections and their relocs.
Given that some builds have over 20k sections (kallsyms etc..)
iterating all that for *each* symbol moved takes a bit of time.
Instead have each symbol keep a list of relocs that reference it.
This *vastly* improves build times for certain configs.
Reported-by: Borislav Petkov <bp@alien8.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/Y2LlRA7x+8UsE1xf@hirez.programming.kicks-ass.net
When code is compiled with:
-fpatchable-function-entry=${PADDING_BYTES},${PADDING_BYTES}
functions will have PADDING_BYTES of NOP in front of them. Unwinders
and other things that symbolize code locations will typically
attribute these bytes to the preceding function.
Given that these bytes nominally belong to the following symbol this
mis-attribution is confusing.
Inspired by the fact that CFI_CLANG emits __cfi_##name symbols to
claim these bytes, allow objtool to emit __pfx_##name symbols to do
the same.
Therefore add the objtool --prefix=N argument, to conditionally place
a __pfx_##name symbol at N bytes ahead of symbol 'name' when: all
these preceding bytes are NOP and name-N is an instruction boundary.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Yujie Liu <yujie.liu@intel.com>
Link: https://lkml.kernel.org/r/20221028194453.526899822@infradead.org
Due to how gelf_update_sym*() requires an Elf_Data pointer, and how
libelf keeps Elf_Data in a linked list per section,
elf_update_symbol() ends up having to iterate this list on each
update to find the correct Elf_Data for the index'ed symbol.
By allocating one Elf_Data per new symbol, the list grows per new
symbol, giving an effective O(n^2) insertion time. This is obviously
bloody terrible.
Therefore over-allocate the Elf_Data when an extention is needed.
Except it turns out libelf disregards Elf_Scn::sh_size in favour of
the sum of Elf_Data::d_size. IOW it will happily write out all the
unused space and fill it with:
0000000000000000 0 NOTYPE LOCAL DEFAULT UND
entries (aka zeros). Which obviously violates the STB_LOCAL placement
rule, and is a general pain in the backside for not being the desired
behaviour.
Manually fix-up the Elf_Data size to avoid this problem before calling
elf_update().
This significantly improves performance when adding a significant
number of symbols.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Yujie Liu <yujie.liu@intel.com>
Link: https://lkml.kernel.org/r/20221028194453.461658986@infradead.org
