commit 79cd2a11224eab86d6673fe8a11d2046ae9d2757 upstream.

The linker script arch/x86/kernel/vmlinux.lds.S matches the thunk
sections ".text.__x86.*" from arch/x86/lib/retpoline.S as follows:

  .text {
    [...]
    TEXT_TEXT
    [...]
    __indirect_thunk_start = .;
    *(.text.__x86.*)
    __indirect_thunk_end = .;
    [...]
  }

Macro TEXT_TEXT references TEXT_MAIN which normally expands to only
".text". However, with CONFIG_LTO_CLANG, TEXT_MAIN becomes
".text .text.[0-9a-zA-Z_]*" which wrongly matches also the thunk
sections. The output layout is then different than expected. For
instance, the currently defined range [__indirect_thunk_start,
__indirect_thunk_end] becomes empty.

Prevent the problem by using ".." as the first separator, for example,
".text..__x86.indirect_thunk". This pattern is utilized by other
explicit section names which start with one of the standard prefixes,
such as ".text" or ".data", and that need to be individually selected in
the linker script.

  [ nathan: Fix conflicts with SRSO and fold in fix issue brought up by
    Andrew Cooper in post-review:
    https://lore.kernel.org/20230803230323.1478869-1-andrew.cooper3@citrix.com ]

Fixes: dc5723b02e52 ("kbuild: add support for Clang LTO")
Signed-off-by: Petr Pavlu <petr.pavlu@suse.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20230711091952.27944-2-petr.pavlu@suse.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

commit dbf46008775516f7f25c95b7760041c286299783 upstream.

For stack-validation of a frame-pointer build, objtool validates that
every CALL instruction is preceded by a frame-setup. The new SRSO
return thunks violate this with their RSB stuffing trickery.

Extend the __fentry__ exception to also cover the embedded_insn case
used for this. This cures:

  vmlinux.o: warning: objtool: srso_untrain_ret+0xd: call without frame pointer save/setup

Fixes: 4ae68b26c3ab ("objtool/x86: Fix SRSO mess")
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Acked-by: Josh Poimboeuf <jpoimboe@kernel.org>
Link: https://lore.kernel.org/r/20230816115921.GH980931@hirez.programming.kicks-ass.net
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

commit d025b7bac07a6e90b6b98b487f88854ad9247c39 upstream.

Rename the original retbleed return thunk and untrain_ret to
retbleed_return_thunk() and retbleed_untrain_ret().

No functional changes.

Suggested-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20230814121148.909378169@infradead.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

commit d43490d0ab824023e11d0b57d0aeec17a6e0ca13 upstream.

Use the existing configurable return thunk. There is absolute no
justification for having created this __x86_return_thunk alternative.

To clarify, the whole thing looks like:

Zen3/4 does:

  srso_alias_untrain_ret:
	  nop2
	  lfence
	  jmp srso_alias_return_thunk
	  int3

  srso_alias_safe_ret: // aliasses srso_alias_untrain_ret just so
	  add $8, %rsp
	  ret
	  int3

  srso_alias_return_thunk:
	  call srso_alias_safe_ret
	  ud2

While Zen1/2 does:

  srso_untrain_ret:
	  movabs $foo, %rax
	  lfence
	  call srso_safe_ret           (jmp srso_return_thunk ?)
	  int3

  srso_safe_ret: // embedded in movabs instruction
	  add $8,%rsp
          ret
          int3

  srso_return_thunk:
	  call srso_safe_ret
	  ud2

While retbleed does:

  zen_untrain_ret:
	  test $0xcc, %bl
	  lfence
	  jmp zen_return_thunk
          int3

  zen_return_thunk: // embedded in the test instruction
	  ret
          int3

Where Zen1/2 flush the BTB entry using the instruction decoder trick
(test,movabs) Zen3/4 use BTB aliasing. SRSO adds a return sequence
(srso_safe_ret()) which forces the function return instruction to
speculate into a trap (UD2).  This RET will then mispredict and
execution will continue at the return site read from the top of the
stack.

Pick one of three options at boot (evey function can only ever return
once).

  [ bp: Fixup commit message uarch details and add them in a comment in
    the code too. Add a comment about the srso_select_mitigation()
    dependency on retbleed_select_mitigation(). Add moar ifdeffery for
    32-bit builds. Add a dummy srso_untrain_ret_alias() definition for
    32-bit alternatives needing the symbol. ]

Fixes: fb3bd914b3ec ("x86/srso: Add a Speculative RAS Overflow mitigation")
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20230814121148.842775684@infradead.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

commit 4ae68b26c3ab5a82aa271e6e9fc9b1a06e1d6b40 upstream.

Objtool --rethunk does two things:

 - it collects all (tail) call's of __x86_return_thunk and places them
   into .return_sites. These are typically compiler generated, but
   RET also emits this same.

 - it fudges the validation of the __x86_return_thunk symbol; because
   this symbol is inside another instruction, it can't actually find
   the instruction pointed to by the symbol offset and gets upset.

Because these two things pertained to the same symbol, there was no
pressing need to separate these two separate things.

However, alas, along comes SRSO and more crazy things to deal with
appeared.

The SRSO patch itself added the following symbol names to identify as
rethunk:

  'srso_untrain_ret', 'srso_safe_ret' and '__ret'

Where '__ret' is the old retbleed return thunk, 'srso_safe_ret' is a
new similarly embedded return thunk, and 'srso_untrain_ret' is
completely unrelated to anything the above does (and was only included
because of that INT3 vs UD2 issue fixed previous).

Clear things up by adding a second category for the embedded instruction
thing.

Fixes: fb3bd914b3ec ("x86/srso: Add a Speculative RAS Overflow mitigation")
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20230814121148.704502245@infradead.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Upstream commit: fb3bd914b3ec28f5fb697ac55c4846ac2d542855

Add a mitigation for the speculative return address stack overflow
vulnerability found on AMD processors.

The mitigation works by ensuring all RET instructions speculate to
a controlled location, similar to how speculation is controlled in the
retpoline sequence.  To accomplish this, the __x86_return_thunk forces
the CPU to mispredict every function return using a 'safe return'
sequence.

To ensure the safety of this mitigation, the kernel must ensure that the
safe return sequence is itself free from attacker interference.  In Zen3
and Zen4, this is accomplished by creating a BTB alias between the
untraining function srso_untrain_ret_alias() and the safe return
function srso_safe_ret_alias() which results in evicting a potentially
poisoned BTB entry and using that safe one for all function returns.

In older Zen1 and Zen2, this is accomplished using a reinterpretation
technique similar to Retbleed one: srso_untrain_ret() and
srso_safe_ret().

Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Pull objtool updates from Ingo Molnar:

 - Mark arch_cpu_idle_dead() __noreturn, make all architectures &
   drivers that did this inconsistently follow this new, common
   convention, and fix all the fallout that objtool can now detect
   statically

 - Fix/improve the ORC unwinder becoming unreliable due to
   UNWIND_HINT_EMPTY ambiguity, split it into UNWIND_HINT_END_OF_STACK
   and UNWIND_HINT_UNDEFINED to resolve it

 - Fix noinstr violations in the KCSAN code and the lkdtm/stackleak code

 - Generate ORC data for __pfx code

 - Add more __noreturn annotations to various kernel startup/shutdown
   and panic functions

 - Misc improvements & fixes

* tag 'objtool-core-2023-04-27' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (52 commits)
  x86/hyperv: Mark hv_ghcb_terminate() as noreturn
  scsi: message: fusion: Mark mpt_halt_firmware() __noreturn
  x86/cpu: Mark {hlt,resume}_play_dead() __noreturn
  btrfs: Mark btrfs_assertfail() __noreturn
  objtool: Include weak functions in global_noreturns check
  cpu: Mark nmi_panic_self_stop() __noreturn
  cpu: Mark panic_smp_self_stop() __noreturn
  arm64/cpu: Mark cpu_park_loop() and friends __noreturn
  x86/head: Mark *_start_kernel() __noreturn
  init: Mark start_kernel() __noreturn
  init: Mark [arch_call_]rest_init() __noreturn
  objtool: Generate ORC data for __pfx code
  x86/linkage: Fix padding for typed functions
  objtool: Separate prefix code from stack validation code
  objtool: Remove superfluous dead_end_function() check
  objtool: Add symbol iteration helpers
  objtool: Add WARN_INSN()
  scripts/objdump-func: Support multiple functions
  context_tracking: Fix KCSAN noinstr violation
  objtool: Add stackleak instrumentation to uaccess safe list
  ...

Pull btrfs updates from David Sterba:
 "Mostly core changes and cleanups, some notable fixes and two
  performance improvements in directory logging.

  The IO path cleanups are removing or refactoring old code, scrub main
  loop has been completely rewritten also refactoring old code.

  There are some changes to non-btrfs code, mostly trivial, the cgroup
  punt bio logic is only moved from generic code.

  Performance improvements:

   - improve logging changes in a directory during one transaction,
     avoid iterating over items and reduce lock contention (fsync time
     4x lower)

   - when logging directory entries during one transaction, reduce
     locking of subvolume trees by checking tree-log instead
     (improvement in throughput and latency for concurrent access to a
     subvolume)

  Notable fixes:

   - dev-replace:
      - properly honor read mode when requested to avoid reading from
        source device
      - target device won't be used for eventual read repair, this is
        unreliable for NODATASUM files
      - when there are unpaired (and unrepairable) metadata during
        replace, exit early with error and don't try to finish whole
        operation

   - scrub ioctl properly rejects unknown flags

   - fix global block reserve calculations

   - fix partial direct io write when there's a page fault in the
     middle, iomap will try to continue with partial request but the
     btrfs part did not match that, this can lead to zeros written
     instead of data

  Core changes:

   - io path:
      - continued cleanups and refactoring around bio handling
      - extent io submit path simplifications and cleanups
      - flush write path simplifications and cleanups
      - rework logic of passing sync mode of bio, with further cleanups

   - rewrite scrub code flow, restructure how the stripes are enumerated
     and verified in a more unified way

   - allow to set lower threshold for block group reclaim in debug mode
     to aid zoned mode testing

   - remove obsolete time-based delayed ref throttling logic when
     truncating items

   - DREW locks are not using percpu variables anymore

   - more warning fixes (-Wmaybe-uninitialized)

   - u64 division simplifications

   - error handling improvements

  Non-btrfs code changes:

   - push cgroup punt bio logic to btrfs code (there was no other user
     of that), the functionality can be now selected separately by
     BLK_CGROUP_PUNT_BIO

   - crc32c_impl removed after removing last uses in btrfs code

   - add btrfs_assertfail() to objtool table"

* tag 'for-6.4-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux: (147 commits)
  btrfs: mark btrfs_assertfail() __noreturn
  btrfs: fix uninitialized variable warnings
  btrfs: use log root when iterating over index keys when logging directory
  btrfs: avoid iterating over all indexes when logging directory
  btrfs: dev-replace: error out if we have unrepaired metadata error during
  btrfs: remove pointless loop at btrfs_get_next_valid_item()
  btrfs: scrub: reject unsupported scrub flags
  btrfs: reinterpret async discard iops_limit=0 as no delay
  btrfs: set default discard iops_limit to 1000
  btrfs: remove unused raid56 functions which were dedicated for scrub
  btrfs: scrub: remove scrub_bio structure
  btrfs: scrub: remove scrub_block and scrub_sector structures
  btrfs: scrub: remove the old scrub recheck code
  btrfs: scrub: remove the old writeback infrastructure
  btrfs: scrub: remove scrub_parity structure
  btrfs: scrub: use scrub_stripe to implement RAID56 P/Q scrub
  btrfs: scrub: switch scrub_simple_mirror() to scrub_stripe infrastructure
  btrfs: scrub: introduce helper to queue a stripe for scrub
  btrfs: scrub: introduce error reporting functionality for scrub_stripe
  btrfs: scrub: introduce a writeback helper for scrub_stripe
  ...

Pull documentation updates from Jonathan Corbet:
 "Commit volume in documentation is relatively low this time, but there
  is still a fair amount going on, including:

   - Reorganize the architecture-specific documentation under
     Documentation/arch

     This makes the structure match the source directory and helps to
     clean up the mess that is the top-level Documentation directory a
     bit. This work creates the new directory and moves x86 and most of
     the less-active architectures there.

     The current plan is to move the rest of the architectures in 6.5,
     with the patches going through the appropriate subsystem trees.

   - Some more Spanish translations and maintenance of the Italian
     translation

   - A new "Kernel contribution maturity model" document from Ted

   - A new tutorial on quickly building a trimmed kernel from Thorsten

  Plus the usual set of updates and fixes"

* tag 'docs-6.4' of git://git.lwn.net/linux: (47 commits)
  media: Adjust column width for pdfdocs
  media: Fix building pdfdocs
  docs: clk: add documentation to log which clocks have been disabled
  docs: trace: Fix typo in ftrace.rst
  Documentation/process: always CC responsible lists
  docs: kmemleak: adjust to config renaming
  ELF: document some de-facto PT_* ABI quirks
  Documentation: arm: remove stih415/stih416 related entries
  docs: turn off "smart quotes" in the HTML build
  Documentation: firmware: Clarify firmware path usage
  docs/mm: Physical Memory: Fix grammar
  Documentation: Add document for false sharing
  dma-api-howto: typo fix
  docs: move m68k architecture documentation under Documentation/arch/
  docs: move parisc documentation under Documentation/arch/
  docs: move ia64 architecture docs under Documentation/arch/
  docs: Move arc architecture docs under Documentation/arch/
  docs: move nios2 documentation under Documentation/arch/
  docs: move openrisc documentation under Documentation/arch/
  docs: move superh documentation under Documentation/arch/
  ...

The old 'copy_user_generic_unrolled' function was oddly implemented for
largely historical reasons: it had been largely based on the uncached
copy case, which has some other concerns.

For example, the __copy_user_nocache() function uses 'movnti' for the
destination stores, and those want the destination to be aligned.  In
contrast, the regular copy function doesn't really care, and trying to
align things only complicates matters.

Also, like the clear_user function, the copy function had some odd
handling of the repeat counts, complicating the exception handling for
no really good reason.  So as with clear_user, just write it to keep all
the byte counts in the %rcx register, exactly like the 'rep movs'
functionality that this replaces.

Unlike a real 'rep movs', we do allow for this to trash a few temporary
registers to not have to unnecessarily save/restore registers on the
stack.

And like the clearing case, rename this to what it now clearly is:
'rep_movs_alternative', and make it one coherent function, so that it
shows up as such in profiles (instead of the odd split between
"copy_user_generic_unrolled" and "copy_user_short_string", the latter of
which was not about strings at all, and which was shared with the
uncached case).

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>