linux.git/arch/x86/entry, branch v6.0

x86/entry: Fix entry_INT80_compat for Xen PV guests

2022-08-16T08:02:52+00:00

Commit

  c89191ce67ef ("x86/entry: Convert SWAPGS to swapgs and remove the definition of SWAPGS")

missed one use case of SWAPGS in entry_INT80_compat(). Removing of
the SWAPGS macro led to asm just using "swapgs", as it is accepting
instructions in capital letters, too.

This in turn leads to splats in Xen PV guests like:

  [   36.145223] general protection fault, maybe for address 0x2d: 0000 [#1] PREEMPT SMP NOPTI
  [   36.145794] CPU: 2 PID: 1847 Comm: ld-linux.so.2 Not tainted 5.19.1-1-default #1 \
	  openSUSE Tumbleweed f3b44bfb672cdb9f235aff53b57724eba8b9411b
  [   36.146608] Hardware name: HP ProLiant ML350p Gen8, BIOS P72 11/14/2013
  [   36.148126] RIP: e030:entry_INT80_compat+0x3/0xa3

Fix that by open coding this single instance of the SWAPGS macro.

Fixes: c89191ce67ef ("x86/entry: Convert SWAPGS to swapgs and remove the definition of SWAPGS")
Signed-off-by: Juergen Gross 
Signed-off-by: Borislav Petkov 
Reviewed-by: Jan Beulich 
Cc:  # 5.19
Link: https://lore.kernel.org/r/20220816071137.4893-1-jgross@suse.com

x86: link vdso and boot with -z noexecstack --no-warn-rwx-segments

2022-08-11T01:30:09+00:00

Users of GNU ld (BFD) from binutils 2.39+ will observe multiple
instances of a new warning when linking kernels in the form:

  ld: warning: arch/x86/boot/pmjump.o: missing .note.GNU-stack section implies executable stack
  ld: NOTE: This behaviour is deprecated and will be removed in a future version of the linker
  ld: warning: arch/x86/boot/compressed/vmlinux has a LOAD segment with RWX permissions

Generally, we would like to avoid the stack being executable.  Because
there could be a need for the stack to be executable, assembler sources
have to opt-in to this security feature via explicit creation of the
.note.GNU-stack feature (which compilers create by default) or command
line flag --noexecstack.  Or we can simply tell the linker the
production of such sections is irrelevant and to link the stack as
--noexecstack.

LLVM's LLD linker defaults to -z noexecstack, so this flag isn't
strictly necessary when linking with LLD, only BFD, but it doesn't hurt
to be explicit here for all linkers IMO.  --no-warn-rwx-segments is
currently BFD specific and only available in the current latest release,
so it's wrapped in an ld-option check.

While the kernel makes extensive usage of ELF sections, it doesn't use
permissions from ELF segments.

Link: https://lore.kernel.org/linux-block/3af4127a-f453-4cf7-f133-a181cce06f73@kernel.dk/
Link: https://sourceware.org/git/?p=binutils-gdb.git;a=commit;h=ba951afb99912da01a6e8434126b8fac7aa75107
Link: https://github.com/llvm/llvm-project/issues/57009
Reported-and-tested-by: Jens Axboe 
Suggested-by: Fangrui Song 
Signed-off-by: Nick Desaulniers 
Signed-off-by: Linus Torvalds

Merge tag 'x86-urgent-2022-08-06' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2022-08-07T00:45:37+00:00

Pull x86 fixes from Ingo Molnar:

 - build fix for old(er) binutils

 - build fix for new GCC

 - kexec boot environment fix

* tag 'x86-urgent-2022-08-06' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/entry: Build thunk_$(BITS) only if CONFIG_PREEMPTION=y
  x86/numa: Use cpumask_available instead of hardcoded NULL check
  x86/bus_lock: Don't assume the init value of DEBUGCTLMSR.BUS_LOCK_DETECT to be zero

Merge tag 'spdx-6.0-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/spdx

2022-08-04T19:12:54+00:00

Pull SPDX updates from Greg KH:
 "Here is the set of SPDX comment updates for 6.0-rc1.

  Nothing huge here, just a number of updated SPDX license tags and
  cleanups based on the review of a number of common patterns in GPLv2
  boilerplate text.

  Also included in here are a few other minor updates, two USB files,
  and one Documentation file update to get the SPDX lines correct.

  All of these have been in the linux-next tree for a very long time"

* tag 'spdx-6.0-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/spdx: (28 commits)
  Documentation: samsung-s3c24xx: Add blank line after SPDX directive
  x86/crypto: Remove stray comment terminator
  treewide: Replace GPLv2 boilerplate/reference with SPDX - gpl-2.0_406.RULE
  treewide: Replace GPLv2 boilerplate/reference with SPDX - gpl-2.0_398.RULE
  treewide: Replace GPLv2 boilerplate/reference with SPDX - gpl-2.0_391.RULE
  treewide: Replace GPLv2 boilerplate/reference with SPDX - gpl-2.0_390.RULE
  treewide: Replace GPLv2 boilerplate/reference with SPDX - gpl-2.0_385.RULE
  treewide: Replace GPLv2 boilerplate/reference with SPDX - gpl-2.0_320.RULE
  treewide: Replace GPLv2 boilerplate/reference with SPDX - gpl-2.0_319.RULE
  treewide: Replace GPLv2 boilerplate/reference with SPDX - gpl-2.0_318.RULE
  treewide: Replace GPLv2 boilerplate/reference with SPDX - gpl-2.0_298.RULE
  treewide: Replace GPLv2 boilerplate/reference with SPDX - gpl-2.0_292.RULE
  treewide: Replace GPLv2 boilerplate/reference with SPDX - gpl-2.0_179.RULE
  treewide: Replace GPLv2 boilerplate/reference with SPDX - gpl-2.0_168.RULE (part 2)
  treewide: Replace GPLv2 boilerplate/reference with SPDX - gpl-2.0_168.RULE (part 1)
  treewide: Replace GPLv2 boilerplate/reference with SPDX - gpl-2.0_160.RULE
  treewide: Replace GPLv2 boilerplate/reference with SPDX - gpl-2.0_152.RULE
  treewide: Replace GPLv2 boilerplate/reference with SPDX - gpl-2.0_149.RULE
  treewide: Replace GPLv2 boilerplate/reference with SPDX - gpl-2.0_147.RULE
  treewide: Replace GPLv2 boilerplate/reference with SPDX - gpl-2.0_133.RULE
  ...

x86/entry: Build thunk_$(BITS) only if CONFIG_PREEMPTION=y

2022-08-04T10:23:50+00:00

With CONFIG_PREEMPTION disabled, arch/x86/entry/thunk_$(BITS).o becomes
an empty object file.

With some old versions of binutils (i.e., 2.35.90.20210113-1ubuntu1) the
GNU assembler doesn't generate a symbol table for empty object files and
objtool fails with the following error when a valid symbol table cannot
be found:

  arch/x86/entry/thunk_64.o: warning: objtool: missing symbol table

To prevent this from happening, build thunk_$(BITS).o only if
CONFIG_PREEMPTION is enabled.

BugLink: https://bugs.launchpad.net/bugs/1911359

Fixes: 320100a5ffe5 ("x86/entry: Remove the TRACE_IRQS cruft")
Signed-off-by: Andrea Righi 
Signed-off-by: Ingo Molnar 
Link: https://lore.kernel.org/r/Ys/Ke7EWjcX+ZlXO@arighi-desktop

x86/entry: Remove UNTRAIN_RET from native_irq_return_ldt

2022-07-14T07:45:12+00:00

UNTRAIN_RET is not needed in native_irq_return_ldt because RET
untraining has already been done at this point.

In addition, when the RETBleed mitigation is IBPB, UNTRAIN_RET clobbers
several registers (AX, CX, DX) so here it trashes user values which are
in these registers.

Signed-off-by: Alexandre Chartre 
Signed-off-by: Borislav Petkov 
Link: https://lore.kernel.org/r/35b0d50f-12d1-10c3-f5e8-d6c140486d4a@oracle.com

x86/entry: Move PUSH_AND_CLEAR_REGS() back into error_entry

2022-07-07T11:39:42+00:00

Commit

  ee774dac0da1 ("x86/entry: Move PUSH_AND_CLEAR_REGS out of error_entry()")

moved PUSH_AND_CLEAR_REGS out of error_entry, into its own function, in
part to avoid calling error_entry() for XenPV.

However, commit

  7c81c0c9210c ("x86/entry: Avoid very early RET")

had to change that because the 'ret' was too early and moved it into
idtentry, bloating the text size, since idtentry is expanded for every
exception vector.

However, with the advent of xen_error_entry() in commit

  d147553b64bad ("x86/xen: Add UNTRAIN_RET")

it became possible to remove PUSH_AND_CLEAR_REGS from idtentry, back
into *error_entry().

Signed-off-by: Peter Zijlstra (Intel) 
Signed-off-by: Borislav Petkov

x86/retbleed: Add fine grained Kconfig knobs

2022-06-29T15:43:41+00:00

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) 
Signed-off-by: Borislav Petkov

x86/speculation: Fix RSB filling with CONFIG_RETPOLINE=n

2022-06-27T08:34:00+00:00

If a kernel is built with CONFIG_RETPOLINE=n, but the user still wants
to mitigate Spectre v2 using IBRS or eIBRS, the RSB filling will be
silently disabled.

There's nothing retpoline-specific about RSB buffer filling.  Remove the
CONFIG_RETPOLINE guards around it.

Signed-off-by: Josh Poimboeuf 
Signed-off-by: Peter Zijlstra (Intel) 
Signed-off-by: Borislav Petkov

objtool: Add entry UNRET validation

2022-06-27T08:34:00+00:00

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) 
Signed-off-by: Borislav Petkov 
Reviewed-by: Josh Poimboeuf 
Signed-off-by: Borislav Petkov