The routine is used on syscall exit and on non-AMD CPUs is guaranteed to be empty. It probably does not need to be a function call even on CPUs which do need the mitigation. [ bp: Make sure it is always inlined so that noinstr marking works. ] Signed-off-by: Mateusz Guzik <mjguzik@gmail.com> Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de> Link: https://lore.kernel.org/r/20240613082637.659133-1-mjguzik@gmail.com
Pull x86 cpu updates from Ingo Molnar: - Rework the x86 CPU vendor/family/model code: introduce the 'VFM' value that is an 8+8+8 bit concatenation of the vendor/family/model value, and add macros that work on VFM values. This simplifies the addition of new Intel models & families, and simplifies existing enumeration & quirk code. - Add support for the AMD 0x80000026 leaf, to better parse topology information - Optimize the NUMA allocation layout of more per-CPU data structures - Improve the workaround for AMD erratum 1386 - Clear TME from /proc/cpuinfo as well, when disabled by the firmware - Improve x86 self-tests - Extend the mce_record tracepoint with the ::ppin and ::microcode fields - Implement recovery for MCE errors in TDX/SEAM non-root mode - Misc cleanups and fixes * tag 'x86-cpu-2024-05-13' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (34 commits) x86/mm: Switch to new Intel CPU model defines x86/tsc_msr: Switch to new Intel CPU model defines x86/tsc: Switch to new Intel CPU model defines x86/cpu: Switch to new Intel CPU model defines x86/resctrl: Switch to new Intel CPU model defines x86/microcode/intel: Switch to new Intel CPU model defines x86/mce: Switch to new Intel CPU model defines x86/cpu: Switch to new Intel CPU model defines x86/cpu/intel_epb: Switch to new Intel CPU model defines x86/aperfmperf: Switch to new Intel CPU model defines x86/apic: Switch to new Intel CPU model defines perf/x86/msr: Switch to new Intel CPU model defines perf/x86/intel/uncore: Switch to new Intel CPU model defines perf/x86/intel/pt: Switch to new Intel CPU model defines perf/x86/lbr: Switch to new Intel CPU model defines perf/x86/intel/cstate: Switch to new Intel CPU model defines x86/bugs: Switch to new Intel CPU model defines x86/bugs: Switch to new Intel CPU model defines x86/cpu/vfm: Update arch/x86/include/asm/intel-family.h x86/cpu/vfm: Add new macros to work with (vendor/family/model) values ...
Pull x86 boot updates from Ingo Molnar:
- Move the kernel cmdline setup earlier in the boot process (again),
to address a split_lock_detect= boot parameter bug
- Ignore relocations in .notes sections
- Simplify boot stack setup
- Re-introduce a bootloader quirk wrt CR4 handling
- Miscellaneous cleanups & fixes
* tag 'x86-boot-2024-05-13' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
x86/boot/64: Clear most of CR4 in startup_64(), except PAE, MCE and LA57
x86/boot: Move kernel cmdline setup earlier in the boot process (again)
x86/build: Clean up arch/x86/tools/relocs.c a bit
x86/boot: Ignore relocations in .notes sections in walk_relocs() too
x86: Rename __{start,end}_init_task to __{start,end}_init_stack
x86/boot: Simplify boot stack setup
Pull x86 asm updates from Ingo Molnar: - Clean up & fix asm() operand modifiers & constraints - Misc cleanups * tag 'x86-asm-2024-05-13' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: x86/alternatives: Remove a superfluous newline in _static_cpu_has() x86/asm/64: Clean up memset16(), memset32(), memset64() assembly constraints in <asm/string_64.h> x86/asm: Use "m" operand constraint in WRUSSQ asm template x86/asm: Use %a instead of %P operand modifier in asm templates x86/asm: Use %c/%n instead of %P operand modifier in asm templates x86/asm: Remove %P operand modifier from altinstr asm templates
The syzbot-reported stack trace from hell in this discussion thread
actually has three nested page faults:
https://lore.kernel.org/r/000000000000d5f4fc0616e816d4@google.com
... and I think that's actually the important thing here:
- the first page fault is from user space, and triggers the vsyscall
emulation.
- the second page fault is from __do_sys_gettimeofday(), and that should
just have caused the exception that then sets the return value to
-EFAULT
- the third nested page fault is due to _raw_spin_unlock_irqrestore() ->
preempt_schedule() -> trace_sched_switch(), which then causes a BPF
trace program to run, which does that bpf_probe_read_compat(), which
causes that page fault under pagefault_disable().
It's quite the nasty backtrace, and there's a lot going on.
The problem is literally the vsyscall emulation, which sets
current->thread.sig_on_uaccess_err = 1;
and that causes the fixup_exception() code to send the signal *despite* the
exception being caught.
And I think that is in fact completely bogus. It's completely bogus
exactly because it sends that signal even when it *shouldn't* be sent -
like for the BPF user mode trace gathering.
In other words, I think the whole "sig_on_uaccess_err" thing is entirely
broken, because it makes any nested page-faults do all the wrong things.
Now, arguably, I don't think anybody should enable vsyscall emulation any
more, but this test case clearly does.
I think we should just make the "send SIGSEGV" be something that the
vsyscall emulation does on its own, not this broken per-thread state for
something that isn't actually per thread.
The x86 page fault code actually tried to deal with the "incorrect nesting"
by having that:
if (in_interrupt())
return;
which ignores the sig_on_uaccess_err case when it happens in interrupts,
but as shown by this example, these nested page faults do not need to be
about interrupts at all.
IOW, I think the only right thing is to remove that horrendously broken
code.
The attached patch looks like the ObviouslyCorrect(tm) thing to do.
NOTE! This broken code goes back to this commit in 2011:
4fc3490114bb ("x86-64: Set siginfo and context on vsyscall emulation faults")
... and back then the reason was to get all the siginfo details right.
Honestly, I do not for a moment believe that it's worth getting the siginfo
details right here, but part of the commit says:
This fixes issues with UML when vsyscall=emulate.
... and so my patch to remove this garbage will probably break UML in this
situation.
I do not believe that anybody should be running with vsyscall=emulate in
2024 in the first place, much less if you are doing things like UML. But
let's see if somebody screams.
Reported-and-tested-by: syzbot+83e7f982ca045ab4405c@syzkaller.appspotmail.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Tested-by: Jiri Olsa <jolsa@kernel.org>
Acked-by: Andy Lutomirski <luto@kernel.org>
Link: https://lore.kernel.org/r/CAHk-=wh9D6f7HUkDgZHKmDCHUQmp+Co89GP+b8+z+G56BKeyNg@mail.gmail.com
Refactor struct cpuinfo_x86 so that the vendor, family, and model
fields are overlaid in a union with a 32-bit field that combines
all three (together with a one byte reserved field in the upper
byte).
This will make it easy, cheap, and reliable to check all three
values at once.
See
https://lore.kernel.org/r/Zgr6kT8oULbnmEXx@agluck-desk3
for why the ordering is (low-to-high bits):
(vendor, family, model)
[ bp: Move comments over the line, add the backstory about the
particular order of the fields. ]
Signed-off-by: Tony Luck <tony.luck@intel.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20240416211941.9369-2-tony.luck@intel.com
Define the symbol __top_init_kernel_stack instead of duplicating the offset from __end_init_task in multiple places. Signed-off-by: Brian Gerst <brgerst@gmail.com> Signed-off-by: Ingo Molnar <mingo@kernel.org> Cc: Kees Cook <keescook@chromium.org> Cc: Uros Bizjak <ubizjak@gmail.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Andy Lutomirski <luto@kernel.org> Link: https://lore.kernel.org/r/20240321180506.89030-1-brgerst@gmail.com
The "P" asm operand modifier is a x86 target-specific modifier. For x86_64, when used with a symbol reference, the "%P" modifier emits "sym" instead of "sym(%rip)". This property is currently used to prevent %RIP-relative addressing in .altinstr sections. %RIP-relative addresses are nowadays correctly handled in .altinstr sections, so remove %P operand modifier from altinstr asm templates. Also note that unlike GCC, clang emits %rip-relative symbol reference with "P" asm operand modifier, so the patch also unifies symbol handling with both compilers. No functional changes intended. Signed-off-by: Uros Bizjak <ubizjak@gmail.com> Signed-off-by: Ingo Molnar <mingo@kernel.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Josh Poimboeuf <jpoimboe@redhat.com> Cc: Ard Biesheuvel <ardb@kernel.org> Cc: "H. Peter Anvin" <hpa@zytor.com> Link: https://lore.kernel.org/r/20240319104418.284519-2-ubizjak@gmail.com
Pull core x86 updates from Ingo Molnar:
- The biggest change is the rework of the percpu code, to support the
'Named Address Spaces' GCC feature, by Uros Bizjak:
- This allows C code to access GS and FS segment relative memory
via variables declared with such attributes, which allows the
compiler to better optimize those accesses than the previous
inline assembly code.
- The series also includes a number of micro-optimizations for
various percpu access methods, plus a number of cleanups of %gs
accesses in assembly code.
- These changes have been exposed to linux-next testing for the
last ~5 months, with no known regressions in this area.
- Fix/clean up __switch_to()'s broken but accidentally working handling
of FPU switching - which also generates better code
- Propagate more RIP-relative addressing in assembly code, to generate
slightly better code
- Rework the CPU mitigations Kconfig space to be less idiosyncratic, to
make it easier for distros to follow & maintain these options
- Rework the x86 idle code to cure RCU violations and to clean up the
logic
- Clean up the vDSO Makefile logic
- Misc cleanups and fixes
* tag 'x86-core-2024-03-11' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (52 commits)
x86/idle: Select idle routine only once
x86/idle: Let prefer_mwait_c1_over_halt() return bool
x86/idle: Cleanup idle_setup()
x86/idle: Clean up idle selection
x86/idle: Sanitize X86_BUG_AMD_E400 handling
sched/idle: Conditionally handle tick broadcast in default_idle_call()
x86: Increase brk randomness entropy for 64-bit systems
x86/vdso: Move vDSO to mmap region
x86/vdso/kbuild: Group non-standard build attributes and primary object file rules together
x86/vdso: Fix rethunk patching for vdso-image-{32,64}.o
x86/retpoline: Ensure default return thunk isn't used at runtime
x86/vdso: Use CONFIG_COMPAT_32 to specify vdso32
x86/vdso: Use $(addprefix ) instead of $(foreach )
x86/vdso: Simplify obj-y addition
x86/vdso: Consolidate targets and clean-files
x86/bugs: Rename CONFIG_RETHUNK => CONFIG_MITIGATION_RETHUNK
x86/bugs: Rename CONFIG_CPU_SRSO => CONFIG_MITIGATION_SRSO
x86/bugs: Rename CONFIG_CPU_IBRS_ENTRY => CONFIG_MITIGATION_IBRS_ENTRY
x86/bugs: Rename CONFIG_CPU_UNRET_ENTRY => CONFIG_MITIGATION_UNRET_ENTRY
x86/bugs: Rename CONFIG_SLS => CONFIG_MITIGATION_SLS
...
Pull x86 cleanups from Ingo Molnar: "Misc cleanups, including a large series from Thomas Gleixner to cure sparse warnings" * tag 'x86-cleanups-2024-03-11' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: x86/nmi: Drop unused declaration of proc_nmi_enabled() x86/callthunks: Use EXPORT_PER_CPU_SYMBOL_GPL() for per CPU variables x86/cpu: Provide a declaration for itlb_multihit_kvm_mitigation x86/cpu: Use EXPORT_PER_CPU_SYMBOL_GPL() for x86_spec_ctrl_current x86/uaccess: Add missing __force to casts in __access_ok() and valid_user_address() x86/percpu: Cure per CPU madness on UP smp: Consolidate smp_prepare_boot_cpu() x86/msr: Add missing __percpu annotations x86/msr: Prepare for including <linux/percpu.h> into <asm/msr.h> perf/x86/amd/uncore: Fix __percpu annotation x86/nmi: Remove an unnecessary IS_ENABLED(CONFIG_SMP) x86/apm_32: Remove dead function apm_get_battery_status() x86/insn-eval: Fix function param name in get_eff_addr_sib()