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2021-09-25x86/umip: Downgrade warning messages to debug loglevelBorislav Petkov1-4/+4
After four years in the wild, those have not fullfilled their initial purpose of pushing people to fix their software to not use UMIP-emulated instructions, and to warn users about the degraded emulation performance. Yet, the only thing that "degrades" performance is overflowing dmesg with those: [Di Sep 7 00:24:05 2021] umip_printk: 1345 callbacks suppressed [Di Sep 7 00:24:05 2021] umip: someapp.exe[29231] ip:14064cdba sp:11b7c0: SIDT instruction cannot be used by applications. [Di Sep 7 00:24:05 2021] umip: someapp.exe[29231] ip:14064cdba sp:11b7c0: For now, expensive software emulation returns the result. ... [Di Sep 7 00:26:06 2021] umip_printk: 2227 callbacks suppressed [Di Sep 7 00:26:06 2021] umip: someapp.exe[29231] ip:14064cdba sp:11b940: SIDT instruction cannot be used by applications. and users don't really care about that - they just want to play their games in wine. So convert those to debug loglevel - in case someone is still interested in them, someone can boot with "debug" on the kernel cmdline. Reported-by: Marcus Rückert <mrueckert@suse.com> Signed-off-by: Borislav Petkov <bp@suse.de> Reviewed-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com> Link: https://lkml.kernel.org/r/20210907200454.30458-1-bp@alien8.de
2021-06-15x86/insn: Extend error reporting from insn_fetch_from_user[_inatomic]()Joerg Roedel1-6/+4
The error reporting from the insn_fetch_from_user*() functions is not very verbose. Extend it to include information on whether the linear RIP could not be calculated or whether the memory access faulted. This will be used in the SEV-ES code to propagate the correct exception depending on what went wrong during instruction fetch. [ bp: Massage comments. ] Signed-off-by: Joerg Roedel <jroedel@suse.de> Signed-off-by: Borislav Petkov <bp@suse.de> Link: https://lkml.kernel.org/r/20210614135327.9921-6-joro@8bytes.org
2021-04-28Merge tag 'x86_core_for_v5.13' of ↵Linus Torvalds1-1/+1
git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip Pull x86 updates from Borislav Petkov: - Turn the stack canary into a normal __percpu variable on 32-bit which gets rid of the LAZY_GS stuff and a lot of code. - Add an insn_decode() API which all users of the instruction decoder should preferrably use. Its goal is to keep the details of the instruction decoder away from its users and simplify and streamline how one decodes insns in the kernel. Convert its users to it. - kprobes improvements and fixes - Set the maximum DIE per package variable on Hygon - Rip out the dynamic NOP selection and simplify all the machinery around selecting NOPs. Use the simplified NOPs in objtool now too. - Add Xeon Sapphire Rapids to list of CPUs that support PPIN - Simplify the retpolines by folding the entire thing into an alternative now that objtool can handle alternatives with stack ops. Then, have objtool rewrite the call to the retpoline with the alternative which then will get patched at boot time. - Document Intel uarch per models in intel-family.h - Make Sub-NUMA Clustering topology the default and Cluster-on-Die the exception on Intel. * tag 'x86_core_for_v5.13' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (53 commits) x86, sched: Treat Intel SNC topology as default, COD as exception x86/cpu: Comment Skylake server stepping too x86/cpu: Resort and comment Intel models objtool/x86: Rewrite retpoline thunk calls objtool: Skip magical retpoline .altinstr_replacement objtool: Cache instruction relocs objtool: Keep track of retpoline call sites objtool: Add elf_create_undef_symbol() objtool: Extract elf_symbol_add() objtool: Extract elf_strtab_concat() objtool: Create reloc sections implicitly objtool: Add elf_create_reloc() helper objtool: Rework the elf_rebuild_reloc_section() logic objtool: Fix static_call list generation objtool: Handle per arch retpoline naming objtool: Correctly handle retpoline thunk calls x86/retpoline: Simplify retpolines x86/alternatives: Optimize optimize_nops() x86: Add insn_decode_kernel() x86/kprobes: Move 'inline' to the beginning of the kprobe_is_ss() declaration ...
2021-03-22x86: Fix various typos in comments, take #2Ingo Molnar1-1/+1
Fix another ~42 single-word typos in arch/x86/ code comments, missed a few in the first pass, in particular in .S files. Signed-off-by: Ingo Molnar <mingo@kernel.org> Cc: Borislav Petkov <bp@alien8.de> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Paolo Bonzini <pbonzini@redhat.com> Cc: Bjorn Helgaas <bhelgaas@google.com> Cc: linux-kernel@vger.kernel.org
2021-03-15x86/insn: Rename insn_decode() to insn_decode_from_regs()Borislav Petkov1-1/+1
Rename insn_decode() to insn_decode_from_regs() to denote that it receives regs as param and uses registers from there during decoding. Free the former name for a more generic version of the function. No functional changes. Signed-off-by: Borislav Petkov <bp@suse.de> Link: https://lkml.kernel.org/r/20210304174237.31945-2-bp@alien8.de
2020-09-07x86/umip: Factor out instruction decodingJoerg Roedel1-22/+1
Factor out the code used to decode an instruction with the correct address and operand sizes to a helper function. No functional changes. Signed-off-by: Joerg Roedel <jroedel@suse.de> Signed-off-by: Borislav Petkov <bp@suse.de> Link: https://lkml.kernel.org/r/20200907131613.12703-10-joro@8bytes.org
2020-09-07x86/umip: Factor out instruction fetchJoerg Roedel1-20/+6
Factor out the code to fetch the instruction from user-space to a helper function. No functional changes. Signed-off-by: Joerg Roedel <jroedel@suse.de> Signed-off-by: Borislav Petkov <bp@suse.de> Link: https://lkml.kernel.org/r/20200907131613.12703-9-joro@8bytes.org
2020-08-20x86/umip: Add emulation/spoofing for SLDT and STR instructionsBrendan Shanks1-13/+27
Add emulation/spoofing of SLDT and STR for both 32- and 64-bit processes. Wine users have found a small number of Windows apps using SLDT that were crashing when run on UMIP-enabled systems. Originally-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com> Reported-by: Andreas Rammhold <andi@notmuch.email> Signed-off-by: Brendan Shanks <bshanks@codeweavers.com> Signed-off-by: Borislav Petkov <bp@suse.de> Acked-by: Andy Lutomirski <luto@kernel.org> Reviewed-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com> Tested-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com> Link: https://lkml.kernel.org/r/20200710224525.21966-1-bshanks@codeweavers.com
2020-04-15x86/umip: Make umip_insns staticJason Yan1-1/+1
Fix the following sparse warning: arch/x86/kernel/umip.c:84:12: warning: symbol 'umip_insns' was not declared. Should it be static? Reported-by: Hulk Robot <hulkci@huawei.com> Signed-off-by: Jason Yan <yanaijie@huawei.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com> Link: https://lkml.kernel.org/r/20200413082213.22934-1-yanaijie@huawei.com
2019-11-26Merge branches 'x86-cpu-for-linus' and 'x86-fpu-for-linus' of ↵Linus Torvalds1-6/+6
git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip Pull x86 cpu and fpu updates from Ingo Molnar: - math-emu fixes - CPUID updates - sanity-check RDRAND output to see whether the CPU at least pretends to produce random data - various unaligned-access across cachelines fixes in preparation of hardware level split-lock detection - fix MAXSMP constraints to not allow !CPUMASK_OFFSTACK kernels with larger than 512 NR_CPUS - misc FPU related cleanups * 'x86-cpu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: x86/cpu: Align the x86_capability array to size of unsigned long x86/cpu: Align cpu_caps_cleared and cpu_caps_set to unsigned long x86/umip: Make the comments vendor-agnostic x86/Kconfig: Rename UMIP config parameter x86/Kconfig: Enforce limit of 512 CPUs with MAXSMP and no CPUMASK_OFFSTACK x86/cpufeatures: Add feature bit RDPRU on AMD x86/math-emu: Limit MATH_EMULATION to 486SX compatibles x86/math-emu: Check __copy_from_user() result x86/rdrand: Sanity-check RDRAND output * 'x86-fpu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: x86/fpu: Use XFEATURE_FP/SSE enum values instead of hardcoded numbers x86/fpu: Shrink space allocated for xstate_comp_offsets x86/fpu: Update stale variable name in comment
2019-11-26Merge tag 'printk-for-5.5' of ↵Linus Torvalds1-3/+3
git://git.kernel.org/pub/scm/linux/kernel/git/pmladek/printk Pull printk updates from Petr Mladek: - Allow to print symbolic error names via new %pe modifier. - Use pr_warn() instead of the remaining pr_warning() calls. Fix formatting of the related lines. - Add VSPRINTF entry to MAINTAINERS. * tag 'printk-for-5.5' of git://git.kernel.org/pub/scm/linux/kernel/git/pmladek/printk: (32 commits) checkpatch: don't warn about new vsprintf pointer extension '%pe' MAINTAINERS: Add VSPRINTF tools lib api: Renaming pr_warning to pr_warn ASoC: samsung: Use pr_warn instead of pr_warning lib: cpu_rmap: Use pr_warn instead of pr_warning trace: Use pr_warn instead of pr_warning dma-debug: Use pr_warn instead of pr_warning vgacon: Use pr_warn instead of pr_warning fs: afs: Use pr_warn instead of pr_warning sh/intc: Use pr_warn instead of pr_warning scsi: Use pr_warn instead of pr_warning platform/x86: intel_oaktrail: Use pr_warn instead of pr_warning platform/x86: asus-laptop: Use pr_warn instead of pr_warning platform/x86: eeepc-laptop: Use pr_warn instead of pr_warning oprofile: Use pr_warn instead of pr_warning of: Use pr_warn instead of pr_warning macintosh: Use pr_warn instead of pr_warning idsn: Use pr_warn instead of pr_warning ide: Use pr_warn instead of pr_warning crypto: n2: Use pr_warn instead of pr_warning ...
2019-11-07x86/umip: Make the comments vendor-agnosticBabu Moger1-6/+6
AMD 2nd generation EPYC processors also support the UMIP feature. Make the comments vendor-agnostic. Signed-off-by: Babu Moger <babu.moger@amd.com> Signed-off-by: Borislav Petkov <bp@suse.de> Cc: Andy Lutomirski <luto@kernel.org> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: Ricardo Neri <ricardo.neri-calderon@linux.intel.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: "x86@kernel.org" <x86@kernel.org> Link: https://lkml.kernel.org/r/157298913784.17462.12654728938970637305.stgit@naples-babu.amd.com
2019-10-18x86: Use pr_warn instead of pr_warningKefeng Wang1-3/+3
As said in commit f2c2cbcc35d4 ("powerpc: Use pr_warn instead of pr_warning"), removing pr_warning so all logging messages use a consistent <prefix>_warn style. Let's do it. Link: http://lkml.kernel.org/r/20191018031850.48498-7-wangkefeng.wang@huawei.com To: linux-kernel@vger.kernel.org Cc: Ingo Molnar <mingo@redhat.com> Cc: Borislav Petkov <bp@alien8.de> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Robert Richter <rric@kernel.org> Cc: Darren Hart <dvhart@infradead.org> Cc: Andy Shevchenko <andy@infradead.org> Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com> Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> Signed-off-by: Petr Mladek <pmladek@suse.com>
2019-09-10x86/umip: Add emulation (spoofing) for UMIP covered instructions in 64-bit ↵Brendan Shanks1-27/+38
processes as well Add emulation (spoofing) of the SGDT, SIDT, and SMSW instructions for 64-bit processes. Wine users have encountered a number of 64-bit Windows games that use these instructions (particularly SGDT), and were crashing when run on UMIP-enabled systems. Originally-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com> Signed-off-by: Brendan Shanks <bshanks@codeweavers.com> Reviewed-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com> Reviewed-by: H. Peter Anvin (Intel) <hpa@zytor.com> Cc: Andy Lutomirski <luto@kernel.org> Cc: Borislav Petkov <bp@alien8.de> Cc: Brian Gerst <brgerst@gmail.com> Cc: Denys Vlasenko <dvlasenk@redhat.com> Cc: Eric W. Biederman <ebiederm@xmission.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Link: https://lkml.kernel.org/r/20190905232222.14900-1-bshanks@codeweavers.com [ Minor edits: capitalization, added 'spoofing' wording. ] Signed-off-by: Ingo Molnar <mingo@kernel.org>
2019-05-29signal: Remove the task parameter from force_sig_faultEric W. Biederman1-1/+1
As synchronous exceptions really only make sense against the current task (otherwise how are you synchronous) remove the task parameter from from force_sig_fault to make it explicit that is what is going on. The two known exceptions that deliver a synchronous exception to a stopped ptraced task have already been changed to force_sig_fault_to_task. The callers have been changed with the following emacs regular expression (with obvious variations on the architectures that take more arguments) to avoid typos: force_sig_fault[(]\([^,]+\)[,]\([^,]+\)[,]\([^,]+\)[,]\W+current[)] -> force_sig_fault(\1,\2,\3) Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2019-05-29signal: Explicitly call force_sig_fault on currentEric W. Biederman1-1/+1
Update the calls of force_sig_fault that pass in a variable that is set to current earlier to explicitly use current. This is to make the next change that removes the task parameter from force_sig_fault easier to verify. Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2018-09-21signal/x86: Use force_sig_fault where appropriateEric W. Biederman1-7/+1
Reviewed-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2018-04-25signal: Ensure every siginfo we send has all bits initializedEric W. Biederman1-0/+1
Call clear_siginfo to ensure every stack allocated siginfo is properly initialized before being passed to the signal sending functions. Note: It is not safe to depend on C initializers to initialize struct siginfo on the stack because C is allowed to skip holes when initializing a structure. The initialization of struct siginfo in tracehook_report_syscall_exit was moved from the helper user_single_step_siginfo into tracehook_report_syscall_exit itself, to make it clear that the local variable siginfo gets fully initialized. In a few cases the scope of struct siginfo has been reduced to make it clear that siginfo siginfo is not used on other paths in the function in which it is declared. Instances of using memset to initialize siginfo have been replaced with calls clear_siginfo for clarity. Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2017-11-23x86/umip: Fix insn_get_code_seg_params()'s return valueBorislav Petkov1-1/+1
In order to save on redundant structs definitions insn_get_code_seg_params() was made to return two 4-bit values in a char but clang complains: arch/x86/lib/insn-eval.c:780:10: warning: implicit conversion from 'int' to 'char' changes value from 132 to -124 [-Wconstant-conversion] return INSN_CODE_SEG_PARAMS(4, 8); ~~~~~~ ^~~~~~~~~~~~~~~~~~~~~~~~~~ ./arch/x86/include/asm/insn-eval.h:16:57: note: expanded from macro 'INSN_CODE_SEG_PARAMS' #define INSN_CODE_SEG_PARAMS(oper_sz, addr_sz) (oper_sz | (addr_sz << 4)) Those two values do get picked apart afterwards the opposite way of how they were ORed so wrt to the LSByte, the return value is the same. But this function returns -EINVAL in the error case, which is an int. So make it return an int which is the native word size anyway and thus fix the clang warning. Reported-by: Kees Cook <keescook@google.com> Reported-by: Nick Desaulniers <nick.desaulniers@gmail.com> Signed-off-by: Borislav Petkov <bp@suse.de> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: ricardo.neri-calderon@linux.intel.com Link: https://lkml.kernel.org/r/20171123091951.1462-1-bp@alien8.de
2017-11-21x86/umip: Print a warning into the syslog if UMIP-protected instructions are ↵Ricardo Neri1-4/+58
used Print a rate-limited warning when a user-space program attempts to execute any of the instructions that UMIP protects (i.e., SGDT, SIDT, SLDT, STR and SMSW). This is useful, because when CONFIG_X86_INTEL_UMIP=y is selected and supported by the hardware, user space programs that try to execute such instructions will receive a SIGSEGV signal that they might not expect. In the specific cases for which emulation is provided (instructions SGDT, SIDT and SMSW in protected and virtual-8086 modes), no signal is generated. However, a warning is helpful to encourage updates in such programs to avoid the use of such instructions. Warnings are printed via a customized printk() function that also provides information about the program that attempted to use the affected instructions. Utility macros are defined to wrap umip_printk() for the error and warning kernel log levels. While here, replace an existing call to the generic rate-limited pr_err() with the new umip_pr_err(). Suggested-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com> Reviewed-by: Thomas Gleixner <tglx@linutronix.de> Cc: Andy Lutomirski <luto@kernel.org> Cc: Borislav Petkov <bp@alien8.de> Cc: Borislav Petkov <bp@suse.de> Cc: Brian Gerst <brgerst@gmail.com> Cc: Denys Vlasenko <dvlasenk@redhat.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Josh Poimboeuf <jpoimboe@redhat.com> Cc: Paolo Bonzini <pbonzini@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Ravi V. Shankar <ravi.v.shankar@intel.com> Cc: Tony Luck <tony.luck@intel.com> Cc: ricardo.neri@intel.com Link: http://lkml.kernel.org/r/1511233476-17088-1-git-send-email-ricardo.neri-calderon@linux.intel.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
2017-11-14x86/umip: Identify the STR and SLDT instructionsRicardo Neri1-8/+16
The STR and SLDT instructions are not emulated by the UMIP code, thus there's no functionality in the decoder to identify them. However, a subsequent commit will introduce a warning about the use of all the instructions that UMIP protect/changes, not only those that are emulated. A first step for that is to add the ability to decode/identify them. Plus, now that STR and SLDT are identified, we need to explicitly avoid their emulation (i.e., not rely on successful identification). Group together all the cases that we do not want to emulate: STR, SLDT and user long mode processes. Signed-off-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com> Cc: Andy Lutomirski <luto@kernel.org> Cc: Borislav Petkov <bp@suse.de> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Paolo Bonzini <pbonzini@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Ravi V. Shankar <ravi.v.shankar@intel.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Tony Luck <tony.luck@intel.com> Cc: ricardo.neri@intel.com Link: http://lkml.kernel.org/r/1510640985-18412-4-git-send-email-ricardo.neri-calderon@linux.intel.com [ Rewrote the changelog, fixed ugly col80 artifact. ] Signed-off-by: Ingo Molnar <mingo@kernel.org>
2017-11-08x86/umip: Force a page fault when unable to copy emulated result to userRicardo Neri1-2/+47
fixup_umip_exception() will be called from do_general_protection(). If the former returns false, the latter will issue a SIGSEGV with SEND_SIG_PRIV. However, when emulation is successful but the emulated result cannot be copied to user space memory, it is more accurate to issue a SIGSEGV with SEGV_MAPERR with the offending address. A new function, inspired in force_sig_info_fault(), is introduced to model the page fault. Signed-off-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com> Reviewed-by: Thomas Gleixner <tglx@linutronix.de> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Andy Lutomirski <luto@kernel.org> Cc: Borislav Petkov <bp@alien8.de> Cc: Borislav Petkov <bp@suse.de> Cc: Brian Gerst <brgerst@gmail.com> Cc: Chen Yucong <slaoub@gmail.com> Cc: Chris Metcalf <cmetcalf@mellanox.com> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: Denys Vlasenko <dvlasenk@redhat.com> Cc: Fenghua Yu <fenghua.yu@intel.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Huang Rui <ray.huang@amd.com> Cc: Jiri Slaby <jslaby@suse.cz> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Josh Poimboeuf <jpoimboe@redhat.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Michael S. Tsirkin <mst@redhat.com> Cc: Paolo Bonzini <pbonzini@redhat.com> Cc: Paul Gortmaker <paul.gortmaker@windriver.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Ravi V. Shankar <ravi.v.shankar@intel.com> Cc: Shuah Khan <shuah@kernel.org> Cc: Tony Luck <tony.luck@intel.com> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: ricardo.neri@intel.com Link: http://lkml.kernel.org/r/1509935277-22138-9-git-send-email-ricardo.neri-calderon@linux.intel.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
2017-11-08x86/umip: Add emulation code for UMIP instructionsRicardo Neri1-0/+321
The feature User-Mode Instruction Prevention present in recent Intel processor prevents a group of instructions (sgdt, sidt, sldt, smsw, and str) from being executed with CPL > 0. Otherwise, a general protection fault is issued. Rather than relaying to the user space the general protection fault caused by the UMIP-protected instructions (in the form of a SIGSEGV signal), it can be trapped and the instruction emulated to provide a dummy result. This allows to both conserve the current kernel behavior and not reveal the system resources that UMIP intends to protect (i.e., the locations of the global descriptor and interrupt descriptor tables, the segment selectors of the local descriptor table, the value of the task state register and the contents of the CR0 register). This emulation is needed because certain applications (e.g., WineHQ and DOSEMU2) rely on this subset of instructions to function. Given that sldt and str are not commonly used in programs that run on WineHQ or DOSEMU2, they are not emulated. Also, emulation is provided only for 32-bit processes; 64-bit processes that attempt to use the instructions that UMIP protects will receive the SIGSEGV signal issued as a consequence of the general protection fault. The instructions protected by UMIP can be split in two groups. Those which return a kernel memory address (sgdt and sidt) and those which return a value (smsw, sldt and str; the last two not emulated). For the instructions that return a kernel memory address, applications such as WineHQ rely on the result being located in the kernel memory space, not the actual location of the table. The result is emulated as a hard-coded value that lies close to the top of the kernel memory. The limit for the GDT and the IDT are set to zero. The instruction smsw is emulated to return the value that the register CR0 has at boot time as set in the head_32. Care is taken to appropriately emulate the results when segmentation is used. That is, rather than relying on USER_DS and USER_CS, the function insn_get_addr_ref() inspects the segment descriptor pointed by the registers in pt_regs. This ensures that we correctly obtain the segment base address and the address and operand sizes even if the user space application uses a local descriptor table. Signed-off-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com> Reviewed-by: Thomas Gleixner <tglx@linutronix.de> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Andy Lutomirski <luto@kernel.org> Cc: Borislav Petkov <bp@alien8.de> Cc: Borislav Petkov <bp@suse.de> Cc: Brian Gerst <brgerst@gmail.com> Cc: Chen Yucong <slaoub@gmail.com> Cc: Chris Metcalf <cmetcalf@mellanox.com> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: Denys Vlasenko <dvlasenk@redhat.com> Cc: Fenghua Yu <fenghua.yu@intel.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Huang Rui <ray.huang@amd.com> Cc: Jiri Slaby <jslaby@suse.cz> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Josh Poimboeuf <jpoimboe@redhat.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Michael S. Tsirkin <mst@redhat.com> Cc: Paolo Bonzini <pbonzini@redhat.com> Cc: Paul Gortmaker <paul.gortmaker@windriver.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Ravi V. Shankar <ravi.v.shankar@intel.com> Cc: Shuah Khan <shuah@kernel.org> Cc: Tony Luck <tony.luck@intel.com> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: ricardo.neri@intel.com Link: http://lkml.kernel.org/r/1509935277-22138-8-git-send-email-ricardo.neri-calderon@linux.intel.com Signed-off-by: Ingo Molnar <mingo@kernel.org>