kernel.git/arch/x86/kernel/traps.c, branch linux-5.12.y

x86/traps: Correct exc_general_protection() and math_error() return paths

2021-04-09T11:45:09Z

Commit 334872a09198 ("x86/traps: Attempt to fixup exceptions in vDSO before signaling") added return statements which bypass calling cond_local_irq_disable(). According to ca4c6a9858c2 ("x86/traps: Make interrupt enable/disable symmetric in C code"), cond_local_irq_disable() is needed because the asm return code no longer disables interrupts. Follow the existing code as an example to use "goto exit" instead of "return" statement. [ bp: Massage commit message. ] Fixes: 334872a09198 ("x86/traps: Attempt to fixup exceptions in vDSO before signaling") Signed-off-by: Thomas Tai Signed-off-by: Borislav Petkov Reviewed-by: Alexandre Chartre Link: https://lkml.kernel.org/r/1617902914-83245-1-git-send-email-thomas.tai@oracle.com

x86/sev-es: Introduce ip_within_syscall_gap() helper

2021-03-08T13:22:17Z

Introduce a helper to check whether an exception came from the syscall gap and use it in the SEV-ES code. Extend the check to also cover the compatibility SYSCALL entry path. Fixes: 315562c9af3d5 ("x86/sev-es: Adjust #VC IST Stack on entering NMI handler") Signed-off-by: Joerg Roedel Signed-off-by: Borislav Petkov Cc: stable@vger.kernel.org # 5.10+ Link: https://lkml.kernel.org/r/20210303141716.29223-2-joro@8bytes.org

x86/split-lock: Avoid returning with interrupts enabled

2020-12-22T21:06:10Z

When a split lock is detected always make sure to disable interrupts before returning from the trap handler. The kernel exit code assumes that all exits run with interrupts disabled, otherwise the SWAPGS sequence can race against interrupts and cause recursing page faults and later panics. The problem will only happen on CPUs with split lock disable functionality, so Icelake Server, Tiger Lake, Snow Ridge, Jacobsville. Fixes: ca4c6a9858c2 ("x86/traps: Make interrupt enable/disable symmetric in C code") Fixes: bce9b042ec73 ("x86/traps: Disable interrupts in exc_aligment_check()") # v5.8+ Signed-off-by: Andi Kleen Cc: Peter Zijlstra Cc: Fenghua Yu Cc: Tony Luck Reviewed-by: Thomas Gleixner Signed-off-by: Linus Torvalds

Merge tag 'core-entry-2020-12-14' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2020-12-15T01:13:53Z

Pull core entry/exit updates from Thomas Gleixner: "A set of updates for entry/exit handling: - More generalization of entry/exit functionality - The consolidation work to reclaim TIF flags on x86 and also for non-x86 specific TIF flags which are solely relevant for syscall related work and have been moved into their own storage space. The x86 specific part had to be merged in to avoid a major conflict. - The TIF_NOTIFY_SIGNAL work which replaces the inefficient signal delivery mode of task work and results in an impressive performance improvement for io_uring. The non-x86 consolidation of this is going to come seperate via Jens. - The selective syscall redirection facility which provides a clean and efficient way to support the non-Linux syscalls of WINE by catching them at syscall entry and redirecting them to the user space emulation. This can be utilized for other purposes as well and has been designed carefully to avoid overhead for the regular fastpath. This includes the core changes and the x86 support code. - Simplification of the context tracking entry/exit handling for the users of the generic entry code which guarantee the proper ordering and protection. - Preparatory changes to make the generic entry code accomodate S390 specific requirements which are mostly related to their syscall restart mechanism" * tag 'core-entry-2020-12-14' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (36 commits) entry: Add syscall_exit_to_user_mode_work() entry: Add exit_to_user_mode() wrapper entry_Add_enter_from_user_mode_wrapper entry: Rename exit_to_user_mode() entry: Rename enter_from_user_mode() docs: Document Syscall User Dispatch selftests: Add benchmark for syscall user dispatch selftests: Add kselftest for syscall user dispatch entry: Support Syscall User Dispatch on common syscall entry kernel: Implement selective syscall userspace redirection signal: Expose SYS_USER_DISPATCH si_code type x86: vdso: Expose sigreturn address on vdso to the kernel MAINTAINERS: Add entry for common entry code entry: Fix boot for !CONFIG_GENERIC_ENTRY x86: Support HAVE_CONTEXT_TRACKING_OFFSTACK context_tracking: Only define schedule_user() on !HAVE_CONTEXT_TRACKING_OFFSTACK archs sched: Detect call to schedule from critical entry code context_tracking: Don't implement exception_enter/exit() on CONFIG_HAVE_CONTEXT_TRACKING_OFFSTACK context_tracking: Introduce HAVE_CONTEXT_TRACKING_OFFSTACK x86: Reclaim unused x86 TI flags ...

x86/traps: Attempt to fixup exceptions in vDSO before signaling

2020-11-18T17:02:50Z

vDSO functions can now leverage an exception fixup mechanism similar to kernel exception fixup. For vDSO exception fixup, the initial user is Intel's Software Guard Extensions (SGX), which will wrap the low-level transitions to/from the enclave, i.e. EENTER and ERESUME instructions, in a vDSO function and leverage fixup to intercept exceptions that would otherwise generate a signal. This allows the vDSO wrapper to return the fault information directly to its caller, obviating the need for SGX applications and libraries to juggle signal handlers. Attempt to fixup vDSO exceptions immediately prior to populating and sending signal information. Except for the delivery mechanism, an exception in a vDSO function should be treated like any other exception in userspace, e.g. any fault that is successfully handled by the kernel should not be directly visible to userspace. Although it's debatable whether or not all exceptions are of interest to enclaves, defer to the vDSO fixup to decide whether to do fixup or generate a signal. Future users of vDSO fixup, if there ever are any, will undoubtedly have different requirements than SGX enclaves, e.g. the fixup vs. signal logic can be made function specific if/when necessary. Suggested-by: Andy Lutomirski Signed-off-by: Sean Christopherson Signed-off-by: Jarkko Sakkinen Signed-off-by: Borislav Petkov Acked-by: Jethro Beekman Link: https://lkml.kernel.org/r/20201112220135.165028-19-jarkko@kernel.org

x86/entry: Move nmi entry/exit into common code

2020-11-04T21:55:36Z

Lockdep state handling on NMI enter and exit is nothing specific to X86. It's not any different on other architectures. Also the extra state type is not necessary, irqentry_state_t can carry the necessary information as well. Move it to common code and extend irqentry_state_t to carry lockdep state. [ Ira: Make exit_rcu and lockdep a union as they are mutually exclusive between the IRQ and NMI exceptions, and add kernel documentation for struct irqentry_state_t ] Signed-off-by: Thomas Gleixner Signed-off-by: Ira Weiny Signed-off-by: Thomas Gleixner Link: https://lore.kernel.org/r/20201102205320.1458656-7-ira.weiny@intel.com

x86/debug: Fix DR_STEP vs ptrace_get_debugreg(6)

2020-10-27T22:15:24Z

Commit d53d9bc0cf78 ("x86/debug: Change thread.debugreg6 to thread.virtual_dr6") changed the semantics of the variable from random collection of bits, to exactly only those bits that ptrace() needs. Unfortunately this lost DR_STEP for PTRACE_{BLOCK,SINGLE}STEP. Furthermore, it turns out that userspace expects DR_STEP to be unconditionally available, even for manual TF usage outside of PTRACE_{BLOCK,SINGLE}_STEP. Fixes: d53d9bc0cf78 ("x86/debug: Change thread.debugreg6 to thread.virtual_dr6") Reported-by: Kyle Huey Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Thomas Gleixner Tested-by: Kyle Huey Link: https://lore.kernel.org/r/20201027183330.GM2628@hirez.programming.kicks-ass.net

x86/debug: Only clear/set ->virtual_dr6 for userspace #DB

2020-10-27T22:15:23Z

The ->virtual_dr6 is the value used by ptrace_{get,set}_debugreg(6). A kernel #DB clearing it could mean spurious malfunction of ptrace() expectations. Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Thomas Gleixner Tested-by: Kyle Huey Link: https://lore.kernel.org/r/20201027093608.028952500@infradead.org

x86/debug: Fix BTF handling

2020-10-27T22:15:23Z

The SDM states that #DB clears DEBUGCTLMSR_BTF, this means that when the bit is set for userspace (TIF_BLOCKSTEP) and a kernel #DB happens first, the BTF bit meant for userspace execution is lost. Have the kernel #DB handler restore the BTF bit when it was requested for userspace. Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Thomas Gleixner Tested-by: Kyle Huey Link: https://lore.kernel.org/r/20201027093607.956147736@infradead.org

Merge tag 'x86_seves_for_v5.10' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2020-10-14T17:21:34Z

Pull x86 SEV-ES support from Borislav Petkov: "SEV-ES enhances the current guest memory encryption support called SEV by also encrypting the guest register state, making the registers inaccessible to the hypervisor by en-/decrypting them on world switches. Thus, it adds additional protection to Linux guests against exfiltration, control flow and rollback attacks. With SEV-ES, the guest is in full control of what registers the hypervisor can access. This is provided by a guest-host exchange mechanism based on a new exception vector called VMM Communication Exception (#VC), a new instruction called VMGEXIT and a shared Guest-Host Communication Block which is a decrypted page shared between the guest and the hypervisor. Intercepts to the hypervisor become #VC exceptions in an SEV-ES guest so in order for that exception mechanism to work, the early x86 init code needed to be made able to handle exceptions, which, in itself, brings a bunch of very nice cleanups and improvements to the early boot code like an early page fault handler, allowing for on-demand building of the identity mapping. With that, !KASLR configurations do not use the EFI page table anymore but switch to a kernel-controlled one. The main part of this series adds the support for that new exchange mechanism. The goal has been to keep this as much as possibly separate from the core x86 code by concentrating the machinery in two SEV-ES-specific files: arch/x86/kernel/sev-es-shared.c arch/x86/kernel/sev-es.c Other interaction with core x86 code has been kept at minimum and behind static keys to minimize the performance impact on !SEV-ES setups. Work by Joerg Roedel and Thomas Lendacky and others" * tag 'x86_seves_for_v5.10' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (73 commits) x86/sev-es: Use GHCB accessor for setting the MMIO scratch buffer x86/sev-es: Check required CPU features for SEV-ES x86/efi: Add GHCB mappings when SEV-ES is active x86/sev-es: Handle NMI State x86/sev-es: Support CPU offline/online x86/head/64: Don't call verify_cpu() on starting APs x86/smpboot: Load TSS and getcpu GDT entry before loading IDT x86/realmode: Setup AP jump table x86/realmode: Add SEV-ES specific trampoline entry point x86/vmware: Add VMware-specific handling for VMMCALL under SEV-ES x86/kvm: Add KVM-specific VMMCALL handling under SEV-ES x86/paravirt: Allow hypervisor-specific VMMCALL handling under SEV-ES x86/sev-es: Handle #DB Events x86/sev-es: Handle #AC Events x86/sev-es: Handle VMMCALL Events x86/sev-es: Handle MWAIT/MWAITX Events x86/sev-es: Handle MONITOR/MONITORX Events x86/sev-es: Handle INVD Events x86/sev-es: Handle RDPMC Events x86/sev-es: Handle RDTSC(P) Events ...