- 09 Sep, 2020 11 commits
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Joerg Roedel authored
When a #VC exception is triggered by user-space, the instruction decoder needs to read the instruction bytes from user addresses. Enhance vc_decode_insn() to safely fetch kernel and user instructions. Signed-off-by:
Joerg Roedel <jroedel@suse.de> Signed-off-by:
Borislav Petkov <bp@suse.de> Link: https://lkml.kernel.org/r/20200907131613.12703-49-joro@8bytes.org
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Joerg Roedel authored
Re-use the handlers for CPUID- and IOIO-caused #VC exceptions in the early boot handler. Signed-off-by:
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Tom Lendacky authored
Add the handlers for #VC exceptions invoked at runtime. Signed-off-by:
Tom Lendacky <thomas.lendacky@amd.com> Signed-off-by:
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Joerg Roedel authored
The #VC handler needs special entry code because: 1. It runs on an IST stack 2. It needs to be able to handle nested #VC exceptions To make this work, the entry code is implemented to pretend it doesn't use an IST stack. When entered from user-mode or early SYSCALL entry path it switches to the task stack. If entered from kernel-mode it tries to switch back to the previous stack in the IRET frame. The stack found in the IRET frame is validated first, and if it is not safe to use it for the #VC handler, the code will switch to a fall-back stack (the #VC2 IST stack). From there, it can cause nested exceptions again. Signed-off-by:
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Joerg Roedel authored
The get_stack_info() functionality is needed in the entry code for the #VC exception handler. Provide a version of it in the .text.noinstr section which can be called safely from there. Signed-off-by:
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Joerg Roedel authored
When an NMI hits in the #VC handler entry code before it has switched to another stack, any subsequent #VC exception in the NMI code-path will overwrite the interrupted #VC handler's stack. Make sure this doesn't happen by explicitly adjusting the #VC IST entry in the NMI handler for the time it can cause #VC exceptions. [ bp: Touchups, spelling fixes. ] Signed-off-by:
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Joerg Roedel authored
Allocate and map an IST stack and an additional fall-back stack for the #VC handler. The memory for the stacks is allocated only when SEV-ES is active. The #VC handler needs to use an IST stack because a #VC exception can be raised from kernel space with unsafe stack, e.g. in the SYSCALL entry path. Since the #VC exception can be nested, the #VC handler switches back to the interrupted stack when entered from kernel space. If switching back is not possible, the fall-back stack is used. Signed-off-by:
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Tom Lendacky authored
The runtime handler needs one GHCB per-CPU. Set them up and map them unencrypted. [ bp: Touchups and simplification. ] Signed-off-by:
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Joerg Roedel authored
Add the infrastructure to handle #VC exceptions when the kernel runs on virtual addresses and has mapped a GHCB. This handler will be used until the runtime #VC handler takes over. Since the handler runs very early, disable instrumentation for sev-es.c. [ bp: Make vc_ghcb_invalidate() __always_inline so that it can be inlined in noinstr functions like __sev_es_nmi_complete(). ] Signed-off-by:
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Joerg Roedel authored
Setup an early handler for #VC exceptions. There is no GHCB mapped yet, so just re-use the vc_no_ghcb_handler(). It can only handle CPUID exit-codes, but that should be enough to get the kernel through verify_cpu() and __startup_64() until it runs on virtual addresses. Signed-off-by:
kernel test robot <lkp@intel.com> Link: https://lkml.kernel.org/r/20200908123517.GA3764@8bytes.org
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Joerg Roedel authored
Setup sev-es.c and include the code from the pre-decompression stage to also build it into the image of the running kernel. Temporarily add __maybe_unused annotations to avoid build warnings until the functions get used. [ bp: Use the non-tracing rd/wrmsr variants because: vmlinux.o: warning: objtool: __sev_es_nmi_complete()+0x11f: \ call to do_trace_write_msr() leaves .noinstr.text section as __sev_es_nmi_complete() is noinstr due to being called from the NMI handler exc_nmi(). ] Signed-off-by:
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- 07 Sep, 2020 29 commits
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Joerg Roedel authored
Refactor the message printed to the kernel log which indicates whether SEV or SME, etc is active. This will scale better in the future when more memory encryption features might be added. Also add SEV-ES to the list of features. [ bp: Massage. ] Signed-off-by:
Kees Cook <keescook@chromium.org> Link: https://lkml.kernel.org/r/20200907131613.12703-38-joro@8bytes.org
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Joerg Roedel authored
Add a sev_es_active() function for checking whether SEV-ES is enabled. Also cache the value of MSR_AMD64_SEV at boot to speed up the feature checking in the running code. [ bp: Remove "!!" in sev_active() too. ] Signed-off-by:
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Joerg Roedel authored
Move the assembly coded dispatch between page-faults and all other exceptions to C code to make it easier to maintain and extend. Also change the return-type of early_make_pgtable() to bool and make it static. Signed-off-by:
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Joerg Roedel authored
Move these two functions from kernel/idt.c to include/asm/desc.h: * init_idt_data() * idt_init_desc() These functions are needed to setup IDT entries very early and need to be called from head64.c. To be usable this early, these functions need to be compiled without instrumentation and the stack-protector feature. These features need to be kept enabled for kernel/idt.c, so head64.c must use its own versions. [ bp: Take Kees' suggested patch title and add his Rev-by. ] Signed-off-by:
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Joerg Roedel authored
Add a separate bringup IDT for the CPU bringup code that will be used until the kernel switches to the idt_table. There are two reasons for a separate IDT: 1) When the idt_table is set up and the secondary CPUs are booted, it contains entries (e.g. IST entries) which require certain CPU state to be set up. This includes a working TSS (for IST), MSR_GS_BASE (for stack protector) or CR4.FSGSBASE (for paranoid_entry) path. By using a dedicated IDT for early boot this state need not to be set up early. 2) The idt_table is static to idt.c, so any function using/modifying must be in idt.c too. That means that all compiler driven instrumentation like tracing or KASAN is also active in this code. But during early CPU bringup the environment is not set up for this instrumentation to work correctly. To avoid all of these hassles and make early exception handling robust, use a dedicated bringup IDT. The IDT is loaded two times, first on the boot CPU while the kernel is still running on direct mapped addresses, and again later after the switch to kernel addresses has happened. The second IDT load happens on the boot and secondary CPUs. Signed-off-by:
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Joerg Roedel authored
Make sure there is a stack once the kernel runs from virtual addresses. At this stage any secondary CPU which boots will have lost its stack because the kernel switched to a new page-table which does not map the real-mode stack anymore. This is needed for handling early #VC exceptions caused by instructions like CPUID. Signed-off-by:
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Joerg Roedel authored
Make sure segments are properly set up before setting up an IDT and doing anything that might cause a #VC exception. This is later needed for early exception handling. Signed-off-by:
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Joerg Roedel authored
Load the GDT right after switching to virtual addresses to make sure there is a defined GDT for exception handling. Signed-off-by:
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Joerg Roedel authored
Handling exceptions during boot requires a working GDT. The kernel GDT can't be used on the direct mapping, so load a startup GDT and setup segments. Signed-off-by:
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Joerg Roedel authored
The code to setup idt_data is needed for early exception handling, but set_intr_gate() can't be used that early because it has pv-ops in its code path which don't work that early. Split out the idt_data initialization part from set_intr_gate() so that it can be used separately. Signed-off-by:
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Tom Lendacky authored
Handle #VC exceptions caused by CPUID instructions. These happen in early boot code when the KASLR code checks for RDTSC. Signed-off-by:
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Joerg Roedel authored
The xgetbv() function is needed in the pre-decompression boot code, but asm/fpu/internal.h can't be included there directly. Doing so opens the door to include-hell due to various include-magic in boot/compressed/misc.h. Avoid that by moving xgetbv()/xsetbv() to a separate header file and include it instead. Signed-off-by:
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Tom Lendacky authored
Add support for decoding and handling #VC exceptions for IOIO events. [ jroedel@suse.de: Adapted code to #VC handling framework ] Co-developed-by:
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Joerg Roedel authored
Force a page-fault on any further accesses to the GHCB page when they shouldn't happen anymore. This will catch any bugs where a #VC exception is raised even though none is expected anymore. Signed-off-by:
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Joerg Roedel authored
Install an exception handler for #VC exception that uses a GHCB. Also add the infrastructure for handling different exit-codes by decoding the instruction that caused the exception and error handling. Signed-off-by:
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Joerg Roedel authored
The functions are needed to map the GHCB for SEV-ES guests. The GHCB is used for communication with the hypervisor, so its content must not be encrypted. After the GHCB is not needed anymore it must be mapped encrypted again so that the running kernel image can safely re-use the memory. Signed-off-by:
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Joerg Roedel authored
The function can fail to create an identity mapping, check for that and bail out if it happens. Signed-off-by:
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Joerg Roedel authored
Call set_sev_encryption_mask() while still on the stage 1 #VC-handler because the stage 2 handler needs the kernel's own page tables to be set up, to which calling set_sev_encryption_mask() is a prerequisite. Signed-off-by:
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Joerg Roedel authored
Add the first handler for #VC exceptions. At stage 1 there is no GHCB yet because the kernel might still be running on the EFI page table. The stage 1 handler is limited to the MSR-based protocol to talk to the hypervisor and can only support CPUID exit-codes, but that is enough to get to stage 2. [ bp: Zap superfluous newlines after rd/wrmsr instruction mnemonics. ] Signed-off-by:
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Joerg Roedel authored
Changing the function to take start and end as parameters instead of start and size simplifies the callers which don't need to calculate the size if they already have start and end. Signed-off-by:
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Joerg Roedel authored
With the page-fault handler in place, he identity mapping can be built on-demand. So remove the code which manually creates the mappings and unexport/remove the functions used for it. Signed-off-by:
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Joerg Roedel authored
When booted through startup_64(), the kernel keeps running on the EFI page table until the KASLR code sets up its own page table. Without KASLR, the pre-decompression boot code never switches off the EFI page table. Change that by unconditionally switching to a kernel-controlled page table after relocation. This makes sure the kernel can make changes to the mapping when necessary, for example map pages unencrypted in SEV and SEV-ES guests. Also, remove the debug_putstr() calls in initialize_identity_maps() because the function now runs before console_init() is called. [ bp: Massage commit message. ] Signed-off-by:
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Joerg Roedel authored
Install a page-fault handler to add an identity mapping to addresses not yet mapped. Also do some checking whether the error code is sane. This makes non SEV-ES machines use the exception handling infrastructure in the pre-decompressions boot code too, making it less likely to break in the future. Signed-off-by:
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Joerg Roedel authored
The file contains only code related to identity-mapped page tables. Rename the file and compile it always in. Signed-off-by:
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Joerg Roedel authored
Add code needed to setup an IDT in the early pre-decompression boot-code. The IDT is loaded first in startup_64, which is after EfiExitBootServices() has been called, and later reloaded when the kernel image has been relocated to the end of the decompression area. This allows to setup different IDT handlers before and after the relocation. Signed-off-by:
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Joerg Roedel authored
The x86-64 ABI defines a red-zone on the stack: The 128-byte area beyond the location pointed to by %rsp is considered to be reserved and shall not be modified by signal or interrupt handlers. Therefore, functions may use this area for temporary data that is not needed across function calls. In particular, leaf functions may use this area for their entire stack frame, rather than adjusting the stack pointer in the prologue and epilogue. This area is known as the red zone. This is not compatible with exception handling, because the IRET frame written by the hardware at the stack pointer and the functions to handle the exception will overwrite the temporary variables of the interrupted function, causing undefined behavior. So disable red-zones for the pre-decompression boot code. Signed-off-by:
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Joerg Roedel authored
Add a function to check whether an instruction has a REP prefix. Signed-off-by:
Masami Hiramatsu <mhiramat@kernel.org> Link: https://lkml.kernel.org/r/20200907131613.12703-12-joro@8bytes.org
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Joerg Roedel authored
Add a function to the instruction decoder which returns the pt_regs offset of the register specified in the reg field of the modrm byte. Signed-off-by:
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Joerg Roedel authored
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:
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