| 1 | /* SPDX-License-Identifier: GPL-2.0 */ |
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| 2 | #include <linux/kernel.h> |
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| 3 | |
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| 4 | #include <asm/desc.h> |
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| 5 | #include <asm/fred.h> |
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| 6 | #include <asm/tlbflush.h> |
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| 7 | #include <asm/traps.h> |
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| 8 | |
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| 9 | /* #DB in the kernel would imply the use of a kernel debugger. */ |
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| 10 | #define FRED_DB_STACK_LEVEL 1UL |
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| 11 | #define FRED_NMI_STACK_LEVEL 2UL |
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| 12 | #define FRED_MC_STACK_LEVEL 2UL |
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| 13 | /* |
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| 14 | * #DF is the highest level because a #DF means "something went wrong |
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| 15 | * *while delivering an exception*." The number of cases for which that |
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| 16 | * can happen with FRED is drastically reduced and basically amounts to |
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| 17 | * "the stack you pointed me to is broken." Thus, always change stacks |
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| 18 | * on #DF, which means it should be at the highest level. |
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| 19 | */ |
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| 20 | #define FRED_DF_STACK_LEVEL 3UL |
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| 21 | |
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| 22 | #define FRED_STKLVL(vector, lvl) ((lvl) << (2 * (vector))) |
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| 23 | |
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| 24 | void cpu_init_fred_exceptions(void) |
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| 25 | { |
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| 26 | /* When FRED is enabled by default, remove this log message */ |
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| 27 | pr_info("Initialize FRED on CPU%d\n" , smp_processor_id()); |
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| 28 | |
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| 29 | wrmsrl(MSR_IA32_FRED_CONFIG, |
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| 30 | /* Reserve for CALL emulation */ |
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| 31 | FRED_CONFIG_REDZONE | |
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| 32 | FRED_CONFIG_INT_STKLVL(0) | |
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| 33 | FRED_CONFIG_ENTRYPOINT(asm_fred_entrypoint_user)); |
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| 34 | |
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| 35 | /* |
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| 36 | * The purpose of separate stacks for NMI, #DB and #MC *in the kernel* |
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| 37 | * (remember that user space faults are always taken on stack level 0) |
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| 38 | * is to avoid overflowing the kernel stack. |
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| 39 | */ |
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| 40 | wrmsrl(MSR_IA32_FRED_STKLVLS, |
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| 41 | FRED_STKLVL(X86_TRAP_DB, FRED_DB_STACK_LEVEL) | |
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| 42 | FRED_STKLVL(X86_TRAP_NMI, FRED_NMI_STACK_LEVEL) | |
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| 43 | FRED_STKLVL(X86_TRAP_MC, FRED_MC_STACK_LEVEL) | |
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| 44 | FRED_STKLVL(X86_TRAP_DF, FRED_DF_STACK_LEVEL)); |
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| 45 | |
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| 46 | /* The FRED equivalents to IST stacks... */ |
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| 47 | wrmsrl(MSR_IA32_FRED_RSP1, __this_cpu_ist_top_va(DB)); |
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| 48 | wrmsrl(MSR_IA32_FRED_RSP2, __this_cpu_ist_top_va(NMI)); |
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| 49 | wrmsrl(MSR_IA32_FRED_RSP3, __this_cpu_ist_top_va(DF)); |
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| 50 | |
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| 51 | /* Enable FRED */ |
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| 52 | cr4_set_bits(X86_CR4_FRED); |
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| 53 | /* Any further IDT use is a bug */ |
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| 54 | idt_invalidate(); |
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| 55 | |
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| 56 | /* Use int $0x80 for 32-bit system calls in FRED mode */ |
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| 57 | setup_clear_cpu_cap(X86_FEATURE_SYSENTER32); |
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| 58 | setup_clear_cpu_cap(X86_FEATURE_SYSCALL32); |
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| 59 | } |
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| 60 | |
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