/* SPDX-License-Identifier: GPL-2.0 */ #include <linux/kernel.h> #include <asm/desc.h> #include <asm/fred.h> #include <asm/tlbflush.h> #include <asm/traps.h> /* #DB in the kernel would imply the use of a kernel debugger. */ #define FRED_DB_STACK_LEVEL 1UL #define FRED_NMI_STACK_LEVEL 2UL #define FRED_MC_STACK_LEVEL 2UL /* * #DF is the highest level because a #DF means "something went wrong * *while delivering an exception*." The number of cases for which that * can happen with FRED is drastically reduced and basically amounts to * "the stack you pointed me to is broken." Thus, always change stacks * on #DF, which means it should be at the highest level. */ #define FRED_DF_STACK_LEVEL 3UL #define FRED_STKLVL(vector, lvl) ((lvl) << (2 * (vector))) void cpu_init_fred_exceptions(void) { /* When FRED is enabled by default, remove this log message */ pr_info("Initialize FRED on CPU%d\n", smp_processor_id()); wrmsrl(MSR_IA32_FRED_CONFIG, /* Reserve for CALL emulation */ FRED_CONFIG_REDZONE | FRED_CONFIG_INT_STKLVL(0) | FRED_CONFIG_ENTRYPOINT(asm_fred_entrypoint_user)); /* * The purpose of separate stacks for NMI, #DB and #MC *in the kernel* * (remember that user space faults are always taken on stack level 0) * is to avoid overflowing the kernel stack. */ wrmsrl(MSR_IA32_FRED_STKLVLS, FRED_STKLVL(X86_TRAP_DB, FRED_DB_STACK_LEVEL) | FRED_STKLVL(X86_TRAP_NMI, FRED_NMI_STACK_LEVEL) | FRED_STKLVL(X86_TRAP_MC, FRED_MC_STACK_LEVEL) | FRED_STKLVL(X86_TRAP_DF, FRED_DF_STACK_LEVEL)); /* The FRED equivalents to IST stacks... */ wrmsrl(MSR_IA32_FRED_RSP1, __this_cpu_ist_top_va(DB)); wrmsrl(MSR_IA32_FRED_RSP2, __this_cpu_ist_top_va(NMI)); wrmsrl(MSR_IA32_FRED_RSP3, __this_cpu_ist_top_va(DF)); /* Enable FRED */ cr4_set_bits(X86_CR4_FRED); /* Any further IDT use is a bug */ idt_invalidate(); /* Use int $0x80 for 32-bit system calls in FRED mode */ setup_clear_cpu_cap(X86_FEATURE_SYSENTER32); setup_clear_cpu_cap(X86_FEATURE_SYSCALL32); }