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