/* SPDX-License-Identifier: GPL-2.0 */#include <linux/kernel.h> #include <asm/desc.h>#include <asm/fred.h>#include <asm/msr.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))) DEFINE_PER_CPU(unsigned long, fred_rsp0);EXPORT_PER_CPU_SYMBOL(fred_rsp0); void cpu_init_fred_exceptions(void){	/*	 * If a kernel event is delivered before a CPU goes to user level for	 * the first time, its SS is NULL thus NULL is pushed into the SS field	 * of the FRED stack frame.  But before ERETS is executed, the CPU may	 * context switch to another task and go to user level.  Then when the	 * CPU comes back to kernel mode, SS is changed to __KERNEL_DS.  Later	 * when ERETS is executed to return from the kernel event handler, a #GP	 * fault is generated because SS doesn't match the SS saved in the FRED	 * stack frame.	 *	 * Initialize SS to __KERNEL_DS when enabling FRED to avoid such #GPs.	 */	loadsegment(ss, __KERNEL_DS); 	wrmsrq(MSR_IA32_FRED_CONFIG,	       /* Reserve for CALL emulation */	       FRED_CONFIG_REDZONE |	       FRED_CONFIG_INT_STKLVL(0) |	       FRED_CONFIG_ENTRYPOINT(asm_fred_entrypoint_user)); 	wrmsrq(MSR_IA32_FRED_STKLVLS, 0); 	/*	 * Ater a CPU offline/online cycle, the FRED RSP0 MSR should be	 * resynchronized with its per-CPU cache.	 */	wrmsrq(MSR_IA32_FRED_RSP0, __this_cpu_read(fred_rsp0)); 	wrmsrq(MSR_IA32_FRED_RSP1, 0);	wrmsrq(MSR_IA32_FRED_RSP2, 0);	wrmsrq(MSR_IA32_FRED_RSP3, 0); 	/* 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_SYSFAST32);	setup_clear_cpu_cap(X86_FEATURE_SYSCALL32);} /* Must be called after setup_cpu_entry_areas() */void cpu_init_fred_rsps(void){	/*	 * 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.	 */	wrmsrq(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... */	wrmsrq(MSR_IA32_FRED_RSP1, __this_cpu_ist_top_va(DB));	wrmsrq(MSR_IA32_FRED_RSP2, __this_cpu_ist_top_va(NMI));	wrmsrq(MSR_IA32_FRED_RSP3, __this_cpu_ist_top_va(DF));}