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
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