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x86/fred: Add FRED initialization functions

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Add cpu_init_fred_exceptions() to:
  - Set FRED entrypoints for events happening in ring 0 and 3.
  - Specify the stack level for IRQs occurred ring 0.
  - Specify dedicated event stacks for #DB/NMI/#MCE/#DF.
  - Enable FRED and invalidtes IDT.
  - Force 32-bit system calls to use "int $0x80" only.

Add fred_complete_exception_setup() to:
  - Initialize system_vectors as done for IDT systems.
  - Set unused sysvec_table entries to fred_handle_spurious_interrupt().

Co-developed-by: Xin Li <xin3.li@intel.com>
Signed-off-by: H. Peter Anvin (Intel) <hpa@zytor.com>
Signed-off-by: Xin Li <xin3.li@intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Tested-by: Shan Kang <shan.kang@intel.com>
Link: https://lore.kernel.org/r/20231205105030.8698-35-xin3.li@intel.com
This commit is contained in:
H. Peter Anvin (Intel) 2023-12-05 02:50:23 -08:00 committed by Borislav Petkov (AMD)
parent 530dce278a
commit cdd99dd873
4 changed files with 86 additions and 0 deletions
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21
arch/x86/entry/entry_fred.c
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@ -133,6 +133,27 @@ void __init fred_install_sysvec(unsigned int sysvec, idtentry_t handler)
sysvec_table[sysvec - FIRST_SYSTEM_VECTOR] = handler;
}
static noinstr void fred_handle_spurious_interrupt(struct pt_regs *regs)
{
spurious_interrupt(regs, regs->fred_ss.vector);
}
void __init fred_complete_exception_setup(void)
{
unsigned int vector;
for (vector = 0; vector < FIRST_EXTERNAL_VECTOR; vector++)
set_bit(vector, system_vectors);
for (vector = 0; vector < NR_SYSTEM_VECTORS; vector++) {
if (sysvec_table[vector])
set_bit(vector + FIRST_SYSTEM_VECTOR, system_vectors);
else
sysvec_table[vector] = fred_handle_spurious_interrupt;
}
fred_setup_done = true;
}
static noinstr void fred_extint(struct pt_regs *regs)
{
unsigned int vector = regs->fred_ss.vector;

5
arch/x86/include/asm/fred.h
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@ -83,8 +83,13 @@ static __always_inline void fred_entry_from_kvm(unsigned int type, unsigned int
asm_fred_entry_from_kvm(ss);
}
void cpu_init_fred_exceptions(void);
void fred_complete_exception_setup(void);
#else /* CONFIG_X86_FRED */
static __always_inline unsigned long fred_event_data(struct pt_regs *regs) { return 0; }
static inline void cpu_init_fred_exceptions(void) { }
static inline void fred_complete_exception_setup(void) { }
static __always_inline void fred_entry_from_kvm(unsigned int type, unsigned int vector) { }
#endif /* CONFIG_X86_FRED */
#endif /* !__ASSEMBLY__ */

1
arch/x86/kernel/Makefile
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@ -48,6 +48,7 @@ obj-y += platform-quirks.o
obj-y += process_$(BITS).o signal.o signal_$(BITS).o
obj-y += traps.o idt.o irq.o irq_$(BITS).o dumpstack_$(BITS).o
obj-y += time.o ioport.o dumpstack.o nmi.o
obj-$(CONFIG_X86_FRED) += fred.o
obj-$(CONFIG_MODIFY_LDT_SYSCALL) += ldt.o
obj-$(CONFIG_X86_KERNEL_IBT) += ibt_selftest.o
obj-y += setup.o x86_init.o i8259.o irqinit.o

59
arch/x86/kernel/fred.c Normal file
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@ -0,0 +1,59 @@
/* 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);
}