Commit cdd99dd8 authored by H. Peter Anvin (Intel)'s avatar H. Peter Anvin (Intel) Committed by Borislav Petkov (AMD)
Browse files

x86/fred: Add FRED initialization functions 



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: default avatarXin Li <xin3.li@intel.com>
Signed-off-by: default avatarH. Peter Anvin (Intel) <hpa@zytor.com>
Signed-off-by: default avatarXin Li <xin3.li@intel.com>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Signed-off-by: default avatarBorislav Petkov (AMD) <bp@alien8.de>
Tested-by: default avatarShan Kang <shan.kang@intel.com>
Link: https://lore.kernel.org/r/20231205105030.8698-35-xin3.li@intel.com
parent 530dce27

arch/x86/entry/entry_fred.c

+21 −0
Original line number Diff line number Diff line
@@ -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;

arch/x86/include/asm/fred.h

+5 −0
Original line number Diff line number Diff line
@@ -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__ */

arch/x86/kernel/Makefile

+1 −0
Original line number Diff line number Diff line
@@ -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

arch/x86/kernel/fred.c

0 → 100644
+59 −0
Original line number Diff line number Diff line 
/* 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);

}