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/* SPDX-License-Identifier: GPL-2.0 */
#ifndef _ASM_X86_DEBUGREG_H
#define _ASM_X86_DEBUGREG_H
#include <linux/bug.h>
#include <uapi/asm/debugreg.h>
DECLARE_PER_CPU(unsigned long, cpu_dr7);
#ifndef CONFIG_PARAVIRT_XXL
/*
* These special macros can be used to get or set a debugging register
*/
#define get_debugreg(var, register) \
(var) = native_get_debugreg(register)
#define set_debugreg(value, register) \
native_set_debugreg(register, value)
#endif
static __always_inline unsigned long native_get_debugreg(int regno)
{
unsigned long val = 0; /* Damn you, gcc! */
switch (regno) {
case 0:
asm("mov %%db0, %0" :"=r" (val));
break;
case 1:
asm("mov %%db1, %0" :"=r" (val));
break;
case 2:
asm("mov %%db2, %0" :"=r" (val));
break;
case 3:
asm("mov %%db3, %0" :"=r" (val));
break;
case 6:
asm("mov %%db6, %0" :"=r" (val));
break;
case 7:
/*
* Apply __FORCE_ORDER to DR7 reads to forbid re-ordering them
* with other code.
*
* This is needed because a DR7 access can cause a #VC exception
* when running under SEV-ES. Taking a #VC exception is not a
* safe thing to do just anywhere in the entry code and
* re-ordering might place the access into an unsafe location.
*
* This happened in the NMI handler, where the DR7 read was
* re-ordered to happen before the call to sev_es_ist_enter(),
* causing stack recursion.
*/
asm volatile("mov %%db7, %0" : "=r" (val) : __FORCE_ORDER);
break;
default:
BUG();
}
return val;
}
static __always_inline void native_set_debugreg(int regno, unsigned long value)
{
switch (regno) {
case 0:
asm("mov %0, %%db0" ::"r" (value));
break;
case 1:
asm("mov %0, %%db1" ::"r" (value));
break;
case 2:
asm("mov %0, %%db2" ::"r" (value));
break;
case 3:
asm("mov %0, %%db3" ::"r" (value));
break;
case 6:
asm("mov %0, %%db6" ::"r" (value));
break;
case 7:
/*
* Apply __FORCE_ORDER to DR7 writes to forbid re-ordering them
* with other code.
*
* While is didn't happen with a DR7 write (see the DR7 read
* comment above which explains where it happened), add the
* __FORCE_ORDER here too to avoid similar problems in the
* future.
*/
asm volatile("mov %0, %%db7" ::"r" (value), __FORCE_ORDER);
break;
default:
BUG();
}
}
static inline void hw_breakpoint_disable(void)
{
/* Zero the control register for HW Breakpoint */
set_debugreg(0UL, 7);
/* Zero-out the individual HW breakpoint address registers */
set_debugreg(0UL, 0);
set_debugreg(0UL, 1);
set_debugreg(0UL, 2);
set_debugreg(0UL, 3);
}
static __always_inline bool hw_breakpoint_active(void)
{
return __this_cpu_read(cpu_dr7) & DR_GLOBAL_ENABLE_MASK;
}
extern void hw_breakpoint_restore(void);
static __always_inline unsigned long local_db_save(void)
{
unsigned long dr7;
if (static_cpu_has(X86_FEATURE_HYPERVISOR) && !hw_breakpoint_active())
return 0;
get_debugreg(dr7, 7);
dr7 &= ~0x400; /* architecturally set bit */
if (dr7)
set_debugreg(0, 7);
/*
* Ensure the compiler doesn't lower the above statements into
* the critical section; disabling breakpoints late would not
* be good.
*/
barrier();
return dr7;
}
static __always_inline void local_db_restore(unsigned long dr7)
{
/*
* Ensure the compiler doesn't raise this statement into
* the critical section; enabling breakpoints early would
* not be good.
*/
barrier();
if (dr7)
set_debugreg(dr7, 7);
}
#ifdef CONFIG_CPU_SUP_AMD
extern void set_dr_addr_mask(unsigned long mask, int dr);
#else
static inline void set_dr_addr_mask(unsigned long mask, int dr) { }
#endif
#endif /* _ASM_X86_DEBUGREG_H */
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