Commit 13cb7349 authored by Linus Torvalds's avatar Linus Torvalds
Browse files

Merge tag 'x86-entry-2020-10-12' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 

Pull x86 entry code updates from Thomas Gleixner:
 "More consolidation and correctness fixes for the debug exception:

   - Ensure BTF synchronization under all circumstances

   - Distangle kernel and user mode #DB further

   - Get ordering vs. the debug notifier correct to make KGDB work more
     reliably.

   - Cleanup historical gunk and make the code simpler to understand"

* tag 'x86-entry-2020-10-12' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/debug: Change thread.debugreg6 to thread.virtual_dr6
  x86/debug: Support negative polarity DR6 bits
  x86/debug: Simplify hw_breakpoint_handler()
  x86/debug: Remove aout_dump_debugregs()
  x86/debug: Remove the historical junk
  x86/debug: Move cond_local_irq_enable() block into exc_debug_user()
  x86/debug: Move historical SYSENTER junk into exc_debug_kernel()
  x86/debug: Simplify #DB signal code
  x86/debug: Remove handle_debug(.user) argument
  x86/debug: Move kprobe_debug_handler() into exc_debug_kernel()
  x86/debug: Sync BTF earlier
parents cc734372 d53d9bc0

arch/x86/include/asm/debugreg.h

+0 −2
Original line number Diff line number Diff line
@@ -90,8 +90,6 @@ static __always_inline bool hw_breakpoint_active(void) 
	return __this_cpu_read(cpu_dr7) & DR_GLOBAL_ENABLE_MASK;

}



extern void aout_dump_debugregs(struct user *dump);



extern void hw_breakpoint_restore(void);



static __always_inline unsigned long local_db_save(void)

arch/x86/include/asm/kprobes.h

+4 −0
Original line number Diff line number Diff line
@@ -106,5 +106,9 @@ extern int kprobe_exceptions_notify(struct notifier_block *self, 
extern int kprobe_int3_handler(struct pt_regs *regs);

extern int kprobe_debug_handler(struct pt_regs *regs);



#else



static inline int kprobe_debug_handler(struct pt_regs *regs) { return 0; }



#endif /* CONFIG_KPROBES */

#endif /* _ASM_X86_KPROBES_H */

arch/x86/include/asm/processor.h

+1 −1
Original line number Diff line number Diff line
@@ -517,7 +517,7 @@ struct thread_struct { 
	/* Save middle states of ptrace breakpoints */

	struct perf_event	*ptrace_bps[HBP_NUM];

	/* Debug status used for traps, single steps, etc... */

	unsigned long           debugreg6;

	unsigned long           virtual_dr6;

	/* Keep track of the exact dr7 value set by the user */

	unsigned long           ptrace_dr7;

	/* Fault info: */

arch/x86/kernel/hw_breakpoint.c

+6 −52
Original line number Diff line number Diff line
@@ -441,42 +441,6 @@ int hw_breakpoint_arch_parse(struct perf_event *bp, 
	return 0;

}



/*

 * Dump the debug register contents to the user.

 * We can't dump our per cpu values because it

 * may contain cpu wide breakpoint, something that

 * doesn't belong to the current task.

 *

 * TODO: include non-ptrace user breakpoints (perf)

 */

void aout_dump_debugregs(struct user *dump)

{

	int i;

	int dr7 = 0;

	struct perf_event *bp;

	struct arch_hw_breakpoint *info;

	struct thread_struct *thread = &current->thread;



	for (i = 0; i < HBP_NUM; i++) {

		bp = thread->ptrace_bps[i];



		if (bp && !bp->attr.disabled) {

			dump->u_debugreg[i] = bp->attr.bp_addr;

			info = counter_arch_bp(bp);

			dr7 |= encode_dr7(i, info->len, info->type);

		} else {

			dump->u_debugreg[i] = 0;

		}

	}



	dump->u_debugreg[4] = 0;

	dump->u_debugreg[5] = 0;

	dump->u_debugreg[6] = current->thread.debugreg6;



	dump->u_debugreg[7] = dr7;

}

EXPORT_SYMBOL_GPL(aout_dump_debugregs);



/*

 * Release the user breakpoints used by ptrace

 */
@@ -490,7 +454,7 @@ void flush_ptrace_hw_breakpoint(struct task_struct *tsk) 
		t->ptrace_bps[i] = NULL;

	}



	t->debugreg6 = 0;

	t->virtual_dr6 = 0;

	t->ptrace_dr7 = 0;

}
@@ -500,7 +464,7 @@ void hw_breakpoint_restore(void) 
	set_debugreg(__this_cpu_read(cpu_debugreg[1]), 1);

	set_debugreg(__this_cpu_read(cpu_debugreg[2]), 2);

	set_debugreg(__this_cpu_read(cpu_debugreg[3]), 3);

	set_debugreg(current->thread.debugreg6, 6);

	set_debugreg(DR6_RESERVED, 6);

	set_debugreg(__this_cpu_read(cpu_dr7), 7);

}

EXPORT_SYMBOL_GPL(hw_breakpoint_restore);
@@ -523,10 +487,10 @@ EXPORT_SYMBOL_GPL(hw_breakpoint_restore); 
 */

static int hw_breakpoint_handler(struct die_args *args)

{

	int i, cpu, rc = NOTIFY_STOP;

	int i, rc = NOTIFY_STOP;

	struct perf_event *bp;

	unsigned long dr6;

	unsigned long *dr6_p;

	unsigned long dr6;



	/* The DR6 value is pointed by args->err */

	dr6_p = (unsigned long *)ERR_PTR(args->err);
@@ -540,14 +504,6 @@ static int hw_breakpoint_handler(struct die_args *args) 
	if ((dr6 & DR_TRAP_BITS) == 0)

		return NOTIFY_DONE;



	/*

	 * Assert that local interrupts are disabled

	 * Reset the DRn bits in the virtualized register value.

	 * The ptrace trigger routine will add in whatever is needed.

	 */

	current->thread.debugreg6 &= ~DR_TRAP_BITS;

	cpu = get_cpu();



	/* Handle all the breakpoints that were triggered */

	for (i = 0; i < HBP_NUM; ++i) {

		if (likely(!(dr6 & (DR_TRAP0 << i))))
@@ -561,7 +517,7 @@ static int hw_breakpoint_handler(struct die_args *args) 
		 */

		rcu_read_lock();



		bp = per_cpu(bp_per_reg[i], cpu);

		bp = this_cpu_read(bp_per_reg[i]);

		/*

		 * Reset the 'i'th TRAP bit in dr6 to denote completion of

		 * exception handling
@@ -592,12 +548,10 @@ static int hw_breakpoint_handler(struct die_args *args) 
	 * breakpoints (to generate signals) and b) when the system has

	 * taken exception due to multiple causes

	 */

	if ((current->thread.debugreg6 & DR_TRAP_BITS) ||

	if ((current->thread.virtual_dr6 & DR_TRAP_BITS) ||

	    (dr6 & (~DR_TRAP_BITS)))

		rc = NOTIFY_DONE;



	put_cpu();



	return rc;

}

arch/x86/kernel/kgdb.c

+3 −2
Original line number Diff line number Diff line
@@ -629,9 +629,10 @@ static void kgdb_hw_overflow_handler(struct perf_event *event, 
	struct task_struct *tsk = current;

	int i;



	for (i = 0; i < 4; i++)

	for (i = 0; i < 4; i++) {

		if (breakinfo[i].enabled)

			tsk->thread.debugreg6 |= (DR_TRAP0 << i);

			tsk->thread.virtual_dr6 |= (DR_TRAP0 << i);

	}

}



void kgdb_arch_late(void)

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