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Commit 8d1a2427 authored by Jan Willeke's avatar Jan Willeke Committed by Martin Schwidefsky
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s390/uprobes: fix user space PER events 



If uprobes are single stepped for example with gdb, the behavior should
now be correct. Before this patch, when gdb was single stepping a uprobe,
the result was a SIGILL.
When PER is active for any storage alteration and a uprobe is hit, a storage
alteration event is indicated. These over indications are filterd out by gdb,
if no change has happened within the observed area.

Signed-off-by: default avatarJan Willeke <willeke@de.ibm.com>
Signed-off-by: default avatarMartin Schwidefsky <schwidefsky@de.ibm.com>
parent ae750974

arch/s390/kernel/uprobes.c

+60 −9
Original line number Diff line number Diff line
@@ -48,6 +48,30 @@ bool arch_uprobe_xol_was_trapped(struct task_struct *tsk) 
	return false;

}



static int check_per_event(unsigned short cause, unsigned long control,

			   struct pt_regs *regs)

{

	if (!(regs->psw.mask & PSW_MASK_PER))

		return 0;

	/* user space single step */

	if (control == 0)

		return 1;

	/* over indication for storage alteration */

	if ((control & 0x20200000) && (cause & 0x2000))

		return 1;

	if (cause & 0x8000) {

		/* all branches */

		if ((control & 0x80800000) == 0x80000000)

			return 1;

		/* branch into selected range */

		if (((control & 0x80800000) == 0x80800000) &&

		    regs->psw.addr >= current->thread.per_user.start &&

		    regs->psw.addr <= current->thread.per_user.end)

			return 1;

	}

	return 0;

}



int arch_uprobe_post_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)

{

	int fixup = probe_get_fixup_type(auprobe->insn);
@@ -71,9 +95,13 @@ int arch_uprobe_post_xol(struct arch_uprobe *auprobe, struct pt_regs *regs) 
		if (regs->psw.addr - utask->xol_vaddr == ilen)

			regs->psw.addr = utask->vaddr + ilen;

	}

	/* If per tracing was active generate trap */

	if (regs->psw.mask & PSW_MASK_PER)

		do_per_trap(regs);

	if (check_per_event(current->thread.per_event.cause,

			    current->thread.per_user.control, regs)) {

		/* fix per address */

		current->thread.per_event.address = utask->vaddr;

		/* trigger per event */

		set_pt_regs_flag(regs, PIF_PER_TRAP);

	}

	return 0;

}
@@ -106,6 +134,7 @@ void arch_uprobe_abort_xol(struct arch_uprobe *auprobe, struct pt_regs *regs) 
	clear_thread_flag(TIF_UPROBE_SINGLESTEP);

	regs->int_code = auprobe->saved_int_code;

	regs->psw.addr = current->utask->vaddr;

	current->thread.per_event.address = current->utask->vaddr;

}



unsigned long arch_uretprobe_hijack_return_addr(unsigned long trampoline,
@@ -146,17 +175,20 @@ static void adjust_psw_addr(psw_t *psw, unsigned long len) 
	__rc;						\

})



#define emu_store_ril(ptr, input)			\

#define emu_store_ril(regs, ptr, input)			\

({							\

	unsigned int mask = sizeof(*(ptr)) - 1;		\

	__typeof__(ptr) __ptr = (ptr);			\

	int __rc = 0;					\

							\

	if (!test_facility(34))				\

		__rc = EMU_ILLEGAL_OP;			\

	else if ((u64 __force)ptr & mask)		\

	else if ((u64 __force)__ptr & mask)		\

		__rc = EMU_SPECIFICATION;		\

	else if (put_user(*(input), ptr))		\

	else if (put_user(*(input), __ptr))		\

		__rc = EMU_ADDRESSING;			\

	if (__rc == 0)					\

		sim_stor_event(regs, __ptr, mask + 1);	\

	__rc;						\

})
@@ -197,6 +229,25 @@ union split_register { 
	s16 s16[4];

};



/*

 * If user per registers are setup to trace storage alterations and an

 * emulated store took place on a fitting address a user trap is generated.

 */

static void sim_stor_event(struct pt_regs *regs, void *addr, int len)

{

	if (!(regs->psw.mask & PSW_MASK_PER))

		return;

	if (!(current->thread.per_user.control & PER_EVENT_STORE))

		return;

	if ((void *)current->thread.per_user.start > (addr + len))

		return;

	if ((void *)current->thread.per_user.end < addr)

		return;

	current->thread.per_event.address = regs->psw.addr;

	current->thread.per_event.cause = PER_EVENT_STORE >> 16;

	set_pt_regs_flag(regs, PIF_PER_TRAP);

}



/*

 * pc relative instructions are emulated, since parameters may not be

 * accessible from the xol area due to range limitations.
@@ -249,13 +300,13 @@ static void handle_insn_ril(struct arch_uprobe *auprobe, struct pt_regs *regs) 
			rc = emu_load_ril((u32 __user *)uptr, &rx->u64);

			break;

		case 0x07: /* sthrl */

			rc = emu_store_ril((u16 __user *)uptr, &rx->u16[3]);

			rc = emu_store_ril(regs, (u16 __user *)uptr, &rx->u16[3]);

			break;

		case 0x0b: /* stgrl */

			rc = emu_store_ril((u64 __user *)uptr, &rx->u64);

			rc = emu_store_ril(regs, (u64 __user *)uptr, &rx->u64);

			break;

		case 0x0f: /* strl */

			rc = emu_store_ril((u32 __user *)uptr, &rx->u32[1]);

			rc = emu_store_ril(regs, (u32 __user *)uptr, &rx->u32[1]);

			break;

		}

		break;