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Commit e1723538 authored by Chris Metcalf's avatar Chris Metcalf
Browse files

arch/tile: work around a hardware issue with the return-address stack 



In certain circumstances we need to do a bunch of jump-and-link
instructions to fill the hardware return-address stack with nonzero values.

Signed-off-by: default avatarChris Metcalf <cmetcalf@tilera.com>
parent 5f639fdc

arch/tile/include/asm/traps.h

+5 −1
Original line number Diff line number Diff line
@@ -64,7 +64,11 @@ void do_breakpoint(struct pt_regs *, int fault_num); 




#ifdef __tilegx__

/* kernel/single_step.c */

void gx_singlestep_handle(struct pt_regs *, int fault_num);



/* kernel/intvec_64.S */

void fill_ra_stack(void);

#endif



#endif /* _ASM_TILE_SYSCALLS_H */
 
#endif /* _ASM_TILE_TRAPS_H */

arch/tile/kernel/intvec_64.S

+12 −0
Original line number Diff line number Diff line
@@ -1156,6 +1156,18 @@ int_unalign: 
	push_extra_callee_saves r0

	j       do_trap



/* Fill the return address stack with nonzero entries. */

STD_ENTRY(fill_ra_stack)

	{

	 move	r0, lr

	 jal	1f

	}

1:	jal	2f

2:	jal	3f

3:	jal	4f

4:	jrp	r0

	STD_ENDPROC(fill_ra_stack)



/* Include .intrpt1 array of interrupt vectors */

	.section ".intrpt1", "ax"

arch/tile/kernel/traps.c

+5 −1
Original line number Diff line number Diff line
@@ -289,7 +289,10 @@ void __kprobes do_trap(struct pt_regs *regs, int fault_num, 
		address = regs->pc;

		break;

#ifdef __tilegx__

	case INT_ILL_TRANS:

	case INT_ILL_TRANS: {

		/* Avoid a hardware erratum with the return address stack. */

		fill_ra_stack();



		signo = SIGSEGV;

		code = SEGV_MAPERR;

		if (reason & SPR_ILL_TRANS_REASON__I_STREAM_VA_RMASK)
@@ -297,6 +300,7 @@ void __kprobes do_trap(struct pt_regs *regs, int fault_num, 
		else

			address = 0;  /* FIXME: GX: single-step for address */

		break;

	}

#endif

	default:

		panic("Unexpected do_trap interrupt number %d", fault_num);