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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: Chris Metcalf <cmetcalf@tilera.com>
This commit is contained in:
Chris Metcalf 2012-03-29 14:52:00 -04:00
parent 5f639fdcd8
commit e17235382d
3 changed files with 22 additions and 2 deletions
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6
arch/tile/include/asm/traps.h
View File

@ -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 */

12
arch/tile/kernel/intvec_64.S
View File

@ -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"

6
arch/tile/kernel/traps.c
View File

@ -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);