Commit 5cc5f19f authored by Max Filippov's avatar Max Filippov
Browse files

xtensa: improve call0 ABI probing 



When call0 userspace ABI support by probing is enabled instructions that
cause illegal instruction exception when PS.WOE is clear are retried
with PS.WOE set before calling c-level exception handler. Record user pc
at which PS.WOE was set in the fast exception handler and clear PS.WOE
in the c-level exception handler if we get there from the same address.

Signed-off-by: default avatarMax Filippov <jcmvbkbc@gmail.com>
parent d7486200

arch/xtensa/include/asm/thread_info.h

+4 −0
Original line number Diff line number Diff line
@@ -56,6 +56,10 @@ struct thread_info { 
	/* result of the most recent exclusive store */

	unsigned long		atomctl8;

#endif

#ifdef CONFIG_USER_ABI_CALL0_PROBE

	/* Address where PS.WOE was enabled by the ABI probing code */

	unsigned long		ps_woe_fix_addr;

#endif



	/*

	 * If i-th bit is set then coprocessor state is loaded into the

arch/xtensa/kernel/asm-offsets.c

+3 −0
Original line number Diff line number Diff line
@@ -88,6 +88,9 @@ int main(void) 
	OFFSET(TI_STSTUS, thread_info, status);

	OFFSET(TI_CPU, thread_info, cpu);

	OFFSET(TI_PRE_COUNT, thread_info, preempt_count);

#ifdef CONFIG_USER_ABI_CALL0_PROBE

	OFFSET(TI_PS_WOE_FIX_ADDR, thread_info, ps_woe_fix_addr);

#endif



	/* struct thread_info (offset from start_struct) */

	DEFINE(THREAD_RA, offsetof (struct task_struct, thread.ra));

arch/xtensa/kernel/entry.S

+5 −0
Original line number Diff line number Diff line
@@ -1056,6 +1056,11 @@ ENTRY(fast_illegal_instruction_user) 
	movi	a3, PS_WOE_MASK

	or	a0, a0, a3

	wsr	a0, ps

#ifdef CONFIG_USER_ABI_CALL0_PROBE

	GET_THREAD_INFO(a3, a2)

	rsr	a0, epc1

	s32i	a0, a3, TI_PS_WOE_FIX_ADDR

#endif

	l32i	a3, a2, PT_AREG3

	l32i	a0, a2, PT_AREG0

	rsr	a2, depc

arch/xtensa/kernel/traps.c

+12 −0
Original line number Diff line number Diff line
@@ -317,6 +317,18 @@ static bool check_div0(struct pt_regs *regs) 


static void do_illegal_instruction(struct pt_regs *regs)

{

#ifdef CONFIG_USER_ABI_CALL0_PROBE

	/*

	 * When call0 application encounters an illegal instruction fast

	 * exception handler will attempt to set PS.WOE and retry failing

	 * instruction.

	 * If we get here we know that that instruction is also illegal

	 * with PS.WOE set, so it's not related to the windowed option

	 * hence PS.WOE may be cleared.

	 */

	if (regs->pc == current_thread_info()->ps_woe_fix_addr)

		regs->ps &= ~PS_WOE_MASK;

#endif

	if (check_div0(regs)) {

		do_div0(regs);

		return;