Commit 9409d2f9 authored by Jordan Niethe's avatar Jordan Niethe Committed by Michael Ellerman
Browse files

powerpc: Support prefixed instructions in alignment handler 



If a prefixed instruction results in an alignment exception, the
SRR1_PREFIXED bit is set. The handler attempts to emulate the
responsible instruction and then increment the NIP past it. Use
SRR1_PREFIXED to determine by how much the NIP should be incremented.

Prefixed instructions are not permitted to cross 64-byte boundaries. If
they do the alignment interrupt is invoked with SRR1 BOUNDARY bit set.
If this occurs send a SIGBUS to the offending process if in user mode.
If in kernel mode call bad_page_fault().

Signed-off-by: default avatarJordan Niethe <jniethe5@gmail.com>
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
Reviewed-by: default avatarAlistair Popple <alistair@popple.id.au>
Link: https://lore.kernel.org/r/20200506034050.24806-29-jniethe5@gmail.com
parent b4657f76

arch/powerpc/kernel/traps.c

+18 −1
Original line number Diff line number Diff line
@@ -588,6 +588,8 @@ static inline int check_io_access(struct pt_regs *regs) 
#define REASON_ILLEGAL		(ESR_PIL | ESR_PUO)

#define REASON_PRIVILEGED	ESR_PPR

#define REASON_TRAP		ESR_PTR

#define REASON_PREFIXED		0

#define REASON_BOUNDARY		0



/* single-step stuff */

#define single_stepping(regs)	(current->thread.debug.dbcr0 & DBCR0_IC)
@@ -602,12 +604,16 @@ static inline int check_io_access(struct pt_regs *regs) 
#define REASON_ILLEGAL		SRR1_PROGILL

#define REASON_PRIVILEGED	SRR1_PROGPRIV

#define REASON_TRAP		SRR1_PROGTRAP

#define REASON_PREFIXED		SRR1_PREFIXED

#define REASON_BOUNDARY		SRR1_BOUNDARY



#define single_stepping(regs)	((regs)->msr & MSR_SE)

#define clear_single_step(regs)	((regs)->msr &= ~MSR_SE)

#define clear_br_trace(regs)	((regs)->msr &= ~MSR_BE)

#endif



#define inst_length(reason)	(((reason) & REASON_PREFIXED) ? 8 : 4)



#if defined(CONFIG_E500)

int machine_check_e500mc(struct pt_regs *regs)

{
@@ -1610,11 +1616,20 @@ void alignment_exception(struct pt_regs *regs) 
{

	enum ctx_state prev_state = exception_enter();

	int sig, code, fixed = 0;

	unsigned long  reason;



	/* We restore the interrupt state now */

	if (!arch_irq_disabled_regs(regs))

		local_irq_enable();



	reason = get_reason(regs);



	if (reason & REASON_BOUNDARY) {

		sig = SIGBUS;

		code = BUS_ADRALN;

		goto bad;

	}



	if (tm_abort_check(regs, TM_CAUSE_ALIGNMENT | TM_CAUSE_PERSISTENT))

		goto bail;
@@ -1623,7 +1638,8 @@ void alignment_exception(struct pt_regs *regs) 
		fixed = fix_alignment(regs);



	if (fixed == 1) {

		regs->nip += 4;	/* skip over emulated instruction */

		/* skip over emulated instruction */

		regs->nip += inst_length(reason);

		emulate_single_step(regs);

		goto bail;

	}
@@ -1636,6 +1652,7 @@ void alignment_exception(struct pt_regs *regs) 
		sig = SIGBUS;

		code = BUS_ADRALN;

	}

bad:

	if (user_mode(regs))

		_exception(sig, regs, code, regs->dar);

	else