[v4,13/16] powerpc: Support prefixed instructions in alignment handler
diff mbox series

Message ID 20200320051809.24332-14-jniethe5@gmail.com
State New
Headers show
Series
  • Initial Prefixed Instruction support
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Commit Message

Jordan Niethe March 20, 2020, 5:18 a.m. UTC
Alignment interrupts can be caused by prefixed instructions accessing
memory. 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: Jordan Niethe <jniethe5@gmail.com>
---
v2: - Move __get_user_instr() and __get_user_instr_inatomic() to this
commit (previously in "powerpc sstep: Prepare to support prefixed
instructions").
    - Rename sufx to suffix
    - Use a macro for calculating instruction length
v3: Move __get_user_{instr(), instr_inatomic()} up with the other
get_user definitions and remove nested if.
v4: Just do the things for alignment_exception(). Other changes handled
elsewhere.
---
 arch/powerpc/kernel/traps.c | 21 ++++++++++++++++++++-
 1 file changed, 20 insertions(+), 1 deletion(-)

Comments

Nicholas Piggin March 23, 2020, 7:05 a.m. UTC | #1
Jordan Niethe's on March 20, 2020 3:18 pm:
> Alignment interrupts can be caused by prefixed instructions accessing
> memory. 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: Jordan Niethe <jniethe5@gmail.com>
> ---
> v2: - Move __get_user_instr() and __get_user_instr_inatomic() to this
> commit (previously in "powerpc sstep: Prepare to support prefixed
> instructions").
>     - Rename sufx to suffix
>     - Use a macro for calculating instruction length
> v3: Move __get_user_{instr(), instr_inatomic()} up with the other
> get_user definitions and remove nested if.
> v4: Just do the things for alignment_exception(). Other changes handled
> elsewhere.
> ---
>  arch/powerpc/kernel/traps.c | 21 ++++++++++++++++++++-
>  1 file changed, 20 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/powerpc/kernel/traps.c b/arch/powerpc/kernel/traps.c
> index a4764b039749..cd8b3043c268 100644
> --- a/arch/powerpc/kernel/traps.c
> +++ b/arch/powerpc/kernel/traps.c
> @@ -583,6 +583,10 @@ 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
> +
> +#define inst_length(reason)	4
>  
>  /* single-step stuff */
>  #define single_stepping(regs)	(current->thread.debug.dbcr0 & DBCR0_IC)
> @@ -597,6 +601,10 @@ 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 inst_length(reason)	(((reason) & REASON_PREFIXED) ? 8 : 4)

Looks good. If you define REASON_BOUNDARY 0, then this will constant
fold away so no need to define it twice.

Thanks,
Nick
Jordan Niethe March 23, 2020, 9:35 a.m. UTC | #2
On Mon, Mar 23, 2020 at 6:09 PM Nicholas Piggin <npiggin@gmail.com> wrote:
>
> Jordan Niethe's on March 20, 2020 3:18 pm:
> > Alignment interrupts can be caused by prefixed instructions accessing
> > memory. 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: Jordan Niethe <jniethe5@gmail.com>
> > ---
> > v2: - Move __get_user_instr() and __get_user_instr_inatomic() to this
> > commit (previously in "powerpc sstep: Prepare to support prefixed
> > instructions").
> >     - Rename sufx to suffix
> >     - Use a macro for calculating instruction length
> > v3: Move __get_user_{instr(), instr_inatomic()} up with the other
> > get_user definitions and remove nested if.
> > v4: Just do the things for alignment_exception(). Other changes handled
> > elsewhere.
> > ---
> >  arch/powerpc/kernel/traps.c | 21 ++++++++++++++++++++-
> >  1 file changed, 20 insertions(+), 1 deletion(-)
> >
> > diff --git a/arch/powerpc/kernel/traps.c b/arch/powerpc/kernel/traps.c
> > index a4764b039749..cd8b3043c268 100644
> > --- a/arch/powerpc/kernel/traps.c
> > +++ b/arch/powerpc/kernel/traps.c
> > @@ -583,6 +583,10 @@ 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
> > +
> > +#define inst_length(reason)  4
> >
> >  /* single-step stuff */
> >  #define single_stepping(regs)        (current->thread.debug.dbcr0 & DBCR0_IC)
> > @@ -597,6 +601,10 @@ 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 inst_length(reason)  (((reason) & REASON_PREFIXED) ? 8 : 4)
>
> Looks good. If you define REASON_BOUNDARY 0, then this will constant
> fold away so no need to define it twice.
Good point.
>
> Thanks,
> Nick

Patch
diff mbox series

diff --git a/arch/powerpc/kernel/traps.c b/arch/powerpc/kernel/traps.c
index a4764b039749..cd8b3043c268 100644
--- a/arch/powerpc/kernel/traps.c
+++ b/arch/powerpc/kernel/traps.c
@@ -583,6 +583,10 @@  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
+
+#define inst_length(reason)	4
 
 /* single-step stuff */
 #define single_stepping(regs)	(current->thread.debug.dbcr0 & DBCR0_IC)
@@ -597,6 +601,10 @@  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 inst_length(reason)	(((reason) & REASON_PREFIXED) ? 8 : 4)
 
 #define single_stepping(regs)	((regs)->msr & MSR_SE)
 #define clear_single_step(regs)	((regs)->msr &= ~MSR_SE)
@@ -1593,11 +1601,20 @@  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;
 
@@ -1606,7 +1623,8 @@  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;
 	}
@@ -1619,6 +1637,7 @@  void alignment_exception(struct pt_regs *regs)
 		sig = SIGBUS;
 		code = BUS_ADRALN;
 	}
+bad:
 	if (user_mode(regs))
 		_exception(sig, regs, code, regs->dar);
 	else