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 <jniet...@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
