Alignment interrupts can be caused by prefixed instructions accessing memory. In the alignment handler the instruction that caused the exception is loaded and attempted emulate. If the instruction is a prefixed instruction load the prefix and suffix to emulate. After emulating increment the NIP by 8.
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. --- arch/powerpc/include/asm/uaccess.h | 25 +++++++++++++++++++++++++ arch/powerpc/kernel/align.c | 8 +++++--- arch/powerpc/kernel/traps.c | 21 ++++++++++++++++++++- 3 files changed, 50 insertions(+), 4 deletions(-) diff --git a/arch/powerpc/include/asm/uaccess.h b/arch/powerpc/include/asm/uaccess.h index 2f500debae21..8903a96cbb4b 100644 --- a/arch/powerpc/include/asm/uaccess.h +++ b/arch/powerpc/include/asm/uaccess.h @@ -105,6 +105,31 @@ static inline int __access_ok(unsigned long addr, unsigned long size, #define __put_user_inatomic(x, ptr) \ __put_user_nosleep((__typeof__(*(ptr)))(x), (ptr), sizeof(*(ptr))) +/* + * When reading an instruction iff it is a prefix, the suffix needs to be also + * loaded. + */ +#define __get_user_instr(x, y, ptr) \ +({ \ + long __gui_ret = 0; \ + y = 0; \ + __gui_ret = __get_user(x, ptr); \ + if (!__gui_ret && IS_PREFIX(x)) \ + __gui_ret = __get_user(y, ptr + 1); \ + __gui_ret; \ +}) + +#define __get_user_instr_inatomic(x, y, ptr) \ +({ \ + long __gui_ret = 0; \ + y = 0; \ + __gui_ret = __get_user_inatomic(x, ptr); \ + if (!__gui_ret && IS_PREFIX(x)) \ + __gui_ret = __get_user_inatomic(y, ptr + 1); \ + __gui_ret; \ +}) + + extern long __put_user_bad(void); /* diff --git a/arch/powerpc/kernel/align.c b/arch/powerpc/kernel/align.c index ba3bf5c3ab62..4984cf681215 100644 --- a/arch/powerpc/kernel/align.c +++ b/arch/powerpc/kernel/align.c @@ -293,7 +293,7 @@ static int emulate_spe(struct pt_regs *regs, unsigned int reg, int fix_alignment(struct pt_regs *regs) { - unsigned int instr; + unsigned int instr, suffix; struct instruction_op op; int r, type; @@ -303,13 +303,15 @@ int fix_alignment(struct pt_regs *regs) */ CHECK_FULL_REGS(regs); - if (unlikely(__get_user(instr, (unsigned int __user *)regs->nip))) + if (unlikely(__get_user_instr(instr, suffix, + (unsigned int __user *)regs->nip))) return -EFAULT; if ((regs->msr & MSR_LE) != (MSR_KERNEL & MSR_LE)) { /* We don't handle PPC little-endian any more... */ if (cpu_has_feature(CPU_FTR_PPC_LE)) return -EIO; instr = swab32(instr); + suffix = swab32(suffix); } #ifdef CONFIG_SPE @@ -334,7 +336,7 @@ int fix_alignment(struct pt_regs *regs) if ((instr & 0xfc0006fe) == (PPC_INST_COPY & 0xfc0006fe)) return -EIO; - r = analyse_instr(&op, regs, instr, PPC_NO_SUFFIX); + r = analyse_instr(&op, regs, instr, suffix); if (r < 0) return -EINVAL; diff --git a/arch/powerpc/kernel/traps.c b/arch/powerpc/kernel/traps.c index 82a3438300fd..d80b82fc1ae3 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 -- 2.17.1