On Monday 14 January 2008 10:59:24 am Luck, Tony wrote: > The compiler team did the hard work for this distilling a problem in > large fortran application which showed up when applied to a 290MB input > data set down to this instruction: > > ldfd f34=[r17],-8 > > Which they noticed incremented r17 by 0x10 rather than decrementing it > by 8 when the value in r17 caused an unaligned data fault. I tracked > it down to some bad instruction decoding in unaligned.c. The code > assumes that the 'x' bit can determine whether the instruction is > an "ldf" or "ldfp" ... which it is for opcode=6 (see table 4-29 on > page 3:302 of the SDM). But for opcode=7 the 'x' bit is irrelevent, > all variants are "ldf" instructions (see table 4-36 on page 3:306). > > Note also that interpreting the instruction as "ldfp" means that the > "paired" floating point register (f35 in the example here) will also > be corrupted. This sounds like a case of the kernel corrupting user data. Are you pushing this into the distro kernels? Do you have bugzilla numbers? > --- > > arch/ia64/kernel/unaligned.c | 11 +++++++---- > 1 file changed, 7 insertions(+), 4 deletions(-) > > --- a/arch/ia64/kernel/unaligned.c 2007-10-19 16:17:25.000000000 -0700 > +++ b/arch/ia64/kernel/unaligned.c 2008-01-11 13:17:41.877317341 -0800 > @@ -1488,16 +1488,19 @@ > case LDFA_OP: > case LDFCCLR_OP: > case LDFCNC_OP: > - case LDF_IMM_OP: > - case LDFA_IMM_OP: > - case LDFCCLR_IMM_OP: > - case LDFCNC_IMM_OP: > if (u.insn.x) > ret = emulate_load_floatpair(ifa, u.insn, regs); > else > ret = emulate_load_float(ifa, u.insn, regs); > break; > > + case LDF_IMM_OP: > + case LDFA_IMM_OP: > + case LDFCCLR_IMM_OP: > + case LDFCNC_IMM_OP: > + ret = emulate_load_float(ifa, u.insn, regs); > + break; > + > case STF_OP: > case STF_IMM_OP: > ret = emulate_store_float(ifa, u.insn, regs); > > > - > To unsubscribe from this list: send the line "unsubscribe linux-ia64" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html > - To unsubscribe from this list: send the line "unsubscribe linux-ia64" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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