| Message ID | 1383244738-5986-4-git-send-email-tommusta@gmail.com (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
On Thu, 2013-10-31 at 13:38 -0500, Tom wrote: > From: Tom Musta <tommusta@gmail.com> > > This patch addresses unaligned single precision floating point loads > and stores in the single-step code. The old implementation > improperly treated an 8 byte structure as an array of two 4 byte > words, which is a classic little endian bug. Do that patch differ from v1 ? I also already merged v1 of this one (the only one I didn't merge is the emulate_step one) Cheers, Ben. > Signed-off-by: Tom Musta <tommusta@gmail.com> > --- > arch/powerpc/lib/sstep.c | 52 +++++++++++++++++++++++++++++++++++---------- > 1 files changed, 40 insertions(+), 12 deletions(-) > > diff --git a/arch/powerpc/lib/sstep.c b/arch/powerpc/lib/sstep.c > index c8743e1..1cfd150 100644 > --- a/arch/powerpc/lib/sstep.c > +++ b/arch/powerpc/lib/sstep.c > @@ -355,22 +355,36 @@ static int __kprobes do_fp_load(int rn, int (*func)(int, unsigned long), > struct pt_regs *regs) > { > int err; > - unsigned long val[sizeof(double) / sizeof(long)]; > + union { > + double dbl; > + unsigned long ul[2]; > + struct { > +#ifdef __BIG_ENDIAN__ > + unsigned _pad_; > + unsigned word; > +#endif > +#ifdef __LITTLE_ENDIAN__ > + unsigned word; > + unsigned _pad_; > +#endif > + } single; > + } data; > unsigned long ptr; > > if (!address_ok(regs, ea, nb)) > return -EFAULT; > if ((ea & 3) == 0) > return (*func)(rn, ea); > - ptr = (unsigned long) &val[0]; > + ptr = (unsigned long) &data.ul; > if (sizeof(unsigned long) == 8 || nb == 4) { > - err = read_mem_unaligned(&val[0], ea, nb, regs); > - ptr += sizeof(unsigned long) - nb; > + err = read_mem_unaligned(&data.ul[0], ea, nb, regs); > + if (nb == 4) > + ptr = (unsigned long)&(data.single.word); > } else { > /* reading a double on 32-bit */ > - err = read_mem_unaligned(&val[0], ea, 4, regs); > + err = read_mem_unaligned(&data.ul[0], ea, 4, regs); > if (!err) > - err = read_mem_unaligned(&val[1], ea + 4, 4, regs); > + err = read_mem_unaligned(&data.ul[1], ea + 4, 4, regs); > } > if (err) > return err; > @@ -382,28 +396,42 @@ static int __kprobes do_fp_store(int rn, int (*func)(int, unsigned long), > struct pt_regs *regs) > { > int err; > - unsigned long val[sizeof(double) / sizeof(long)]; > + union { > + double dbl; > + unsigned long ul[2]; > + struct { > +#ifdef __BIG_ENDIAN__ > + unsigned _pad_; > + unsigned word; > +#endif > +#ifdef __LITTLE_ENDIAN__ > + unsigned word; > + unsigned _pad_; > +#endif > + } single; > + } data; > unsigned long ptr; > > if (!address_ok(regs, ea, nb)) > return -EFAULT; > if ((ea & 3) == 0) > return (*func)(rn, ea); > - ptr = (unsigned long) &val[0]; > + ptr = (unsigned long) &data.ul[0]; > if (sizeof(unsigned long) == 8 || nb == 4) { > - ptr += sizeof(unsigned long) - nb; > + if (nb == 4) > + ptr = (unsigned long)&(data.single.word); > err = (*func)(rn, ptr); > if (err) > return err; > - err = write_mem_unaligned(val[0], ea, nb, regs); > + err = write_mem_unaligned(data.ul[0], ea, nb, regs); > } else { > /* writing a double on 32-bit */ > err = (*func)(rn, ptr); > if (err) > return err; > - err = write_mem_unaligned(val[0], ea, 4, regs); > + err = write_mem_unaligned(data.ul[0], ea, 4, regs); > if (!err) > - err = write_mem_unaligned(val[1], ea + 4, 4, regs); > + err = write_mem_unaligned(data.ul[1], ea + 4, 4, regs); > } > return err; > }
On 11/3/2013 8:34 PM, Benjamin Herrenschmidt wrote: > On Thu, 2013-10-31 at 13:38 -0500, Tom wrote: >> From: Tom Musta <tommusta@gmail.com> >> >> This patch addresses unaligned single precision floating point loads >> and stores in the single-step code. The old implementation >> improperly treated an 8 byte structure as an array of two 4 byte >> words, which is a classic little endian bug. > > Do that patch differ from v1 ? I also already merged v1 of this > one (the only one I didn't merge is the emulate_step one) > > Cheers, > Ben. > Ben: Only patch 1/3 (Enable emulate_step in Little Endian Mode) differs in V2.
On Thu, Oct 31, 2013 at 01:38:58PM -0500, Tom wrote: > From: Tom Musta <tommusta@gmail.com> > > This patch addresses unaligned single precision floating point loads > and stores in the single-step code. The old implementation > improperly treated an 8 byte structure as an array of two 4 byte > words, which is a classic little endian bug. > > Signed-off-by: Tom Musta <tommusta@gmail.com> > --- > arch/powerpc/lib/sstep.c | 52 +++++++++++++++++++++++++++++++++++---------- > 1 files changed, 40 insertions(+), 12 deletions(-) > > diff --git a/arch/powerpc/lib/sstep.c b/arch/powerpc/lib/sstep.c > index c8743e1..1cfd150 100644 > --- a/arch/powerpc/lib/sstep.c > +++ b/arch/powerpc/lib/sstep.c > @@ -355,22 +355,36 @@ static int __kprobes do_fp_load(int rn, int (*func)(int, unsigned long), > struct pt_regs *regs) > { > int err; > - unsigned long val[sizeof(double) / sizeof(long)]; > + union { > + double dbl; > + unsigned long ul[2]; > + struct { > +#ifdef __BIG_ENDIAN__ > + unsigned _pad_; > + unsigned word; > +#endif > +#ifdef __LITTLE_ENDIAN__ > + unsigned word; > + unsigned _pad_; > +#endif > + } single; > + } data; > unsigned long ptr; > > if (!address_ok(regs, ea, nb)) > return -EFAULT; > if ((ea & 3) == 0) > return (*func)(rn, ea); > - ptr = (unsigned long) &val[0]; > + ptr = (unsigned long) &data.ul; > if (sizeof(unsigned long) == 8 || nb == 4) { > - err = read_mem_unaligned(&val[0], ea, nb, regs); > - ptr += sizeof(unsigned long) - nb; > + err = read_mem_unaligned(&data.ul[0], ea, nb, regs); > + if (nb == 4) > + ptr = (unsigned long)&(data.single.word); > } else { > /* reading a double on 32-bit */ > - err = read_mem_unaligned(&val[0], ea, 4, regs); > + err = read_mem_unaligned(&data.ul[0], ea, 4, regs); > if (!err) > - err = read_mem_unaligned(&val[1], ea + 4, 4, regs); > + err = read_mem_unaligned(&data.ul[1], ea + 4, 4, regs); This breaks 32-bit big-endian (as well as making the code longer and more complex). In fact, to make this work for 64-bit little-endian, all you really needed to do was ifdef out the statement: ptr += sizeof(unsigned long) - nb; Paul.
On Wed, Dec 11, 2013 at 02:54:40PM +1100, Paul Mackerras wrote: > On Thu, Oct 31, 2013 at 01:38:58PM -0500, Tom wrote: > > From: Tom Musta <tommusta@gmail.com> > > > > This patch addresses unaligned single precision floating point loads > > and stores in the single-step code. The old implementation > > improperly treated an 8 byte structure as an array of two 4 byte > > words, which is a classic little endian bug. > > > > Signed-off-by: Tom Musta <tommusta@gmail.com> > > --- > > arch/powerpc/lib/sstep.c | 52 +++++++++++++++++++++++++++++++++++---------- > > 1 files changed, 40 insertions(+), 12 deletions(-) > > > > diff --git a/arch/powerpc/lib/sstep.c b/arch/powerpc/lib/sstep.c > > index c8743e1..1cfd150 100644 > > --- a/arch/powerpc/lib/sstep.c > > +++ b/arch/powerpc/lib/sstep.c > > @@ -355,22 +355,36 @@ static int __kprobes do_fp_load(int rn, int (*func)(int, unsigned long), > > struct pt_regs *regs) > > { > > int err; > > - unsigned long val[sizeof(double) / sizeof(long)]; > > + union { > > + double dbl; > > + unsigned long ul[2]; > > + struct { > > +#ifdef __BIG_ENDIAN__ > > + unsigned _pad_; > > + unsigned word; > > +#endif > > +#ifdef __LITTLE_ENDIAN__ > > + unsigned word; > > + unsigned _pad_; > > +#endif > > + } single; > > + } data; > > unsigned long ptr; > > > > if (!address_ok(regs, ea, nb)) > > return -EFAULT; > > if ((ea & 3) == 0) > > return (*func)(rn, ea); > > - ptr = (unsigned long) &val[0]; > > + ptr = (unsigned long) &data.ul; > > if (sizeof(unsigned long) == 8 || nb == 4) { > > - err = read_mem_unaligned(&val[0], ea, nb, regs); > > - ptr += sizeof(unsigned long) - nb; > > + err = read_mem_unaligned(&data.ul[0], ea, nb, regs); > > + if (nb == 4) > > + ptr = (unsigned long)&(data.single.word); > > } else { > > /* reading a double on 32-bit */ > > - err = read_mem_unaligned(&val[0], ea, 4, regs); > > + err = read_mem_unaligned(&data.ul[0], ea, 4, regs); > > if (!err) > > - err = read_mem_unaligned(&val[1], ea + 4, 4, regs); > > + err = read_mem_unaligned(&data.ul[1], ea + 4, 4, regs); > > This breaks 32-bit big-endian (as well as making the code longer and > more complex). And in fact none of this code will get executed in little-endian mode anyway, since we still have this in the middle of emulate_step(): /* * Following cases are for loads and stores, so bail out * if we're in little-endian mode. */ if (regs->msr & MSR_LE) return 0; Paul.
On 12/10/2013 10:57 PM, Paul Mackerras wrote: > On Wed, Dec 11, 2013 at 02:54:40PM +1100, Paul Mackerras wrote: >> This breaks 32-bit big-endian (as well as making the code longer and >> more complex). > > And in fact none of this code will get executed in little-endian mode > anyway, since we still have this in the middle of emulate_step(): > > /* > * Following cases are for loads and stores, so bail out > * if we're in little-endian mode. > */ > if (regs->msr & MSR_LE) > return 0; > > Paul. > See patch 1/3 to explain how it becomes relevant in LE. I will take another look at the change.
On 12/12/2013 9:08 AM, Tom Musta wrote: > On 12/10/2013 10:57 PM, Paul Mackerras wrote: >> On Wed, Dec 11, 2013 at 02:54:40PM +1100, Paul Mackerras wrote: > >>> This breaks 32-bit big-endian (as well as making the code longer and >>> more complex). >> >> And in fact none of this code will get executed in little-endian mode >> anyway, since we still have this in the middle of emulate_step(): >> >> /* >> * Following cases are for loads and stores, so bail out >> * if we're in little-endian mode. >> */ >> if (regs->msr & MSR_LE) >> return 0; >> >> Paul. >> > > See patch 1/3 to explain how it becomes relevant in LE. > > I will take another look at the change. > It appears that patch 1/3 never got picked up, even though I thought Ben & I had worked through that. And I agree that the code could be simpler. I will work up a patch to address these two issues.
On Thu, Dec 12, 2013 at 02:33:36PM -0600, Tom Musta wrote: > On 12/12/2013 9:08 AM, Tom Musta wrote: > > On 12/10/2013 10:57 PM, Paul Mackerras wrote: > >> On Wed, Dec 11, 2013 at 02:54:40PM +1100, Paul Mackerras wrote: > > > >>> This breaks 32-bit big-endian (as well as making the code longer and > >>> more complex). > >> > >> And in fact none of this code will get executed in little-endian mode > >> anyway, since we still have this in the middle of emulate_step(): > >> > >> /* > >> * Following cases are for loads and stores, so bail out > >> * if we're in little-endian mode. > >> */ > >> if (regs->msr & MSR_LE) > >> return 0; > >> > >> Paul. > >> > > > > See patch 1/3 to explain how it becomes relevant in LE. > > > > I will take another look at the change. > > > > It appears that patch 1/3 never got picked up, even though I thought Ben & I > had worked through that. > > And I agree that the code could be simpler. I will work up a patch to address > these two issues. The other thing that's important for us to know is how you are testing these changes. For something like this I'd like to see a description of the tests you have done in the commit message. I have been hacking on sstep.c pretty heavily myself recently, so we will need to coordinate on the changes. Paul.
diff --git a/arch/powerpc/lib/sstep.c b/arch/powerpc/lib/sstep.c index c8743e1..1cfd150 100644 --- a/arch/powerpc/lib/sstep.c +++ b/arch/powerpc/lib/sstep.c @@ -355,22 +355,36 @@ static int __kprobes do_fp_load(int rn, int (*func)(int, unsigned long), struct pt_regs *regs) { int err; - unsigned long val[sizeof(double) / sizeof(long)]; + union { + double dbl; + unsigned long ul[2]; + struct { +#ifdef __BIG_ENDIAN__ + unsigned _pad_; + unsigned word; +#endif +#ifdef __LITTLE_ENDIAN__ + unsigned word; + unsigned _pad_; +#endif + } single; + } data; unsigned long ptr; if (!address_ok(regs, ea, nb)) return -EFAULT; if ((ea & 3) == 0) return (*func)(rn, ea); - ptr = (unsigned long) &val[0]; + ptr = (unsigned long) &data.ul; if (sizeof(unsigned long) == 8 || nb == 4) { - err = read_mem_unaligned(&val[0], ea, nb, regs); - ptr += sizeof(unsigned long) - nb; + err = read_mem_unaligned(&data.ul[0], ea, nb, regs); + if (nb == 4) + ptr = (unsigned long)&(data.single.word); } else { /* reading a double on 32-bit */ - err = read_mem_unaligned(&val[0], ea, 4, regs); + err = read_mem_unaligned(&data.ul[0], ea, 4, regs); if (!err) - err = read_mem_unaligned(&val[1], ea + 4, 4, regs); + err = read_mem_unaligned(&data.ul[1], ea + 4, 4, regs); } if (err) return err; @@ -382,28 +396,42 @@ static int __kprobes do_fp_store(int rn, int (*func)(int, unsigned long), struct pt_regs *regs) { int err; - unsigned long val[sizeof(double) / sizeof(long)]; + union { + double dbl; + unsigned long ul[2]; + struct { +#ifdef __BIG_ENDIAN__ + unsigned _pad_; + unsigned word; +#endif +#ifdef __LITTLE_ENDIAN__ + unsigned word; + unsigned _pad_; +#endif + } single; + } data; unsigned long ptr; if (!address_ok(regs, ea, nb)) return -EFAULT; if ((ea & 3) == 0) return (*func)(rn, ea); - ptr = (unsigned long) &val[0]; + ptr = (unsigned long) &data.ul[0]; if (sizeof(unsigned long) == 8 || nb == 4) { - ptr += sizeof(unsigned long) - nb; + if (nb == 4) + ptr = (unsigned long)&(data.single.word); err = (*func)(rn, ptr); if (err) return err; - err = write_mem_unaligned(val[0], ea, nb, regs); + err = write_mem_unaligned(data.ul[0], ea, nb, regs); } else { /* writing a double on 32-bit */ err = (*func)(rn, ptr); if (err) return err; - err = write_mem_unaligned(val[0], ea, 4, regs); + err = write_mem_unaligned(data.ul[0], ea, 4, regs); if (!err) - err = write_mem_unaligned(val[1], ea + 4, 4, regs); + err = write_mem_unaligned(data.ul[1], ea + 4, 4, regs); } return err; }