| Message ID | 20100323140702.GB21836@in.ibm.com (mailing list archive) |
|---|---|
| State | Superseded |
| Delegated to: | Benjamin Herrenschmidt |
| Headers | show |
On Tue, Mar 23, 2010 at 07:37:02PM +0530, K.Prasad wrote: > Index: linux-2.6.ppc64_test/arch/powerpc/kernel/exceptions-64s.S > =================================================================== > --- linux-2.6.ppc64_test.orig/arch/powerpc/kernel/exceptions-64s.S > +++ linux-2.6.ppc64_test/arch/powerpc/kernel/exceptions-64s.S > @@ -735,6 +735,9 @@ _STATIC(do_hash_page) > std r3,_DAR(r1) > std r4,_DSISR(r1) > > + andis. r0,r4,0x0040 /* Data Address Breakpoint match? */ Minor comment: why not DSISR_DABRMATCH@h instead of 0x0040? > + bne- handle_dabr_fault > + > andis. r0,r4,0xa450 /* weird error? */ > bne- handle_page_fault /* if not, try to insert a HPTE */ > BEGIN_FTR_SECTION > @@ -823,6 +826,15 @@ END_FW_FTR_SECTION_IFCLR(FW_FEATURE_ISER > bl .raw_local_irq_restore > b 11f > > +/* We have a data breakpoint exception - handle it */ > +handle_dabr_fault: > + /* Populate the pt_regs structure */ Another minor comment: that comment isn't accurate since you're not putting anything in the pt_regs, just getting arguments to do_dabr from it. > + ld r4,_DAR(r1) > + ld r5,_DSISR(r1) > + addi r3,r1,STACK_FRAME_OVERHEAD > + bl .do_dabr > + b .ret_from_except_lite > + > /* Here we have a page fault that hash_page can't handle. */ > handle_page_fault: > ENABLE_INTS > Index: linux-2.6.ppc64_test/arch/powerpc/mm/fault.c > =================================================================== > --- linux-2.6.ppc64_test.orig/arch/powerpc/mm/fault.c > +++ linux-2.6.ppc64_test/arch/powerpc/mm/fault.c > @@ -151,7 +151,7 @@ int __kprobes do_page_fault(struct pt_re > if (!user_mode(regs) && (address >= TASK_SIZE)) > return SIGSEGV; > > -#if !(defined(CONFIG_4xx) || defined(CONFIG_BOOKE)) > +#if !(defined(CONFIG_4xx) || defined(CONFIG_BOOKE) || defined(CONFIG_PPC64)) If we added similar code to head_32.S, we could probably remove this whole ifdef block. But that can be done in a later patch. Paul.
On Tue, 2010-03-30 at 16:24 +1100, Paul Mackerras wrote: > On Tue, Mar 23, 2010 at 07:37:02PM +0530, K.Prasad wrote: > > > Index: linux-2.6.ppc64_test/arch/powerpc/kernel/exceptions-64s.S > > =================================================================== > > --- linux-2.6.ppc64_test.orig/arch/powerpc/kernel/exceptions-64s.S > > +++ linux-2.6.ppc64_test/arch/powerpc/kernel/exceptions-64s.S > > @@ -735,6 +735,9 @@ _STATIC(do_hash_page) > > std r3,_DAR(r1) > > std r4,_DSISR(r1) > > > > + andis. r0,r4,0x0040 /* Data Address Breakpoint match? */ > > Minor comment: why not DSISR_DABRMATCH@h instead of 0x0040? > > > + bne- handle_dabr_fault > > + > > andis. r0,r4,0xa450 /* weird error? */ > > bne- handle_page_fault /* if not, try to insert a HPTE */ > > BEGIN_FTR_SECTION > > @@ -823,6 +826,15 @@ END_FW_FTR_SECTION_IFCLR(FW_FEATURE_ISER > > bl .raw_local_irq_restore > > b 11f I would move your new test to the "weird error" case (ie, after the bne- handle_page_fault) to avoid hitting the fast path. Cheers, Ben.
On Tue, Mar 30, 2010 at 04:24:42PM +1100, Paul Mackerras wrote: > On Tue, Mar 23, 2010 at 07:37:02PM +0530, K.Prasad wrote: > > > Index: linux-2.6.ppc64_test/arch/powerpc/kernel/exceptions-64s.S > > =================================================================== > > --- linux-2.6.ppc64_test.orig/arch/powerpc/kernel/exceptions-64s.S > > +++ linux-2.6.ppc64_test/arch/powerpc/kernel/exceptions-64s.S > > @@ -735,6 +735,9 @@ _STATIC(do_hash_page) > > std r3,_DAR(r1) > > std r4,_DSISR(r1) > > > > + andis. r0,r4,0x0040 /* Data Address Breakpoint match? */ > > Minor comment: why not DSISR_DABRMATCH@h instead of 0x0040? > Sure...I didn't realise that the upper 16-bits could be extracted as shown above....I've implemented the suggestion in the next version of the patch sent here: linuxppc-dev message-id:20100330095809.GA14403@in.ibm.com. > > + bne- handle_dabr_fault > > + > > andis. r0,r4,0xa450 /* weird error? */ > > bne- handle_page_fault /* if not, try to insert a HPTE */ > > BEGIN_FTR_SECTION > > @@ -823,6 +826,15 @@ END_FW_FTR_SECTION_IFCLR(FW_FEATURE_ISER > > bl .raw_local_irq_restore > > b 11f > > > > +/* We have a data breakpoint exception - handle it */ > > +handle_dabr_fault: > > + /* Populate the pt_regs structure */ > > Another minor comment: that comment isn't accurate since you're not > putting anything in the pt_regs, just getting arguments to do_dabr > from it. > Thanks for pointing it out...it has been removed. Thanks, K.Prasad
On Tue, Mar 30, 2010 at 04:32:25PM +1100, Benjamin Herrenschmidt wrote: > On Tue, 2010-03-30 at 16:24 +1100, Paul Mackerras wrote: > > On Tue, Mar 23, 2010 at 07:37:02PM +0530, K.Prasad wrote: > > > > > Index: linux-2.6.ppc64_test/arch/powerpc/kernel/exceptions-64s.S > > > =================================================================== > > > --- linux-2.6.ppc64_test.orig/arch/powerpc/kernel/exceptions-64s.S > > > +++ linux-2.6.ppc64_test/arch/powerpc/kernel/exceptions-64s.S > > > @@ -735,6 +735,9 @@ _STATIC(do_hash_page) > > > std r3,_DAR(r1) > > > std r4,_DSISR(r1) > > > > > > + andis. r0,r4,0x0040 /* Data Address Breakpoint match? */ > > > > Minor comment: why not DSISR_DABRMATCH@h instead of 0x0040? > > > > > + bne- handle_dabr_fault > > > + > > > andis. r0,r4,0xa450 /* weird error? */ > > > bne- handle_page_fault /* if not, try to insert a HPTE */ > > > BEGIN_FTR_SECTION > > > @@ -823,6 +826,15 @@ END_FW_FTR_SECTION_IFCLR(FW_FEATURE_ISER > > > bl .raw_local_irq_restore > > > b 11f > > I would move your new test to the "weird error" case (ie, after the bne- > handle_page_fault) to avoid hitting the fast path. > Done that...so basically the branch to handle_page_fault will happen only if 0xa410 matches. The changes can be seen here: linuxppc-dev: message-id: 20100330095925.GB14403@in.ibm.com. Thanks, K.Prasad
Index: linux-2.6.ppc64_test/arch/powerpc/kernel/exceptions-64s.S =================================================================== --- linux-2.6.ppc64_test.orig/arch/powerpc/kernel/exceptions-64s.S +++ linux-2.6.ppc64_test/arch/powerpc/kernel/exceptions-64s.S @@ -735,6 +735,9 @@ _STATIC(do_hash_page) std r3,_DAR(r1) std r4,_DSISR(r1) + andis. r0,r4,0x0040 /* Data Address Breakpoint match? */ + bne- handle_dabr_fault + andis. r0,r4,0xa450 /* weird error? */ bne- handle_page_fault /* if not, try to insert a HPTE */ BEGIN_FTR_SECTION @@ -823,6 +826,15 @@ END_FW_FTR_SECTION_IFCLR(FW_FEATURE_ISER bl .raw_local_irq_restore b 11f +/* We have a data breakpoint exception - handle it */ +handle_dabr_fault: + /* Populate the pt_regs structure */ + ld r4,_DAR(r1) + ld r5,_DSISR(r1) + addi r3,r1,STACK_FRAME_OVERHEAD + bl .do_dabr + b .ret_from_except_lite + /* Here we have a page fault that hash_page can't handle. */ handle_page_fault: ENABLE_INTS Index: linux-2.6.ppc64_test/arch/powerpc/mm/fault.c =================================================================== --- linux-2.6.ppc64_test.orig/arch/powerpc/mm/fault.c +++ linux-2.6.ppc64_test/arch/powerpc/mm/fault.c @@ -151,7 +151,7 @@ int __kprobes do_page_fault(struct pt_re if (!user_mode(regs) && (address >= TASK_SIZE)) return SIGSEGV; -#if !(defined(CONFIG_4xx) || defined(CONFIG_BOOKE)) +#if !(defined(CONFIG_4xx) || defined(CONFIG_BOOKE) || defined(CONFIG_PPC64)) if (error_code & DSISR_DABRMATCH) { /* DABR match */ do_dabr(regs, address, error_code);
Data address breakpoint exceptions are currently handled along with page-faults which require interrupts to remain in enabled state. Since exception handling for data breakpoints aren't pre-empt safe, we handle them separately. Signed-off-by: K.Prasad <prasad@linux.vnet.ibm.com> --- arch/powerpc/kernel/exceptions-64s.S | 12 ++++++++++++ arch/powerpc/mm/fault.c | 2 +- 2 files changed, 13 insertions(+), 1 deletion(-)