| Message ID | 20180404231943.29581-2-bsingharora@gmail.com (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | Add support for memcpy_mcsafe | expand |
On Thu, 5 Apr 2018 09:19:41 +1000 Balbir Singh <bsingharora@gmail.com> wrote: > The code currently assumes PAGE_SHIFT as the shift value of > the pfn, this works correctly (mostly) for user space pages, > but the correct thing to do is It would be good to actually explain the problem in the changelog. I would have thought pte_pfn returns a PAGE_SIZE based pfn value? > > 1. Extrace the shift value returned via the pte-walk API's ^^^ extract? > 2. Use the shift value to access the instruction address. > > Note, the final physical address still use PAGE_SHIFT for > computation. handle_ierror() is not modified and handle_derror() > is modified just for extracting the correct instruction > address. > > Fixes: ba41e1e1ccb9 ("powerpc/mce: Hookup derror (load/store) UE errors") > > Signed-off-by: Balbir Singh <bsingharora@gmail.com> > --- > arch/powerpc/kernel/mce_power.c | 17 ++++++++++------- > 1 file changed, 10 insertions(+), 7 deletions(-) > > diff --git a/arch/powerpc/kernel/mce_power.c b/arch/powerpc/kernel/mce_power.c > index fe6fc63251fe..69c8cc1e8e4f 100644 > --- a/arch/powerpc/kernel/mce_power.c > +++ b/arch/powerpc/kernel/mce_power.c > @@ -36,7 +36,8 @@ > * Convert an address related to an mm to a PFN. NOTE: we are in real > * mode, we could potentially race with page table updates. > */ > -static unsigned long addr_to_pfn(struct pt_regs *regs, unsigned long addr) > +static unsigned long addr_to_pfn(struct pt_regs *regs, unsigned long addr, > + unsigned int *shift) > { > pte_t *ptep; > unsigned long flags; > @@ -49,9 +50,9 @@ static unsigned long addr_to_pfn(struct pt_regs *regs, unsigned long addr) > > local_irq_save(flags); > if (mm == current->mm) > - ptep = find_current_mm_pte(mm->pgd, addr, NULL, NULL); > + ptep = find_current_mm_pte(mm->pgd, addr, NULL, shift); > else > - ptep = find_init_mm_pte(addr, NULL); > + ptep = find_init_mm_pte(addr, shift); > local_irq_restore(flags); > if (!ptep || pte_special(*ptep)) > return ULONG_MAX; > @@ -353,13 +354,14 @@ static int mce_find_instr_ea_and_pfn(struct pt_regs *regs, uint64_t *addr, > unsigned long pfn, instr_addr; > struct instruction_op op; > struct pt_regs tmp = *regs; > + unsigned int shift; > > - pfn = addr_to_pfn(regs, regs->nip); > + pfn = addr_to_pfn(regs, regs->nip, &shift); > if (pfn != ULONG_MAX) { > - instr_addr = (pfn << PAGE_SHIFT) + (regs->nip & ~PAGE_MASK); > + instr_addr = (pfn << shift) + (regs->nip & ((1 << shift) - 1)); > instr = *(unsigned int *)(instr_addr); > if (!analyse_instr(&op, &tmp, instr)) { > - pfn = addr_to_pfn(regs, op.ea); > + pfn = addr_to_pfn(regs, op.ea, &shift); > *addr = op.ea; > *phys_addr = (pfn << PAGE_SHIFT); > return 0; > @@ -437,7 +439,8 @@ static int mce_handle_ierror(struct pt_regs *regs, > unsigned long pfn; > > if (get_paca()->in_mce < MAX_MCE_DEPTH) { > - pfn = addr_to_pfn(regs, regs->nip); > + pfn = addr_to_pfn(regs, regs->nip, > + NULL); > if (pfn != ULONG_MAX) { > *phys_addr = > (pfn << PAGE_SHIFT);
On Thu, 5 Apr 2018 09:49:00 +1000 Nicholas Piggin <npiggin@gmail.com> wrote: > On Thu, 5 Apr 2018 09:19:41 +1000 > Balbir Singh <bsingharora@gmail.com> wrote: > > > The code currently assumes PAGE_SHIFT as the shift value of > > the pfn, this works correctly (mostly) for user space pages, > > but the correct thing to do is > > It would be good to actually explain the problem in the > changelog. I would have thought pte_pfn returns a > PAGE_SIZE based pfn value? > The issue is hidden inside of hugepte_offset() as invoked by __find_linux_pte(). I will send a new version because the code needs to do << (shift - PAGE_SHIFT) for instruction address. > > > > 1. Extrace the shift value returned via the pte-walk API's > > ^^^ extract? Thanks, yes, typo! Balbir Singh.
diff --git a/arch/powerpc/kernel/mce_power.c b/arch/powerpc/kernel/mce_power.c index fe6fc63251fe..69c8cc1e8e4f 100644 --- a/arch/powerpc/kernel/mce_power.c +++ b/arch/powerpc/kernel/mce_power.c @@ -36,7 +36,8 @@ * Convert an address related to an mm to a PFN. NOTE: we are in real * mode, we could potentially race with page table updates. */ -static unsigned long addr_to_pfn(struct pt_regs *regs, unsigned long addr) +static unsigned long addr_to_pfn(struct pt_regs *regs, unsigned long addr, + unsigned int *shift) { pte_t *ptep; unsigned long flags; @@ -49,9 +50,9 @@ static unsigned long addr_to_pfn(struct pt_regs *regs, unsigned long addr) local_irq_save(flags); if (mm == current->mm) - ptep = find_current_mm_pte(mm->pgd, addr, NULL, NULL); + ptep = find_current_mm_pte(mm->pgd, addr, NULL, shift); else - ptep = find_init_mm_pte(addr, NULL); + ptep = find_init_mm_pte(addr, shift); local_irq_restore(flags); if (!ptep || pte_special(*ptep)) return ULONG_MAX; @@ -353,13 +354,14 @@ static int mce_find_instr_ea_and_pfn(struct pt_regs *regs, uint64_t *addr, unsigned long pfn, instr_addr; struct instruction_op op; struct pt_regs tmp = *regs; + unsigned int shift; - pfn = addr_to_pfn(regs, regs->nip); + pfn = addr_to_pfn(regs, regs->nip, &shift); if (pfn != ULONG_MAX) { - instr_addr = (pfn << PAGE_SHIFT) + (regs->nip & ~PAGE_MASK); + instr_addr = (pfn << shift) + (regs->nip & ((1 << shift) - 1)); instr = *(unsigned int *)(instr_addr); if (!analyse_instr(&op, &tmp, instr)) { - pfn = addr_to_pfn(regs, op.ea); + pfn = addr_to_pfn(regs, op.ea, &shift); *addr = op.ea; *phys_addr = (pfn << PAGE_SHIFT); return 0; @@ -437,7 +439,8 @@ static int mce_handle_ierror(struct pt_regs *regs, unsigned long pfn; if (get_paca()->in_mce < MAX_MCE_DEPTH) { - pfn = addr_to_pfn(regs, regs->nip); + pfn = addr_to_pfn(regs, regs->nip, + NULL); if (pfn != ULONG_MAX) { *phys_addr = (pfn << PAGE_SHIFT);
The code currently assumes PAGE_SHIFT as the shift value of the pfn, this works correctly (mostly) for user space pages, but the correct thing to do is 1. Extrace the shift value returned via the pte-walk API's 2. Use the shift value to access the instruction address. Note, the final physical address still use PAGE_SHIFT for computation. handle_ierror() is not modified and handle_derror() is modified just for extracting the correct instruction address. Fixes: ba41e1e1ccb9 ("powerpc/mce: Hookup derror (load/store) UE errors") Signed-off-by: Balbir Singh <bsingharora@gmail.com> --- arch/powerpc/kernel/mce_power.c | 17 ++++++++++------- 1 file changed, 10 insertions(+), 7 deletions(-)