> Make get_user_insn() able to cope with huge PMDs.
>
> Next, make do_fault_siginfo() more robust when get_user_insn() can't
> actually fetch the instruction. In particular, use the MMU announced
> fault address when that happens, instead of calling
> compute_effective_address() and computing garbage.
>
> Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
This patch happens to introduce a compile failure on a computer that has
THP diabled:
CC arch/sparc/mm/fault_64.o
arch/sparc/mm/fault_64.c: In function ʽget_user_insnʼ:
arch/sparc/mm/fault_64.c:117:3: error: implicit declaration of function ʽpmd_pfnʼ [-Werror=implicit-function-declaration]
arch/sparc/include/asm/pgtable_64.h has pmd_pfn declared only for THP.
> ---
> arch/sparc/mm/fault_64.c | 75 ++++++++++++++++++++++++++++++------------------
> 1 file changed, 47 insertions(+), 28 deletions(-)
>
> diff --git a/arch/sparc/mm/fault_64.c b/arch/sparc/mm/fault_64.c
> index 69bb818..cf0d05d 100644
> --- a/arch/sparc/mm/fault_64.c
> +++ b/arch/sparc/mm/fault_64.c
> @@ -96,38 +96,48 @@ static unsigned int get_user_insn(unsigned long tpc)
> pte_t *ptep, pte;
> unsigned long pa;
> u32 insn = 0;
> - unsigned long pstate;
>
> if (pgd_none(*pgdp))
> - goto outret;
> + goto out;
> pudp = pud_offset(pgdp, tpc);
> if (pud_none(*pudp))
> - goto outret;
> - pmdp = pmd_offset(pudp, tpc);
> - if (pmd_none(*pmdp))
> - goto outret;
> + goto out;
>
> /* This disables preemption for us as well. */
> - __asm__ __volatile__("rdpr %%pstate, %0" : "=r" (pstate));
> - __asm__ __volatile__("wrpr %0, %1, %%pstate"
> - : : "r" (pstate), "i" (PSTATE_IE));
> - ptep = pte_offset_map(pmdp, tpc);
> - pte = *ptep;
> - if (!pte_present(pte))
> - goto out;
> + local_irq_disable();
> +
> + pmdp = pmd_offset(pudp, tpc);
> + if (pmd_none(*pmdp))
> + goto out_irq_enable;
>
> - pa = (pte_pfn(pte) << PAGE_SHIFT);
> - pa += (tpc & ~PAGE_MASK);
> + if (pmd_trans_huge(*pmdp)) {
> + if (pmd_trans_splitting(*pmdp))
> + goto out_irq_enable;
>
> - /* Use phys bypass so we don't pollute dtlb/dcache. */
> - __asm__ __volatile__("lduwa [%1] %2, %0"
> - : "=r" (insn)
> - : "r" (pa), "i" (ASI_PHYS_USE_EC));
> + pa = pmd_pfn(*pmdp) << PAGE_SHIFT;
> + pa += tpc & ~HPAGE_MASK;
>
> + /* Use phys bypass so we don't pollute dtlb/dcache. */
> + __asm__ __volatile__("lduwa [%1] %2, %0"
> + : "=r" (insn)
> + : "r" (pa), "i" (ASI_PHYS_USE_EC));
> + } else {
> + ptep = pte_offset_map(pmdp, tpc);
> + pte = *ptep;
> + if (pte_present(pte)) {
> + pa = (pte_pfn(pte) << PAGE_SHIFT);
> + pa += (tpc & ~PAGE_MASK);
> +
> + /* Use phys bypass so we don't pollute dtlb/dcache. */
> + __asm__ __volatile__("lduwa [%1] %2, %0"
> + : "=r" (insn)
> + : "r" (pa), "i" (ASI_PHYS_USE_EC));
> + }
> + pte_unmap(ptep);
> + }
> +out_irq_enable:
> + local_irq_enable();
> out:
> - pte_unmap(ptep);
> - __asm__ __volatile__("wrpr %0, 0x0, %%pstate" : : "r" (pstate));
> -outret:
> return insn;
> }
>
> @@ -153,7 +163,8 @@ show_signal_msg(struct pt_regs *regs, int sig, int code,
> }
>
> static void do_fault_siginfo(int code, int sig, struct pt_regs *regs,
> - unsigned int insn, int fault_code)
> + unsigned long fault_addr, unsigned int insn,
> + int fault_code)
> {
> unsigned long addr;
> siginfo_t info;
> @@ -161,10 +172,18 @@ static void do_fault_siginfo(int code, int sig, struct pt_regs *regs,
> info.si_code = code;
> info.si_signo = sig;
> info.si_errno = 0;
> - if (fault_code & FAULT_CODE_ITLB)
> + if (fault_code & FAULT_CODE_ITLB) {
> addr = regs->tpc;
> - else
> - addr = compute_effective_address(regs, insn, 0);
> + } else {
> + /* If we were able to probe the faulting instruction, use it
> + * to compute a precise fault address. Otherwise use the fault
> + * time provided address which may only have page granularity.
> + */
> + if (insn)
> + addr = compute_effective_address(regs, insn, 0);
> + else
> + addr = fault_addr;
> + }
> info.si_addr = (void __user *) addr;
> info.si_trapno = 0;
>
> @@ -239,7 +258,7 @@ static void __kprobes do_kernel_fault(struct pt_regs *regs, int si_code,
> /* The si_code was set to make clear whether
> * this was a SEGV_MAPERR or SEGV_ACCERR fault.
> */
> - do_fault_siginfo(si_code, SIGSEGV, regs, insn, fault_code);
> + do_fault_siginfo(si_code, SIGSEGV, regs, address, insn, fault_code);
> return;
> }
>
> @@ -525,7 +544,7 @@ do_sigbus:
> * Send a sigbus, regardless of whether we were in kernel
> * or user mode.
> */
> - do_fault_siginfo(BUS_ADRERR, SIGBUS, regs, insn, fault_code);
> + do_fault_siginfo(BUS_ADRERR, SIGBUS, regs, address, insn, fault_code);
>
> /* Kernel mode? Handle exceptions or die */
> if (regs->tstate & TSTATE_PRIV)
>
--
Meelis Roos (mroos@xxxxx) http://www.cs.ut.ee/~mroos/
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