[PATCH 3.13 021/187] sparc64: Fix top-level fault handling bugs.

Kamal Mostafa
2014-09-15T22:18:24Z

From: "David S. Miller" <davem@davemloft.net>

[ Upstream commit 70ffc6ebaead783ac8dafb1e87df0039bb043596 ]

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@davemloft.net>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
---
arch/sparc/mm/fault_64.c | 82 ++++++++++++++++++++++++++++++------------------
1 file changed, 52 insertions(+), 30 deletions(-)

diff --git a/arch/sparc/mm/fault_64.c b/arch/sparc/mm/fault_64.c
index 69bb818..a8ff0d1 100644
--- a/arch/sparc/mm/fault_64.c
+++ b/arch/sparc/mm/fault_64.c
@@ -96,38 +96,51 @@ 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;
+ if (pgd_none(*pgdp) || unlikely(pgd_bad(*pgdp)))
+ goto out;
pudp = pud_offset(pgdp, tpc);
- if (pud_none(*pudp))
- goto outret;
- pmdp = pmd_offset(pudp, tpc);
- if (pmd_none(*pmdp))
- goto outret;
+ if (pud_none(*pudp) || unlikely(pud_bad(*pudp)))
+ 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();

- pa = (pte_pfn(pte) << PAGE_SHIFT);
- pa += (tpc & ~PAGE_MASK);
+ pmdp = pmd_offset(pudp, tpc);
+ if (pmd_none(*pmdp) || unlikely(pmd_bad(*pmdp)))
+ goto out_irq_enable;
+
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
+ 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
+#endif
+ {
+ 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 +166,8 @@ 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 +175,18 @@ 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 +261,7 @@ 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 +547,7 @@ 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)
--
1.9.1