Re: [PATCH V7 04/10] arm64: exception: handle Synchronous External Abort

[Baicar, Tyler]

On 1/17/2017 3:23 AM, James Morse wrote:

Hi Tyler,

On 16/01/17 11:53, Will Deacon wrote:

On Thu, Jan 12, 2017 at 11:15:18AM -0700, Tyler Baicar wrote:

SEA exceptions are often caused by an uncorrected hardware
error, and are handled when data abort and instruction abort
exception classes have specific values for their Fault Status
Code.
When SEA occurs, before killing the process, go through
the handlers registered in the notification list.
Update fault_info[] with specific SEA faults so that the
new SEA handler is used.
diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c
index 05d2bd7..81039c7 100644
--- a/arch/arm64/mm/fault.c
+++ b/arch/arm64/mm/fault.c
@@ -480,6 +496,28 @@ static int do_bad(unsigned long addr, unsigned int esr, 
struct pt_regs *regs)
        return 1;
  }

+/*

+ * This abort handler deals with Synchronous External Abort.
+ * It calls notifiers, and then returns "fault".
+ */
+static int do_sea(unsigned long addr, unsigned int esr, struct pt_regs *regs)
+{
+       struct siginfo info;
+
+       atomic_notifier_call_chain(&sea_handler_chain, 0, NULL);
+
+       pr_err("Synchronous External Abort: %s (0x%08x) at 0x%016lx\n",
+                fault_name(esr), esr, addr);
+
+       info.si_signo = SIGBUS;
+       info.si_errno = 0;
+       info.si_code  = 0;
+       info.si_addr  = (void __user *)addr;
+       arm64_notify_die("", regs, &info, esr);
+
+       return 0;
+}
+
  static const struct fault_info {
        int     (*fn)(unsigned long addr, unsigned int esr, struct pt_regs 
*regs);
        int     sig;
@@ -502,22 +540,22 @@ static const struct fault_info {
        { do_page_fault,        SIGSEGV, SEGV_ACCERR,   "level 1 permission 
fault"    },
        { do_page_fault,        SIGSEGV, SEGV_ACCERR,   "level 2 permission 
fault"    },
        { do_page_fault,        SIGSEGV, SEGV_ACCERR,   "level 3 permission 
fault"    },
-       { do_bad,               SIGBUS,  0,             "synchronous external 
abort"  },
+       { do_sea,               SIGBUS,  0,             "synchronous external 
abort"  },
        { do_bad,               SIGBUS,  0,             "unknown 17"            
      },
        { do_bad,               SIGBUS,  0,             "unknown 18"            
      },
        { do_bad,               SIGBUS,  0,             "unknown 19"            
      },
-       { do_bad,               SIGBUS,  0,             "synchronous abort 
(translation table walk)" },
-       { do_bad,               SIGBUS,  0,             "synchronous abort 
(translation table walk)" },
-       { do_bad,               SIGBUS,  0,             "synchronous abort 
(translation table walk)" },
-       { do_bad,               SIGBUS,  0,             "synchronous abort 
(translation table walk)" },
-       { do_bad,               SIGBUS,  0,             "synchronous parity 
error"    },
+       { do_sea,               SIGBUS,  0,             "level 0 SEA (translation 
table walk)"        },
+       { do_sea,               SIGBUS,  0,             "level 1 SEA (translation 
table walk)"        },
+       { do_sea,               SIGBUS,  0,             "level 2 SEA (translation 
table walk)"        },
+       { do_sea,               SIGBUS,  0,             "level 3 SEA (translation 
table walk)"        },

Perhaps I wasn't clear enough in my previous review, but please expand the
acronym for strings and comments.

The 'SEA' in this user-string doesn't add anything. Now that these use do_sea()
instead of do_bad(), when they are printed won't it be:

Synchronous External Abort: level 3 SEA (translation table walk) (...) at ....

Good point, yes they will:

+       pr_err("Synchronous External Abort: %s (0x%08x) at 0x%016lx\n",
+                fault_name(esr), esr, addr);

I can just remove SEA here then.

Thanks,
Tyler


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