[v2] ARC: prevent showing irrelevant exception info in signal message

Message ID 20180807135945.2948-1-Eugeniy.Paltsev@synopsys.com
State New
Headers show
Series
  • [v2] ARC: prevent showing irrelevant exception info in signal message
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Commit Message

Eugeniy Paltsev Aug. 7, 2018, 1:59 p.m.
We process signals in the end of syscall/exception handler.
It the signal is fatal we print register's content using
show_regs function. show_regs() also prints information about
last exception happened.

In case of multicore system we can catch the situation when we
will print wrong information about exception. See the example:

Patch

diff --git a/arch/arc/include/asm/bug.h b/arch/arc/include/asm/bug.h
index 21ec82466d62..b68f7f82f2d8 100644
--- a/arch/arc/include/asm/bug.h
+++ b/arch/arc/include/asm/bug.h
@@ -16,6 +16,7 @@ 
 struct task_struct;
 
 void show_regs(struct pt_regs *regs);
+void show_exception_mesg(struct pt_regs *regs);
 void show_stacktrace(struct task_struct *tsk, struct pt_regs *regs);
 void show_kernel_fault_diag(const char *str, struct pt_regs *regs,
 			    unsigned long address);
diff --git a/arch/arc/kernel/traps.c b/arch/arc/kernel/traps.c
index b123558bf0bb..5d83b2fe5f12 100644
--- a/arch/arc/kernel/traps.c
+++ b/arch/arc/kernel/traps.c
@@ -50,6 +50,7 @@  unhandled_exception(const char *str, struct pt_regs *regs, siginfo_t *info)
 		tsk->thread.fault_address = (__force unsigned int)info->si_addr;
 
 		force_sig_info(info->si_signo, info, tsk);
+		show_exception_mesg(regs);
 
 	} else {
 		/* If not due to copy_(to|from)_user, we are doomed */
diff --git a/arch/arc/kernel/troubleshoot.c b/arch/arc/kernel/troubleshoot.c
index e8d9fb452346..fdfba1942a06 100644
--- a/arch/arc/kernel/troubleshoot.c
+++ b/arch/arc/kernel/troubleshoot.c
@@ -101,13 +101,13 @@  static void show_faulting_vma(unsigned long address, char *buf)
 			if (IS_ERR(nm))
 				nm = "?";
 		}
-		pr_info("    @off 0x%lx in [%s]\n"
-			"    VMA: 0x%08lx to 0x%08lx\n",
+
+		pr_cont("[off 0x%lx in %s, VMA: %08lx:%08lx] ",
 			vma->vm_start < TASK_UNMAPPED_BASE ?
 				address : address - vma->vm_start,
 			nm, vma->vm_start, vma->vm_end);
 	} else
-		pr_info("    @No matching VMA found\n");
+		pr_cont("[No matching VMA found] ");
 
 	up_read(&active_mm->mmap_sem);
 }
@@ -117,7 +117,7 @@  static void show_ecr_verbose(struct pt_regs *regs)
 	unsigned int vec, cause_code;
 	unsigned long address;
 
-	pr_info("\n[ECR   ]: 0x%08lx => ", regs->event);
+	pr_cont("\n  ECR: 0x%08lx => ", regs->event);
 
 	/* For Data fault, this is data address not instruction addr */
 	address = current->thread.fault_address;
@@ -165,10 +165,42 @@  static void show_ecr_verbose(struct pt_regs *regs)
 	}
 }
 
+static inline void show_exception_mesg_u(struct pt_regs *regs)
+{
+	struct task_struct *tsk = current;
+	char *buf;
+
+	pr_info("Exception: %s[%d]: at %pS ",
+		tsk->comm, task_pid_nr(tsk), (void *)regs->ret);
+
+	buf = (char *)__get_free_page(GFP_NOWAIT);
+	if (buf) {
+		show_faulting_vma(regs->ret, buf);
+		free_page((unsigned long)buf);
+	}
+
+	show_ecr_verbose(regs);
+}
+
+static inline void show_exception_mesg_k(struct pt_regs *regs)
+{
+	pr_info("Exception: at %pS:", (void *)regs->ret);
+
+	show_ecr_verbose(regs);
+}
+
 /************************************************************************
  *  API called by rest of kernel
  ***********************************************************************/
 
+void show_exception_mesg(struct pt_regs *regs)
+{
+	if (user_mode(regs))
+		show_exception_mesg_u(regs);
+	else
+		show_exception_mesg_k(regs);
+}
+
 void show_regs(struct pt_regs *regs)
 {
 	struct task_struct *tsk = current;
@@ -182,15 +214,10 @@  void show_regs(struct pt_regs *regs)
 	print_task_path_n_nm(tsk, buf);
 	show_regs_print_info(KERN_INFO);
 
-	show_ecr_verbose(regs);
-
-	pr_info("[EFA   ]: 0x%08lx\n[BLINK ]: %pS\n[ERET  ]: %pS\n",
-		current->thread.fault_address,
+	pr_info("[ECR   ]: 0x%08lx\n[EFA   ]: 0x%08lx\n[BLINK ]: %pS\n[ERET  ]: %pS\n",
+		regs->event, current->thread.fault_address,
 		(void *)regs->blink, (void *)regs->ret);
 
-	if (user_mode(regs))
-		show_faulting_vma(regs->ret, buf); /* faulting code, not data */
-
 	pr_info("[STAT32]: 0x%08lx", regs->status32);
 
 #define STS_BIT(r, bit)	r->status32 & STATUS_##bit##_MASK ? #bit" " : ""
@@ -233,6 +260,8 @@  void show_kernel_fault_diag(const char *str, struct pt_regs *regs,
 	/* Show fault description */
 	pr_info("\n%s\n", str);
 
+	show_exception_mesg(regs);
+
 	/* Caller and Callee regs */
 	show_regs(regs);
 
diff --git a/arch/arc/mm/fault.c b/arch/arc/mm/fault.c
index b884bbd6f354..d9c6958a1702 100644
--- a/arch/arc/mm/fault.c
+++ b/arch/arc/mm/fault.c
@@ -202,6 +202,7 @@  void do_page_fault(unsigned long address, struct pt_regs *regs)
 		/* info.si_code has been set above */
 		info.si_addr = (void __user *)address;
 		force_sig_info(SIGSEGV, &info, tsk);
+		show_exception_mesg(regs);
 		return;
 	}
 
@@ -241,4 +242,5 @@  void do_page_fault(unsigned long address, struct pt_regs *regs)
 	info.si_code = BUS_ADRERR;
 	info.si_addr = (void __user *)address;
 	force_sig_info(SIGBUS, &info, tsk);
+	show_exception_mesg(regs);
 }