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X86: Use shorter addresses in i386 segfault printks

PATCH New Andi Kleen 1 participant 2 messages Jan 3, 2008

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Memory management x86 MM core x86 MM
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Andi Kleen

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#0 lore raw

PATCH 1/2 X86: Use shorter addresses in i386 segfault printks

Signed-off-by Andi Kleen <[email protected]>
---
 arch/x86/mm/fault_32.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
arch/x86/mm/fault_32.c +1 -1
Index: linux/arch/x86/mm/fault_32.c
===================================================================
@@ -549,7 +549,7 @@ bad_area_nosemaphore:
 
 		if (show_unhandled_signals && unhandled_signal(tsk, SIGSEGV) &&
 		    printk_ratelimit()) {
-			printk("%s%s[%d]: segfault at %08lx ip %08lx "
+			printk("%s%s[%d]: segfault at %lx ip %08lx "
 			    "sp %08lx error %lx\n",
 			    task_pid_nr(tsk) > 1 ? KERN_INFO : KERN_EMERG,
 			    tsk->comm, task_pid_nr(tsk), address, regs->ip,
author
#1 lore raw

PATCH 2/2 X86: Print which shared library/executable faulted in segfault etc. messages v2

They now look like

hal-resmgr[13791]: segfault at 3c rip 2b9c8caec182 rsp 7fff1e825d30 error 4 in libacl.so.1.1.0[2b9c8caea000+6000]

This makes it easier to pinpoint bugs to specific libraries.

And printing the offset into a mapping also always allows to find the correct fault point in a library even with randomized mappings. Previously there was no way to actually find the correct code address inside the randomized mapping.

Relies on earlier patch to shorten the printk formats.

They are often now longer than 80 characters, but I think that's worth it.

Patch for i386 and x86-64.

[includes fix from Eric Dumazet to check d_path error value]

Signed-off-by Andi Kleen <[email protected]>
---
 arch/x86/kernel/signal_32.c |    7 +++++--
 arch/x86/kernel/signal_64.c |    7 +++++--
 arch/x86/kernel/traps_32.c  |    7 +++++--
 arch/x86/mm/fault_32.c      |    4 +++-
 include/linux/mm.h          |    1 +
 mm/memory.c                 |   31 +++++++++++++++++++++++++++++++
 6 files changed, 50 insertions(+), 7 deletions(-)
include/linux/mm.h +1 -0
Index: linux/include/linux/mm.h
===================================================================
@@ -1145,6 +1145,7 @@ extern int randomize_va_space;
 #endif
 
 const char * arch_vma_name(struct vm_area_struct *vma);
+void print_vma_addr(char *prefix, unsigned long rip);
 
 struct page *sparse_mem_map_populate(unsigned long pnum, int nid);
 pgd_t *vmemmap_pgd_populate(unsigned long addr, int node);
mm/memory.c +31 -0
Index: linux/mm/memory.c
===================================================================
@@ -2746,3 +2746,34 @@ int access_process_vm(struct task_struct
 
 	return buf - old_buf;
 }
+
+/*
+ * Print the name of a VMA.
+ */
+void print_vma_addr(char *prefix, unsigned long ip)
+{
+	struct mm_struct *mm = current->mm;
+	struct vm_area_struct *vma;
+
+	down_read(&mm->mmap_sem);
+	vma = find_vma(mm, ip);
+	if (vma && vma->vm_file) {
+		struct file *f = vma->vm_file;
+		char *buf = (char *)__get_free_page(GFP_KERNEL);
+		if (buf) {
+			char *p, *s;
+
+			p = d_path(f->f_dentry, f->f_vfsmnt, buf, PAGE_SIZE);
+			if (IS_ERR(p))
+				p = "?";
+			s = strrchr(p, '/');
+			if (s)
+				p = s+1;
+			printk("%s%s[%lx+%lx]", prefix, p,
+					vma->vm_start,
+					vma->vm_end - vma->vm_start);
+			free_page((unsigned long)buf);
+		}
+	}
+	up_read(&current->mm->mmap_sem);
+}
arch/x86/kernel/signal_32.c +5 -2
Index: linux/arch/x86/kernel/signal_32.c
===================================================================
@@ -198,12 +198,15 @@ asmlinkage int sys_sigreturn(unsigned lo
 	return ax;
 
 badframe:
-	if (show_unhandled_signals && printk_ratelimit())
+	if (show_unhandled_signals && printk_ratelimit()) {
 		printk("%s%s[%d] bad frame in sigreturn frame:%p ip:%lx"
-		       " sp:%lx oeax:%lx\n",
+		       " sp:%lx oeax:%lx",
 		    task_pid_nr(current) > 1 ? KERN_INFO : KERN_EMERG,
 		    current->comm, task_pid_nr(current), frame, regs->ip,
 		    regs->sp, regs->orig_ax);
+		print_vma_addr(" in ", regs->ip);
+		printk("\n");
+	}
 
 	force_sig(SIGSEGV, current);
 	return 0;
arch/x86/kernel/signal_64.c +5 -2
Index: linux/arch/x86/kernel/signal_64.c
===================================================================
@@ -481,9 +481,12 @@ do_notify_resume(struct pt_regs *regs, v
 void signal_fault(struct pt_regs *regs, void __user *frame, char *where)
 { 
 	struct task_struct *me = current; 
-	if (show_unhandled_signals && printk_ratelimit())
-		printk("%s[%d] bad frame in %s frame:%p ip:%lx sp:%lx orax:%lx\n",
+	if (show_unhandled_signals && printk_ratelimit()) {
+		printk("%s[%d] bad frame in %s frame:%p ip:%lx sp:%lx orax:%lx",
 	       me->comm,me->pid,where,frame,regs->ip,regs->sp,regs->orig_ax);
+		print_vma_addr(" in ", regs->ip);
+		printk("\n");
+	}
 
 	force_sig(SIGSEGV, me); 
 }
arch/x86/kernel/traps_32.c +5 -2
Index: linux/arch/x86/kernel/traps_32.c
===================================================================
@@ -605,11 +605,14 @@ void __kprobes do_general_protection(str
 	current->thread.error_code = error_code;
 	current->thread.trap_no = 13;
 	if (show_unhandled_signals && unhandled_signal(current, SIGSEGV) &&
-	    printk_ratelimit())
+	    printk_ratelimit()) {
 		printk(KERN_INFO
-		    "%s[%d] general protection ip:%lx sp:%lx error:%lx\n",
+		    "%s[%d] general protection ip:%lx sp:%lx error:%lx",
 		    current->comm, task_pid_nr(current),
 		    regs->ip, regs->sp, error_code);
+		print_vma_addr(" in ", regs->ip);
+		printk("\n");
+	}
 
 	force_sig(SIGSEGV, current);
 	return;
arch/x86/mm/fault_32.c +3 -1
Index: linux/arch/x86/mm/fault_32.c
===================================================================
@@ -550,10 +550,12 @@ bad_area_nosemaphore:
 		if (show_unhandled_signals && unhandled_signal(tsk, SIGSEGV) &&
 		    printk_ratelimit()) {
 			printk("%s%s[%d]: segfault at %lx ip %08lx "
-			    "sp %08lx error %lx\n",
+			    "sp %08lx error %lx",
 			    task_pid_nr(tsk) > 1 ? KERN_INFO : KERN_EMERG,
 			    tsk->comm, task_pid_nr(tsk), address, regs->ip,
 			    regs->sp, error_code);
+			print_vma_addr(" in ", regs->ip);
+			printk("\n");
 		}
 		tsk->thread.cr2 = address;
 		/* Kernel addresses are always protection faults */