[PATCH] [20/20] x86: Print which shared library/executable faulted in segfault etc. messages

Andi Kleen
2008-01-03T00:56:41Z

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.

Signed-off-by: Andi Kleen <ak@suse.de>

---
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 | 27 +++++++++++++++++++++++++++
6 files changed, 46 insertions(+), 7 deletions(-)

Index: linux/include/linux/mm.h
===================================================================
--- linux.orig/include/linux/mm.h
+++ 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);
Index: linux/mm/memory.c
===================================================================
--- linux.orig/mm/memory.c
+++ linux/mm/memory.c
@@ -2746,3 +2746,30 @@ 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);
+ 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);
+}
Index: linux/arch/x86/kernel/signal_32.c
===================================================================
--- linux.orig/arch/x86/kernel/signal_32.c
+++ 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;
Index: linux/arch/x86/kernel/signal_64.c
===================================================================
--- linux.orig/arch/x86/kernel/signal_64.c
+++ 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);
}
Index: linux/arch/x86/kernel/traps_32.c
===================================================================
--- linux.orig/arch/x86/kernel/traps_32.c
+++ linux/arch/x86/kernel/traps_32.c
@@ -673,11 +673,14 @@ 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;
Index: linux/arch/x86/mm/fault_32.c
===================================================================
--- linux.orig/arch/x86/mm/fault_32.c
+++ 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 */