Fix backtraces for kernel core dumps.

1 files changed, 19 insertions, 5 deletions

diff --git a/gnu/usr.bin/binutils/gdb/i386nbsd-nat.c b/gnu/usr.bin/binutils/gdb/i386nbsd-nat.c
index 22af0117e4e..c1f700de2cb 100644
--- a/gnu/usr.bin/binutils/gdb/i386nbsd-nat.c
+++ b/gnu/usr.bin/binutils/gdb/i386nbsd-nat.c
@@ -60,14 +60,28 @@ i386nbsd_supply_pcb (struct regcache *regcache, struct pcb *pcb)
   if (pcb->pcb_esp == 0)
     return 0;
 
+  /* Read the stack frame, and check its validity.  We do this by
+     checking if the saved interrupt priority level in the stack frame
+     looks reasonable..  */
   read_memory (pcb->pcb_esp, (char *) &sf, sizeof sf);
-  pcb->pcb_esp += sizeof (struct switchframe);
-  regcache_raw_supply (regcache, I386_EDI_REGNUM, &sf.sf_edi);
-  regcache_raw_supply (regcache, I386_ESI_REGNUM, &sf.sf_esi);
+  if ((unsigned int) sf.sf_ppl < 0x100 && (sf.sf_ppl & 0xf) == 0)
+    {
+      /* Yes, we have a frame that matches cpu_switch().  */
+      pcb->pcb_esp += sizeof (struct switchframe);
+      regcache_raw_supply (regcache, I386_EDI_REGNUM, &sf.sf_edi);
+      regcache_raw_supply (regcache, I386_ESI_REGNUM, &sf.sf_esi);
+      regcache_raw_supply (regcache, I386_EBX_REGNUM, &sf.sf_ebx);
+      regcache_raw_supply (regcache, I386_EIP_REGNUM, &sf.sf_eip);
+    }
+  else
+    {
+      /* No, the pcb must have been last updated by savectx().  */
+      pcb->pcb_esp += 4;
+      regcache_raw_supply (regcache, I386_EIP_REGNUM, &sf);
+    }
+
   regcache_raw_supply (regcache, I386_EBP_REGNUM, &pcb->pcb_ebp);
   regcache_raw_supply (regcache, I386_ESP_REGNUM, &pcb->pcb_esp);
-  regcache_raw_supply (regcache, I386_EBX_REGNUM, &sf.sf_ebx);
-  regcache_raw_supply (regcache, I386_EIP_REGNUM, &sf.sf_eip);
 
   return 1;
 }