[Crash-utility] 32 bit linux-2.6.24-git8 user_regs_struct change breaks opening kdump crashfiles

[Joe Porter]

Hello crash,

The user_regs_struct was redefined in linux-2.6.24-git8/include/asm-x86/user_32.h.

This results in the following error when opening 32 bit kdump crashfiles:
-------------------------------------------------------------------------
please wait... (determining panic task)
crash: invalid structure member offset: user_regs_struct_ebp
       FILE: netdump.c  LINE: 687  FUNCTION: get_netdump_panic_task()

[/sbin/crash] error trace: 80e09f4 => 8154159 => 814fc3f => 813ec75

  813ec75: OFFSET_verify+126
  814fc3f: get_netdump_panic_task+1196
  8154159: get_kdump_panic_task+11
  80e09f4: get_dumpfile_panic_task+153
--------------------------------------------------------------------

I've inserted a patch to crash-4.0-7.4/x86.c that fixes this for all linux-2.6.24-git8
and later kernels (2.6.25 -> 2.6.28-rc5).  I've also inserted the kernel change that
caused the breakage.

The fix is bad because it breaks all kernels <= linux-2.6.24-git7.  

A better fix would be backward and forward compatible with all kernels, but since there
was a lot of hardwired code revolving around the old 32 bit user_regs_struct I thought I
would just submit this patch to expose the problem and maybe look for a better fix in the
next crash update.

thx, joe

--- crash-4.0-7.4.orig/x86.c	2008-10-14 09:35:40.000000000 -0400
+++ crash-4.0-7.4/x86.c	2008-11-17 13:37:40.000000000 -0500
@@ -1774,29 +1774,39 @@
 			machdep->flags |= OMIT_FRAME_PTR;
 		STRUCT_SIZE_INIT(user_regs_struct, "user_regs_struct");
 		MEMBER_OFFSET_INIT(user_regs_struct_ebp,
-			"user_regs_struct", "ebp");
+			"user_regs_struct", "bp");
 		MEMBER_OFFSET_INIT(user_regs_struct_esp,
-			"user_regs_struct", "esp");
+			"user_regs_struct", "sp");
 		if (!VALID_STRUCT(user_regs_struct)) {
 			/*  Use this hardwired version -- sometimes the 
 			 *  debuginfo doesn't pick this up even though
 			 *  it exists in the kernel; it shouldn't change.
 			 */
 			struct x86_user_regs_struct {
-			        long ebx, ecx, edx, esi, edi, ebp, eax;
-			        unsigned short ds, __ds, es, __es;
-			        unsigned short fs, __fs, gs, __gs;
-			        long orig_eax, eip;
-			        unsigned short cs, __cs;
-			        long eflags, esp;
-			        unsigned short ss, __ss;
+				unsigned long   bx;
+				unsigned long   cx;
+				unsigned long   dx;
+				unsigned long   si;
+				unsigned long   di;
+				unsigned long   bp;
+				unsigned long   ax;
+				unsigned long   ds;
+				unsigned long   es;
+				unsigned long   fs;
+				unsigned long   gs;
+				unsigned long   orig_ax;
+				unsigned long   ip;
+				unsigned long   cs;
+				unsigned long   flags;
+				unsigned long   sp;
+				unsigned long   ss;
 			};
 			ASSIGN_SIZE(user_regs_struct) = 
 				sizeof(struct x86_user_regs_struct);
 			ASSIGN_OFFSET(user_regs_struct_ebp) =
-				offsetof(struct x86_user_regs_struct, ebp);
+				offsetof(struct x86_user_regs_struct, bp);
 			ASSIGN_OFFSET(user_regs_struct_esp) =
-				offsetof(struct x86_user_regs_struct, esp);
+				offsetof(struct x86_user_regs_struct, sp);
 		}
 		MEMBER_OFFSET_INIT(thread_struct_cr3, "thread_struct", "cr3");
 		STRUCT_SIZE_INIT(cpuinfo_x86, "cpuinfo_x86");

--------------------------------------------------------------------------------

--- linux-2.6.24-git7/include/asm-x86/user_32.h 2008-01-24 17:58:37.000000000 -0500
+++ linux-2.6.24-git8/include/asm-x86/user_32.h 2008-11-11
18:56:13.000000000 -0500
@@ -75,13 +75,23 @@
  * doesn't use the extra segment registers)
  */
 struct user_regs_struct {
-       long ebx, ecx, edx, esi, edi, ebp, eax;
-       unsigned short ds, __ds, es, __es;
-       unsigned short fs, __fs, gs, __gs;
-       long orig_eax, eip;
-       unsigned short cs, __cs;
-       long eflags, esp;
-       unsigned short ss, __ss;
+       unsigned long   bx;
+       unsigned long   cx;
+       unsigned long   dx;
+       unsigned long   si;
+       unsigned long   di;
+       unsigned long   bp;
+       unsigned long   ax;
+       unsigned long   ds;
+       unsigned long   es;
+       unsigned long   fs;
+       unsigned long   gs;
+       unsigned long   orig_ax;
+       unsigned long   ip;
+       unsigned long   cs;
+       unsigned long   flags;
+       unsigned long   sp;
+       unsigned long   ss;
 };

 /* When the kernel dumps core, it starts by dumping the user struct -