[Crash-utility] Re: [PATCH 0/3] Display local variables & function parameters from stack frames

[Dave Anderson]

Dave Anderson wrote:
>
> That all being said, here's what I can do for you.  I will take your new
> functions that you've added to netdump.c, and their protos in defs.h,
> and apply them to the next crash utility release.  Since they are not being
> used by anybody but your module at the moment, it's harmless to add them,
> and then you will not have to patch the crash sources at all in your
> subsequent module patch/posts.

I take that back...

You're first going to have to fix this proposed netdump.c function:

+static void* get_x86_regs_from_elf_notes(struct task_context *tc)
+{
+        Elf32_Nhdr *note;

An x86 kdump can be either a 32-bit or 64-bit ELF vmcore, but the default
is 64-bit.  You have defined only one "note" pointer as an Elf32_hdr pointer.

+        size_t len;
+        char *pt_regs;
+       ulong regs_size;
+
+       if((tc->task == tt->panic_task) ||
+             (is_task_active(tc->task))){
+               if (nd->num_prstatus_notes > 1)
+                       note = (Elf32_Nhdr *)
+                               nd->nt_prstatus_percpu[tc->processor];
+               else
+                       note = (Elf64_Nhdr *)nd->nt_prstatus;

And then above you determine first whether there is more than one prstatus 
note (i.e., more than one cpu), and then based upon that you're assigning 
the "note" pointer to the appropriate location.  But for the single-cpu 
you make it an Elf64_Nhdr pointer?  I realize it's just used as a address
value, but it's just not right.  (BTW, compile crash with "make warn"
instead of just "make")  

Anyway, you can conceivably have these i386 combinations:

 1. single-cpu, a 32-bit ELF header, and 1 prstatus note  (netdump or kdump)
 2. single-cpu, a 64-bit ELF header, and 1 prstatus note  (kdump only)
 3. multiple-cpu, a 32-bit ELF header, and 1 prstatus note (netdump only)
 4. multiple-cpu, a 32-bit ELF header, and more-than-one prstatus note (kdump)
 5. multiple-cpu, a 64-bit ELF header, and more-than-one prstatus note (kdump)

But  below you just default to an Elf32_Nhdr structure:
 
+
+               len = sizeof(Elf32_Nhdr);
+               len = roundup(len + note->n_namesz, 4);
+               pt_regs = (void *)((char *)note + len +
+                       MEMBER_OFFSET("elf_prstatus", "pr_reg"));
+       /* NEED TO BE FIXED: Hack to get the proper alignment */
+               pt_regs +=4;
+       }
+       else
+               error(FATAL, "\n cannot determine register set for the task %s"
+                       "bailing out\n ", tc->comm);
+       return pt_regs;

You'll first need to determine whether it's a 32-bit or 64-bit header
being used, and then whether to to point to the single prstatus note or 
to the correct one in the NR_CPUS-bounded array of prstatus notes.

Dave