[Crash-utility] x86 remap allocator in kernel 3.0

[Dave Anderson]

----- Original Message -----
> 
> 
> ----- Original Message -----
> > On 01/11/2012 06:53 AM, Petr Tesarik wrote:
> > > Dne Út 10. ledna 2012 19:23:24 Petr Tesarik napsal(a):
> > >> Dne Út 10. ledna 2012 19:14:32 Petr Tesarik napsal(a):
> > ... [ cut ] ...
> > >> crash>  vtop f2800080
> > >> VIRTUAL   PHYSICAL
> > >> f2800080  1fde00080
> > >>
> > >> PAGE DIRECTORY: c08ed000
> > >>    PGD: c08ed018 =>  8ea001
> > >>    PMD:   8eaca0 =>  80000001fde001e3
> > >>   PAGE: 1fde00000  (2MB)
> > >>
> > >>        PTE         PHYSICAL   FLAGS
> > >> 80000001fde001e3  1fde00000
> > >>  (PRESENT|RW|ACCESSED|DIRTY|PSE|GLOBAL|NX)
> > >>
> > >>    PAGE     PHYSICAL   MAPPING    INDEX CNT FLAGS
> > >
> > > BTW the data from struct page is really missing here. I traced
> > > this down to an
> > > integer overflow in dump_memory_nodes():
> > ... [ cut ] ...
> > > David (Mair), could you address this, as already discussed in
> > > private mails,
> > > please?
> > 
> > The attached patch fixes this for me.
> 
> Hmmm, not so much for me...
> 
> When I test the patch on RHEL5, RHEL6 and Fedora x86 kernels, the
> command always fails like this:
> 
> crash> kmem -n
> NODE    SIZE    PGLIST_DATA   BOOTMEM_DATA   NODE_ZONES
>   0    262075     c0a3a680      c0aa5ce8      c0a3a680
>                                               c0a3b1c0
>                                               c0a3bd00
>                                               c0a3c840
> MEM_MAP      START_PADDR    START_MAPNR
> Segmentation fault
> $
>  
> I haven't look into it, and this is probably not related:
> 
> cc -c -g -DX86 -m32 -D_FILE_OFFSET_BITS=64 -DGDB_7_3_1  memory.c
> -Wall -O2 -Wstrict-prototypes -Wmissing-prototypes -fstack-protector
> memory.c: In function 'dump_memory_nodes':
> memory.c:13410: warning: cast to pointer from integer of different
> size
> memory.c:13199: warning: 'node_start_paddr' may be used uninitialized
> in this function
> 
> But from under gdb:
> 
> crash> kmem -n
> [Detaching after fork from child process 16870.]
> 
> Program received signal SIGSEGV, Segmentation fault.
> 0x0809cd94 in mkstring (s=0xffe8a8bc "  c0a3a680  ", size=16,
> flags=133, opt=0x1000 <Address 0x1000 out of bounds>)
>     at tools.c:1620
> 1620                    sprintf(s, "%llx", *((ulonglong *)opt));
> (gdb) bt
> #0  0x0809cd94 in mkstring (s=0xffe8a8bc "  c0a3a680  ", size=16,
> flags=133, opt=0x1000 <Address 0x1000 out of bounds>)
>     at tools.c:1620
> #1  0x080b1ad7 in dump_memory_nodes (initialize=0) at memory.c:13406
> #2  0x080d46cc in cmd_kmem () at memory.c:4221
> #3  0x080941b8 in exec_command () at main.c:751
> #4  0x08093fe6 in main_loop () at main.c:699
> #5  0x081db622 in current_interp_command_loop ()
> #6  0x081dbf01 in captured_command_loop ()
> #7  0x081db0a4 in catch_errors ()
> #8  0x081dce07 in captured_main ()
> #9  0x081db0a4 in catch_errors ()
> #10 0x081dce49 in gdb_main ()
> #11 0x081dce99 in gdb_main_entry ()
> #12 0x08116668 in gdb_main_loop (argc=2, argv=0xffe8d494) at
> gdb_interface.c:75
> #13 0x08093ce0 in main (argc=3, argv=0xffe8d494) at main.c:603
> (gdb) p opt
> $1 = 0x1000 <Address 0x1000 out of bounds>
> (gdb)
> 
> I thought it might be just an x86 issue, but it also fails
> the same way on RHEL5, RHEL6 and Fedora x86_64 kernels.
> 
> Dave

It's because of this:

-                           mkstring(buf2, strlen("START_PADDR"),
-                               CENTER|LONG_HEX|RJUST, MKSTR(node_start_paddr)),
+                           mkstring(buf2, strlen("   START_PADDR  "),
+                               CENTER|LONGLONG_HEX|RJUST, MKSTR(node_start_paddr)),

When using MKSTR() with a longlong, it needs to be passed its address, i.e.:

+                           mkstring(buf2, strlen("   START_PADDR  "),
+                               CENTER|LONGLONG_HEX|RJUST, MKSTR(&node_start_paddr)),

That fixes the SIGSEGV, but the formatting is still a bit unpredictable 
because the 2nd and 3rd fields don't always line up correctly.

Dave