[Crash-utility] Re: nr_cpus is not calculated properly
----- "Wei Jiang" <talk90091e(a)gmail.com> wrote:
Hi,
I found nr_cpus is not calculated properly in 32 bits(x86) at
crash-4.0-8.9.
Around line 140 in file lkcd_v8.c.
137 * to find out how many CPUs are configured.
138 */
139 offset = offsetof(dump_header_asm_t, dha_smp_regs[0]);
140 nr_cpus = (hdr_size - offset) / sizeof(dump_CPU_info_t);
141
142 fprintf(stderr, "CPU number NR_CPUS %d \n", NR_CPUS);
143 fprintf(stderr, "header_asm_t size %d \n",
sizeof(dump_header_asm_t));
And in the corresponding head file.
# cat -n lkcd_dump_v8.h|grep -A 20 434
434 /* smp specific */
435 uint32_t dha_smp_num_cpus;
436 uint32_t dha_dumping_cpu;
437 struct pt_regs dha_smp_regs[NR_CPUS];
438 uint32_t dha_smp_current_task[NR_CPUS];
439 uint32_t dha_stack[NR_CPUS];
440 uint32_t dha_stack_ptr[NR_CPUS];
441 } __attribute__((packed)) dump_header_asm_t;
442
443 /*
444 * CPU specific part of dump_header_asm_t
445 */
446 typedef struct dump_CPU_info_s {
447 struct pt_regs dha_smp_regs;
448 uint64_t dha_smp_current_task;
449 uint64_t dha_stack;
450 uint64_t dha_stack_ptr;
451 } __attribute__ ((packed)) dump_CPU_info_t;
452
453
454 /*
As we know, on x86(32 bits), uint32_t is 4 bytes and uint64_t is 8
bytes.
So this line
140 nr_cpus = (hdr_size - offset) / sizeof(dump_CPU_info_t);
would not get a correct nr_cpus due to the sizeof().
A patch to fix this problem as below.
BTW, what exactly are the ramifications without the patch -- does the
crash session die during initialization? How come nobody ran into
this issue given that the code has been in place for almost 2 years?
4.0-4.8 - ...
- Change for support of LKCD dumpfile version 8 and later to determine
the backtrace starting registers from the dumpfile header. Increase
(maximum) NR_CPUS for ia64 to 4096.
(bwalle(a)suse.de)
...
(10/30/07)
Anyway, the patch looks reasonable to me, but I don't touch the LKCD
code without a sign-off from the LKCD maintainers on this mailing
list.
LKCD maintainers -- do you have any objection to this patch?
Thanks,
Dave
Thanks.
-Wj
--- lkcd_dump_v8.h.orig 2009-04-16 13:14:22.000000000 -0400
+++ lkcd_dump_v8.h 2009-06-10 03:31:37.815122032 -0400
@@ -445,9 +445,9 @@ typedef struct _dump_header_asm_s {
*/
typedef struct dump_CPU_info_s {
struct pt_regs dha_smp_regs;
- uint64_t dha_smp_current_task;
- uint64_t dha_stack;
- uint64_t dha_stack_ptr;
+ uint32_t dha_smp_current_task;
+ uint32_t dha_stack;
+ uint32_t dha_stack_ptr;
} __attribute__ ((packed)) dump_CPU_info_t;