10:45 a.m.
----- "Chandru" <chandru(a)in.ibm.com> wrote:
This thread relates to an old issue discussed earlier here ...
https://www.redhat.com/archives/crash-utility/2008-April/msg00007.html.
The following patch currently fixes the issue. The kernel cpu possible,present
and online cpu map is not available until cpu_maps_init() initializes them. Hence
we remap the nd->nt_prstatus_percpu array to online cpus right after a call to
this function.
A couple points:
Signed-off-by: Chandru Siddalingappa
<chandru(a)linux.vnet.ibm.com>
Cc: Haren Myneni <haren(a)us.ibm.com>
---
--- crash-4.0-8.10/ppc64.c.orig 2009-06-08 16:08:09.000000000 +0530
+++ crash-4.0-8.10/ppc64.c 2009-06-08 18:47:04.000000000 +0530
@@ -2407,13 +2407,11 @@ ppc64_paca_init(void)
if (!symbol_exists("paca"))
error(FATAL, "PPC64: Could not find 'paca' symbol\n");
- if (cpu_map_addr("present"))
- map = PRESENT;
- else if (cpu_map_addr("online"))
- map = ONLINE;
+ if (cpu_map_addr("possible"))
+ map = POSSIBLE;
else
error(FATAL,
- "PPC64: cannot find 'cpu_present_map' or 'cpu_online_map'
symbols\n");
+ "PPC64: cannot find 'cpu_possible_map' symbol\n");
if (!MEMBER_EXISTS("paca_struct", "data_offset"))
return;
Depending upon "cpu_possible_map" breaks backwards-compatibility for old
kernels that don't even have a "cpu_possible_map". The function will still
need to fallback to *something* that exists instead of killing the whole
crash session.
@@ -2424,7 +2422,7 @@ ppc64_paca_init(void)
cpu_paca_buf = GETBUF(SIZE(ppc64_paca));
if (!(nr_paca = get_array_length("paca", NULL, 0)))
- nr_paca = NR_CPUS;
+ nr_paca = kt->kernel_NR_CPUS;
if (nr_paca > NR_CPUS) {
error(WARNING,
It is possible that kt->kernel_NR_CPUS may not even be initialized
at this point in time -- and for that matter, it is possible that
kt->kernel_NR_CPUS may *never* be initialized. So for that reason,
whenever it is used, the code first checks for a non-zero value.
and if zero, defaults to the compiled-in, equal-to-or-higher,
value of NR_CPUS.
@@ -2435,7 +2433,7 @@ ppc64_paca_init(void)
for (i = cpus = 0; i < nr_paca; i++) {
/*
- * CPU present (or online)?
+ * CPU in possible map ?
*/
if (!in_cpu_map(map, i))
continue;
--- crash-4.0-8.10/kernel.c.orig 2009-06-08 16:07:53.000000000 +0530
+++ crash-4.0-8.10/kernel.c 2009-06-08 16:48:53.000000000 +0530
@@ -74,6 +74,9 @@ kernel_init()
cpu_maps_init();
+ if (KDUMP_DUMPFILE())
+ map_prstatus_array();
+
kt->stext = symbol_value("_stext");
kt->etext = symbol_value("_etext");
get_text_init_space();
--- crash-4.0-8.10/netdump.c.orig 2009-06-08 16:07:58.000000000 +0530
+++ crash-4.0-8.10/netdump.c 2009-06-08 17:40:36.000000000 +0530
@@ -45,6 +45,35 @@ static void check_dumpfile_size(char *);
(machine_type("IA64") || machine_type("PPC64"))
/*
+ * kdump installs NT_PRSTATUS elf sections only to the cpus
+ * that were online during dumping. Hence we call into
+ * this function after reading the cpu map from the kernel,
+ * to remap the NT_PRSTATUS sections only to the online cpus
+ */
+void map_prstatus_array(void)
+{
+ void *nt_ptr;
+ int i, j;
+
+ /* temporary buffer to hold the prstatus_percpu array */
+ if ((nt_ptr = (void *)calloc(nd->num_prstatus_notes,
+ sizeof(void *))) == NULL)
+ error(FATAL,
+ "cannot allocate a buffer to hold prstatus_percpu array\n");
+
+ memcpy((void *)nt_ptr, nd->nt_prstatus_percpu,
+ nd->num_prstatus_notes * sizeof(void *));
+ memset(nd->nt_prstatus_percpu, 0, nd->num_prstatus_notes);
+
+ /* re-populate the array with the sections mapping to online cpus
*/
+ for (i = 0, j = 0; i < kt->kernel_NR_CPUS; i++)
+ if (in_cpu_map(ONLINE, i))
+ ((unsigned long *)nd->nt_prstatus_percpu)[i] =
+ ((unsigned long *)nt_ptr)[j++];
+ free(nt_ptr);
+}
Same thing with kt->kernel_NR_CPUS usage above...
+
+/*
* Determine whether a file is a netdump/diskdump/kdump creation,
* and if TRUE, initialize the vmcore_data structure.
*/
@@ -618,7 +647,7 @@ get_netdump_panic_task(void)
crashing_cpu = -1;
if (kernel_symbol_exists("crashing_cpu")) {
get_symbol_data("crashing_cpu", sizeof(int), &i);
- if ((i >= 0) && (i < nd->num_prstatus_notes)) {
+ if ((i >= 0) && in_cpu_map(ONLINE, i)) {
crashing_cpu = i;
if (CRASHDEBUG(1))
error(INFO,
@@ -2236,7 +2265,7 @@ get_netdump_regs_ppc64(struct bt_info *b
* CPUs if they responded to an IPI.
*/
if (nd->num_prstatus_notes > 1) {
- if (bt->tc->processor >= nd->num_prstatus_notes)
+ if (!nd->nt_prstatus_percpu[bt->tc->processor])
error(FATAL,
"cannot determine NT_PRSTATUS ELF note "
"for %s task: %lx\n",
And lastly, when I run a kernel with this patch against a set of x86_64-only
dumpfiles, I get a segmentation violation like this on certain kdump kernels:
...
please wait... (determining panic task)
Program received signal SIGSEGV, Segmentation fault.
0x000000000051c79c in get_netdump_panic_task () at netdump.c:719
719 len = roundup(len + note64->n_namesz, 4);
(gdb) bt
#0 0x000000000051c79c in get_netdump_panic_task () at netdump.c:719
#1 0x0000000000521ae5 in get_kdump_panic_task () at netdump.c:2316
#2 0x00000000004a5550 in get_dumpfile_panic_task () at task.c:5493
#3 0x00000000004a51b1 in panic_search () at task.c:5386
#4 0x00000000004a2ef6 in get_panic_context () at task.c:4574
#5 0x00000000004974ee in task_init () at task.c:456
#6 0x0000000000449e3a in main_loop () at main.c:536
...
And if I remove the call to map_prstatus_array(), it works OK again.
I haven't dug into what changed to cause the problem though...
Dave