if must include symbol of crash_notes to use bt for target=ARM

[taigerhu]

hi

I met below warning when to use bt in version 7.2.8 to analyze offline ramdump for ARM.

bt: WARNING: cannot determine starting stack frame for task

i already checked related issue and code, i added debug code, and found no crash_notes symbol, note that arm_get_crash_notes():

 544 static void
 545 arm_get_crash_notes(void)
 546 {
 547         struct machine_specific *ms = machdep->machspec;
 548         ulong crash_notes;
 549         Elf32_Nhdr *note;
 550         ulong offset;
 551         char *buf, *p;
 552         ulong *notes_ptrs;
 553         ulong i, found;
 554
 555         if (!symbol_exists("crash_notes"))
 556                 return;

only arm_init() will call arm_get_crash_notes().

		if (!ACTIVE())
			arm_get_crash_notes();

And the "crash_notes' is from kexec, rt?

139#ifdef CONFIG_KEXEC
140#include <linux/kexec.h>
141
142static ssize_t show_crash_notes(struct device *dev, struct device_attribute *attr,
143				char *buf)

so, kernel must configurate CONFIG_KEXEC=y to use bt command to analyze dumpfile for ARM/ARM64?

btw: seems lots of android kernel do not enable the CONFIG_KEXEC.

Thx.,

[k-hagio]

so, kernel must configurate CONFIG_KEXEC=y to use bt command to analyze dumpfile for ARM/ARM64?

Looks so in the current implementation. I'm not familiar with ramdump and not sure if there is a way to get CPU registers without the crash_notes. I think they are needed to use bt command for active tasks.

[praton1729]

@taigerhu I tried with CONFIG_KEXEC enabled on a Qualcomm chipset but still, I get the same error when I try bt. I checked the panic_task_regs also through help -m but they are still coming out to be zero, I have verified by adding debug logs that crash notes exist after enabling CONFIG_KEXEC.