powerpc: Invoke kdump for system reset exception

Invoke kdump for system reset exception

Dump restart operation from HMC raises system reset exception (0x100) and xmon is invoked(even if kdump kernel is loaded). User has to exit from xmon by saying 'Don't recover' to invoke kdump. Modify this behaviour so that xmon will return immediately for system reset exception and kdump kernel will be invoked (if its loaded). If kdump kernel is not loaded, proceed with xmon

---
 arch/powerpc/xmon/xmon.c |    9 +++++++++
 1 files changed, 9 insertions(+), 0 deletions(-)

index e1f33a8..6847334 100644
@@ -23,6 +23,7 @@
 #include <linux/interrupt.h>
 #include <linux/irq.h>
 #include <linux/bug.h>
+#include <linux/kexec.h>
 
 #include <asm/ptrace.h>
 #include <asm/string.h>

@@ -348,6 +349,14 @@ static int xmon_core(struct pt_regs *regs, int fromipi)
 	unsigned long timeout;
 #endif
 
+	/*
+	 * If the exception is 0x100 and if kexec crash image is loaded,
+	 * continue with kexec_crash
+	 */
+	if (kexec_should_crash(current) && kexec_crash_image &&
+					regs->trap == 0x100)
+		return 0;
+
 	local_irq_save(flags);
 
 	bp = in_breakpoint_table(regs->nip, &offset);

1.6.2.5

Hi Mohan !

This is not right. The way things -should- already work is that xmon will only kick in if it's been enabled (aka initialized). This happens normally if either:

- CONFIG_XMON_DEFAULT is set, which forces enable it at boot. This
should not be set on distro kernels

- The command line says xmon=early or xmon=on, in which case xmon will
be enabled during early boot (and in the case of xmon=early, you'll drop into it early during boot, for example to get a chance to set some breakpoints).

So on a normal distro kernel, where CONFIG_XMON_DEFAULT should not be set (if it is, they need to fix it), xmon will not be initialized, and a System Reset exception should trigger a kdump. If it doesn't, then there's a bug elsewhere, but the fix isn't to modify xmon.

Cheers,
Ben.