unwabi mismatch in 2.4.X kernels breaks oops call trace (unwind)

From: Bob Montgomery <bob.montgomery_at_hp.com>
Date: 2004-02-10 11:48:57
Oops stack unwinding was broken in 2.4.22 by this patch that was
picked up from 2.5/2.6:
--- 1.5/arch/ia64/kernel/entry.h	Mon Feb  9 13:41:40 2004
+++ 1.6/arch/ia64/kernel/entry.h	Mon Feb  9 13:41:40 2004
@@ -14,7 +14,7 @@
 #define SW(f)		(IA64_SWITCH_STACK_##f##_OFFSET)
 #define PT_REGS_SAVES(off)			\
-	.unwabi @svr4, 'i';			\
+	.unwabi 3, 'i';				\
 	.fframe IA64_PT_REGS_SIZE+16+(off);	\
 	.spillsp rp, PT(CR_IIP)+16+(off);	\
 	.spillsp ar.pfs, PT(CR_IFS)+16+(off);	\

If we want to keep this change in 2.4.X, we need to also change the
test in desc_abi (unwind.c) to check for abi == 3 instead of 0.

static inline void
desc_abi (unsigned char abi, unsigned char context, struct unw_state_record *sr){
        if (abi == 0 && context == 'i') {
                sr->flags |= UNW_FLAG_INTERRUPT_FRAME;
                UNW_DPRINT(3, "unwind.%s: interrupt frame\n", __FUNCTION__);
                UNW_DPRINT(0, "unwind%s: ignoring unwabi(abi=0x%x,context=0x%x)\n",
                                __FUNCTION__, abi, context);

Otherwise we can just back the entry.h patch out.  So my question
is: Is there a compelling reason to change the abi number from 0 to
3 in 2.4.X kernels?  Is there an outside tool that cares, or is it
sufficient for these two snippets of kernel code to merely agree on
some number?

Bob Montgomery

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Received on Mon Feb 9 19:52:37 2004

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