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Date:      Wed, 4 Jan 2017 21:13:22 +0000 (UTC)
From:      John Baldwin <jhb@FreeBSD.org>
To:        src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org
Subject:   svn commit: r311309 - head/sys/mips/mips
Message-ID:  <201701042113.v04LDMQR096552@repo.freebsd.org>
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Author: jhb
Date: Wed Jan  4 21:13:21 2017
New Revision: 311309
URL: https://svnweb.freebsd.org/changeset/base/311309

Log:
  Further refine MIPS stack traces across trapframes.
  
  Use the trapframe unwinder recently added for kernel stack overflow
  panics for frames crossing MipsKernGenException and MipsKernIntr.
  This provides more reliably unwinding across nested interrupts and
  exceptions in the kernel.
  
  While here, dump the value of the CAUSE and BADVADDR registers when
  crossing a trapframe.
  
  Submitted by:	rwatson (original version)
  Obtained from:	CheriBSD
  Sponsored by:	DARPA / AFRL

Modified:
  head/sys/mips/mips/db_trace.c

Modified: head/sys/mips/mips/db_trace.c
==============================================================================
--- head/sys/mips/mips/db_trace.c	Wed Jan  4 20:56:03 2017	(r311308)
+++ head/sys/mips/mips/db_trace.c	Wed Jan  4 21:13:21 2017	(r311309)
@@ -141,11 +141,12 @@ stacktrace_subr(register_t pc, register_
 	 */
 	int valid_args[4];
 	register_t args[4];
-	register_t va, subr;
+	register_t va, subr, cause, badvaddr;
 	unsigned instr, mask;
 	unsigned int frames = 0;
 	int more, stksize, j;
 	register_t	next_ra;
+	bool trapframe;
 
 /* Jump here when done with a frame, to start a new one */
 loop:
@@ -160,6 +161,7 @@ loop:
 	next_ra = 0;
 	stksize = 0;
 	subr = 0;
+	trapframe = false;
 	if (frames++ > 100) {
 		(*printfn) ("\nstackframe count exceeded\n");
 		/* return breaks stackframe-size heuristics with gcc -O2 */
@@ -183,17 +185,21 @@ loop:
 	 * preceding "j ra" at the tail of the preceding function. Depends
 	 * on relative ordering of functions in exception.S, swtch.S.
 	 */
-	if (pcBetween(MipsKernGenException, MipsUserGenException))
+	if (pcBetween(MipsKernGenException, MipsUserGenException)) {
 		subr = (uintptr_t)MipsKernGenException;
-	else if (pcBetween(MipsUserGenException, MipsKernIntr))
+		trapframe = true;
+	} else if (pcBetween(MipsUserGenException, MipsKernIntr))
 		subr = (uintptr_t)MipsUserGenException;
-	else if (pcBetween(MipsKernIntr, MipsUserIntr))
+	else if (pcBetween(MipsKernIntr, MipsUserIntr)) {
 		subr = (uintptr_t)MipsKernIntr;
-	else if (pcBetween(MipsUserIntr, MipsTLBInvalidException))
+		trapframe = true;
+	} else if (pcBetween(MipsUserIntr, MipsTLBInvalidException))
 		subr = (uintptr_t)MipsUserIntr;
-	else if (pcBetween(MipsTLBInvalidException, MipsTLBMissException))
+	else if (pcBetween(MipsTLBInvalidException, MipsTLBMissException)) {
 		subr = (uintptr_t)MipsTLBInvalidException;
-	else if (pcBetween(fork_trampoline, savectx))
+		if (pc == (uintptr_t)MipsKStackOverflow)
+			trapframe = true;
+	} else if (pcBetween(fork_trampoline, savectx))
 		subr = (uintptr_t)fork_trampoline;
 	else if (pcBetween(savectx, cpu_throw))
 		subr = (uintptr_t)savectx;
@@ -215,11 +221,11 @@ loop:
 	}
 
 	/*
-	 * For a kernel stack overflow, skip to the output and
-	 * afterwards pull the previous registers out of the trapframe
-	 * instead of decoding the function prologue.
+	 * For a trapframe, skip to the output and afterwards pull the
+	 * previous registers out of the trapframe instead of decoding
+	 * the function prologue.
 	 */
-	if (pc == (uintptr_t)MipsKStackOverflow)
+	if (trapframe)
 		goto done;
 
 	/*
@@ -398,19 +404,24 @@ done:
 	    (uintmax_t)(u_register_t) sp,
 	    stksize);
 
-	if (pc == (uintptr_t)MipsKStackOverflow) {
+	if (trapframe) {
 #define	TF_REG(base, reg)	((base) + CALLFRAME_SIZ + ((reg) * SZREG))
 #if defined(__mips_n64) || defined(__mips_n32)
 		pc = kdbpeekd((int *)TF_REG(sp, PC));
 		ra = kdbpeekd((int *)TF_REG(sp, RA));
 		sp = kdbpeekd((int *)TF_REG(sp, SP));
+		cause = kdbpeekd((int *)TF_REG(sp, CAUSE));
+		badvaddr = kdbpeekd((int *)TF_REG(sp, BADVADDR));
 #else
 		pc = kdbpeek((int *)TF_REG(sp, PC));
 		ra = kdbpeek((int *)TF_REG(sp, RA));
 		sp = kdbpeek((int *)TF_REG(sp, SP));
+		cause = kdbpeek((int *)TF_REG(sp, CAUSE));
+		badvaddr = kdbpeek((int *)TF_REG(sp, BADVADDR));
 #endif
 #undef TF_REG
-		(*printfn) ("--- Kernel Stack Overflow ---\n");
+		(*printfn) ("--- exception, cause %jx badvaddr %jx ---\n",
+		    (uintmax_t)cause, (uintmax_t)badvaddr);
 		goto loop;
 	} else if (ra) {
 		if (pc == ra && stksize == 0)

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