linux-kernel - [PATCH] arch/tile: return SIGBUS for addresses that are unaligned AND invalid

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Message-Id: <201203302105.q2UL5AuJ006312@farm-0012.internal.tilera.com>
Date:	Fri, 30 Mar 2012 16:24:41 -0400
From:	Chris Metcalf <cmetcalf@...era.com>
To:	Chris Metcalf <cmetcalf@...era.com>, linux-kernel@...r.kernel.org
Subject: [PATCH] arch/tile: return SIGBUS for addresses that are unaligned AND invalid

Previously we were returning SIGSEGV in this case.  It seems cleaner
to return SIGBUS since the hardware figures out alignment traps
before TLB violations, so SIGBUS is the "more correct" signal.

Signed-off-by: Chris Metcalf <cmetcalf@...era.com>
---
 arch/tile/kernel/single_step.c |   31 +++++++++++++++++++------------
 1 files changed, 19 insertions(+), 12 deletions(-)

diff --git a/arch/tile/kernel/single_step.c b/arch/tile/kernel/single_step.c
index b231ef4..36ccd37 100644
--- a/arch/tile/kernel/single_step.c
+++ b/arch/tile/kernel/single_step.c
@@ -152,6 +152,25 @@ static tile_bundle_bits rewrite_load_store_unaligned(
 	if (((unsigned long)addr % size) == 0)
 		return bundle;
 
+	/*
+	 * Return SIGBUS with the unaligned address, if requested.
+	 * Note that we return SIGBUS even for completely invalid addresses
+	 * as long as they are in fact unaligned; this matches what the
+	 * tilepro hardware would be doing, if it could provide us with the
+	 * actual bad address in an SPR, which it doesn't.
+	 */
+	if (unaligned_fixup == 0) {
+		siginfo_t info = {
+			.si_signo = SIGBUS,
+			.si_code = BUS_ADRALN,
+			.si_addr = addr
+		};
+		trace_unhandled_signal("unaligned trap", regs,
+				       (unsigned long)addr, SIGBUS);
+		force_sig_info(info.si_signo, &info, current);
+		return (tilepro_bundle_bits) 0;
+	}
+
 	/* Handle unaligned load/store */
 	if (mem_op == MEMOP_LOAD || mem_op == MEMOP_LOAD_POSTINCR) {
 		unsigned short val_16;
@@ -199,18 +218,6 @@ static tile_bundle_bits rewrite_load_store_unaligned(
 		return (tile_bundle_bits) 0;
 	}
 
-	if (unaligned_fixup == 0) {
-		siginfo_t info = {
-			.si_signo = SIGBUS,
-			.si_code = BUS_ADRALN,
-			.si_addr = addr
-		};
-		trace_unhandled_signal("unaligned trap", regs,
-				       (unsigned long)addr, SIGBUS);
-		force_sig_info(info.si_signo, &info, current);
-		return (tile_bundle_bits) 0;
-	}
-
 	if (unaligned_printk || unaligned_fixup_count == 0) {
 		pr_info("Process %d/%s: PC %#lx: Fixup of"
 			" unaligned %s at %#lx.\n",
-- 
1.6.5.2

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