linux-kernel - [PATCH] arm: kgdb: fix NUMREGBYTES so that gdb

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Message-Id: <20180405200916.27964-1-drivshin@awxrd.com>
Date:   Thu,  5 Apr 2018 16:09:16 -0400
From:   David Rivshin <drivshin@...rd.com>
To:     linux-arm-kernel@...ts.infradead.org,
        kgdb-bugreport@...ts.sourceforge.net,
        Jason Wessel <jason.wessel@...driver.com>,
        Daniel Thompson <daniel.thompson@...aro.org>
Cc:     linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        Rabin Vincent <rabin@....in>
Subject: [PATCH] arm: kgdb: fix NUMREGBYTES so that gdb_regs[] is the correct size

From: David Rivshin <DRivshin@...worx.com>

NUMREGBYTES (which is used as the size for gdb_regs[]) is incorrectly based
on DBG_MAX_REG_NUM instead of GDB_MAX_REGS. DBG_MAX_REG_NUM is the number
of total registers, while GDB_MAX_REGS is the number of 'unsigned longs'
it takes to serialize those registers. Since FP registers require 3
'unsigned longs' each, DBG_MAX_REG_NUM is smaller than GDB_MAX_REGS.

This causes GDB 8.0 give the following error on connect:
"Truncated register 19 in remote 'g' packet"

This also causes the register serialization/deserialization logic to
overflow gdb_regs[], overwriting whatever follows.

Fixes: 834b2964b7ab ("kgdb,arm: fix register dump")
Cc: <stable@...r.kernel.org> # 2.6.37+
Signed-off-by: David Rivshin <drivshin@...worx.com>
---
 arch/arm/include/asm/kgdb.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/arm/include/asm/kgdb.h b/arch/arm/include/asm/kgdb.h
index 3b73fdcf3627a..8de1100d10674 100644
--- a/arch/arm/include/asm/kgdb.h
+++ b/arch/arm/include/asm/kgdb.h
@@ -77,7 +77,7 @@ extern int kgdb_fault_expected;
 
 #define KGDB_MAX_NO_CPUS	1
 #define BUFMAX			400
-#define NUMREGBYTES		(DBG_MAX_REG_NUM << 2)
+#define NUMREGBYTES		(GDB_MAX_REGS << 2)
 #define NUMCRITREGBYTES		(32 << 2)
 
 #define _R0			0

base-commit: 0adb32858b0bddf4ada5f364a84ed60b196dbcda
-- 
2.14.3