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From 3c8788dbb70b40e737d4b8e30cab81406e5c5091 Mon Sep 17 00:00:00 2001

From: Max Filippov <jcmvbkbc@gmail.com>

Date: Wed, 2 Aug 2017 00:36:05 -0700

Subject: [PATCH] xtensa: fix memory corruption by broken sysregs

​

In some xtensa configurations there may be system/user registers in

xtensa-modules with negative index. ISA initialization for such config

may clobber heap and result in program termination.

Don't update lookup table entries for register with negative indices.

They are not directly accessible via RSR/WSR/XSR or RUR/WUR, so this

change should not affect processing of valid assembly/binary code.

​

bfd/

2017-08-02  Max Filippov  <jcmvbkbc@gmail.com>

​

    * xtensa-isa.c (xtensa_isa_init): Don't update lookup table

    entries for sysregs with negative indices.

​

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>

---

Backported from: d84ed528d4817b0ff854006b65a9f6ec75f0407a

​

 bfd/xtensa-isa.c | 3 ++-

 1 file changed, 2 insertions(+), 1 deletion(-)

​

diff --git a/bfd/xtensa-isa.c b/bfd/xtensa-isa.c

index 8da75bea8109..8c6ee88fdeae 100644

--- a/bfd/xtensa-isa.c

+++ b/bfd/xtensa-isa.c

@@ -292,7 +292,8 @@ xtensa_isa_init (xtensa_isa_status *errno_p, char **error_msg_p)

       xtensa_sysreg_internal *sreg = &isa->sysregs[n];

       is_user = sreg->is_user;

-      isa->sysreg_table[is_user][sreg->number] = n;

+      if (sreg->number >= 0)

+   isa->sysreg_table[is_user][sreg->number] = n;

     }

   /* Set up the interface lookup table.  */

-- 

2.1.4

​