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[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.

2017-08-02  Max Filippov  <>

	* xtensa-isa.c (xtensa_isa_init): Don't update lookup table
	entries for sysregs with negative indices.
 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.  */

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