MIPS: OCTEON: make get_system_type() thread-safe

commit 608308682addfdc7b8e2aee88f0e028331d88e4d upstream.

get_system_type() is not thread-safe on OCTEON. It uses static data,
also more dangerous issue is that it's calling cvmx_fuse_read_byte()
every time without any synchronization. Currently it's possible to get
processes stuck looping forever in kernel simply by launching multiple
readers of /proc/cpuinfo:

	(while true; do cat /proc/cpuinfo > /dev/null; done) &
	(while true; do cat /proc/cpuinfo > /dev/null; done) &
	...

Fix by initializing the system type string only once during the early
boot.

Signed-off-by: Aaro Koskinen <aaro.koskinen@nsn.com>
Reviewed-by: Markos Chandras <markos.chandras@imgtec.com>
Patchwork: http://patchwork.linux-mips.org/patch/7437/
Signed-off-by: James Hogan <james.hogan@imgtec.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/arch/mips/cavium-octeon/setup.c b/arch/mips/cavium-octeon/setup.c
index 2d9028f..3c5f61c 100644 (file)
--- a/arch/mips/cavium-octeon/setup.c
+++ b/arch/mips/cavium-octeon/setup.c
@@ -266,6 +266,18 @@ static irqreturn_t octeon_rlm_interrupt(int cpl, void *dev_id)
 }
 #endif
 
+static char __read_mostly octeon_system_type[80];
+
+static int __init init_octeon_system_type(void)
+{
+       snprintf(octeon_system_type, sizeof(octeon_system_type), "%s (%s)",
+               cvmx_board_type_to_string(octeon_bootinfo->board_type),
+               octeon_model_get_string(read_c0_prid()));
+
+       return 0;
+}
+early_initcall(init_octeon_system_type);
+
 /**
  * Return a string representing the system type
  *
@@ -273,11 +285,7 @@ static irqreturn_t octeon_rlm_interrupt(int cpl, void *dev_id)
  */
 const char *octeon_board_type_string(void)
 {
-       static char name[80];
-       sprintf(name, "%s (%s)",
-               cvmx_board_type_to_string(octeon_bootinfo->board_type),
-               octeon_model_get_string(read_c0_prid()));
-       return name;
+       return octeon_system_type;
 }
 
 const char *get_system_type(void)