[PATCH rcu 07/11] rcutorture: Make cur_ops->format_gp_seqs take buffer length

[Paul E. McKenney]

The Tree and Tiny implementations of rcutorture_format_gp_seqs() use
hard-coded constants for the length of the buffer that they format into.
This is of course an accident waiting to happen, so this commit therefore
makes them take a length argument.  The rcutorture calling code uses
ARRAY_SIZE() to safely compute this new argument.

Signed-off-by: Paul E. McKenney <paul...@kernel.org>
---
 kernel/rcu/rcu.h        | 2 +-
 kernel/rcu/rcutorture.c | 8 +++++---
 kernel/rcu/tiny.c       | 4 ++--
 kernel/rcu/tree.c       | 4 ++--
 4 files changed, 10 insertions(+), 8 deletions(-)

diff --git a/kernel/rcu/rcu.h b/kernel/rcu/rcu.h
index d2a91f705a4ab..eed2951a4962d 100644
--- a/kernel/rcu/rcu.h
+++ b/kernel/rcu/rcu.h
@@ -591,7 +591,7 @@ void do_trace_rcu_torture_read(const char *rcutorturename,
 static inline void rcu_gp_set_torture_wait(int duration) { }
 #endif
 unsigned long long rcutorture_gather_gp_seqs(void);
-void rcutorture_format_gp_seqs(unsigned long long seqs, char *cp);
+void rcutorture_format_gp_seqs(unsigned long long seqs, char *cp, size_t len);
 
 #ifdef CONFIG_TINY_SRCU
 
diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
index 0f5a945427190..2e6e8664e4038 100644
--- a/kernel/rcu/rcutorture.c
+++ b/kernel/rcu/rcutorture.c
@@ -411,7 +411,7 @@ struct rcu_torture_ops {
        void (*gp_slow_unregister)(atomic_t *rgssp);
        bool (*reader_blocked)(void);
        unsigned long long (*gather_gp_seqs)(void);
-       void (*format_gp_seqs)(unsigned long long seqs, char *cp);
+       void (*format_gp_seqs)(unsigned long long seqs, char *cp, size_t len);
        long cbflood_max;
        int irq_capable;
        int can_boost;
@@ -3699,8 +3699,10 @@ rcu_torture_cleanup(void)
                                char buf2[20+1];
                                char sepchar = '-';
 
-                               cur_ops->format_gp_seqs(err_segs[i].rt_gp_seq, 
buf1);
-                               
cur_ops->format_gp_seqs(err_segs[i].rt_gp_seq_end, buf2);
+                               cur_ops->format_gp_seqs(err_segs[i].rt_gp_seq,
+                                                       buf1, ARRAY_SIZE(buf1));
+                               
cur_ops->format_gp_seqs(err_segs[i].rt_gp_seq_end,
+                                                       buf2, ARRAY_SIZE(buf2));
                                if (err_segs[i].rt_gp_seq == 
err_segs[i].rt_gp_seq_end) {
                                        if (buf2[0]) {
                                                for (j = 0; buf2[j]; j++)
diff --git a/kernel/rcu/tiny.c b/kernel/rcu/tiny.c
index b97c64e99a905..6380fbd27557a 100644
--- a/kernel/rcu/tiny.c
+++ b/kernel/rcu/tiny.c
@@ -264,9 +264,9 @@ unsigned long long rcutorture_gather_gp_seqs(void)
 }
 EXPORT_SYMBOL_GPL(rcutorture_gather_gp_seqs);
 
-void rcutorture_format_gp_seqs(unsigned long long seqs, char *cp)
+void rcutorture_format_gp_seqs(unsigned long long seqs, char *cp, size_t len)
 {
-       snprintf(cp, 8, "g%04llx", seqs & 0xffffULL);
+       snprintf(cp, len, "g%04llx", seqs & 0xffffULL);
 }
 EXPORT_SYMBOL_GPL(rcutorture_format_gp_seqs);
 #endif
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index ac596596e7717..1d201455aa7c3 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -569,13 +569,13 @@ unsigned long long rcutorture_gather_gp_seqs(void)
 EXPORT_SYMBOL_GPL(rcutorture_gather_gp_seqs);
 
 /* Format grace-period sequence numbers for rcutorture diagnostics. */
-void rcutorture_format_gp_seqs(unsigned long long seqs, char *cp)
+void rcutorture_format_gp_seqs(unsigned long long seqs, char *cp, size_t len)
 {
        unsigned int egp = (seqs >> 16) & 0xffffffULL;
        unsigned int ggp = (seqs >> 40) & 0xffffULL;
        unsigned int pgp = seqs & 0xffffULL;
 
-       snprintf(cp, 20, "g%04x:e%06x:p%04x", ggp, egp, pgp);
+       snprintf(cp, len, "g%04x:e%06x:p%04x", ggp, egp, pgp);
 }
 EXPORT_SYMBOL_GPL(rcutorture_format_gp_seqs);
 
-- 
2.40.1