--- /dev/null
+From 82d91965519c20639c24aadd022b2859461562bc Mon Sep 17 00:00:00 2001
+From: Romain Naour <romain.naour@gmail.com>
+Date: Tue, 27 Apr 2021 14:54:28 +0200
+Subject: [PATCH] sparc64: avoid stringop-overread warning to access Machine
+ description datas
+
+gcc-11 warns about what appears to be an out-of-range array access but
+stop the build due to -Werror added to cflags:
+
+arch/sparc/kernel/mdesc.c: In function 'mdesc_node_by_name':
+arch/sparc/kernel/mdesc.c:647:22: error: 'strcmp' reading 1 or more bytes from a region of size 0 [-Werror=stringop-overread]
+ 647 | if (!strcmp(names + ep[ret].name_offset, name))
+ | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+arch/sparc/kernel/mdesc.c:77:33: note: at offset 16 into source object 'mdesc' of size 16
+ 77 | struct mdesc_hdr mdesc;
+ | ^~~~~
+arch/sparc/kernel/mdesc.c: In function 'mdesc_get_property':
+arch/sparc/kernel/mdesc.c:692:22: error: 'strcmp' reading 1 or more bytes from a region of size 0 [-Werror=stringop-overread]
+ 692 | if (!strcmp(names + ep->name_offset, name)) {
+ | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+arch/sparc/kernel/mdesc.c:77:33: note: at offset 16 into source object 'mdesc' of size 16
+ 77 | struct mdesc_hdr mdesc;
+ | ^~~~~
+arch/sparc/kernel/mdesc.c: In function 'mdesc_next_arc':
+arch/sparc/kernel/mdesc.c:719:21: error: 'strcmp' reading 1 or more bytes from a region of size 0 [-Werror=stringop-overread]
+ 719 | if (strcmp(names + ep->name_offset, arc_type))
+ | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+arch/sparc/kernel/mdesc.c:77:33: note: at offset 16 into source object 'mdesc' of size 16
+ 77 | struct mdesc_hdr mdesc;
+ | ^~~~~
+cc1: all warnings being treated as errors
+
+The issue was initially reported to gcc [1] where it was analized.
+As suggested, change the struct mdesc_elem * accesses from the end
+of mdesc to those from the beginning of the data array.
+
+Update the prototype of node_block(), name_block() and data_block()
+since the code really seems to want to do is to compute the address
+somewhere into the chunk pointed to by hp.
+
+[1] https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100262
+
+Upstream status: Pending
+https://www.spinics.net/lists/sparclinux/msg26385.html
+
+Signed-off-by: Romain Naour <romain.naour@gmail.com>
+---
+ arch/sparc/kernel/mdesc.c | 37 +++++++++++++++++++++----------------
+ 1 file changed, 21 insertions(+), 16 deletions(-)
+
+diff --git a/arch/sparc/kernel/mdesc.c b/arch/sparc/kernel/mdesc.c
+index 8e645ddac58e..3403555aa1e2 100644
+--- a/arch/sparc/kernel/mdesc.c
++++ b/arch/sparc/kernel/mdesc.c
+@@ -75,6 +75,7 @@ struct mdesc_handle {
+ refcount_t refcnt;
+ unsigned int handle_size;
+ struct mdesc_hdr mdesc;
++ char data[];
+ };
+
+ typedef int (*mdesc_node_info_get_f)(struct mdesc_handle *, u64,
+@@ -610,26 +611,30 @@ int mdesc_get_node_info(struct mdesc_handle *hp, u64 node,
+ }
+ EXPORT_SYMBOL(mdesc_get_node_info);
+
+-static struct mdesc_elem *node_block(struct mdesc_hdr *mdesc)
++static struct mdesc_elem *node_block(struct mdesc_handle *hp)
+ {
+- return (struct mdesc_elem *) (mdesc + 1);
++ return (struct mdesc_elem *) hp + offsetof(struct mdesc_handle, data);
+ }
+
+-static void *name_block(struct mdesc_hdr *mdesc)
++static void *name_block(struct mdesc_handle *hp)
+ {
+- return ((void *) node_block(mdesc)) + mdesc->node_sz;
++ struct mdesc_hdr *mdesc = &hp->mdesc;
++
++ return ((void *) node_block(hp)) + mdesc->node_sz;
+ }
+
+-static void *data_block(struct mdesc_hdr *mdesc)
++static void *data_block(struct mdesc_handle *hp)
+ {
+- return ((void *) name_block(mdesc)) + mdesc->name_sz;
++ struct mdesc_hdr *mdesc = &hp->mdesc;
++
++ return ((void *) name_block(hp)) + mdesc->name_sz;
+ }
+
+ u64 mdesc_node_by_name(struct mdesc_handle *hp,
+ u64 from_node, const char *name)
+ {
+- struct mdesc_elem *ep = node_block(&hp->mdesc);
+- const char *names = name_block(&hp->mdesc);
++ struct mdesc_elem *ep = node_block(hp);
++ const char *names = name_block(hp);
+ u64 last_node = hp->mdesc.node_sz / 16;
+ u64 ret;
+
+@@ -657,15 +662,15 @@ EXPORT_SYMBOL(mdesc_node_by_name);
+ const void *mdesc_get_property(struct mdesc_handle *hp, u64 node,
+ const char *name, int *lenp)
+ {
+- const char *names = name_block(&hp->mdesc);
++ const char *names = name_block(hp);
+ u64 last_node = hp->mdesc.node_sz / 16;
+- void *data = data_block(&hp->mdesc);
++ void *data = data_block(hp);
+ struct mdesc_elem *ep;
+
+ if (node == MDESC_NODE_NULL || node >= last_node)
+ return NULL;
+
+- ep = node_block(&hp->mdesc) + node;
++ ep = node_block(hp) + node;
+ ep++;
+ for (; ep->tag != MD_NODE_END; ep++) {
+ void *val = NULL;
+@@ -702,8 +707,8 @@ EXPORT_SYMBOL(mdesc_get_property);
+
+ u64 mdesc_next_arc(struct mdesc_handle *hp, u64 from, const char *arc_type)
+ {
+- struct mdesc_elem *ep, *base = node_block(&hp->mdesc);
+- const char *names = name_block(&hp->mdesc);
++ struct mdesc_elem *ep, *base = node_block(hp);
++ const char *names = name_block(hp);
+ u64 last_node = hp->mdesc.node_sz / 16;
+
+ if (from == MDESC_NODE_NULL || from >= last_node)
+@@ -728,7 +733,7 @@ EXPORT_SYMBOL(mdesc_next_arc);
+
+ u64 mdesc_arc_target(struct mdesc_handle *hp, u64 arc)
+ {
+- struct mdesc_elem *ep, *base = node_block(&hp->mdesc);
++ struct mdesc_elem *ep, *base = node_block(hp);
+
+ ep = base + arc;
+
+@@ -738,8 +743,8 @@ EXPORT_SYMBOL(mdesc_arc_target);
+
+ const char *mdesc_node_name(struct mdesc_handle *hp, u64 node)
+ {
+- struct mdesc_elem *ep, *base = node_block(&hp->mdesc);
+- const char *names = name_block(&hp->mdesc);
++ struct mdesc_elem *ep, *base = node_block(hp);
++ const char *names = name_block(hp);
+ u64 last_node = hp->mdesc.node_sz / 16;
+
+ if (node == MDESC_NODE_NULL || node >= last_node)
+--
+2.30.2
+
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