[PATCH v4 09/22] stack: fix unaligned accesses on 128-bit

[David Marchand <david.marchand@redhat.com>]

Caught by UBSan:

../lib/eal/x86/include/rte_atomic_64.h:206:21: runtime error:
	member access within misaligned address 0x7ffd9c67f228 for
	type 'const rte_int128_t', which requires 16 byte alignment
	0x7ffd9c67f228: note: pointer points here
 00 00 00 00  c0 5d 3e 00 01 00 00 00  01 00 00 00 00 00 00 00
              ^
 00 00 00 00 00 00 00 00  00 00 00 00
SUMMARY: UndefinedBehaviorSanitizer: undefined-behavior
	../lib/eal/x86/include/rte_atomic_64.h:206:21 in
	../lib/eal/x86/include/rte_atomic_64.h:206:21: runtime error:
	member access within misaligned address 0x7ffd9c67f228 for type
	'const union rte_int128_t::(anonymous at
	../lib/eal/include/generic/rte_atomic.h:1102:2)', which requires
	16 byte alignment
0x7ffd9c67f228: note: pointer points here
 00 00 00 00  c0 5d 3e 00 01 00 00 00  01 00 00 00 00 00 00 00
              ^
 00 00 00 00 00 00 00 00  00 00 00 00
SUMMARY: UndefinedBehaviorSanitizer: undefined-behavior
	../lib/eal/x86/include/rte_atomic_64.h:206:21 in
	../lib/eal/x86/include/rte_atomic_64.h:206:16: runtime error:
	load of misaligned address 0x7ffd9c67f228 for type
	'const uint64_t' (aka 'const unsigned long'), which requires
	16 byte alignment
0x7ffd9c67f228: note: pointer points here
 00 00 00 00  c0 5d 3e 00 01 00 00 00  01 00 00 00 00 00 00 00
              ^
 00 00 00 00 00 00 00 00  00 00 00 00
SUMMARY: UndefinedBehaviorSanitizer: undefined-behavior
	../lib/eal/x86/include/rte_atomic_64.h:206:21 in

Rather than explicitly set alignment in callers, mark the structure
itself with an alignment constraint.

Fixes: 3340202f5954 ("stack: add lock-free implementation")

Signed-off-by: David Marchand <david.marchand@redhat.com>
Acked-by: Bruce Richardson <bruce.richardson@intel.com>
Acked-by: Konstantin Ananyev <konstantin.ananyev@huawei.com>
---
Changes since v3:
- changed rte_stack_lf_head struct alignment,

---
 devtools/libabigail.abignore | 8 ++++++++
 lib/stack/rte_stack.h        | 4 ++--
 2 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/devtools/libabigail.abignore b/devtools/libabigail.abignore
index 96ae32455f..c65bea2b51 100644
--- a/devtools/libabigail.abignore
+++ b/devtools/libabigail.abignore
@@ -47,3 +47,11 @@
         name = rte_node
         has_size_change = no
         has_data_member_inserted_between = {offset_after(original_process), offset_of(xstat_off)}
+
+;;;;;;;;;;;;;;;;;;;
+; DONT MERGE THIS ;
+;;;;;;;;;;;;;;;;;;;
+
+[suppress_type]
+	name = rte_stack_lf_list
+	has_size_change = yes
diff --git a/lib/stack/rte_stack.h b/lib/stack/rte_stack.h
index 4439adfc42..fd17ac791d 100644
--- a/lib/stack/rte_stack.h
+++ b/lib/stack/rte_stack.h
@@ -33,14 +33,14 @@ struct rte_stack_lf_elem {
 	struct rte_stack_lf_elem *next;	/**< Next pointer */
 };
 
-struct rte_stack_lf_head {
+struct __rte_aligned(16) rte_stack_lf_head {
 	struct rte_stack_lf_elem *top; /**< Stack top */
 	uint64_t cnt; /**< Modification counter for avoiding ABA problem */
 };
 
 struct rte_stack_lf_list {
 	/** List head */
-	alignas(16) struct rte_stack_lf_head head;
+	struct rte_stack_lf_head head;
 	/** List len */
 	RTE_ATOMIC(uint64_t) len;
 };
-- 
2.50.0