selftests/bpf: Test rhtab kptr cancellation semanticsgrafted

Resizable hash-map updates and deletions must not perform full special-field
destruction in their caller context. In particular, a referenced kptr must
remain attached to the allocation until the memory allocator destructor can
release it safely.

Add separate coverage for both affected paths. The update test stores a task
kptr, replaces the ordinary value bytes with BPF_EXIST, and verifies that the
kptr survived. The delete test removes an element and exchanges its kptr
through the still-valid map-value pointer before the allocation is reclaimed.

Both cases observe a NULL kptr when rhtab uses bpf_obj_free_fields(). They
recover and release the reference after rhtab switches to cancellation
semantics.

Signed-off-by: Nuoqi Gui <gnq25@mails.tsinghua.edu.cn>
[ kkd: Split update and delete coverage and rewrote the commit log ]
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20260904104203.345917-5-memxor@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

2 files changed, 64 insertions, 0 deletions

diff --git a/tools/arch/xtensa/include/asm/barrier.h b/tools/arch/xtensa/include/asm/barrier.h
new file mode 100644
index 000000000..583800bd7
--- /dev/null
+++ b/tools/arch/xtensa/include/asm/barrier.h
@@ -0,0 +1,18 @@
+/*
+ * Copied from the kernel sources to tools/:
+ *
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License.  See the file "COPYING" in the main directory of this archive
+ * for more details.
+ *
+ * Copyright (C) 2001 - 2012 Tensilica Inc.
+ */
+
+#ifndef _TOOLS_LINUX_XTENSA_SYSTEM_H
+#define _TOOLS_LINUX_XTENSA_SYSTEM_H
+
+#define mb()  ({ __asm__ __volatile__("memw" : : : "memory"); })
+#define rmb() barrier()
+#define wmb() mb()
+
+#endif /* _TOOLS_LINUX_XTENSA_SYSTEM_H */
diff --git a/tools/arch/xtensa/include/uapi/asm/mman.h b/tools/arch/xtensa/include/uapi/asm/mman.h
new file mode 100644
index 000000000..f2b08c990
--- /dev/null
+++ b/tools/arch/xtensa/include/uapi/asm/mman.h
@@ -0,0 +1,46 @@
+/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
+#ifndef TOOLS_ARCH_XTENSA_UAPI_ASM_MMAN_FIX_H
+#define TOOLS_ARCH_XTENSA_UAPI_ASM_MMAN_FIX_H
+#define MADV_DODUMP	17
+#define MADV_DOFORK	11
+#define MADV_DONTDUMP   16
+#define MADV_DONTFORK	10
+#define MADV_DONTNEED	4
+#define MADV_FREE	8
+#define MADV_HUGEPAGE	14
+#define MADV_MERGEABLE   12
+#define MADV_NOHUGEPAGE	15
+#define MADV_NORMAL	0
+#define MADV_RANDOM	1
+#define MADV_REMOVE	9
+#define MADV_SEQUENTIAL	2
+#define MADV_UNMERGEABLE 13
+#define MADV_WILLNEED	3
+#define MAP_ANONYMOUS	0x0800
+#define MAP_DENYWRITE	0x2000
+#define MAP_EXECUTABLE	0x4000
+#define MAP_FILE	0
+#define MAP_FIXED	0x010
+#define MAP_GROWSDOWN	0x1000
+#define MAP_HUGETLB	0x80000
+#define MAP_LOCKED	0x8000
+#define MAP_NONBLOCK	0x20000
+#define MAP_NORESERVE	0x0400
+#define MAP_POPULATE	0x10000
+#define MAP_STACK	0x40000
+#define PROT_EXEC	0x4
+#define PROT_GROWSDOWN	0x01000000
+#define PROT_GROWSUP	0x02000000
+#define PROT_NONE	0x0
+#define PROT_READ	0x1
+#define PROT_SEM	0x10
+#define PROT_WRITE	0x2
+/* MADV_HWPOISON is undefined on xtensa, fix it for perf */
+#define MADV_HWPOISON	100
+/* MADV_SOFT_OFFLINE is undefined on xtensa, fix it for perf */
+#define MADV_SOFT_OFFLINE 101
+/* MAP_32BIT is undefined on xtensa, fix it for perf */
+#define MAP_32BIT	0
+/* MAP_UNINITIALIZED is undefined on xtensa, fix it for perf */
+#define MAP_UNINITIALIZED	0
+#endif