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>

1 files changed, 42 insertions, 0 deletions

diff --git a/arch/powerpc/boot/stdlib.c b/arch/powerpc/boot/stdlib.c
new file mode 100644
index 000000000..868b019d6
--- /dev/null
+++ b/arch/powerpc/boot/stdlib.c
@@ -0,0 +1,42 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * stdlib functions
+ *
+ * Author: Scott Wood <scottwood@freescale.com>
+ *
+ * Copyright (c) 2007 Freescale Semiconductor, Inc.
+ */
+
+#include "stdlib.h"
+
+/* Not currently supported: leading whitespace, sign, 0x prefix, zero base */
+unsigned long long int strtoull(const char *ptr, char **end, int base)
+{
+	unsigned long long ret = 0;
+
+	if (base > 36)
+		goto out;
+
+	while (*ptr) {
+		int digit;
+
+		if (*ptr >= '0' && *ptr <= '9' && *ptr < '0' + base)
+			digit = *ptr - '0';
+		else if (*ptr >= 'A' && *ptr < 'A' + base - 10)
+			digit = *ptr - 'A' + 10;
+		else if (*ptr >= 'a' && *ptr < 'a' + base - 10)
+			digit = *ptr - 'a' + 10;
+		else
+			break;
+
+		ret *= base;
+		ret += digit;
+		ptr++;
+	}
+
+out:
+	if (end)
+		*end = (char *)ptr;
+
+	return ret;
+}