git: 1b4e08b4832d - main - linuxkpi: Support non-NULL zero-size pointers

The branch main has been updated by dumbbell:

URL: https://cgit.FreeBSD.org/src/commit/?id=1b4e08b4832deeea4b9121cdaed4f6700bdab03f

commit 1b4e08b4832deeea4b9121cdaed4f6700bdab03f
Author:     Jean-Sébastien Pédron <dumbbell@FreeBSD.org>
AuthorDate: 2023-02-20 20:50:29 +0000
Commit:     Jean-Sébastien Pédron <dumbbell@FreeBSD.org>
CommitDate: 2023-03-20 20:47:36 +0000

    linuxkpi: Support non-NULL zero-size pointers
    
    DRM drivers set some pointers to `ZERO_SIZE_PTR` directly (without
    allocating anything), to treat pointers which were "initialized" (set to
    `ZERO_SIZE_PTR`) with no memory allocation like really allocated
    pointers. NULL isn't used because it represents a third state.
    
    Reviewed by:    emaste, manu
    Approved by:    emaste, manu
    Differential Revision:  https://reviews.freebsd.org/D39055
---
 sys/compat/linuxkpi/common/include/linux/slab.h | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/sys/compat/linuxkpi/common/include/linux/slab.h b/sys/compat/linuxkpi/common/include/linux/slab.h
index 915f33acf67e..a2cce4cfe75a 100644
--- a/sys/compat/linuxkpi/common/include/linux/slab.h
+++ b/sys/compat/linuxkpi/common/include/linux/slab.h
@@ -90,7 +90,8 @@ struct linux_kmem_cache;
 /* drm-kmod 5.4 compat */
 #define kfree_async(ptr)	kfree(ptr);
 
-#define ZERO_OR_NULL_PTR(x)	((x) == NULL)
+#define	ZERO_SIZE_PTR		((void *)16)
+#define ZERO_OR_NULL_PTR(x)	((x) == NULL || (x) == ZERO_SIZE_PTR)
 
 static inline gfp_t
 linux_check_m_flags(gfp_t flags)
@@ -195,6 +196,9 @@ extern void linux_kfree_async(void *);
 static inline void
 kfree(const void *ptr)
 {
+	if (ZERO_OR_NULL_PTR(ptr))
+		return;
+
 	if (curthread->td_critnest != 0)
 		linux_kfree_async(__DECONST(void *, ptr));
 	else
@@ -204,6 +208,9 @@ kfree(const void *ptr)
 static __inline void
 kfree_sensitive(const void *ptr)
 {
+	if (ZERO_OR_NULL_PTR(ptr))
+		return;
+
 	zfree(__DECONST(void *, ptr), M_KMALLOC);
 }