[Xen-devel] [PATCH V2 3/6] [RFC] xen/common: Introduce _xrealloc function

[Oleksandr Tyshchenko <olekstysh@xxxxxxxxx>]

From: Oleksandr Tyshchenko <oleksandr_tyshchenko@xxxxxxxx>

Next patch in this series will make use of it.

Original patch was initially posted by Sameer Goel:
https://lists.xen.org/archives/html/xen-devel/2017-06/msg00858.html

This could be considered as another attempt to add it:
https://www.mail-archive.com/kexec@xxxxxxxxxxxxxxxxxxx/msg21335.html

Signed-off-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@xxxxxxxx>
CC: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
CC: George Dunlap <George.Dunlap@xxxxxxxxxxxxx>
CC: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
CC: Jan Beulich <jbeulich@xxxxxxxx>
CC: Julien Grall <julien.grall@xxxxxxx>
CC: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
CC: Stefano Stabellini <sstabellini@xxxxxxxxxx>
CC: Tim Deegan <tim@xxxxxxx>
CC: Wei Liu <wl@xxxxxxx>

---
   [As it was previously discussed with Julien in IRC]

   The reason for this patch to be an RFC is that patch itself is not
   completely correct and I don't fully understand what/how should
   be done for this patch to be accepted. Or whether community even
   wants this to go in. So, to avoid bike shedding, the first target is
   to collect feedback from the maintainers.

   In a nutshell, the upcoming "iommu_fwspec" support on ARM
   is going to use xrealloc when adding new device ID.
   
   We really want to have "iommu_fwspec" support which will give us
   a generic abstract way to add new device to the IOMMU based on
   the generic IOMMU DT binding.
   
   This is how Linux does:
   https://github.com/torvalds/linux/blob/master/drivers/iommu/iommu.c#L2257
   and we are doing the similar in next patch of this thread:
   "iommu/arm: Add lightweight iommu_fwspec support"
---
 xen/common/xmalloc_tlsf.c | 21 +++++++++++++++++++++
 xen/include/xen/xmalloc.h |  1 +
 2 files changed, 22 insertions(+)

diff --git a/xen/common/xmalloc_tlsf.c b/xen/common/xmalloc_tlsf.c
index 2076953..c080763 100644
--- a/xen/common/xmalloc_tlsf.c
+++ b/xen/common/xmalloc_tlsf.c
@@ -610,6 +610,27 @@ void *_xzalloc(unsigned long size, unsigned long align)
     return p ? memset(p, 0, size) : p;
 }
 
+void *_xrealloc(void *p, unsigned long new_size, unsigned long align)
+{
+    void *new_p;
+
+    if ( !new_size )
+    {
+        xfree(p);
+        return NULL;
+    }
+
+    new_p = _xmalloc(new_size, align);
+
+    if ( new_p && p )
+    {
+        memcpy(new_p, p, new_size);
+        xfree(p);
+    }
+
+    return new_p;
+}
+
 void xfree(void *p)
 {
     struct bhdr *b;
diff --git a/xen/include/xen/xmalloc.h b/xen/include/xen/xmalloc.h
index b486fe4..63961ef 100644
--- a/xen/include/xen/xmalloc.h
+++ b/xen/include/xen/xmalloc.h
@@ -51,6 +51,7 @@ extern void xfree(void *);
 /* Underlying functions */
 extern void *_xmalloc(unsigned long size, unsigned long align);
 extern void *_xzalloc(unsigned long size, unsigned long align);
+extern void *_xrealloc(void *p, unsigned long new_size, unsigned long align);
 
 static inline void *_xmalloc_array(
     unsigned long size, unsigned long align, unsigned long num)
-- 
2.7.4


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