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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [xen staging] xen/sort: Switch to an extern inline implementation
commit 8cb0341a61fa8e6e27e8715e4c2db379f38e90ab
Author: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
AuthorDate: Sat Oct 30 22:13:55 2021 +0100
Commit: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
CommitDate: Wed Feb 23 15:33:42 2022 +0000
xen/sort: Switch to an extern inline implementation
There are exactly 3 callers of sort() in the hypervisor. Callbacks in a
tight
loop like this are problematic for performance, especially with Spectre v2
protections, which is why extern inline is used commonly by libraries.
Both ARM callers pass in NULL for the swap function, and while this might
seem
like an attractive option at first, it causes generic_swap() to be used,
which
forced a byte-wise copy. Provide real swap functions so the compiler can
optimise properly, which is very important for ARM downstreams where
milliseconds until the system is up matters.
This is also important for Control Flow Integrity schemes (e.g. x86 CET-IBT,
ARM BTI), because tagged function(s) performing an arbitrary length swap of
two arbitrary pointers is a very valuable gadget for an attacker.
No functional change.
Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
Reviewed-by: Bertrand Marquis <bertrand.marquis@xxxxxxx>
Acked-by: Julien Grall <jgrall@xxxxxxxxxx>
---
xen/arch/arm/bootfdt.c | 9 +++++-
xen/arch/arm/io.c | 9 +++++-
xen/include/xen/sort.h | 55 +++++++++++++++++++++++++++++++++-
xen/lib/sort.c | 80 ++------------------------------------------------
4 files changed, 72 insertions(+), 81 deletions(-)
diff --git a/xen/arch/arm/bootfdt.c b/xen/arch/arm/bootfdt.c
index afaa0e249b..e318ef9603 100644
--- a/xen/arch/arm/bootfdt.c
+++ b/xen/arch/arm/bootfdt.c
@@ -448,6 +448,13 @@ static int __init cmp_memory_node(const void *key, const
void *elem)
return 0;
}
+static void __init swap_memory_node(void *_a, void *_b, size_t size)
+{
+ struct membank *a = _a, *b = _b;
+
+ SWAP(*a, *b);
+}
+
/**
* boot_fdt_info - initialize bootinfo from a DTB
* @fdt: flattened device tree binary
@@ -472,7 +479,7 @@ size_t __init boot_fdt_info(const void *fdt, paddr_t paddr)
* the banks sorted in ascending order. So sort them through.
*/
sort(bootinfo.mem.bank, bootinfo.mem.nr_banks, sizeof(struct membank),
- cmp_memory_node, NULL);
+ cmp_memory_node, swap_memory_node);
early_print_info();
diff --git a/xen/arch/arm/io.c b/xen/arch/arm/io.c
index 729287e37c..1a066f9ae5 100644
--- a/xen/arch/arm/io.c
+++ b/xen/arch/arm/io.c
@@ -80,6 +80,13 @@ static int cmp_mmio_handler(const void *key, const void
*elem)
return 0;
}
+static void swap_mmio_handler(void *_a, void *_b, size_t size)
+{
+ struct mmio_handler *a = _a, *b = _b;
+
+ SWAP(*a, *b);
+}
+
static const struct mmio_handler *find_mmio_handler(struct domain *d,
paddr_t gpa)
{
@@ -170,7 +177,7 @@ void register_mmio_handler(struct domain *d,
/* Sort mmio handlers in ascending order based on base address */
sort(vmmio->handlers, vmmio->num_entries, sizeof(struct mmio_handler),
- cmp_mmio_handler, NULL);
+ cmp_mmio_handler, swap_mmio_handler);
write_unlock(&vmmio->lock);
}
diff --git a/xen/include/xen/sort.h b/xen/include/xen/sort.h
index a403652948..2f52ff85b9 100644
--- a/xen/include/xen/sort.h
+++ b/xen/include/xen/sort.h
@@ -3,8 +3,61 @@
#include <xen/types.h>
+/*
+ * sort - sort an array of elements
+ * @base: pointer to data to sort
+ * @num: number of elements
+ * @size: size of each element
+ * @cmp: pointer to comparison function
+ * @swap: pointer to swap function
+ *
+ * This function does a heapsort on the given array. You may provide a
+ * swap function optimized to your element type.
+ *
+ * Sorting time is O(n log n) both on average and worst-case. While
+ * qsort is about 20% faster on average, it suffers from exploitable
+ * O(n*n) worst-case behavior and extra memory requirements that make
+ * it less suitable for kernel use.
+ */
+#ifndef SORT_IMPLEMENTATION
+extern gnu_inline
+#endif
void sort(void *base, size_t num, size_t size,
int (*cmp)(const void *, const void *),
- void (*swap)(void *, void *, size_t));
+ void (*swap)(void *, void *, size_t))
+{
+ /* pre-scale counters for performance */
+ size_t i = (num / 2) * size, n = num * size, c, r;
+
+ /* heapify */
+ while ( i > 0 )
+ {
+ for ( r = i -= size; r * 2 + size < n; r = c )
+ {
+ c = r * 2 + size;
+ if ( (c < n - size) && (cmp(base + c, base + c + size) < 0) )
+ c += size;
+ if ( cmp(base + r, base + c) >= 0 )
+ break;
+ swap(base + r, base + c, size);
+ }
+ }
+
+ /* sort */
+ for ( i = n; i > 0; )
+ {
+ i -= size;
+ swap(base, base + i, size);
+ for ( r = 0; r * 2 + size < i; r = c )
+ {
+ c = r * 2 + size;
+ if ( (c < i - size) && (cmp(base + c, base + c + size) < 0) )
+ c += size;
+ if ( cmp(base + r, base + c) >= 0 )
+ break;
+ swap(base + r, base + c, size);
+ }
+ }
+}
#endif /* __XEN_SORT_H__ */
diff --git a/xen/lib/sort.c b/xen/lib/sort.c
index 35ce0d7abd..b7e78cc0e8 100644
--- a/xen/lib/sort.c
+++ b/xen/lib/sort.c
@@ -4,81 +4,5 @@
* Jan 23 2005 Matt Mackall <mpm@xxxxxxxxxxx>
*/
-#include <xen/types.h>
-
-static void u32_swap(void *a, void *b, size_t size)
-{
- uint32_t t = *(uint32_t *)a;
-
- *(uint32_t *)a = *(uint32_t *)b;
- *(uint32_t *)b = t;
-}
-
-static void generic_swap(void *a, void *b, size_t size)
-{
- char t;
-
- do {
- t = *(char *)a;
- *(char *)a++ = *(char *)b;
- *(char *)b++ = t;
- } while ( --size > 0 );
-}
-
-/*
- * sort - sort an array of elements
- * @base: pointer to data to sort
- * @num: number of elements
- * @size: size of each element
- * @cmp: pointer to comparison function
- * @swap: pointer to swap function or NULL
- *
- * This function does a heapsort on the given array. You may provide a
- * swap function optimized to your element type.
- *
- * Sorting time is O(n log n) both on average and worst-case. While
- * qsort is about 20% faster on average, it suffers from exploitable
- * O(n*n) worst-case behavior and extra memory requirements that make
- * it less suitable for kernel use.
- */
-
-void sort(void *base, size_t num, size_t size,
- int (*cmp)(const void *, const void *),
- void (*swap)(void *, void *, size_t size))
-{
- /* pre-scale counters for performance */
- size_t i = (num / 2) * size, n = num * size, c, r;
-
- if ( !swap )
- swap = (size == 4 ? u32_swap : generic_swap);
-
- /* heapify */
- while ( i > 0 )
- {
- for ( r = i -= size; r * 2 + size < n; r = c )
- {
- c = r * 2 + size;
- if ( (c < n - size) && (cmp(base + c, base + c + size) < 0) )
- c += size;
- if ( cmp(base + r, base + c) >= 0 )
- break;
- swap(base + r, base + c, size);
- }
- }
-
- /* sort */
- for ( i = n; i > 0; )
- {
- i -= size;
- swap(base, base + i, size);
- for ( r = 0; r * 2 + size < i; r = c )
- {
- c = r * 2 + size;
- if ( (c < i - size) && (cmp(base + c, base + c + size) < 0) )
- c += size;
- if ( cmp(base + r, base + c) >= 0 )
- break;
- swap(base + r, base + c, size);
- }
- }
-}
+#define SORT_IMPLEMENTATION
+#include <xen/sort.h>
--
generated by git-patchbot for /home/xen/git/xen.git#staging
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