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Message-Id: <20220106203709.1525763-1-ccross@google.com>
Date: Thu, 6 Jan 2022 12:37:09 -0800
From: Colin Cross <ccross@...gle.com>
To: musl@...ts.openwall.com
Cc: Colin Cross <ccross@...gle.com>
Subject: [PATCH] Add mallinfo2 and mallinfo
glibc introduced mallinfo2 [1], which solves some of the arguments [2]
against including mallinfo in musl by expanding the width of the
returned counters from int to size_t.
This patch implements mallinfo2 without requiring any additional
metadata. It iterates through the meta_areas and metas in order
to count mmap, large and small allocations, and produces ordblks,
hblks, hblkhd, uordblks and fordblks values.
Once mallinfo2 exists, it is trivial to implement mallinfo that caps
the mallinfo2 outputs such that they fit in the int fields returned
by mallinfo.
[1] https://sourceware.org/git/?p=glibc.git;a=commit;h=e3960d1c57e57f33e0e846d615788f4ede73b945
[2] https://www.openwall.com/lists/musl/2018/01/17/2
---
The motivation for this patch is an attempt to use musl instead of glibc
to build host tools used when building the Android platform and the
tools that are distributed to app developers as part of the Android SDK.
mallinfo is used in a variety of third-party code built as part of
building Android, and tests and benchmarks in the Android tree.
The implementation has been lightly tested with bionic's malloc.mallinfo
and malloc.mallinfo2 tests, which verify that a variety of different
allocation sizes result in an increase of the uordblks value by at
least the usable size of the returned allocation.
I can keep this as a local patch in Android if it is still not acceptable
for musl.
dynamic.list | 1 +
include/malloc.h | 30 ++++++++++++++
src/malloc/mallocng/mallinfo.c | 73 ++++++++++++++++++++++++++++++++++
3 files changed, 104 insertions(+)
create mode 100644 src/malloc/mallocng/mallinfo.c
diff --git a/dynamic.list b/dynamic.list
index ee0d363b..84d13c53 100644
--- a/dynamic.list
+++ b/dynamic.list
@@ -14,6 +14,7 @@ memalign;
posix_memalign;
aligned_alloc;
malloc_usable_size;
+mallinfo;
timezone;
daylight;
diff --git a/include/malloc.h b/include/malloc.h
index 35f8b19c..98ba0100 100644
--- a/include/malloc.h
+++ b/include/malloc.h
@@ -18,6 +18,36 @@ void *memalign(size_t, size_t);
size_t malloc_usable_size(void *);
+struct mallinfo {
+ int arena;
+ int ordblks;
+ int smblks;
+ int hblks;
+ int hblkhd;
+ int usmblks;
+ int fsmblks;
+ int uordblks;
+ int fordblks;
+ int keepcost;
+};
+
+struct mallinfo mallinfo(void);
+
+struct mallinfo2 {
+ size_t arena;
+ size_t ordblks;
+ size_t smblks;
+ size_t hblks;
+ size_t hblkhd;
+ size_t usmblks;
+ size_t fsmblks;
+ size_t uordblks;
+ size_t fordblks;
+ size_t keepcost;
+};
+
+struct mallinfo2 mallinfo2(void);
+
#ifdef __cplusplus
}
#endif
diff --git a/src/malloc/mallocng/mallinfo.c b/src/malloc/mallocng/mallinfo.c
new file mode 100644
index 00000000..c60840b1
--- /dev/null
+++ b/src/malloc/mallocng/mallinfo.c
@@ -0,0 +1,73 @@
+#include <limits.h>
+#include <malloc.h>
+#include <stddef.h>
+
+#include "glue.h"
+#include "meta.h"
+
+static void accumulate_meta(struct mallinfo2 *mi, struct meta *g) {
+ int sc = g->sizeclass;
+ if (sc >= 48) {
+ // Large mmap allocation
+ mi->hblks++;
+ mi->uordblks += g->maplen*4096;
+ mi->hblkhd += g->maplen*4096;
+ } else {
+ if (g->freeable && !g->maplen) {
+ // Small size slots are embedded in a larger slot, avoid double counting
+ // by subtracing the size of the larger slot from the total used memory.
+ struct meta* outer_g = get_meta((void*)g->mem);
+ int outer_sc = outer_g->sizeclass;
+ int outer_sz = size_classes[outer_sc]*UNIT;
+ mi->uordblks -= outer_sz;
+ }
+ int sz = size_classes[sc]*UNIT;
+ int mask = g->avail_mask | g->freed_mask;
+ int nr_unused = __builtin_popcount(mask);
+ mi->ordblks += nr_unused;
+ mi->uordblks += sz*(g->last_idx+1-nr_unused);
+ mi->fordblks += sz*nr_unused;
+ }
+}
+
+static void accumulate_meta_area(struct mallinfo2 *mi, struct meta_area *ma) {
+ for (int i=0; i<ma->nslots; i++) {
+ if (ma->slots[i].mem) {
+ accumulate_meta(mi, &ma->slots[i]);
+ }
+ }
+}
+
+struct mallinfo2 mallinfo2() {
+ struct mallinfo2 mi = {0};
+
+ rdlock();
+ struct meta_area *ma = ctx.meta_area_head;
+ while (ma) {
+ accumulate_meta_area(&mi, ma);
+ ma = ma->next;
+ }
+ unlock();
+
+ return mi;
+}
+
+#define cap(x) ((x > INT_MAX) ? INT_MAX : x)
+
+struct mallinfo mallinfo() {
+ struct mallinfo mi = {0};
+ struct mallinfo2 mi2 = mallinfo2();
+
+ mi.arena = cap(mi2.arena);
+ mi.ordblks = cap(mi2.ordblks);
+ mi.smblks = cap(mi2.smblks);
+ mi.hblks = cap(mi2.hblks);
+ mi.hblkhd = cap(mi2.hblkhd);
+ mi.usmblks = cap(mi2.usmblks);
+ mi.fsmblks = cap(mi2.fsmblks);
+ mi.uordblks = cap(mi2.uordblks);
+ mi.fordblks = cap(mi2.fordblks);
+ mi.keepcost = cap(mi2.keepcost);
+
+ return mi;
+}
--
2.34.1.448.ga2b2bfdf31-goog
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