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From 6cc3ccc67e0dda654fc839377af2818a296f0007 Mon Sep 17 00:00:00 2001
From: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Date: Mon, 16 Aug 2021 11:14:20 -0300
Subject: [PATCH 3/7] malloc: Move mmap logic to its own function
So it can be used with different pagesize and flags.
Reviewed-by: DJ Delorie <dj@redhat.com>
---
malloc/malloc.c | 164 ++++++++++++++++++++++++++----------------------
1 file changed, 88 insertions(+), 76 deletions(-)
diff --git a/malloc/malloc.c b/malloc/malloc.c
index 57db4dd9a5..6b6ec53db1 100644
--- a/malloc/malloc.c
+++ b/malloc/malloc.c
@@ -2412,6 +2412,85 @@ do_check_malloc_state (mstate av)
be extended or replaced.
*/
+static void *
+sysmalloc_mmap (INTERNAL_SIZE_T nb, size_t pagesize, int extra_flags, mstate av)
+{
+ long int size;
+
+ /*
+ Round up size to nearest page. For mmapped chunks, the overhead is one
+ SIZE_SZ unit larger than for normal chunks, because there is no
+ following chunk whose prev_size field could be used.
+
+ See the front_misalign handling below, for glibc there is no need for
+ further alignments unless we have have high alignment.
+ */
+ if (MALLOC_ALIGNMENT == CHUNK_HDR_SZ)
+ size = ALIGN_UP (nb + SIZE_SZ, pagesize);
+ else
+ size = ALIGN_UP (nb + SIZE_SZ + MALLOC_ALIGN_MASK, pagesize);
+
+ /* Don't try if size wraps around 0. */
+ if ((unsigned long) (size) <= (unsigned long) (nb))
+ return MAP_FAILED;
+
+ char *mm = (char *) MMAP (0, size,
+ mtag_mmap_flags | PROT_READ | PROT_WRITE,
+ extra_flags);
+ if (mm == MAP_FAILED)
+ return mm;
+
+ madvise_thp (mm, size);
+
+ /*
+ The offset to the start of the mmapped region is stored in the prev_size
+ field of the chunk. This allows us to adjust returned start address to
+ meet alignment requirements here and in memalign(), and still be able to
+ compute proper address argument for later munmap in free() and realloc().
+ */
+
+ INTERNAL_SIZE_T front_misalign; /* unusable bytes at front of new space */
+
+ if (MALLOC_ALIGNMENT == CHUNK_HDR_SZ)
+ {
+ /* For glibc, chunk2mem increases the address by CHUNK_HDR_SZ and
+ MALLOC_ALIGN_MASK is CHUNK_HDR_SZ-1. Each mmap'ed area is page
+ aligned and therefore definitely MALLOC_ALIGN_MASK-aligned. */
+ assert (((INTERNAL_SIZE_T) chunk2mem (mm) & MALLOC_ALIGN_MASK) == 0);
+ front_misalign = 0;
+ }
+ else
+ front_misalign = (INTERNAL_SIZE_T) chunk2mem (mm) & MALLOC_ALIGN_MASK;
+
+ mchunkptr p; /* the allocated/returned chunk */
+
+ if (front_misalign > 0)
+ {
+ ptrdiff_t correction = MALLOC_ALIGNMENT - front_misalign;
+ p = (mchunkptr) (mm + correction);
+ set_prev_size (p, correction);
+ set_head (p, (size - correction) | IS_MMAPPED);
+ }
+ else
+ {
+ p = (mchunkptr) mm;
+ set_prev_size (p, 0);
+ set_head (p, size | IS_MMAPPED);
+ }
+
+ /* update statistics */
+ int new = atomic_exchange_and_add (&mp_.n_mmaps, 1) + 1;
+ atomic_max (&mp_.max_n_mmaps, new);
+
+ unsigned long sum;
+ sum = atomic_exchange_and_add (&mp_.mmapped_mem, size) + size;
+ atomic_max (&mp_.max_mmapped_mem, sum);
+
+ check_chunk (av, p);
+
+ return chunk2mem (p);
+}
+
static void *
sysmalloc (INTERNAL_SIZE_T nb, mstate av)
{
@@ -2449,81 +2528,10 @@ sysmalloc (INTERNAL_SIZE_T nb, mstate av)
|| ((unsigned long) (nb) >= (unsigned long) (mp_.mmap_threshold)
&& (mp_.n_mmaps < mp_.n_mmaps_max)))
{
- char *mm; /* return value from mmap call*/
-
- try_mmap:
- /*
- Round up size to nearest page. For mmapped chunks, the overhead
- is one SIZE_SZ unit larger than for normal chunks, because there
- is no following chunk whose prev_size field could be used.
-
- See the front_misalign handling below, for glibc there is no
- need for further alignments unless we have have high alignment.
- */
- if (MALLOC_ALIGNMENT == CHUNK_HDR_SZ)
- size = ALIGN_UP (nb + SIZE_SZ, pagesize);
- else
- size = ALIGN_UP (nb + SIZE_SZ + MALLOC_ALIGN_MASK, pagesize);
+ char *mm = sysmalloc_mmap (nb, pagesize, 0, av);
+ if (mm != MAP_FAILED)
+ return mm;
tried_mmap = true;
-
- /* Don't try if size wraps around 0 */
- if ((unsigned long) (size) > (unsigned long) (nb))
- {
- mm = (char *) (MMAP (0, size,
- mtag_mmap_flags | PROT_READ | PROT_WRITE, 0));
-
- if (mm != MAP_FAILED)
- {
- madvise_thp (mm, size);
-
- /*
- The offset to the start of the mmapped region is stored
- in the prev_size field of the chunk. This allows us to adjust
- returned start address to meet alignment requirements here
- and in memalign(), and still be able to compute proper
- address argument for later munmap in free() and realloc().
- */
-
- if (MALLOC_ALIGNMENT == CHUNK_HDR_SZ)
- {
- /* For glibc, chunk2mem increases the address by
- CHUNK_HDR_SZ and MALLOC_ALIGN_MASK is
- CHUNK_HDR_SZ-1. Each mmap'ed area is page
- aligned and therefore definitely
- MALLOC_ALIGN_MASK-aligned. */
- assert (((INTERNAL_SIZE_T) chunk2mem (mm) & MALLOC_ALIGN_MASK) == 0);
- front_misalign = 0;
- }
- else
- front_misalign = (INTERNAL_SIZE_T) chunk2mem (mm) & MALLOC_ALIGN_MASK;
- if (front_misalign > 0)
- {
- correction = MALLOC_ALIGNMENT - front_misalign;
- p = (mchunkptr) (mm + correction);
- set_prev_size (p, correction);
- set_head (p, (size - correction) | IS_MMAPPED);
- }
- else
- {
- p = (mchunkptr) mm;
- set_prev_size (p, 0);
- set_head (p, size | IS_MMAPPED);
- }
-
- /* update statistics */
-
- int new = atomic_exchange_and_add (&mp_.n_mmaps, 1) + 1;
- atomic_max (&mp_.max_n_mmaps, new);
-
- unsigned long sum;
- sum = atomic_exchange_and_add (&mp_.mmapped_mem, size) + size;
- atomic_max (&mp_.max_mmapped_mem, sum);
-
- check_chunk (av, p);
-
- return chunk2mem (p);
- }
- }
}
/* There are no usable arenas and mmap also failed. */
@@ -2600,8 +2608,12 @@ sysmalloc (INTERNAL_SIZE_T nb, mstate av)
}
}
else if (!tried_mmap)
- /* We can at least try to use to mmap memory. */
- goto try_mmap;
+ {
+ /* We can at least try to use to mmap memory. */
+ char *mm = sysmalloc_mmap (nb, pagesize, 0, av);
+ if (mm != MAP_FAILED)
+ return mm;
+ }
}
else /* av == main_arena */
--
2.33.0
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