[PATCH v5 3/4] Introduce GIT_MMAP_LIMIT to allow testing expected mmap size
From: Steffen Prohaska <hidden>
Date: 2016-06-15 23:02:20
Subsystem:
the rest · Maintainer:
Linus Torvalds
Similar to testing expectations about malloc with GIT_ALLOC_LIMIT (see
commit d41489 and previous commit), it can be useful to test
expectations about mmap.
This introduces a new environment variable GIT_MMAP_LIMIT to limit the
largest allowed mmap length. xmmap() is modified to check the limit.
Together with GIT_ALLOC_LIMIT tests can now easily confirm expectations
about memory consumption.
GIT_MMAP_LIMIT will be used in the next commit to test that data will be
streamed to an external filter without mmaping the entire file.
[commit d41489]: d41489a6424308dc9a0409bc2f6845aa08bd4f7d Add more large
blob test cases
Signed-off-by: Steffen Prohaska <redacted>
---
sha1_file.c | 21 ++++++++++++++++++++-
1 file changed, 20 insertions(+), 1 deletion(-)
diff --git a/sha1_file.c b/sha1_file.c
index 00c07f2..3204f66 100644
--- a/sha1_file.c
+++ b/sha1_file.c@@ -663,10 +663,29 @@ void release_pack_memory(size_t need) ; /* nothing */ } +static void mmap_limit_check(size_t length) +{ + static size_t limit = SIZE_MAX; + if (limit == SIZE_MAX) { + const char *var = "GIT_MMAP_LIMIT"; + unsigned long val = 0; + const char *env = getenv(var); + if (env && !git_parse_ulong(env, &val)) + die("Failed to parse %s", var); + limit = val; + } + if (limit && length > limit) + die("attempting to mmap %"PRIuMAX" over limit %"PRIuMAX, + (uintmax_t)length, (uintmax_t)limit); +} + void *xmmap(void *start, size_t length, int prot, int flags, int fd, off_t offset) { - void *ret = mmap(start, length, prot, flags, fd, offset); + void *ret; + + mmap_limit_check(length); + ret = mmap(start, length, prot, flags, fd, offset); if (ret == MAP_FAILED) { if (!length) return NULL;
--
2.1.0.8.gd3b6067