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authorIan Jackson <ian.jackson@eu.citrix.com>2012-06-28 18:43:25 +0100
committerIan Jackson <ian.jackson@eu.citrix.com>2012-06-28 18:43:25 +0100
commit27e1ccd1db641b4f57c8249a6e4d7492140dd285 (patch)
treed7b36cf04a52d929987f26afba33a5dbf8598995 /tools/libxl/libxl_aoutils.c
parent145511d2ce456a6590f28e14e32b7c4cce1c4c69 (diff)
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libxl: Do not pass NULL as gc_opt; introduce NOGC
In 25182:6c3345d7e9d9 the practice of passing NULL to gc-using memory allocation functions was introduced. However, the arrangements there were not correct as committed, because the error handling and logging depends on getting a ctx from the gc - so an allocation error would in fact result in libxl dereferencing NULL. Instead, provide a special dummy gc in the ctx, called `nogc_gc'. It is marked out specially by having alloc_maxsize==-1, which is otherwise invalid. Functions which need to actually look into the gc use the new test function gc_is_real (whose purpose is mainly clarity of the code) to check whether the gc is the dummy one, and do nothing if it is. And we provide a helper macro NOGC which uses the in-scope real gc to find the ctx and hence the dummy gc (and which replaces the previous #define NOGC NULL). Change all callers which pass 0 or NULL to an allocation function to use NOGC or &ctx->nogc_gc, as applicable in the context. We add a comment near the definition of LIBXL_INIT_GC pointing out that it isn't any more the only place a libxl__gc struct is initialised, for the benefit of anyone changing the contents of gc's in the future. Also, actually document that libxl__ptr_add is legal with ptr==NULL, and change a couple of calls not to check for NULL argument. Reported-by: Bamvor Jian Zhang <bjzhang@suse.com> Signed-off-by: Ian Jackson <ian.jackson@eu.citrix.com> Cc: Bamvor Jian Zhang <bjzhang@suse.com> Acked-by: Ian Campbell <Ian.Campbell@citrix.com> Committed-by: Ian Jackson <Ian.Jackson@eu.citrix.com>
Diffstat (limited to 'tools/libxl/libxl_aoutils.c')
-rw-r--r--tools/libxl/libxl_aoutils.c3
1 files changed, 2 insertions, 1 deletions
diff --git a/tools/libxl/libxl_aoutils.c b/tools/libxl/libxl_aoutils.c
index 7f8d6d3bf6..99972a23b0 100644
--- a/tools/libxl/libxl_aoutils.c
+++ b/tools/libxl/libxl_aoutils.c
@@ -77,6 +77,7 @@ static void datacopier_check_state(libxl__egc *egc, libxl__datacopier_state *dc)
void libxl__datacopier_prefixdata(libxl__egc *egc, libxl__datacopier_state *dc,
const void *data, size_t len)
{
+ EGC_GC;
libxl__datacopier_buf *buf;
/*
* It is safe for this to be called immediately after _start, as
@@ -88,7 +89,7 @@ void libxl__datacopier_prefixdata(libxl__egc *egc, libxl__datacopier_state *dc,
assert(len < dc->maxsz - dc->used);
- buf = libxl__zalloc(0, sizeof(*buf) - sizeof(buf->buf) + len);
+ buf = libxl__zalloc(NOGC, sizeof(*buf) - sizeof(buf->buf) + len);
buf->used = len;
memcpy(buf->buf, data, len);