* [Qemu-devel] [PATCH] Do not abort on qemu_malloc(0) in production builds
@ 2009-12-09 19:04 Anthony Liguori
2009-12-09 19:28 ` Markus Armbruster
0 siblings, 1 reply; 4+ messages in thread
From: Anthony Liguori @ 2009-12-09 19:04 UTC (permalink / raw)
To: qemu-devel; +Cc: Anthony Liguori, Avi Kivity, Mark Armbruster
qemu_malloc() does not allow size=0 to be passed in and aborts on this behavior.
Unfortunately, there is good reason to believe that within qemu, there are a
number of, so far, undetected places that assume size=0 can be safely passed.
Since we do not want to abort unnecessarily in production builds, return
qemu_malloc(1) whenever the version file indicates that this is a production
build.
Also introduce --enable-zero-malloc/--disable-zero-malloc to make this behavior
overridable.
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
---
configure | 24 +++++++++++++++++++++++-
qemu-malloc.c | 17 +++++++++++++----
2 files changed, 36 insertions(+), 5 deletions(-)
diff --git a/configure b/configure
index a29839e..ede820e 100755
--- a/configure
+++ b/configure
@@ -256,6 +256,7 @@ blobs="yes"
pkgversion=""
check_utests="no"
user_pie="no"
+zero_malloc=""
# OS specific
if check_define __linux__ ; then
@@ -600,6 +601,10 @@ for opt do
;;
--enable-docs) docs="yes"
;;
+ --enable-zero-malloc) zero_malloc="yes"
+ ;;
+ --disable-zero-malloc) zero_malloc="no"
+ ;;
*) echo "ERROR: unknown option $opt"; show_help="yes"
;;
esac
@@ -752,6 +757,8 @@ echo " --enable-linux-aio enable Linux AIO support"
echo " --enable-io-thread enable IO thread"
echo " --disable-blobs disable installing provided firmware blobs"
echo " --kerneldir=PATH look for kernel includes in PATH"
+echo " --enable-zero-malloc allow allocations of zero size"
+echo " --disable-zero-malloc abort on allocations of zero size"
echo ""
echo "NOTE: The object files are built at the place where configure is launched"
exit 1
@@ -1792,8 +1799,9 @@ fi
# Consult white-list to determine whether to enable werror
# by default. Only enable by default for git builds
+z_version=`cut -f3 -d. $source_path/VERSION`
+
if test -z "$werror" ; then
- z_version=`cut -f3 -d. $source_path/VERSION`
if test "$z_version" = "50" -a \
"$linux" = "yes" ; then
werror="yes"
@@ -1802,6 +1810,16 @@ if test -z "$werror" ; then
fi
fi
+# Disable zero malloc errors for official releases unless explicitly told to
+# enable/disable
+if test -z "$zero_malloc" ; then
+ if test "$z_version" = "50" ; then
+ zero_malloc="no"
+ else
+ zero_malloc="yes"
+ fi
+fi
+
if test "$werror" = "yes" ; then
QEMU_CFLAGS="-Werror $QEMU_CFLAGS"
fi
@@ -2109,6 +2127,10 @@ fi
echo "CONFIG_UNAME_RELEASE=\"$uname_release\"" >> $config_host_mak
+if test "$zero_malloc" = "yes" ; then
+ echo "CONFIG_ZERO_MALLOC=y" >> $config_host_mak
+fi
+
# USB host support
case "$usb" in
linux)
diff --git a/qemu-malloc.c b/qemu-malloc.c
index 295d185..e82af26 100644
--- a/qemu-malloc.c
+++ b/qemu-malloc.c
@@ -42,21 +42,30 @@ void qemu_free(void *ptr)
free(ptr);
}
+static int allow_zero_malloc(void)
+{
+#if defined(CONFIG_ZERO_MALLOC)
+ return 1;
+#else
+ return 0;
+#endif
+}
+
void *qemu_malloc(size_t size)
{
- if (!size) {
+ if (!size && !allow_zero_malloc()) {
abort();
}
- return oom_check(malloc(size));
+ return oom_check(malloc(size ? size : 1));
}
void *qemu_realloc(void *ptr, size_t size)
{
if (size) {
return oom_check(realloc(ptr, size));
- } else {
+ } else if (allow_zero_malloc()) {
if (ptr) {
- return realloc(ptr, size);
+ return realloc(ptr, size ? size : 1);
}
}
abort();
--
1.6.2.5
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [Qemu-devel] [PATCH] Do not abort on qemu_malloc(0) in production builds
2009-12-09 19:04 [Qemu-devel] [PATCH] Do not abort on qemu_malloc(0) in production builds Anthony Liguori
@ 2009-12-09 19:28 ` Markus Armbruster
2009-12-09 21:03 ` Anthony Liguori
0 siblings, 1 reply; 4+ messages in thread
From: Markus Armbruster @ 2009-12-09 19:28 UTC (permalink / raw)
To: Anthony Liguori; +Cc: qemu-devel, Avi Kivity
Anthony Liguori <aliguori@us.ibm.com> writes:
> qemu_malloc() does not allow size=0 to be passed in and aborts on this behavior.
>
> Unfortunately, there is good reason to believe that within qemu, there are a
> number of, so far, undetected places that assume size=0 can be safely passed.
> Since we do not want to abort unnecessarily in production builds, return
> qemu_malloc(1) whenever the version file indicates that this is a production
> build.
>
> Also introduce --enable-zero-malloc/--disable-zero-malloc to make this behavior
> overridable.
>
> Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
> ---
> configure | 24 +++++++++++++++++++++++-
> qemu-malloc.c | 17 +++++++++++++----
> 2 files changed, 36 insertions(+), 5 deletions(-)
>
[...]
> diff --git a/qemu-malloc.c b/qemu-malloc.c
> index 295d185..e82af26 100644
> --- a/qemu-malloc.c
> +++ b/qemu-malloc.c
> @@ -42,21 +42,30 @@ void qemu_free(void *ptr)
> free(ptr);
> }
>
> +static int allow_zero_malloc(void)
> +{
> +#if defined(CONFIG_ZERO_MALLOC)
> + return 1;
> +#else
> + return 0;
> +#endif
> +}
> +
> void *qemu_malloc(size_t size)
> {
> - if (!size) {
> + if (!size && !allow_zero_malloc()) {
> abort();
> }
> - return oom_check(malloc(size));
> + return oom_check(malloc(size ? size : 1));
> }
>
> void *qemu_realloc(void *ptr, size_t size)
> {
> if (size) {
> return oom_check(realloc(ptr, size));
> - } else {
> + } else if (allow_zero_malloc()) {
> if (ptr) {
> - return realloc(ptr, size);
> + return realloc(ptr, size ? size : 1);
> }
> }
> abort();
This still aborts on qemu_realloc(NULL, 0), even with
CONFIG_ZERO_MALLOC. Intentional?
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [Qemu-devel] [PATCH] Do not abort on qemu_malloc(0) in production builds
2009-12-09 19:28 ` Markus Armbruster
@ 2009-12-09 21:03 ` Anthony Liguori
2009-12-09 21:35 ` Markus Armbruster
0 siblings, 1 reply; 4+ messages in thread
From: Anthony Liguori @ 2009-12-09 21:03 UTC (permalink / raw)
To: Markus Armbruster; +Cc: Anthony Liguori, qemu-devel, Avi Kivity
Markus Armbruster wrote:
> Anthony Liguori <aliguori@us.ibm.com> writes:
>
>
>> qemu_malloc() does not allow size=0 to be passed in and aborts on this behavior.
>>
>> Unfortunately, there is good reason to believe that within qemu, there are a
>> number of, so far, undetected places that assume size=0 can be safely passed.
>> Since we do not want to abort unnecessarily in production builds, return
>> qemu_malloc(1) whenever the version file indicates that this is a production
>> build.
>>
>> Also introduce --enable-zero-malloc/--disable-zero-malloc to make this behavior
>> overridable.
>>
>> Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
>> ---
>> configure | 24 +++++++++++++++++++++++-
>> qemu-malloc.c | 17 +++++++++++++----
>> 2 files changed, 36 insertions(+), 5 deletions(-)
>>
>>
> [...]
>
>> diff --git a/qemu-malloc.c b/qemu-malloc.c
>> index 295d185..e82af26 100644
>> --- a/qemu-malloc.c
>> +++ b/qemu-malloc.c
>> @@ -42,21 +42,30 @@ void qemu_free(void *ptr)
>> free(ptr);
>> }
>>
>> +static int allow_zero_malloc(void)
>> +{
>> +#if defined(CONFIG_ZERO_MALLOC)
>> + return 1;
>> +#else
>> + return 0;
>> +#endif
>> +}
>> +
>> void *qemu_malloc(size_t size)
>> {
>> - if (!size) {
>> + if (!size && !allow_zero_malloc()) {
>> abort();
>> }
>> - return oom_check(malloc(size));
>> + return oom_check(malloc(size ? size : 1));
>> }
>>
>> void *qemu_realloc(void *ptr, size_t size)
>> {
>> if (size) {
>> return oom_check(realloc(ptr, size));
>> - } else {
>> + } else if (allow_zero_malloc()) {
>> if (ptr) {
>> - return realloc(ptr, size);
>> + return realloc(ptr, size ? size : 1);
>> }
>> }
>> abort();
>>
>
> This still aborts on qemu_realloc(NULL, 0), even with
> CONFIG_ZERO_MALLOC. Intentional?
>
I guess not. Should it? Seems like a very strange case..
Regards,
Anthony Liguori
--
Regards,
Anthony Liguori
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [Qemu-devel] [PATCH] Do not abort on qemu_malloc(0) in production builds
2009-12-09 21:03 ` Anthony Liguori
@ 2009-12-09 21:35 ` Markus Armbruster
0 siblings, 0 replies; 4+ messages in thread
From: Markus Armbruster @ 2009-12-09 21:35 UTC (permalink / raw)
To: Anthony Liguori; +Cc: Anthony Liguori, qemu-devel, Avi Kivity
Anthony Liguori <aliguori@linux.vnet.ibm.com> writes:
> Markus Armbruster wrote:
>> This still aborts on qemu_realloc(NULL, 0), even with
>> CONFIG_ZERO_MALLOC. Intentional?
>>
> I guess not. Should it? Seems like a very strange case..
It is a strange case, but I think the point of this commit is not to
abort on conditions perceived strange ;)
I think it should follow C89 and behave exactly like qemu_malloc(0).
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2009-12-09 21:35 UTC | newest]
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2009-12-09 19:04 [Qemu-devel] [PATCH] Do not abort on qemu_malloc(0) in production builds Anthony Liguori
2009-12-09 19:28 ` Markus Armbruster
2009-12-09 21:03 ` Anthony Liguori
2009-12-09 21:35 ` Markus Armbruster
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