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* [PATCH] nolibc: Don't use `malloc()` and `free()` as the function name
@ 2022-01-23  7:42 Ammar Faizi
  2022-01-23 16:36 ` Jens Axboe
  0 siblings, 1 reply; 2+ messages in thread
From: Ammar Faizi @ 2022-01-23  7:42 UTC (permalink / raw)
  To: Jens Axboe
  Cc: io-uring Mailing List, GNU/Weeb Mailing List,
	Tea Inside Mailing List, Ammar Faizi, Miyasaki Kohaku,
	Alviro Iskandar Setiawan

Miyasaki reports that liburing with CONFIG_NOLIBC breaks apps that
use libc. The first spotted issue was a realloc() call that results
in an invalid pointer, and then the program exits with SIGABRT.

The cause is liburing nolibc overrides malloc() and free() from the
libc (especially when we statically link the "liburing.a" to the apps
that use libc).

The malloc() and free() from liburing nolibc use hand-coded Assembly
to invoke mmap() and munmap() syscall directly. That means any
allocation from malloc() is not a valid object with respect to the
libc, and free() will also break the app if we use it to free a
pointer from a libc function (e.g., strdup()).

liburing nolibc should not break any libc app.

This renames the malloc() and free() to __uring_malloc() and
__uring_free(). Also, add new inline functions to wrap the malloc()
and free(), they are uring_malloc() and uring_free(). These wrappers
will call the appropriate functions depending on CONFIG_NOLIBC.

Fixes: f48ee3168cdc325233825603269f304d348d323c ("Add nolibc build support")
Cc: Tea Inside Mailing List <[email protected]>
Reported-by: Miyasaki Kohaku <[email protected]>
Tested-by: Miyasaki Kohaku <[email protected]>
Co-authored-by: Alviro Iskandar Setiawan <[email protected]>
Signed-off-by: Alviro Iskandar Setiawan <[email protected]>
Signed-off-by: Ammar Faizi <[email protected]>
---
 src/lib.h    | 20 ++++++++++++++++++++
 src/nolibc.c |  4 ++--
 src/setup.c  |  6 +++---
 3 files changed, 25 insertions(+), 5 deletions(-)

diff --git a/src/lib.h b/src/lib.h
index 58d91be..bd02805 100644
--- a/src/lib.h
+++ b/src/lib.h
@@ -25,6 +25,26 @@
 })
 #endif
 
+void *__uring_malloc(size_t len);
+void __uring_free(void *p);
+
+static inline void *uring_malloc(size_t len)
+{
+#ifdef CONFIG_NOLIBC
+	return __uring_malloc(len);
+#else
+	return malloc(len);
+#endif
+}
+
+static inline void uring_free(void *ptr)
+{
+#ifdef CONFIG_NOLIBC
+	__uring_free(ptr);
+#else
+	free(ptr);
+#endif
+}
 
 static inline long get_page_size(void)
 {
diff --git a/src/nolibc.c b/src/nolibc.c
index 251780b..f7848d3 100644
--- a/src/nolibc.c
+++ b/src/nolibc.c
@@ -23,7 +23,7 @@ struct uring_heap {
 	char		user_p[] __attribute__((__aligned__));
 };
 
-void *malloc(size_t len)
+void *__uring_malloc(size_t len)
 {
 	struct uring_heap *heap;
 
@@ -36,7 +36,7 @@ void *malloc(size_t len)
 	return heap->user_p;
 }
 
-void free(void *p)
+void __uring_free(void *p)
 {
 	struct uring_heap *heap;
 
diff --git a/src/setup.c b/src/setup.c
index 891fc43..1e4dbf4 100644
--- a/src/setup.c
+++ b/src/setup.c
@@ -178,7 +178,7 @@ struct io_uring_probe *io_uring_get_probe_ring(struct io_uring *ring)
 	int r;
 
 	len = sizeof(*probe) + 256 * sizeof(struct io_uring_probe_op);
-	probe = malloc(len);
+	probe = uring_malloc(len);
 	if (!probe)
 		return NULL;
 	memset(probe, 0, len);
@@ -187,7 +187,7 @@ struct io_uring_probe *io_uring_get_probe_ring(struct io_uring *ring)
 	if (r >= 0)
 		return probe;
 
-	free(probe);
+	uring_free(probe);
 	return NULL;
 }
 
@@ -208,7 +208,7 @@ struct io_uring_probe *io_uring_get_probe(void)
 
 void io_uring_free_probe(struct io_uring_probe *probe)
 {
-	free(probe);
+	uring_free(probe);
 }
 
 static inline int __fls(int x)
-- 
2.32.0



^ permalink raw reply related	[flat|nested] 2+ messages in thread

* Re: [PATCH] nolibc: Don't use `malloc()` and `free()` as the function name
  2022-01-23  7:42 [PATCH] nolibc: Don't use `malloc()` and `free()` as the function name Ammar Faizi
@ 2022-01-23 16:36 ` Jens Axboe
  0 siblings, 0 replies; 2+ messages in thread
From: Jens Axboe @ 2022-01-23 16:36 UTC (permalink / raw)
  To: Ammar Faizi
  Cc: Alviro Iskandar Setiawan, Tea Inside Mailing List,
	io-uring Mailing List, GNU/Weeb Mailing List, Miyasaki Kohaku

On Sun, 23 Jan 2022 14:42:30 +0700, Ammar Faizi wrote:
> Miyasaki reports that liburing with CONFIG_NOLIBC breaks apps that
> use libc. The first spotted issue was a realloc() call that results
> in an invalid pointer, and then the program exits with SIGABRT.
> 
> The cause is liburing nolibc overrides malloc() and free() from the
> libc (especially when we statically link the "liburing.a" to the apps
> that use libc).
> 
> [...]

Applied, thanks!

[1/1] nolibc: Don't use `malloc()` and `free()` as the function name
      commit: 29ff69397fa13478b5619201347c51159874279e

Best regards,
-- 
Jens Axboe



^ permalink raw reply	[flat|nested] 2+ messages in thread

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