[LTP] [RFC PATCH 1/1] syscalls/brk: use direct syscall

[Teo Couprie Diaz]

Direct usage of brk is discouraged in favor of using malloc. Also, brk was
removed from POSIX in POSIX.1-2001.
In particular, the Musl libc's brk always returns -ENOMEM which causes
the LTP tests to exit prematurely. Invoking the syscall directly allows
them to properly validate brk behavior.

Use tst_syscall() and handle the failure cases ourselves, as
we don't depend on the libc to do it anymore.

The patch also removes the dependency on sbrk to get the current break
as it has the same issues. Instead, call tst_syscall(__NR_brk, 0) which
always returns the current break.

Update brk01 to use void* to unify it with brk02.

Signed-off-by: Teo Couprie Diaz <teo.coupriediaz@arm.com>
---
 testcases/kernel/syscalls/brk/brk01.c | 15 ++++++---------
 testcases/kernel/syscalls/brk/brk02.c | 14 ++++++--------
 2 files changed, 12 insertions(+), 17 deletions(-)

diff --git a/testcases/kernel/syscalls/brk/brk01.c b/testcases/kernel/syscalls/brk/brk01.c
index a9b89bce5..d4596c20f 100644
--- a/testcases/kernel/syscalls/brk/brk01.c
+++ b/testcases/kernel/syscalls/brk/brk01.c
@@ -9,14 +9,15 @@
 #include <errno.h>
 
 #include "tst_test.h"
+#include "lapi/syscalls.h"
 
 void verify_brk(void)
 {
-	uintptr_t cur_brk, new_brk;
-	uintptr_t inc = getpagesize() * 2 - 1;
+	void *cur_brk, *new_brk;
+	size_t inc = getpagesize() * 2 - 1;
 	unsigned int i;
 
-	cur_brk = (uintptr_t)sbrk(0);
+	cur_brk = (void *)tst_syscall(__NR_brk, 0);
 
 	for (i = 0; i < 33; i++) {
 		switch (i % 3) {
@@ -31,16 +32,12 @@ void verify_brk(void)
 		break;
 		}
 
-		TST_EXP_PASS_SILENT(brk((void *)new_brk), "brk()");
-		if (!TST_PASS)
-			return;
-
-		cur_brk = (uintptr_t)sbrk(0);
+		cur_brk = (void *)tst_syscall(__NR_brk, new_brk);
 
 		if (cur_brk != new_brk) {
 			tst_res(TFAIL,
 				"brk() failed to set address have %p expected %p",
-				(void *)cur_brk, (void *)new_brk);
+				cur_brk, new_brk);
 			return;
 		}
 
diff --git a/testcases/kernel/syscalls/brk/brk02.c b/testcases/kernel/syscalls/brk/brk02.c
index 11e803cb4..dabda30c2 100644
--- a/testcases/kernel/syscalls/brk/brk02.c
+++ b/testcases/kernel/syscalls/brk/brk02.c
@@ -14,24 +14,22 @@
 #include <unistd.h>
 #include <sys/mman.h>
 #include "tst_test.h"
+#include "lapi/syscalls.h"
 
 void brk_down_vmas(void)
 {
-	void *brk_addr = sbrk(0);
-
-	if (brk_addr == (void *) -1)
-		tst_brk(TBROK, "sbrk() failed");
+	void *brk_addr = (void *)tst_syscall(__NR_brk, 0);
 
 	unsigned long page_size = getpagesize();
 	void *addr = brk_addr + page_size;
 
-	if (brk(addr)) {
+	if ((void *)tst_syscall(__NR_brk, addr) < addr) {
 		tst_res(TFAIL | TERRNO, "Cannot expand brk() by page size");
 		return;
 	}
 
 	addr += page_size;
-	if (brk(addr)) {
+	if ((void *)tst_syscall(__NR_brk, addr) < addr) {
 		tst_res(TFAIL | TERRNO, "Cannot expand brk() by 2x page size");
 		return;
 	}
@@ -42,12 +40,12 @@ void brk_down_vmas(void)
 	}
 
 	addr += page_size;
-	if (brk(addr)) {
+	if ((void *)tst_syscall(__NR_brk, addr) < addr) {
 		tst_res(TFAIL | TERRNO, "Cannot expand brk() after mprotect");
 		return;
 	}
 
-	if (brk(brk_addr)) {
+	if ((void *)tst_syscall(__NR_brk, brk_addr) != brk_addr) {
 		tst_res(TFAIL | TERRNO, "Cannot restore brk() to start address");
 		return;
 	}
-- 
2.25.1