[i-g-t,5/7] Make string commands dynamic allocate

Commit Message

Rodrigo Siqueira July 7, 2018, 11:23 p.m. UTC

This patch fix the following GCC warning:

intel_gvtg_test.c: In function ‘create_guest’:
intel_gvtg_test.c:127:50: warning: ‘%s’ directive writing up to 4095
bytes into a region of size 4077 [-Wformat-overflow=]
[..]
intel_gvtg_test.c:127:5: note: ‘sprintf’ output between 36 and 8226
bytes into a destination of size 4096
[..]

This patch changes the approach for allocating memory to handle QEMU
commands by dynamically allocate space to save the whole command.

Signed-off-by: Rodrigo Siqueira <[e-mail]>
---
 tools/intel_gvtg_test.c | 27 ++++++++++++++++++---------
 1 file changed, 18 insertions(+), 9 deletions(-)

Comments

Arkadiusz Hiler July 11, 2018, 12:26 p.m. UTC | #1

On Sat, Jul 07, 2018 at 08:23:30PM -0300, Rodrigo Siqueira wrote:
> This patch fix the following GCC warning:
> 
> intel_gvtg_test.c: In function ‘create_guest’:
> intel_gvtg_test.c:127:50: warning: ‘%s’ directive writing up to 4095
> bytes into a region of size 4077 [-Wformat-overflow=]
> [..]
> intel_gvtg_test.c:127:5: note: ‘sprintf’ output between 36 and 8226
> bytes into a destination of size 4096
> [..]
> 
> This patch changes the approach for allocating memory to handle QEMU
> commands by dynamically allocate space to save the whole command.
> 
> Signed-off-by: Rodrigo Siqueira <[e-mail]>
> ---
>  tools/intel_gvtg_test.c | 27 ++++++++++++++++++---------
>  1 file changed, 18 insertions(+), 9 deletions(-)
> 
> diff --git a/tools/intel_gvtg_test.c b/tools/intel_gvtg_test.c
> index 659b7956..93c05e37 100644
> --- a/tools/intel_gvtg_test.c
> +++ b/tools/intel_gvtg_test.c
> @@ -120,16 +120,25 @@ static int check_tools(void)
>  
>  static void create_guest(void)
>  {
> -    char create_qcow_cmd[PATH_MAX] = {0};
> -    char create_vgpu_cmd[PATH_MAX] = {0};
> -    char create_instance_cmd[PATH_MAX] = {0};
> +    unsigned int max_size_cmd = sysconf(_SC_ARG_MAX);

That's 2097152 on my system. Quite an overkill. I know that we have lazy
page table assigement, but memseting the whole 2GB defeats it.

The qemu invocation looks like  the longest one, and we have 3
components that may take up to PATH_MAX each and some extra stuff, so
going with 4*PATH_MAX should be enough.

BTW, why do you memset it to 0 before each sprintf?

Patch

diff --git a/tools/intel_gvtg_test.c b/tools/intel_gvtg_test.c
index 659b7956..93c05e37 100644
--- a/tools/intel_gvtg_test.c
+++ b/tools/intel_gvtg_test.c
@@ -120,16 +120,25 @@  static int check_tools(void)
 
 static void create_guest(void)
 {
-    char create_qcow_cmd[PATH_MAX] = {0};
-    char create_vgpu_cmd[PATH_MAX] = {0};
-    char create_instance_cmd[PATH_MAX] = {0};
+    unsigned int max_size_cmd = sysconf(_SC_ARG_MAX);
+    char *command;
 
-    sprintf(create_qcow_cmd, "qemu-img create -b %s -f qcow2 %s.qcow2",
+    command = malloc(max_size_cmd);
+    if (!command)
+        return;
+
+    sprintf(command, "qemu-img create -b %s -f qcow2 %s.qcow2",
             hda_path, hda_path);
-    sprintf(create_vgpu_cmd, "echo \"%s\" > /sys/bus/pci/devices/0000:00:02.0/"
+    igt_assert_eq(system(command), 0);
+    memset(command, 0, max_size_cmd);
+
+    sprintf(command, "echo \"%s\" > /sys/bus/pci/devices/0000:00:02.0/"
            "mdev_supported_types/$(ls /sys/bus/pci/devices/0000:00:02.0/"
            "mdev_supported_types |awk {'print $1'}|tail -1)/create", uuid);
-    sprintf(create_instance_cmd, "%s -m 2048 -smp 2 -M pc -name gvtg_guest"
+    igt_assert_eq(system(command), 0);
+    memset(command, 0, max_size_cmd);
+
+    sprintf(command, "%s -m 2048 -smp 2 -M pc -name gvtg_guest"
            " -hda %s.qcow2 -bios %s -enable-kvm --net nic,macaddr=%s -net"
            " tap,script=/etc/qemu-ifup -vga cirrus -k en-us"
            " -serial stdio -vnc :1 -machine kernel_irqchip=on -global"
@@ -137,9 +146,9 @@  static void create_guest(void)
            " -usb -usbdevice tablet -device vfio-pci,sysfsdev="
            "/sys/bus/pci/devices/0000:00:02.0/%s &",
            qemu_path, hda_path, bios_path, mac_addr, uuid);
-    igt_assert_eq(system(create_qcow_cmd), 0);
-    igt_assert_eq(system(create_vgpu_cmd), 0);
-    igt_assert_eq(system(create_instance_cmd), 0);
+    igt_assert_eq(system(command), 0);
+
+    free(command);
 }
 
 static void destroy_all_guest(void)