On 19/10/23 12:11, Julien Grall wrote:
Hi,
On 19/10/2023 09:43, Simone Ballarin wrote:
On 19/10/23 10:19, Julien Grall wrote:
Hi Simone,
On 19/10/2023 08:34, Simone Ballarin wrote:
On 18/10/23 17:03, Julien Grall wrote:
Hi,
On 18/10/2023 15:18, Simone Ballarin wrote:
Rule 13.1: Initializer lists shall not contain persistent side
effects
This patch moves expressions with side-effects into new variables
before
the initializer lists.
Looking at the code, I feel the commit message should be a bit more
verbose because they are no apparent side-effects.
Function calls do not necessarily have side-effects, in these
cases the
GCC pure or const attributes are added when possible.
You are only adding pure in this patch.
No functional changes.
Signed-off-by: Simone Ballarin <[email protected]>
---
Function attributes pure and const do not need to be added as GCC
attributes, they can be added using ECLAIR configurations.
---
xen/arch/arm/device.c | 6 +++---
xen/arch/arm/guestcopy.c | 12 ++++++++----
xen/arch/arm/include/asm/current.h | 2 +-
3 files changed, 12 insertions(+), 8 deletions(-)
diff --git a/xen/arch/arm/device.c b/xen/arch/arm/device.c
index 1f631d3274..e9be078415 100644
--- a/xen/arch/arm/device.c
+++ b/xen/arch/arm/device.c
@@ -319,6 +319,8 @@ int handle_device(struct domain *d, struct
dt_device_node *dev, p2m_type_t p2mt,
int res;
paddr_t addr, size;
bool own_device = !dt_device_for_passthrough(dev);
+ bool dev_is_hostbridge = is_pci_passthrough_enabled() &&
+ device_get_class(dev) ==
DEVICE_PCI_HOSTBRIDGE;
The commit message suggests that the code is moved because there
are side-effects. But none of them should have any side-effects.
device_get_class contains an 'ASSERT(dev != NULL)' which is definitely
a side-effect.
Just to confirm my understanding, the side-effect here would be the
fact that it traps and then panic(). IOW, if the trap was
hypothetically replaced by a while (1), then it would not be an
issue. is it correct? >
No, it isn't. A infinite loop is a side effect.
I am not sure why. There are no change of state here.
I can see two solutions:
1) Remove the ASSERT(). It is only here to make the NULL
dereference obvious in debug build. That said, the stack trace for a
NULL dereference would still be as clear.
Removing the ASSERT just to make MISRA happy does not sound good to me.
I didn't suggest the ASSERT() just ot make MISRA happy. I suggested it
because it has no value here (we still have stack track if there are any
issue).
2) Replace the ASSERT with a proper check if ( !dev ) return
DEVICE_UNKONWN. AFAIU, we would not be able to add a
ASSERT_UNREACHABLE() because this would be again a perceived
side-effect.
Replacing it with a proper check can be a solution, but I still prefer
to add a deviation or move the invocation outside the initializer list.
In general, I am not in favor of adding deviation if we can avoid them
because the code can changed and therefore either moot the deviation or
hide any other issue.
Ok, I will proceed with option 1.
[...]
Yes, sorry I was looking to the wrong definition.
In ARM the problem is the presence of a *volatile* ASM.
Please take a look here:
https://saas.eclairit.com:3787/fs/var/local/eclair/XEN.ecdf/ECLAIR_normal/arm/for-4.19/ARM64-Set2/latest/PROJECT.ecd;/by_service/MC3R1.R13.1.html#{"select":true,"selection":{"hiddenAreaKinds":[],"hiddenSubareaKinds":[],"show":true,"selector":{"enabled":true,"negated":false,"kind":0,"domain":"fingerprint","inputs":[{"enabled":true,"text":"0da7f0c9aea5491eba343618f965c81f5d7aed3c"}]}}}
Ok. So the problem is the READ_SYSREG(...). Is there a way we can
encapsulate the call so we don't need to use your propose trick or
deviate at every use of 'current'?
The point is that we need to move "READ_SYSREG(TPIDR_EL2)" outside
the initializer (there are no advantages in wrapping it on a function
if the function cannot be declared pure).
The proposed solution seems to me the cleanest way do to it. I do not
see any other acceptable solutions.
Cheers,
--
Simone Ballarin, M.Sc.
Field Application Engineer, BUGSENG (https://bugseng.com)
