Messages in this thread | | | Date | Sat, 25 Jan 2014 19:55:46 +0800 | From | Chen Gang <> | Subject | Re: [PATCH] drivers: staging: lustre: lustre: include: add "__attribute__((packed))" for the related union |
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On 01/21/2014 06:36 PM, James Hogan wrote: > Hi Dan, > > On 20/01/14 21:13, Dan Carpenter wrote: >> I made a quick and dirty sparse patch to check for this. I don't think >> I will bother trying to send it to sparse upstream, but you can if you >> want to. >> >> It found 289 unions which might need a __packed added. The lustre >> unions were not in my allmodconfig so they're not listed. > > Thanks a lot for this, it seems to be useful. I'm adapting it to reduce > false negatives (e.g. omitting the check if the struct/union is already > packed), and I imagine it could be made to only warn about padded > unpacked structs/unions which are used as nested members of packed > structs/unions. It wouldn't catch everything but would probably catch a > lot of cases that are most likely to be genuine since they would have > been packed at the outer level for a reason. > >> Perhaps there could be a command line option or a pragma so that unions >> will work in the kernel. We don't care about linking to outside >> libraries. > > We still interact with userland via structs and unions, so it would > probably have to exclude anything in uapi/. >
Thank all of you firstly.
But excuse me, I am still not quit clear that: "what need we do enough to solve this feature issue?"
So I guess our current result is:
- It is not a good idea to only let kernel to fit with compiler.
- It is not a good idea to only let compiler to fit with kernel.
- Need let compiler and kernel to fit with each other:
- compiler will print related warning, but not break compiling. so metag compiler need be improvement (check and warn for it).
- if check alignment explicitly in kernel source code, it need be fixed within kernel: "apply related patches (pack each struct or union), but the related patch comments need be improved".
Is what I guess correct?
Thanks. -- Chen Gang
Open, share and attitude like air, water and life which God blessed
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