Messages in this thread | | | From | Christoph Hellwig <> | Subject | remove the last set_fs() in common code, and remove it for x86 and powerpc v2 | Date | Thu, 27 Aug 2020 17:00:20 +0200 |
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Hi all,
this series removes the last set_fs() used to force a kernel address space for the uaccess code in the kernel read/write/splice code, and then stops implementing the address space overrides entirely for x86 and powerpc.
The file system part has been posted a few times, and the read/write side has been pretty much unchanced. For splice this series drops the conversion of the seq_file and sysctl code to the iter ops, and thus loses the splice support for them. The reasons for that is that it caused a lot of churn for not much use - splice for these small files really isn't much of a win, even if existing userspace uses it. All callers I found do the proper fallback, but if this turns out to be an issue the conversion can be resurrected.
Besides x86 and powerpc I plan to eventually convert all other architectures, although this will be a slow process, starting with the easier ones once the infrastructure is merged. The process to convert architectures is roughtly:
(1) ensure there is no set_fs(KERNEL_DS) left in arch specific code (2) implement __get_kernel_nofault and __put_kernel_nofault (3) remove the arch specific address limitation functionality
Changes since v1: - drop the patch to remove the non-iter ops for /dev/zero and /dev/null as they caused a performance regression - don't enable user access in __get_kernel on powerpc - xfail the set_fs() based lkdtm tests
Diffstat:
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