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1654c37ddb
Merge arm64 support for proper 'unsafe' user accessor functionality, with 'asm goto' for handling exceptions. The arm64 user access code used the slow fallback code for the user access code, which generates horrendous code for things like strncpy_from_user(), because it causes us to generate code for SW PAN and for range checking for every individual word. Teach arm64 about 'user_access_begin()' and the so-called 'unsafe' user access functions that take an error label and use 'asm goto' to make all the exception handling be entirely out of line. [ These user access functions are called 'unsafe' not because the concept is unsafe, but because the low-level accessor functions absolutely have to be protected by the 'user_access_begin()' code, because that's what does the range checking. So the accessor functions have that scary name to make sure people don't think they are usable on their own, and cannot be mis-used the way our old "double underscore" versions of __get_user() and friends were ] The "(early part)" of the branch is because the full branch also improved on the "access_ok()" function, but the exact semantics of TBI (top byte ignore) have to be discussed before doing that part. So this just does the low-level accessor update to use "asm goto". * 'arm64-uaccess' (early part): arm64: start using 'asm goto' for put_user() arm64: start using 'asm goto' for get_user() when available |
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