On Sun, May 02, 2021 at 01:39:16PM -0500, Eric W. Biederman wrote: > The one thing that this doesn't do is give you a 64bit field > on 32bit architectures. > > On 32bit builds the layout is: > > int si_signo; > int si_errno; > int si_code; > void __user *_addr; > > So I believe if the first 3 fields were moved into the _sifields union > si_perf could define a 64bit field as it's first member and it would not > break anything else. > > Given that the data field is 64bit that seems desirable. The data field is fundamentally an address, it is internally a u64 because the perf ring buffer has u64 alignment and it saves on compat crap etc. So for the 32bit/compat case the high bits will always be 0 and truncating into an unsigned long is fine.
