Hi, Christophe. On Mon, Jul 30, 2018 at 06:30:47PM +0200, LEROY Christophe wrote: > Murilo Opsfelder Araujo <muri...@linux.ibm.com> a écrit : > > > Hi, Christophe. > > > > On Fri, Jul 27, 2018 at 06:40:23PM +0200, LEROY Christophe wrote: > > > Murilo Opsfelder Araujo <muri...@linux.ibm.com> a écrit : > > > > > > > Simplify the message format by using REG_FMT as the register format. > > > > This > > > > avoids having two different formats and avoids checking for MSR_64BIT. > > > > > > Are you sure it is what we want ? > > > > Yes. > > > > > Won't it change the behaviour for a 32 bits app running on a 64bits > > > kernel ? > > > > In fact, this changes how many zeroes are prefixed when displaying the > > registers > > (%016lx vs. %08lx format). For example, 32-bits userspace, 64-bits kernel: > > Indeed that's what I suspected. What is the real benefit of this change ? > Why not keep the current format for 32bits userspace ? All those leading > zeroes are pointless to me.
One of the benefits is simplifying the code by removing some checks. Another is deduplicating almost identical format strings in favor of a unified one. After reading Joe's comment [1], %px seems to be the format we're looking for. An extract from Documentation/core-api/printk-formats.rst: "%px is functionally equivalent to %lx (or %lu). %px is preferred because it is more uniquely grep'able." So I guess we don't need to worry about the format (%016lx vs. %08lx), let's just use %px, as per the guideline. [1] https://lore.kernel.org/lkml/26f07092cdde378ebb42c1034badde1b56521c36.ca...@perches.com/ Cheers Murilo
