On Sat, Jan 09, 2021 at 08:59:01PM +0100, Heinrich Schuchardt wrote: > Am 9. Januar 2021 20:40:04 MEZ schrieb Tom Rini <tr...@konsulko.com>: > >On Sat, Jan 09, 2021 at 08:33:40PM +0100, Heinrich Schuchardt wrote: > >> On 1/9/21 7:58 PM, Tom Rini wrote: > >> > On Sat, Jan 09, 2021 at 08:47:07PM +0200, Andy Shevchenko wrote: > >> > > On Sat, Jan 9, 2021 at 8:06 PM Heinrich Schuchardt > ><xypron.g...@gmx.de> wrote: > >> > > > > >> > > > The comment for initrd_high in the coding and in README were > >contradicting > >> > > > and neither fully described what the coding does. > >> > > > > >> > > > Clarify the usage of the special value ~0UL for the environment > >variable > >> > > > initrd_high. > >> > > > >> > > All those F:s are hard to read in the comments and documentation > >and > >> > > typo prone. I would prefer to rephrase like "all 1:s value in 32- > >or > >> > > 64-bit format" or alike. > >> > > >> > If we're going to improve this we should also note it's discouraged > >> > unless you know for certain there will be no overlap and it's > >strongly > >> > discouraged in default environments. > >> > >> What exactly is discouraged? > >> > >> * setting initrd_high to a value != ~0? Here I would agree. > >> * setting intird_high to ~0? Why should we copy initrd to a > >> different place? Is it for some outdated Linux release? > > > >We should always default to allowing the initrd to be relocated because > >we can see (in many cases) overlap that will lead to failure to boot > >but > >this forces us to ignore that. Having good default load values means > >we > >don't have a problem here. > > We have an initrd that is already in memory. What could it overlap > with that is not already overwritten?
Having the kernel and initrd too close in memory has the kernel BSS overwrite the initrd. This has happened time and time again before I went around making some platforms have reasonable (ie kernel early, ramdisk in lowmem but beyond where a kernel+bss can be, etc) defaults and pushing others to do the same. > Can you provide the text you want to see here? Off-hand, it should look more like the big comment block in include/configs/ti_armv7_common.h and reference the Linux booting on arm/arm64 documents while noting that other architectures have the same fundamental issues and their exact limits may or may not be as well documented. -- Tom
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