Re: [Kgdb-bugreport] [PATCH] Documentation: DocBook: kgdb: update CONFIG_STRICT_KERNEL_RWX info
Status: Beta
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jwessel
From: Daniel T. <dan...@li...> - 2017-04-21 09:43:35
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On 21/04/17 03:26, Li Qiang wrote: > > @Daniel > > 2017-04-20 23:28 GMT+08:00 Daniel Thompson <dan...@li... > <mailto:dan...@li...>>: > > On 19/04/17 02:58, Li Qiang wrote: > > CONFIG_STRICT_KERNEL_RWX is no longer selectable on most > architectures. > Update this info to thedocumentation. > > > "git grep STRICT_KERNEL_RWX" comes up with nothing. > > > It was introduced in commit 0f5bf6d0afe4be6e1391908ff2d6dc9730e91550. Oops. I did the grep on the wrong machine :-( and therefore on an older kernel than I thought... > It is selectable on any architecture? If not we should remove it > entirely! > > The 'STRICT_KERNEL_RWX' is renamed from 'CONFIG_DEBUG_RODATA > '. The original option is selectable. > > I'm not sure is this selectable on any architecture. So... having found the right kernel, it looks to me like only arm, arm64, parisc, s390 and x86 define ARCH_HAS_STRICT_KERNEL_RWX. Of these five, only arm defines ARCH_OPTIONAL_KERNEL_RWX and makes it user selectable. > > @Jonathan > > On Tue, 18 Apr 2017 18:58:45 -0700 > Li Qiang <li...@gm... <mailto:li...@gm...>> wrote: > > > CONFIG_STRICT_KERNEL_RWX is no longer selectable on most architectures. > > Update this info to the documentation. > > > > Signed-off-by: Li Qiang <liq...@36... <mailto:liq...@36...>> > > --- > > Documentation/DocBook/kgdb.tmpl | 4 +++- > > 1 file changed, 3 insertions(+), 1 deletion(-) > > > > diff --git a/Documentation/DocBook/kgdb.tmpl b/Documentation/DocBook/kgdb.tmpl > > index 856ac20..ef0b67b 100644 > > --- a/Documentation/DocBook/kgdb.tmpl > > +++ b/Documentation/DocBook/kgdb.tmpl > > @@ -121,7 +121,9 @@ > > If kgdb supports it for the architecture you are using, you can > > use hardware breakpoints if you desire to run with the > > CONFIG_STRICT_KERNEL_RWX option turned on, else you need to turn off > > - this option. > > + this option. In most architectures, this option is not selectable. > > + For this situation, it can be turned off by adding a runtime parameter > > + 'rodata=off'. > > So this is an improvement, I guess, though the paragraph remains kind of > confusing. Is there any chance we could actually just say which > architectures can use hardware breakpoints, and which should boot with > rodata=off? > > > I think this is unnecessary as it is not common to change the > default CONFIG_STRICT_KERNEL_RWX /add rodata=off. > We here give this hint because CONFIG_STRICT_KERNEL_RWX is renamed > from CONFIG_DEBUG_RODATA. > And the latter is selectable, this can help the peoples who > think CONFIG_STRICT_KERNEL_RWX is also selectable. Having looked at the earlier part of the paragraph I think the info about rodata actually needs to be introduced slightly earlier (and rodata should be presented as the primary way to do it because 4 of the 5 architectures don't make STRICT_KERNEL_RWX optional). Something like: If the architecture that you are using supports making the text section read-only (CONFIG_STRICT_KERNEL_RWX), you should consider turning it off by adding 'rodata=off' to the kernel commandline or, if your architecture makes CONFIG_STRICT_KERNEL_RWX optional, by disabling this config option. Alternatively, if your architecture supports hardware breakpoints, these can be used to provide limited breakpoint support if you desire to run with a read-only text section. Daniel. |