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Date: Thu, 5 Jun 2014 11:14:49 +0200 From: Petr Mládek <pmladek@...e.cz> To: Steven Rostedt <rostedt@...dmis.org> Cc: Frederic Weisbecker <fweisbec@...il.com>, Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>, Jan Beulich <jbeulich@...e.com>, Jiri Kosina <jkosina@...e.cz>, linux-kernel@...r.kernel.org, x86@...nel.org Subject: Re: [PATCH] ftrace/x86: Use kernel identity mapping only when CONFIG_DEBUG_RODATA enabled On Wed 2014-06-04 14:37:28, Steven Rostedt wrote: > On Wed, 4 Jun 2014 17:42:46 +0200 > Petr Mladek <pmladek@...e.cz> wrote: > > > This is just a tiny optimization. The remapping is not needed when the > > kernel text mapping is read write all the time. > > This is true, but I think I rather have it still do it the same. The > less variables in the code modification the better. The more changes > per config option, the less things tend to get tested. > > This is a micro optimization to something that is hardly a fast path. It makes sense. Let's leave it as is. Best Regards, Petr > > > > Suggested-by: Jan Beulich <jbeulich@...e.com> > > Signed-off-by: Petr Mladek <pmladek@...e.cz> > > --- > > arch/x86/kernel/ftrace.c | 3 ++- > > 1 file changed, 2 insertions(+), 1 deletion(-) > > > > diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c > > index cbc4a91b131e..a7a517bb793e 100644 > > --- a/arch/x86/kernel/ftrace.c > > +++ b/arch/x86/kernel/ftrace.c > > @@ -79,6 +79,7 @@ within(unsigned long addr, unsigned long start, unsigned long end) > > > > static unsigned long text_ip_addr(unsigned long ip) > > { > > +#ifdef CONFIG_DEBUG_RODATA > > /* > > * On x86_64, kernel text mappings are mapped read-only with > > * CONFIG_DEBUG_RODATA. So we use the kernel identity mapping instead > > @@ -89,7 +90,7 @@ static unsigned long text_ip_addr(unsigned long ip) > > */ > > if (within(ip, (unsigned long)_text, (unsigned long)_etext)) > > ip = (unsigned long)__va(__pa_symbol(ip)); > > - > > +#endif > > return ip; > > } > > > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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