On Wed, Feb 26, 2014 at 11:15:07AM +0000, Russell King - ARM Linux wrote: > On Wed, Feb 26, 2014 at 12:11:20PM +0100, Uwe Kleine-König wrote: > > The toolchain problem described in commit f6537f2f0eba > > (scripts/kallsyms: filter symbols not in kernel address space) makes it > > necessary to filter out some kernel symbols from /proc/kallsyms to make > > perf happy. > > > > For that to work correctly the address used to filter should be just > > below the kernel text segment. Depending on kernel configuration > > CONFIG_PAGE_OFFSET is not the right address to use. See the comments > > introduced by this commit for the glory details. > > Is there any reason why PAGE_OFFSET should not be DRAM_BASE for nommu? Nothing I'm aware of[1]. Talking to Arnd earlier today on irc: 1393409816 < ukleinek> arnd: PAGE_OFFSET doesn't make much sense on !MMU, does it? 1393409828 < arnd> no 1393409844 < arnd> but I think we just set it to PHYS_OFFSET normally 1393409864 < arnd> which does the right thing, except with XIP_KERNEL, where the kernel doesn't actually run from RAM PAGE_OFFSET is only set to PLAT_PHYS_OFFSET (for !MMU) in arch/arm/include/asm/memory.h which in turn is set to CONFIG_PHYS_OFFSET which is: hex "Physical address of main memory" if MMU ... default DRAM_BASE if !MMU So yes, I think we can do: diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig --- a/arch/arm/Kconfig +++ b/arch/arm/Kconfig @@ -1595,6 +1595,7 @@ endchoice config PAGE_OFFSET hex + default DRAM_BASE if !MMU default 0x40000000 if VMSPLIT_1G default 0x80000000 if VMSPLIT_2G default 0xC0000000 and then drop the MMU case in the patch that is discussed here and also simplify a few other locations. I'll test a bit with this and then send it out with a few other fixes I have in the queue. For stable I'd still suggest not to do this though but stick to the original patch that started this thread. Best regards Uwe [1] maybe apart from being only one of serveral things that could be improved for !MMU. -- Pengutronix e.K. | Uwe Kleine-König | Industrial Linux Solutions | http://www.pengutronix.de/ | -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html