From mboxrd@z Thu Jan 1 00:00:00 1970 From: tony@atomide.com (Tony Lindgren) Date: Mon, 7 Jul 2014 04:19:48 -0700 Subject: [PATCH 0/4] ABI updates In-Reply-To: <20140704195134.GJ21766@n2100.arm.linux.org.uk> References: <20140704195134.GJ21766@n2100.arm.linux.org.uk> Message-ID: <20140707111947.GP28884@atomide.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org * Russell King - ARM Linux [140704 12:56]: > As a result of the recent discussions about android, several issues > have been identified with existing kernels: > > 1. HWCAP_SWP does not properly reflect whether the SWP instruction > should be used. Turn HWCAP_SWP off on ARMv6+ where the exclusives > are available. > > 2. SWP is unsafe when running on a SMP CPU; there is no bus locking > between the read and write parts of the instruction execution. > Force SWP emulation on ARMv7+ where we can disable the SWP > instruction. > > 3. Reporting of alignment faults - kernel mode faults are silent due to > the requirements of the network stack, but we can note where the > last one occurs. > > Testing reveals that at least my OMAP4430 userspace (supplied from TI) > executes lots of SWP instructions, which is something that wasn't known > before this patch. > > Many systems today are not configured with SWP emulation enabled on SMP. > This means that the SWP instruction is available, but unsafe. > > arch/arm/kernel/setup.c | 29 ++++++++++++++++++++++------- > arch/arm/kernel/swp_emulate.c | 4 ++++ > arch/arm/mm/Kconfig | 2 +- > arch/arm/mm/alignment.c | 4 +++- > 4 files changed, 30 insertions(+), 9 deletions(-) Tried testing this on omap2 which is ARMv6 with no K, but got this: arch/arm/kernel/setup.c: In function ?elf_hwcap_fixup?: arch/arm/kernel/setup.c:405:2: error: implicit declaration of function ?read_cpuid_part? [-Werror=implicit-function-declaration] That should be read_cpuid_part_number instead. After fixing that, omap2 booted fine, so for ARMv6 with no K: Tested-by: Ton Lindgren