Merge branch 'fixes' of git://git.linaro.org/people/rmk/linux-arm

Pull ARM fixes from Russell King:
 "The usual collection of random fixes.  Also some further fixes to the
  last set of security fixes, and some more from Will (which you may
  already have in a slightly different form)"

* 'fixes' of git://git.linaro.org/people/rmk/linux-arm:
  ARM: 7807/1: kexec: validate CPU hotplug support
  ARM: 7812/1: rwlocks: retry trylock operation if strex fails on free lock
  ARM: 7811/1: locks: use early clobber in arch_spin_trylock
  ARM: 7810/1: perf: Fix array out of bounds access in armpmu_map_hw_event()
  ARM: 7809/1: perf: fix event validation for software group leaders
  ARM: Fix FIQ code on VIVT CPUs
  ARM: Fix !kuser helpers case
  ARM: Fix the world famous typo with is_gate_vma()

1 files changed, 16 insertions, 4 deletions

diff --git a/arch/arm/kernel/machine_kexec.c b/arch/arm/kernel/machine_kexec.c
index 4fb074c446bf..d7c82df69243 100644
--- a/arch/arm/kernel/machine_kexec.c
+++ b/arch/arm/kernel/machine_kexec.c
@@ -15,6 +15,7 @@
 #include <asm/mmu_context.h>
 #include <asm/cacheflush.h>
 #include <asm/mach-types.h>
+#include <asm/smp_plat.h>
 #include <asm/system_misc.h>
 
 extern const unsigned char relocate_new_kernel[];
@@ -39,6 +40,14 @@ int machine_kexec_prepare(struct kimage *image)
 	int i, err;
 
 	/*
+	 * Validate that if the current HW supports SMP, then the SW supports
+	 * and implements CPU hotplug for the current HW. If not, we won't be
+	 * able to kexec reliably, so fail the prepare operation.
+	 */
+	if (num_possible_cpus() > 1 && !platform_can_cpu_hotplug())
+		return -EINVAL;
+
+	/*
 	 * No segment at default ATAGs address. try to locate
 	 * a dtb using magic.
 	 */
@@ -134,10 +143,13 @@ void machine_kexec(struct kimage *image)
 	unsigned long reboot_code_buffer_phys;
 	void *reboot_code_buffer;
 
-	if (num_online_cpus() > 1) {
-		pr_err("kexec: error: multiple CPUs still online\n");
-		return;
-	}
+	/*
+	 * This can only happen if machine_shutdown() failed to disable some
+	 * CPU, and that can only happen if the checks in
+	 * machine_kexec_prepare() were not correct. If this fails, we can't
+	 * reliably kexec anyway, so BUG_ON is appropriate.
+	 */
+	BUG_ON(num_online_cpus() > 1);
 
 	page_list = image->head & PAGE_MASK;