powerpc fixes for 3.19

Wire up sys_execveat(). Tested on 32 & 64 bit.
 
 Fix for kdump on LE systems with cpus hot unplugged.
 
 Revert Anton's fix for "kernel BUG at kernel/smpboot.c:134!", this broke other
 platforms, we'll do a proper fix for 3.20.
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Merge tag 'powerpc-3.19-3' of git://git.kernel.org/pub/scm/linux/kernel/git/mpe/linux

Pull powerpc fixes from Michael Ellerman:

 - Wire up sys_execveat(). Tested on 32 & 64 bit.

 - Fix for kdump on LE systems with cpus hot unplugged.

 - Revert Anton's fix for "kernel BUG at kernel/smpboot.c:134!", this
   broke other platforms, we'll do a proper fix for 3.20.

* tag 'powerpc-3.19-3' of git://git.kernel.org/pub/scm/linux/kernel/git/mpe/linux:
  Revert "powerpc: Secondary CPUs must set cpu_callin_map after setting active and online"
  powerpc/kdump: Ignore failure in enabling big endian exception during crash
  powerpc: Wire up sys_execveat() syscall

arch/powerpc/include/asm/kexec.h

@@ -86,6 +86,11 @@ extern int overlaps_crashkernel(unsigned long start, unsigned long size);
 extern void reserve_crashkernel(void);
 extern void machine_kexec_mask_interrupts(void);
 
+static inline bool kdump_in_progress(void)
+{
+	return crashing_cpu >= 0;
+}
+
 #else /* !CONFIG_KEXEC */
 static inline void crash_kexec_secondary(struct pt_regs *regs) { }
 
@@ -106,6 +111,11 @@ static inline int crash_shutdown_unregister(crash_shutdown_t handler)
 	return 0;
 }
 
+static inline bool kdump_in_progress(void)
+{
+	return false;
+}
+
 #endif /* CONFIG_KEXEC */
 #endif /* ! __ASSEMBLY__ */
 #endif /* __KERNEL__ */

arch/powerpc/include/asm/systbl.h

@@ -366,3 +366,4 @@ SYSCALL_SPU(seccomp)
 SYSCALL_SPU(getrandom)
 SYSCALL_SPU(memfd_create)
 SYSCALL_SPU(bpf)
+COMPAT_SYS(execveat)

arch/powerpc/include/asm/unistd.h

@@ -12,7 +12,7 @@
 #include <uapi/asm/unistd.h>
 
 
-#define __NR_syscalls		362
+#define __NR_syscalls		363
 
 #define __NR__exit __NR_exit
 #define NR_syscalls	__NR_syscalls

arch/powerpc/include/uapi/asm/unistd.h

@@ -384,5 +384,6 @@
 #define __NR_getrandom		359
 #define __NR_memfd_create	360
 #define __NR_bpf		361
+#define __NR_execveat		362
 
 #endif /* _UAPI_ASM_POWERPC_UNISTD_H_ */

arch/powerpc/kernel/machine_kexec_64.c

@@ -330,7 +330,7 @@ void default_machine_kexec(struct kimage *image)
         * using debugger IPI.
         */
 
-	if (crashing_cpu == -1)
+	if (!kdump_in_progress())
 		kexec_prepare_cpus();
 
 	pr_debug("kexec: Starting switchover sequence.\n");

arch/powerpc/kernel/smp.c

@@ -700,6 +700,7 @@ void start_secondary(void *unused)
 	smp_store_cpu_info(cpu);
 	set_dec(tb_ticks_per_jiffy);
 	preempt_disable();
+	cpu_callin_map[cpu] = 1;
 
 	if (smp_ops->setup_cpu)
 		smp_ops->setup_cpu(cpu);
@@ -738,14 +739,6 @@ void start_secondary(void *unused)
 	notify_cpu_starting(cpu);
 	set_cpu_online(cpu, true);
 
-	/*
-	 * CPU must be marked active and online before we signal back to the
-	 * master, because the scheduler needs to see the cpu_online and
-	 * cpu_active bits set.
-	 */
-	smp_wmb();
-	cpu_callin_map[cpu] = 1;
-
 	local_irq_enable();
 
 	cpu_startup_entry(CPUHP_ONLINE);

arch/powerpc/platforms/pseries/lpar.c

@@ -43,6 +43,7 @@
 #include <asm/trace.h>
 #include <asm/firmware.h>
 #include <asm/plpar_wrappers.h>
+#include <asm/kexec.h>
 #include <asm/fadump.h>
 
 #include "pseries.h"
@@ -267,8 +268,13 @@ static void pSeries_lpar_hptab_clear(void)
 		 * out to the user, but at least this will stop us from
 		 * continuing on further and creating an even more
 		 * difficult to debug situation.
+		 *
+		 * There is a known problem when kdump'ing, if cpus are offline
+		 * the above call will fail. Rather than panicking again, keep
+		 * going and hope the kdump kernel is also little endian, which
+		 * it usually is.
 		 */
-		if (rc)
+		if (rc && !kdump_in_progress())
 			panic("Could not enable big endian exceptions");
 	}
 #endif