arm64: compat: Check for AArch32 state

Make sure we have AArch32 state available for running COMPAT
binaries and also for switching the personality to PER_LINUX32.

Signed-off-by: Yury Norov <ynorov@caviumnetworks.com>
[ Added cap bit, checks for HWCAP, personality ]
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Tested-by: Yury Norov <ynorov@caviumnetworks.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>

3 files changed, 17 insertions, 3 deletions

diff --git a/arch/arm64/include/asm/elf.h b/arch/arm64/include/asm/elf.h
index 24ed037f09fd..7a09c48c0475 100644
--- a/arch/arm64/include/asm/elf.h
+++ b/arch/arm64/include/asm/elf.h
@@ -177,7 +177,8 @@ typedef compat_elf_greg_t		compat_elf_gregset_t[COMPAT_ELF_NGREG];
 
 /* AArch32 EABI. */
 #define EF_ARM_EABI_MASK                0xff000000
-#define compat_elf_check_arch(x)        (((x)->e_machine == EM_ARM) && \
+#define compat_elf_check_arch(x)        (system_supports_32bit_el0() && \
+                                         ((x)->e_machine == EM_ARM) && \
                                          ((x)->e_flags & EF_ARM_EABI_MASK))
 
 #define compat_start_thread             compat_start_thread
diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index 40a23f24559d..8e62d61f6c42 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -987,7 +987,8 @@ void verify_local_cpu_capabilities(void)
 
         verify_local_cpu_features(arm64_features);
         verify_local_elf_hwcaps(arm64_elf_hwcaps);
-        verify_local_elf_hwcaps(compat_elf_hwcaps);
+        if (system_supports_32bit_el0())
+                verify_local_elf_hwcaps(compat_elf_hwcaps);
 }
 
 static void __init setup_feature_capabilities(void)
@@ -1004,7 +1005,9 @@ void __init setup_cpu_features(void)
         /* Set the CPU feature capabilies */
         setup_feature_capabilities();
         setup_elf_hwcaps(arm64_elf_hwcaps);
-        setup_elf_hwcaps(compat_elf_hwcaps);
+
+        if (system_supports_32bit_el0())
+                setup_elf_hwcaps(compat_elf_hwcaps);
 
         /* Advertise that we have computed the system capabilities */
         set_sys_caps_initialised();
diff --git a/arch/arm64/kernel/sys.c b/arch/arm64/kernel/sys.c
index 75151aaf1a52..26fe8ea93ea2 100644
--- a/arch/arm64/kernel/sys.c
+++ b/arch/arm64/kernel/sys.c
@@ -25,6 +25,7 @@
 #include <linux/sched.h>
 #include <linux/slab.h>
 #include <linux/syscalls.h>
+#include <asm/cpufeature.h>
 
 asmlinkage long sys_mmap(unsigned long addr, unsigned long len,
                          unsigned long prot, unsigned long flags,
@@ -36,11 +37,20 @@ asmlinkage long sys_mmap(unsigned long addr, unsigned long len,
         return sys_mmap_pgoff(addr, len, prot, flags, fd, off >> PAGE_SHIFT);
 }
 
+SYSCALL_DEFINE1(arm64_personality, unsigned int, personality)
+{
+        if (personality(personality) == PER_LINUX32 &&
+                !system_supports_32bit_el0())
+                return -EINVAL;
+        return sys_personality(personality);
+}
+
 /*
  * Wrappers to pass the pt_regs argument.
  */
 asmlinkage long sys_rt_sigreturn_wrapper(void);
 #define sys_rt_sigreturn        sys_rt_sigreturn_wrapper
+#define sys_personality         sys_arm64_personality
 
 #undef __SYSCALL
 #define __SYSCALL(nr, sym)      [nr] = sym,