[PATCH 3/4] ARM: implement get_tls syscall

[Nicolas Pitre]

When there is no dedicated register to hold the tp value and no MMU
to provide a fixed address kuser helper entry point, all that is
left as fallback is a syscall.

Signed-off-by: Nicolas Pitre <nico at linaro.org>
---
 arch/arm/include/uapi/asm/unistd.h | 1 +
 arch/arm/kernel/traps.c            | 3 +++
 2 files changed, 4 insertions(+)

diff --git a/arch/arm/include/uapi/asm/unistd.h b/arch/arm/include/uapi/asm/unistd.h
index 28bd456494..575b25fc29 100644
--- a/arch/arm/include/uapi/asm/unistd.h
+++ b/arch/arm/include/uapi/asm/unistd.h
@@ -35,5 +35,6 @@
 #define __ARM_NR_usr26			(__ARM_NR_BASE+3)
 #define __ARM_NR_usr32			(__ARM_NR_BASE+4)
 #define __ARM_NR_set_tls		(__ARM_NR_BASE+5)
+#define __ARM_NR_get_tls		(__ARM_NR_BASE+6)
 
 #endif /* _UAPI__ASM_ARM_UNISTD_H */
diff --git a/arch/arm/kernel/traps.c b/arch/arm/kernel/traps.c
index 948c648fea..43c0560f7b 100644
--- a/arch/arm/kernel/traps.c
+++ b/arch/arm/kernel/traps.c
@@ -647,6 +647,9 @@ asmlinkage int arm_syscall(int no, struct pt_regs *regs)
 		set_tls(regs->ARM_r0);
 		return 0;
 
+	case NR(get_tls):
+		return current_thread_info()->tp_value[0];
+
 	default:
 		/* Calls 9f00xx..9f07ff are defined to return -ENOSYS
 		   if not implemented, rather than raising SIGILL.  This
-- 
2.9.4