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[PATCH][AARCH64]End frame record chain correctly


Hi all,

This is a simple patch to make the end of frame record chain correctly according to AArch64 AAPCS.
Currently, the FP(x29) is overwritten by SP in the very beginning of _start.

aarch64-none-linux-gnueabi target has been tested on the model. No new issues.

Is this Okay to commit?


From the Procedure Call Standard for ARM 64-bit Architecture documentation: "Conforming code shall construct a linked list of stack-frames. Each frame shall link to the frame of its caller by means of a frame record of two 64-bit values on the stack. The frame record for the innermost frame (belonging to the most recent routine invocation) shall be pointed to by the Frame Pointer register (FP). The lowest addressed double-word shall point to the previous frame record and the highest addressed double-word shall contain the value passed in LR on entry to the current function. The end of the frame record chain is indicated by the address zero in the address for the previous frame."



ChangeLog:

2014-10-31  Renlin Li  <Renlin.Li@arm.com>

    * sysdeps/aarch64/start.S: Delete x29 overwritten assignment.
diff --git a/sysdeps/aarch64/start.S b/sysdeps/aarch64/start.S
index 35d603a..69b45ea 100644
--- a/sysdeps/aarch64/start.S
+++ b/sysdeps/aarch64/start.S
@@ -47,7 +47,6 @@ _start:
 	/* Create an initial frame with 0 LR and FP */
 	mov	x29, #0
 	mov	x30, #0
-	mov	x29, sp
 
 	/* Setup rtld_fini in argument register */
 	mov	x5, x0

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