PIE: make call to GDT relocation fixup generalized

When a Firmware is complied as Position Independent Executable it needs
to request GDT fixup by passing size of the memory region to
el3_entrypoint_common macro.
The Global descriptor table fixup will be done early on during cold boot
process of primary core.

Currently only BL31 supports PIE, but in future when BL2_AT_EL3 will be
compiled as PIE, it can simply pass fixup size to the common el3
entrypoint macro to fixup GDT.

The reason for this patch was to overcome the bug introduced by SHA
330ead80

 which called fixup routine for each core causing
re-initializing of global pointers thus overwriting any changes
done by the previous core.

Change-Id: I55c792cc3ea9e7eef34c2e4653afd04572c4f055
Signed-off-by: Manish Pandey <manish.pandey2@arm.com>

bl1/aarch64/bl1_entrypoint.S

@@ -30,7 +30,8 @@ func bl1_entrypoint
 		_secondary_cold_boot=!COLD_BOOT_SINGLE_CPU	\
 		_init_memory=1					\
 		_init_c_runtime=1				\
-		_exception_vectors=bl1_exceptions
+		_exception_vectors=bl1_exceptions		\
+		_pie_fixup_size=0
 
 	/* --------------------------------------------------------------------
 	 * Perform BL1 setup

bl2/aarch64/bl2_el3_entrypoint.S

@@ -26,7 +26,8 @@ func bl2_entrypoint
 		_secondary_cold_boot=!COLD_BOOT_SINGLE_CPU      \
 		_init_memory=1                                  \
 		_init_c_runtime=1                               \
-		_exception_vectors=bl2_el3_exceptions
+		_exception_vectors=bl2_el3_exceptions		\
+		_pie_fixup_size=0
 
 	/* ---------------------------------------------
 	 * Restore parameters of boot rom

bl31/aarch64/bl31_entrypoint.S

@@ -32,17 +32,6 @@ func bl31_entrypoint
 	mov	x22, x2
 	mov	x23, x3
 
-	/* --------------------------------------------------------------------
-	 * If PIE is enabled, fixup the Global descriptor Table and dynamic
-	 * relocations
-	 * --------------------------------------------------------------------
-	 */
-#if ENABLE_PIE
-	mov_imm	x0, BL31_BASE
-	mov_imm	x1, BL31_LIMIT
-	bl	fixup_gdt_reloc
-#endif /* ENABLE_PIE */
-
 #if !RESET_TO_BL31
 	/* ---------------------------------------------------------------------
 	 * For !RESET_TO_BL31 systems, only the primary CPU ever reaches
@@ -59,7 +48,8 @@ func bl31_entrypoint
 		_secondary_cold_boot=0				\
 		_init_memory=0					\
 		_init_c_runtime=1				\
-		_exception_vectors=runtime_exceptions
+		_exception_vectors=runtime_exceptions		\
+		_pie_fixup_size=BL31_LIMIT - BL31_BASE
 #else
 
 	/* ---------------------------------------------------------------------
@@ -74,7 +64,8 @@ func bl31_entrypoint
 		_secondary_cold_boot=!COLD_BOOT_SINGLE_CPU	\
 		_init_memory=1					\
 		_init_c_runtime=1				\
-		_exception_vectors=runtime_exceptions
+		_exception_vectors=runtime_exceptions		\
+		_pie_fixup_size=BL31_LIMIT - BL31_BASE
 
 	/* ---------------------------------------------------------------------
 	 * For RESET_TO_BL31 systems, BL31 is the first bootloader to run so
@@ -174,7 +165,8 @@ func bl31_warm_entrypoint
 		_secondary_cold_boot=0				\
 		_init_memory=0					\
 		_init_c_runtime=0				\
-		_exception_vectors=runtime_exceptions
+		_exception_vectors=runtime_exceptions		\
+		_pie_fixup_size=0
 
 	/*
 	 * We're about to enable MMU and participate in PSCI state coordination.

include/arch/aarch64/el3_common_macros.S

@@ -232,11 +232,18 @@
  *
  * _exception_vectors:
  *	Address of the exception vectors to program in the VBAR_EL3 register.
+ *
+ * _pie_fixup_size:
+ *	Size of memory region to fixup Global Descriptor Table (GDT).
+ *
+ *	A non-zero value is expected when firmware needs GDT to be fixed-up.
+ *
  * -----------------------------------------------------------------------------
  */
 	.macro el3_entrypoint_common					\
 		_init_sctlr, _warm_boot_mailbox, _secondary_cold_boot,	\
-		_init_memory, _init_c_runtime, _exception_vectors
+		_init_memory, _init_c_runtime, _exception_vectors,	\
+		_pie_fixup_size
 
 	.if \_init_sctlr
 		/* -------------------------------------------------------------
@@ -283,6 +290,26 @@
 	do_cold_boot:
 	.endif /* _warm_boot_mailbox */
 
+	.if \_pie_fixup_size
+#if ENABLE_PIE
+		/*
+		 * ------------------------------------------------------------
+		 * If PIE is enabled fixup the Global descriptor Table only
+		 * once during primary core cold boot path.
+		 *
+		 * Compile time base address, required for fixup, is calculated
+		 * using "pie_fixup" label present within first page.
+		 * ------------------------------------------------------------
+		 */
+	pie_fixup:
+		ldr	x0, =pie_fixup
+		and	x0, x0, #~(PAGE_SIZE - 1)
+		mov_imm	x1, \_pie_fixup_size
+		add	x1, x1, x0
+		bl	fixup_gdt_reloc
+#endif /* ENABLE_PIE */
+	.endif /* _pie_fixup_size */
+
 	/* ---------------------------------------------------------------------
 	 * Set the exception vectors.
 	 * ---------------------------------------------------------------------