powerpc: Define empty_zero_page[] in C

At the time being, empty_zero_page[] is defined in each
platform head.S.

Define it in mm/mem.c instead, and put it in BSS section instead
of the DATA section. Commit 5227cfa71f9e ("arm64: mm: place
empty_zero_page in bss") explains why it is interesting to have
it in BSS.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/5838caffa269e0957c5a50cc85477876220298b0.1623063174.git.christophe.leroy@csgroup.eu

7 files changed, 3 insertions, 28 deletions

diff --git a/arch/powerpc/kernel/head_40x.S b/arch/powerpc/kernel/head_40x.S
index 2717aa860cae..92b6c7356161 100644
--- a/arch/powerpc/kernel/head_40x.S
+++ b/arch/powerpc/kernel/head_40x.S
@@ -709,10 +709,6 @@ _GLOBAL(abort)
 	.align	12
 	.globl	sdata
 sdata:
-	.globl	empty_zero_page
-empty_zero_page:
-	.space	4096
-EXPORT_SYMBOL(empty_zero_page)
 	.globl	swapper_pg_dir
 swapper_pg_dir:
 	.space	PGD_TABLE_SIZE
diff --git a/arch/powerpc/kernel/head_44x.S b/arch/powerpc/kernel/head_44x.S
index 2c4ffec027a2..e037eb615757 100644
--- a/arch/powerpc/kernel/head_44x.S
+++ b/arch/powerpc/kernel/head_44x.S
@@ -1241,10 +1241,6 @@ head_start_common:
 	.align	PAGE_SHIFT
 	.globl	sdata
 sdata:
-	.globl	empty_zero_page
-empty_zero_page:
-	.space	PAGE_SIZE
-EXPORT_SYMBOL(empty_zero_page)
 
 /*
  * To support >32-bit physical addresses, we use an 8KB pgdir.
diff --git a/arch/powerpc/kernel/head_64.S b/arch/powerpc/kernel/head_64.S
index ece7f97bafff..730838c7ca39 100644
--- a/arch/powerpc/kernel/head_64.S
+++ b/arch/powerpc/kernel/head_64.S
@@ -1012,8 +1012,3 @@ start_here_common:
 	.globl	swapper_pg_dir
 swapper_pg_dir:
 	.space	PGD_TABLE_SIZE
-
-	.globl	empty_zero_page
-empty_zero_page:
-	.space	PAGE_SIZE
-EXPORT_SYMBOL(empty_zero_page)
diff --git a/arch/powerpc/kernel/head_8xx.S b/arch/powerpc/kernel/head_8xx.S
index 817df9fe7fb3..5ce42dfac061 100644
--- a/arch/powerpc/kernel/head_8xx.S
+++ b/arch/powerpc/kernel/head_8xx.S
@@ -795,12 +795,6 @@ _GLOBAL(mmu_pin_tlb)
 	.data
 	.globl	sdata
 sdata:
-	.globl	empty_zero_page
-	.align	PAGE_SHIFT
-empty_zero_page:
-	.space	PAGE_SIZE
-EXPORT_SYMBOL(empty_zero_page)
-
 	.globl	swapper_pg_dir
 swapper_pg_dir:
 	.space	PGD_TABLE_SIZE
diff --git a/arch/powerpc/kernel/head_book3s_32.S b/arch/powerpc/kernel/head_book3s_32.S
index 0b82672ff7a6..59ddd68d60bf 100644
--- a/arch/powerpc/kernel/head_book3s_32.S
+++ b/arch/powerpc/kernel/head_book3s_32.S
@@ -1216,11 +1216,6 @@ setup_usbgecko_bat:
 	.data
 	.globl	sdata
 sdata:
-	.globl	empty_zero_page
-empty_zero_page:
-	.space	4096
-EXPORT_SYMBOL(empty_zero_page)
-
 	.globl	swapper_pg_dir
 swapper_pg_dir:
 	.space	PGD_TABLE_SIZE
diff --git a/arch/powerpc/kernel/head_fsl_booke.S b/arch/powerpc/kernel/head_fsl_booke.S
index ab718fd5e2a2..f33bc5a8e73e 100644
--- a/arch/powerpc/kernel/head_fsl_booke.S
+++ b/arch/powerpc/kernel/head_fsl_booke.S
@@ -1221,10 +1221,6 @@ _GLOBAL(restore_to_as0)
 	.align	12
 	.globl	sdata
 sdata:
-	.globl	empty_zero_page
-empty_zero_page:
-	.space	4096
-EXPORT_SYMBOL(empty_zero_page)
 	.globl	swapper_pg_dir
 swapper_pg_dir:
 	.space	PGD_TABLE_SIZE
diff --git a/arch/powerpc/mm/mem.c b/arch/powerpc/mm/mem.c
index a6b36a40897a..77fce7aa7dc5 100644
--- a/arch/powerpc/mm/mem.c
+++ b/arch/powerpc/mm/mem.c
@@ -28,6 +28,9 @@
 unsigned long long memory_limit;
 bool init_mem_is_free;
 
+unsigned long empty_zero_page[PAGE_SIZE / sizeof(unsigned long)] __page_aligned_bss;
+EXPORT_SYMBOL(empty_zero_page);
+
 pgprot_t phys_mem_access_prot(struct file *file, unsigned long pfn,
 			      unsigned long size, pgprot_t vma_prot)
 {