crypto: x86 - make constants readonly, allow linker to merge them

A lot of asm-optimized routines in arch/x86/crypto/ keep its
constants in .data. This is wrong, they should be on .rodata.

Mnay of these constants are the same in different modules.
For example, 128-bit shuffle mask 0x000102030405060708090A0B0C0D0E0F
exists in at least half a dozen places.

There is a way to let linker merge them and use just one copy.
The rules are as follows: mergeable objects of different sizes
should not share sections. You can't put them all in one .rodata
section, they will lose "mergeability".

GCC puts its mergeable constants in ".rodata.cstSIZE" sections,
or ".rodata.cstSIZE.<object_name>" if -fdata-sections is used.
This patch does the same:

	.section .rodata.cst16.SHUF_MASK, "aM", @progbits, 16

It is important that all data in such section consists of
16-byte elements, not larger ones, and there are no implicit
use of one element from another.

When this is not the case, use non-mergeable section:

	.section .rodata[.VAR_NAME], "a", @progbits

This reduces .data by ~15 kbytes:

    text    data     bss     dec      hex filename
11097415 2705840 2630712 16433967  fac32f vmlinux-prev.o
11112095 2690672 2630712 16433479  fac147 vmlinux.o

Merged objects are visible in System.map:

ffffffff81a28810 r POLY
ffffffff81a28810 r POLY
ffffffff81a28820 r TWOONE
ffffffff81a28820 r TWOONE
ffffffff81a28830 r PSHUFFLE_BYTE_FLIP_MASK <- merged regardless of
ffffffff81a28830 r SHUF_MASK   <------------- the name difference
ffffffff81a28830 r SHUF_MASK
ffffffff81a28830 r SHUF_MASK
..
ffffffff81a28d00 r K512 <- merged three identical 640-byte tables
ffffffff81a28d00 r K512
ffffffff81a28d00 r K512

Use of object names in section name suffixes is not strictly necessary,
but might help if someday link stage will use garbage collection
to eliminate unused sections (ld --gc-sections).

Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com>
CC: Herbert Xu <herbert@gondor.apana.org.au>
CC: Josh Poimboeuf <jpoimboe@redhat.com>
CC: Xiaodong Liu <xiaodong.liu@intel.com>
CC: Megha Dey <megha.dey@intel.com>
CC: linux-crypto@vger.kernel.org
CC: x86@kernel.org
CC: linux-kernel@vger.kernel.org
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

3 files changed, 14 insertions, 4 deletions

diff --git a/arch/x86/crypto/sha512-mb/sha512_mb_mgr_flush_avx2.S b/arch/x86/crypto/sha512-mb/sha512_mb_mgr_flush_avx2.S
index 3ddba19..7c629ca 100644
--- a/arch/x86/crypto/sha512-mb/sha512_mb_mgr_flush_avx2.S
+++ b/arch/x86/crypto/sha512-mb/sha512_mb_mgr_flush_avx2.S
@@ -280,12 +280,18 @@ ENTRY(sha512_mb_mgr_get_comp_job_avx2)
 	pop     %rbx
         ret
 ENDPROC(sha512_mb_mgr_get_comp_job_avx2)
-.data
 
-.align 16
+.section	.rodata.cst8.one, "aM", @progbits, 8
+.align 8
 one:
 .quad  1
+
+.section	.rodata.cst8.two, "aM", @progbits, 8
+.align 8
 two:
 .quad  2
+
+.section	.rodata.cst8.three, "aM", @progbits, 8
+.align 8
 three:
 .quad  3
diff --git a/arch/x86/crypto/sha512-mb/sha512_mb_mgr_submit_avx2.S b/arch/x86/crypto/sha512-mb/sha512_mb_mgr_submit_avx2.S
index 815f07b..4ba709b 100644
--- a/arch/x86/crypto/sha512-mb/sha512_mb_mgr_submit_avx2.S
+++ b/arch/x86/crypto/sha512-mb/sha512_mb_mgr_submit_avx2.S
@@ -209,8 +209,9 @@ return_null:
 	xor     job_rax, job_rax
 	jmp     return
 ENDPROC(sha512_mb_mgr_submit_avx2)
-.data
 
+/* UNUSED?
+.section	.rodata.cst16, "aM", @progbits, 16
 .align 16
 H0:     .int  0x6a09e667
 H1:     .int  0xbb67ae85
@@ -220,3 +221,4 @@ H4:     .int  0x510e527f
 H5:     .int  0x9b05688c
 H6:     .int  0x1f83d9ab
 H7:     .int  0x5be0cd19
+*/
diff --git a/arch/x86/crypto/sha512-mb/sha512_x4_avx2.S b/arch/x86/crypto/sha512-mb/sha512_x4_avx2.S
index 31ab1ef..e22e907 100644
--- a/arch/x86/crypto/sha512-mb/sha512_x4_avx2.S
+++ b/arch/x86/crypto/sha512-mb/sha512_x4_avx2.S
@@ -361,7 +361,7 @@ Lrounds_16_xx:
 	ret
 ENDPROC(sha512_x4_avx2)
 
-.data
+.section	.rodata.K512_4, "a", @progbits
 .align 64
 K512_4:
 	.octa 0x428a2f98d728ae22428a2f98d728ae22,\
@@ -525,5 +525,7 @@ K512_4:
 	.octa 0x6c44198c4a4758176c44198c4a475817,\
 		0x6c44198c4a4758176c44198c4a475817
 
+.section	.rodata.cst32.PSHUFFLE_BYTE_FLIP_MASK, "aM", @progbits, 32
+.align 32
 PSHUFFLE_BYTE_FLIP_MASK: .octa 0x08090a0b0c0d0e0f0001020304050607
                          .octa 0x18191a1b1c1d1e1f1011121314151617