[PATCH v4 1/6] powerpc/fsl_booke/kaslr: refactor kaslr_legal_offset() and kaslr_early_init()

[Jason Yan]

Some code refactor in kaslr_legal_offset() and kaslr_early_init(). No
functional change. This is a preparation for KASLR fsl_booke64.

Signed-off-by: Jason Yan <yanai...@huawei.com>
Cc: Scott Wood <o...@buserror.net>
Cc: Diana Craciun <diana.crac...@nxp.com>
Cc: Michael Ellerman <m...@ellerman.id.au>
Cc: Christophe Leroy <christophe.le...@c-s.fr>
Cc: Benjamin Herrenschmidt <b...@kernel.crashing.org>
Cc: Paul Mackerras <pau...@samba.org>
Cc: Nicholas Piggin <npig...@gmail.com>
Cc: Kees Cook <keesc...@chromium.org>
---
 arch/powerpc/mm/nohash/kaslr_booke.c | 34 +++++++++++++++-------------
 1 file changed, 18 insertions(+), 16 deletions(-)

diff --git a/arch/powerpc/mm/nohash/kaslr_booke.c 
b/arch/powerpc/mm/nohash/kaslr_booke.c
index 4a75f2d9bf0e..6ebff31fefcc 100644
--- a/arch/powerpc/mm/nohash/kaslr_booke.c
+++ b/arch/powerpc/mm/nohash/kaslr_booke.c
@@ -25,6 +25,7 @@ struct regions {
        unsigned long pa_start;
        unsigned long pa_end;
        unsigned long kernel_size;
+       unsigned long linear_sz;
        unsigned long dtb_start;
        unsigned long dtb_end;
        unsigned long initrd_start;
@@ -260,11 +261,23 @@ static __init void get_cell_sizes(const void *fdt, int 
node, int *addr_cells,
                *size_cells = fdt32_to_cpu(*prop);
 }
 
-static unsigned long __init kaslr_legal_offset(void *dt_ptr, unsigned long 
index,
-                                              unsigned long offset)
+static unsigned long __init kaslr_legal_offset(void *dt_ptr, unsigned long 
random)
 {
        unsigned long koffset = 0;
        unsigned long start;
+       unsigned long index;
+       unsigned long offset;
+
+       /*
+        * Decide which 64M we want to start
+        * Only use the low 8 bits of the random seed
+        */
+       index = random & 0xFF;
+       index %= regions.linear_sz / SZ_64M;
+
+       /* Decide offset inside 64M */
+       offset = random % (SZ_64M - regions.kernel_size);
+       offset = round_down(offset, SZ_16K);
 
        while ((long)index >= 0) {
                offset = memstart_addr + index * SZ_64M + offset;
@@ -289,10 +302,9 @@ static inline __init bool kaslr_disabled(void)
 static unsigned long __init kaslr_choose_location(void *dt_ptr, phys_addr_t 
size,
                                                  unsigned long kernel_sz)
 {
-       unsigned long offset, random;
+       unsigned long random;
        unsigned long ram, linear_sz;
        u64 seed;
-       unsigned long index;
 
        kaslr_get_cmdline(dt_ptr);
        if (kaslr_disabled())
@@ -333,22 +345,12 @@ static unsigned long __init kaslr_choose_location(void 
*dt_ptr, phys_addr_t size
        regions.dtb_start = __pa(dt_ptr);
        regions.dtb_end = __pa(dt_ptr) + fdt_totalsize(dt_ptr);
        regions.kernel_size = kernel_sz;
+       regions.linear_sz = linear_sz;
 
        get_initrd_range(dt_ptr);
        get_crash_kernel(dt_ptr, ram);
 
-       /*
-        * Decide which 64M we want to start
-        * Only use the low 8 bits of the random seed
-        */
-       index = random & 0xFF;
-       index %= linear_sz / SZ_64M;
-
-       /* Decide offset inside 64M */
-       offset = random % (SZ_64M - kernel_sz);
-       offset = round_down(offset, SZ_16K);
-
-       return kaslr_legal_offset(dt_ptr, index, offset);
+       return kaslr_legal_offset(dt_ptr, random);
 }
 
 /*
-- 
2.17.2