[PATCH 5.7 79/79] arm64: kaslr: Use standard early random function

Greg Kroah-Hartman
2020-08-10T15:25:42Z

From: Guenter Roeck <linux@roeck-us.net>

commit 9bceb80b3cc483e6763c39a4928402fa82815d3e upstream.

Commit 585524081ecd ("random: random.h should include archrandom.h, not
the other way around") tries to fix a problem with recursive inclusion
of linux/random.h and arch/archrandom.h for arm64. Unfortunately, this
results in the following compile error if ARCH_RANDOM is disabled.

arch/arm64/kernel/kaslr.c: In function 'kaslr_early_init':
arch/arm64/kernel/kaslr.c:128:6: error: implicit declaration of function '__early_cpu_has_rndr'; did you mean '__early_pfn_to_nid'? [-Werror=implicit-function-declaration]
if (__early_cpu_has_rndr()) {
^~~~~~~~~~~~~~~~~~~~
__early_pfn_to_nid
arch/arm64/kernel/kaslr.c:131:7: error: implicit declaration of function '__arm64_rndr' [-Werror=implicit-function-declaration]
if (__arm64_rndr(&raw))
^~~~~~~~~~~~

The problem is that arch/archrandom.h is only included from
linux/random.h if ARCH_RANDOM is enabled. If not, __arm64_rndr() and
__early_cpu_has_rndr() are undeclared, causing the problem.

Use arch_get_random_seed_long_early() instead of arm64 specific
functions to solve the problem.

Reported-by: Qian Cai <cai@lca.pw>
Fixes: 585524081ecd ("random: random.h should include archrandom.h, not the other way around")
Cc: Qian Cai <cai@lca.pw>
Cc: Mark Brown <broonie@kernel.org>
Reviewed-by: Mark Rutland <mark.rutland@arm.com>
Reviewed-by: Mark Brown <broonie@kernel.org>
Tested-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Sedat Dilek <sedat.dilek@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
arch/arm64/kernel/kaslr.c | 12 +++++-------
1 file changed, 5 insertions(+), 7 deletions(-)

--- a/arch/arm64/kernel/kaslr.c
+++ b/arch/arm64/kernel/kaslr.c
@@ -84,6 +84,7 @@ u64 __init kaslr_early_init(u64 dt_phys)
void *fdt;
u64 seed, offset, mask, module_range;
const u8 *cmdline, *str;
+ unsigned long raw;
int size;

/*
@@ -122,15 +123,12 @@ u64 __init kaslr_early_init(u64 dt_phys)
}

/*
- * Mix in any entropy obtainable architecturally, open coded
- * since this runs extremely early.
+ * Mix in any entropy obtainable architecturally if enabled
+ * and supported.
*/
- if (__early_cpu_has_rndr()) {
- unsigned long raw;

- if (__arm64_rndr(&raw))
- seed ^= raw;
- }
+ if (arch_get_random_seed_long_early(&raw))
+ seed ^= raw;

if (!seed) {
kaslr_status = KASLR_DISABLED_NO_SEED;