[Minios-devel] [UNIKRAFT PATCH v2 2/4] lib/ukswrand: Add seed generating function

[Vlad-Andrei BĂDOIU (78692) <vlad_andrei.badoiu@xxxxxxxxxxxxxxx>]

This patch adds a new function, _get_random_seed32 for seed generaton. If the
pre-compiled config option is not selected, then rdrand is used on x86 and
ukplat_wall_clock on ARM.

Signed-off-by: Vlad-Andrei Badoiu <vlad_andrei.badoiu@xxxxxxxxxxxxxxx>
---
 lib/ukswrand/Config.uk           |  7 +++++++
 lib/ukswrand/include/uk/swrand.h | 20 ++++++++++++++++++++
 lib/ukswrand/mwc.c               |  2 +-
 3 files changed, 28 insertions(+), 1 deletion(-)

diff --git a/lib/ukswrand/Config.uk b/lib/ukswrand/Config.uk
index c58371bb..8db3af03 100644
--- a/lib/ukswrand/Config.uk
+++ b/lib/ukswrand/Config.uk
@@ -14,10 +14,17 @@ config LIBUKSWRAND_MWC
                Use multiply-with-carry algorithm
 endchoice
 
+config LIBUKSWRAND_USE_INITIALSEED
+       bool "Use a pre-compiled seed"
+       default y
+
+if LIBUKSWRAND_USE_INITIALSEED
 config LIBUKSWRAND_INITIALSEED
        int "Initial random seed"
        default 23
 
+endif
+
 config LIBUKSWRAND_DEVFS
        bool "Register random and urandom device to devfs"
        select LIBDEVFS
diff --git a/lib/ukswrand/include/uk/swrand.h b/lib/ukswrand/include/uk/swrand.h
index 77912182..a3a1e227 100644
--- a/lib/ukswrand/include/uk/swrand.h
+++ b/lib/ukswrand/include/uk/swrand.h
@@ -39,6 +39,7 @@
 #include <uk/arch/types.h>
 #include <uk/plat/lcpu.h>
 #include <uk/config.h>
+#include <uk/plat/time.h>
 
 #ifdef __cplusplus
 extern "C" {
@@ -53,6 +54,25 @@ extern struct uk_swrand uk_swrand_def;
 void uk_swrand_init_r(struct uk_swrand *r, __u32 seed);
 __u32 uk_swrand_randr_r(struct uk_swrand *r);
 
+static inline __u32 _get_random_seed32(void)
+{
+       __u32 val;
+
+#ifdef CONFIG_LIBUKSWRAND_USE_INITIALSEED
+       return CONFIG_LIBUKSWRAND_INITIALSEED;
+#endif
+
+#ifdef CONFIG_ARCH_X86_64
+       asm volatile ("rdrand %%eax;"
+               : "=a" (val));
+       return val;
+#endif
+
+       /* TODO: Generate the seed randomly on ARM */
+       val = (__u32)ukplat_wall_clock();
+       return val;
+}
+
 /* Uses the pre-initialized default generator  */
 /* TODO: Add assertion when we can test if we are in interrupt context */
 /* TODO: Revisit with multi-CPU support */
diff --git a/lib/ukswrand/mwc.c b/lib/ukswrand/mwc.c
index 820aa2a2..6d785c07 100644
--- a/lib/ukswrand/mwc.c
+++ b/lib/ukswrand/mwc.c
@@ -99,7 +99,7 @@ __u32 uk_swrand_randr_r(struct uk_swrand *r)
 static void _uk_swrand_ctor(void)
 {
        uk_pr_info("Initialize random number generator...\n");
-       uk_swrand_init_r(&uk_swrand_def, CONFIG_LIBUKSWRAND_INITIALSEED);
+       uk_swrand_init_r(&uk_swrand_def, _get_random_seed32());
 }
 
 UK_CTOR_FUNC(UK_SWRAND_CTOR_PRIO, _uk_swrand_ctor);
-- 
2.20.1


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