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authorLinus Torvalds <torvalds@linux-foundation.org>2024-07-24 10:29:50 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2024-07-24 10:29:50 -0700
commit7a3fad30fd8b4b5e370906b3c554f64026f56c2f (patch)
treead1f004b3157bf01db1295b6de37df8673089989 /include/vdso
parentd1e9a63dcd7248385bbbccf1650d69e4af914f05 (diff)
parentad8070cb1b4bd40aa19a5e3f7c24d7f62c71b382 (diff)
Merge tag 'random-6.11-rc1-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/crng/random
Pull random number generator updates from Jason Donenfeld: "This adds getrandom() support to the vDSO. First, it adds a new kind of mapping to mmap(2), MAP_DROPPABLE, which lets the kernel zero out pages anytime under memory pressure, which enables allocating memory that never gets swapped to disk but also doesn't count as being mlocked. Then, the vDSO implementation of getrandom() is introduced in a generic manner and hooked into random.c. Next, this is implemented on x86. (Also, though it's not ready for this pull, somebody has begun an arm64 implementation already) Finally, two vDSO selftests are added. There are also two housekeeping cleanup commits" * tag 'random-6.11-rc1-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/crng/random: MAINTAINERS: add random.h headers to RNG subsection random: note that RNDGETPOOL was removed in 2.6.9-rc2 selftests/vDSO: add tests for vgetrandom x86: vdso: Wire up getrandom() vDSO implementation random: introduce generic vDSO getrandom() implementation mm: add MAP_DROPPABLE for designating always lazily freeable mappings
Diffstat (limited to 'include/vdso')
-rw-r--r--include/vdso/datapage.h11
-rw-r--r--include/vdso/getrandom.h46
2 files changed, 57 insertions, 0 deletions
diff --git a/include/vdso/datapage.h b/include/vdso/datapage.h
index 7647e0946f50..b85f24cac3f5 100644
--- a/include/vdso/datapage.h
+++ b/include/vdso/datapage.h
@@ -117,6 +117,16 @@ struct vdso_data {
struct arch_vdso_data arch_data;
};
+/**
+ * struct vdso_rng_data - vdso RNG state information
+ * @generation: counter representing the number of RNG reseeds
+ * @is_ready: boolean signaling whether the RNG is initialized
+ */
+struct vdso_rng_data {
+ u64 generation;
+ u8 is_ready;
+};
+
/*
* We use the hidden visibility to prevent the compiler from generating a GOT
* relocation. Not only is going through a GOT useless (the entry couldn't and
@@ -128,6 +138,7 @@ struct vdso_data {
*/
extern struct vdso_data _vdso_data[CS_BASES] __attribute__((visibility("hidden")));
extern struct vdso_data _timens_data[CS_BASES] __attribute__((visibility("hidden")));
+extern struct vdso_rng_data _vdso_rng_data __attribute__((visibility("hidden")));
/**
* union vdso_data_store - Generic vDSO data page
diff --git a/include/vdso/getrandom.h b/include/vdso/getrandom.h
new file mode 100644
index 000000000000..a8b7c14b0ae0
--- /dev/null
+++ b/include/vdso/getrandom.h
@@ -0,0 +1,46 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2022-2024 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
+ */
+
+#ifndef _VDSO_GETRANDOM_H
+#define _VDSO_GETRANDOM_H
+
+#include <linux/types.h>
+
+#define CHACHA_KEY_SIZE 32
+#define CHACHA_BLOCK_SIZE 64
+
+/**
+ * struct vgetrandom_state - State used by vDSO getrandom().
+ *
+ * @batch: One and a half ChaCha20 blocks of buffered RNG output.
+ *
+ * @key: Key to be used for generating next batch.
+ *
+ * @batch_key: Union of the prior two members, which is exactly two full
+ * ChaCha20 blocks in size, so that @batch and @key can be filled
+ * together.
+ *
+ * @generation: Snapshot of @rng_info->generation in the vDSO data page at
+ * the time @key was generated.
+ *
+ * @pos: Offset into @batch of the next available random byte.
+ *
+ * @in_use: Reentrancy guard for reusing a state within the same thread
+ * due to signal handlers.
+ */
+struct vgetrandom_state {
+ union {
+ struct {
+ u8 batch[CHACHA_BLOCK_SIZE * 3 / 2];
+ u32 key[CHACHA_KEY_SIZE / sizeof(u32)];
+ };
+ u8 batch_key[CHACHA_BLOCK_SIZE * 2];
+ };
+ u64 generation;
+ u8 pos;
+ bool in_use;
+};
+
+#endif /* _VDSO_GETRANDOM_H */