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Backport patch for riscv64 architecture support

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This commit is contained in:
eabdullin 2026-05-27 16:56:28 +03:00
commit f79dbea1a1
2 changed files with 97 additions and 0 deletions
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15
config.yaml Normal file
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@ -0,0 +1,15 @@
actions:
- modify_release:
- suffix: ".alma.1"
enabled: true
- changelog_entry:
- name: "Eduard Abdullin"
email: "eabdullin@almalinux.org"
line:
- "Backport patch for riscv64 architecture support"
- add_files:
- type: "patch"
name: "jitterentropy-riscv64.patch"
number: 1000

82
files/jitterentropy-riscv64.patch Normal file
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From 9671e0f658ef70bdadf18a060870f76eeb3f5f90 Mon Sep 17 00:00:00 2001
From: Eduard Abdullin <eabdullin@cloudlinux.com>
Date: Wed, 27 May 2026 11:48:00 +0500
Subject: [PATCH] Backport upstream commit 59dc5997: native riscv64 timer
The jitterentropy library v3.7.0 fails to build on riscv64 with -std=c11
because none of the architecture-specific branches in
jitterentropy-base-user.h match __riscv. Compilation falls through to
the generic clock_gettime() path, which glibc hides behind
_POSIX_C_SOURCE >= 199309L in C11 mode:
jitterentropy-base-user.h: In function 'jent_get_nstime':
jitterentropy-base-user.h:235:13: error: implicit declaration of
function 'clock_gettime' [-Wimplicit-function-declaration]
jitterentropy-base-user.h:235:27: error: 'CLOCK_REALTIME' undeclared
Upstream resolved this on 2026-04-25 in commit 59dc5997 ('refactor
architecture specific code'), which adds a native riscv branch using
the rdtime CSR via the rdtime pseudo-instruction. That commit is a
large refactor (17 files, +1544/-1499 lines) and has not yet appeared
in any tagged release; the next upstream release (3.7.1) will carry it.
Backport the riscv branch only, simplified for RV64. The timer
implementation is verbatim from upstream arch/jitterentropy-arch-timer.h;
only the structural wrapper differs (arch dispatch fused with the
function body, as in v3.7.0). RV32 (rdtimeh/rdtime retry pair) is
intentionally omitted because AlmaLinux only targets RV64 (riscv64).
Using the native time CSR rather than clock_gettime() also preserves
the entropy quality of the library: clock_gettime(CLOCK_REALTIME) is
subject to NTP steering and lacks the cycle-level resolution required
by the jitter entropy source on which all other architectures already
rely (rdtsc on x86, cntvct_el0 on aarch64, stcke on s390x, mftb on
ppc64le).
Drop this patch when jitterentropy is rebased to >= 3.7.1.
---
jitterentropy-base-user.h | 28 +++++++++++++++++++++++++++-
1 file changed, 27 insertions(+), 1 deletion(-)
diff --git jitterentropy-base-user.h jitterentropy-base-user.h
index 0cfc526..77e3b38 100644
--- jitterentropy-base-user.h
+++ jitterentropy-base-user.h
@@ -203,7 +203,33 @@ static inline void jent_get_nstime(uint64_t *out)
*out = (uint64_t)__builtin_ppc_get_timebase();
}
-#else /* (__x86_64__) || (__i386__) || (__aarch64__) || (__s390x__) || (__powerpc__) */
+#elif defined(__riscv)
+/*
+ * Backport of upstream commit 59dc5997 ("refactor architecture specific
+ * code", 2026-04-25) -- riscv branch only, simplified for RV64. To be
+ * obsoleted by jitterentropy >= 3.7.1, which carries the same logic in
+ * arch/jitterentropy-arch-timer.h (with full RV32 support).
+ *
+ * The "time" CSR is the platform timer and is reliably accessible from
+ * user mode on Linux (the kernel enables [s|m]counteren.TM). The "cycle"
+ * CSR has higher resolution but is not always user-readable. Override
+ * RISCV_NSTIME_INSN to switch sources, e.g. to "rdcycle".
+ *
+ * AlmaLinux only targets RV64 (riscv64); RV32 support is intentionally
+ * not backported (it would require a rdtimeh/rdtime retry pair).
+ */
+# ifndef RISCV_NSTIME_INSN
+# define RISCV_NSTIME_INSN "rdtime"
+# endif
+
+static inline void jent_get_nstime(uint64_t *out)
+{
+ uint64_t ctr_val;
+ __asm__ __volatile__(RISCV_NSTIME_INSN " %0" : "=r" (ctr_val));
+ *out = ctr_val;
+}
+
+#else /* (__x86_64__) || (__i386__) || (__aarch64__) || (__s390x__) || (__powerpc__) || (__riscv) */
static inline void jent_get_nstime(uint64_t *out)
{
--
2.51.0