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Message-ID: <20261004024852.275144-1-alex@alexrp.com>
Date: Sun, 4 Oct 2026 04:48:52 +0200
From: Alex Rønne Petersen <alex@...xrp.com>
To: musl@...ts.openwall.com
Cc: Alex Rønne Petersen <alex@...xrp.com>
Subject: [PATCH] riscv: declare all vector registers as clobbers of syscalls
The kernel intentionally clobbers vector registers (by setting them to all 1s).
musl didn't declare this, so with a compiler targeting the V extension, this
could lead to all sorts of breakage that at first glance looks like
miscompilations.
---
arch/riscv32/syscall_arch.h | 9 ++++++++-
arch/riscv64/syscall_arch.h | 9 ++++++++-
2 files changed, 16 insertions(+), 2 deletions(-)
diff --git a/arch/riscv32/syscall_arch.h b/arch/riscv32/syscall_arch.h
index 70d2773f..9149cb9e 100644
--- a/arch/riscv32/syscall_arch.h
+++ b/arch/riscv32/syscall_arch.h
@@ -3,9 +3,16 @@
((union { long long ll; long l[2]; }){ .ll = x }).l[1]
#define __SYSCALL_LL_O(x) __SYSCALL_LL_E((x))
+#define SYSCALL_CLOBBERLIST \
+ "v0" , "v1", "v2", "v3", "v4", "v5", "v6", "v7", \
+ "v8", "v9", "v10", "v11", "v12", "v13", "v14", "v15", \
+ "v16", "v17", "v18", "v19", "v20", "v21", "v22", "v23", \
+ "v24", "v25", "v26", "v27", "v28", "v29", "v30", "v31", \
+ "vl", "vtype", "vxsat", "vxrm", "memory"
+
#define __asm_syscall(...) \
__asm__ __volatile__ ("ecall\n\t" \
- : "=r"(a0) : __VA_ARGS__ : "memory"); \
+ : "=r"(a0) : __VA_ARGS__ : SYSCALL_CLOBBERLIST); \
return a0; \
static inline long __syscall0(long n)
diff --git a/arch/riscv64/syscall_arch.h b/arch/riscv64/syscall_arch.h
index 81993fc8..6e05c9b3 100644
--- a/arch/riscv64/syscall_arch.h
+++ b/arch/riscv64/syscall_arch.h
@@ -1,9 +1,16 @@
#define __SYSCALL_LL_E(x) (x)
#define __SYSCALL_LL_O(x) (x)
+#define SYSCALL_CLOBBERLIST \
+ "v0" , "v1", "v2", "v3", "v4", "v5", "v6", "v7", \
+ "v8", "v9", "v10", "v11", "v12", "v13", "v14", "v15", \
+ "v16", "v17", "v18", "v19", "v20", "v21", "v22", "v23", \
+ "v24", "v25", "v26", "v27", "v28", "v29", "v30", "v31", \
+ "vl", "vtype", "vxsat", "vxrm", "memory"
+
#define __asm_syscall(...) \
__asm__ __volatile__ ("ecall\n\t" \
- : "=r"(a0) : __VA_ARGS__ : "memory"); \
+ : "=r"(a0) : __VA_ARGS__ : SYSCALL_CLOBBERLIST); \
return a0; \
static inline long __syscall0(long n)
--
2.53.0
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