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Message-Id: <20180105220738.11616-1-palmer@sifive.com>
Date: Fri, 5 Jan 2018 14:07:38 -0800
From: Palmer Dabbelt <palmer@...ive.com>
To: linux-kernel@...r.kernel.org
Cc: patches@...ups.riscv.org, Palmer Dabbelt <palmer@...belt.com>,
Palmer Dabbelt <palmer@...ive.com>
Subject: [PATCH v2] RISC-V: Make __NR_riscv_flush_icache visible to userspace
From: Palmer Dabbelt <palmer@...belt.com>
We were hoping to avoid making this visible to userspace, but it looks
like we're going to have to because QEMU's user-mode emulation doesn't
want to emulate a vDSO. Having vDSO-only system calls was a bit
unothodox anyway, so I think in this case it's OK to just make the
actual system call number public.
This patch simply moves the definition of __NR_riscv_flush_icache
availiable to userspace, which results in the deletion of the now empty
vdso-syscalls.h.
Changes since v1:
* I've moved the definition into uapi/asm/syscalls.h rathen than
uapi/asm/unistd.h. This allows me to keep asm/unistd.h, so we can
keep the syscall table macros sane.
* As a side effect of the above, this no longer disables all system
calls on RISC-V. Whoops!
Signed-off-by: Palmer Dabbelt <palmer@...ive.com>
---
arch/riscv/include/asm/unistd.h | 1 +
arch/riscv/include/asm/vdso-syscalls.h | 28 ----------------------------
arch/riscv/include/uapi/asm/syscalls.h | 26 ++++++++++++++++++++++++++
arch/riscv/kernel/syscall_table.c | 1 -
arch/riscv/kernel/vdso/flush_icache.S | 1 -
5 files changed, 27 insertions(+), 30 deletions(-)
delete mode 100644 arch/riscv/include/asm/vdso-syscalls.h
create mode 100644 arch/riscv/include/uapi/asm/syscalls.h
diff --git a/arch/riscv/include/asm/unistd.h b/arch/riscv/include/asm/unistd.h
index 9f250ed007cd..2f704a5c4196 100644
--- a/arch/riscv/include/asm/unistd.h
+++ b/arch/riscv/include/asm/unistd.h
@@ -14,3 +14,4 @@
#define __ARCH_HAVE_MMU
#define __ARCH_WANT_SYS_CLONE
#include <uapi/asm/unistd.h>
+#include <uapi/asm/syscalls.h>
diff --git a/arch/riscv/include/asm/vdso-syscalls.h b/arch/riscv/include/asm/vdso-syscalls.h
deleted file mode 100644
index a2ccf1894929..000000000000
--- a/arch/riscv/include/asm/vdso-syscalls.h
+++ /dev/null
@@ -1,28 +0,0 @@
-/*
- * Copyright (C) 2017 SiFive
- *
- * This program is free software; you can redistribute it and/or modify
- * it under the terms of the GNU General Public License version 2 as
- * published by the Free Software Foundation.
- *
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
- * GNU General Public License for more details.
- *
- * You should have received a copy of the GNU General Public License
- * along with this program. If not, see <http://www.gnu.org/licenses/>.
- */
-
-#ifndef _ASM_RISCV_VDSO_SYSCALLS_H
-#define _ASM_RISCV_VDSO_SYSCALLS_H
-
-#ifdef CONFIG_SMP
-
-/* These syscalls are only used by the vDSO and are not in the uapi. */
-#define __NR_riscv_flush_icache (__NR_arch_specific_syscall + 15)
-__SYSCALL(__NR_riscv_flush_icache, sys_riscv_flush_icache)
-
-#endif
-
-#endif /* _ASM_RISCV_VDSO_H */
diff --git a/arch/riscv/include/uapi/asm/syscalls.h b/arch/riscv/include/uapi/asm/syscalls.h
new file mode 100644
index 000000000000..818655b0d535
--- /dev/null
+++ b/arch/riscv/include/uapi/asm/syscalls.h
@@ -0,0 +1,26 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2017 SiFive
+ */
+
+#ifndef _ASM__UAPI__SYSCALLS_H
+#define _ASM__UAPI__SYSCALLS_H
+
+/*
+ * Allows the instruction cache to be flushed from userspace. Despite RISC-V
+ * having a direct 'fence.i' instruction available to userspace (which we
+ * can't trap!), that's not actually viable when running on Linux because the
+ * kernel might schedule a process on another hart. There is no way for
+ * userspace to handle this without invoking the kernel (as it doesn't know the
+ * thread->hart mappings), so we've defined a RISC-V specific system call to
+ * flush the instruction cache.
+ *
+ * __NR_riscv_flush_icache is defined to flush the instruction cache over an
+ * address range, with the flush applying to either all threads or just the
+ * caller. We don't currently do anything with the address range, that's just
+ * in there for forwards compatibility.
+ */
+#define __NR_riscv_flush_icache (__NR_arch_specific_syscall + 15)
+__SYSCALL(__NR_riscv_flush_icache, sys_riscv_flush_icache)
+
+#endif
diff --git a/arch/riscv/kernel/syscall_table.c b/arch/riscv/kernel/syscall_table.c
index a5bd6401f95e..ade52b903a43 100644
--- a/arch/riscv/kernel/syscall_table.c
+++ b/arch/riscv/kernel/syscall_table.c
@@ -23,5 +23,4 @@
void *sys_call_table[__NR_syscalls] = {
[0 ... __NR_syscalls - 1] = sys_ni_syscall,
#include <asm/unistd.h>
-#include <asm/vdso-syscalls.h>
};
diff --git a/arch/riscv/kernel/vdso/flush_icache.S b/arch/riscv/kernel/vdso/flush_icache.S
index b0fbad74e873..023e4d4aef58 100644
--- a/arch/riscv/kernel/vdso/flush_icache.S
+++ b/arch/riscv/kernel/vdso/flush_icache.S
@@ -13,7 +13,6 @@
#include <linux/linkage.h>
#include <asm/unistd.h>
-#include <asm/vdso-syscalls.h>
.text
/* int __vdso_flush_icache(void *start, void *end, unsigned long flags); */
--
2.13.6
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