linux-kernel - [PATCHv4 13/19] kernel: add ksys

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Date:   Mon,  2 Jul 2018 12:04:09 +0100
From:   Mark Rutland <mark.rutland@....com>
To:     linux-arm-kernel@...ts.infradead.org, will.deacon@....com
Cc:     linux-kernel@...r.kernel.org, catalin.marinas@....com,
        dave.martin@....com, hch@...radead.org, james.morse@....com,
        linux@...inikbrodowski.net, linux-fsdevel@...r.kernel.org,
        marc.zyngier@....com, mark.rutland@....com, viro@...iv.linux.org.uk
Subject: [PATCHv4 13/19] kernel: add ksys_personality()

Using this helper allows us to avoid the in-kernel call to the
sys_personality() syscall. The ksys_ prefix denotes that this function
is meant as a drop-in replacement for the syscall. In particular, it
uses the same calling convention as sys_personality().

Since ksys_personality is trivial, it is implemented directly in
<linux/syscalls.h>, as we do for ksys_close() and friends.

This helper is necessary to enable conversion of arm64's syscall
handling to use pt_regs wrappers.

Signed-off-by: Mark Rutland <mark.rutland@....com>
Reviewed-by: Dominik Brodowski <linux@...inikbrodowski.net>
Cc: Al Viro <viro@...iv.linux.org.uk>
Cc: Christoph Hellwig <hch@...radead.org>
Cc: Dave Martin <dave.martin@....com>
---
 include/linux/syscalls.h | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
index a368a68cb667..abfe12d8a9c5 100644
--- a/include/linux/syscalls.h
+++ b/include/linux/syscalls.h
@@ -80,6 +80,7 @@ union bpf_attr;
 #include <linux/unistd.h>
 #include <linux/quota.h>
 #include <linux/key.h>
+#include <linux/personality.h>
 #include <trace/syscall.h>
 
 #ifdef CONFIG_ARCH_HAS_SYSCALL_WRAPPER
@@ -1281,4 +1282,14 @@ static inline long ksys_truncate(const char __user *pathname, loff_t length)
 	return do_sys_truncate(pathname, length);
 }
 
+static inline unsigned int ksys_personality(unsigned int personality)
+{
+	unsigned int old = current->personality;
+
+	if (personality != 0xffffffff)
+		set_personality(personality);
+
+	return old;
+}
+
 #endif
-- 
2.11.0