Re: [PATCH v5 2/3] asm-generic: Add generic seccomp.h for secure computing mode 1

From: AKASHI Takahiro
Date: Thu Jul 24 2014 - 01:17:30 EST

On 07/24/2014 01:41 PM, Kees Cook wrote:
On Wed, Jul 23, 2014 at 8:40 PM, Andy Lutomirski <luto@xxxxxxxxxxxxxx> wrote:
On 07/22/2014 02:14 AM, AKASHI Takahiro wrote:

Those values (__NR_seccomp_*) are used solely in secure_computing()
to identify mode 1 system calls. If compat system calls have different
syscall numbers, asm/seccomp.h may override them.

Acked-by: Arnd Bergmann <arnd@xxxxxxxx>
Signed-off-by: AKASHI Takahiro <takahiro.akashi@xxxxxxxxxx>
include/asm-generic/seccomp.h | 28 ++++++++++++++++++++++++++++
1 file changed, 28 insertions(+)
create mode 100644 include/asm-generic/seccomp.h

diff --git a/include/asm-generic/seccomp.h b/include/asm-generic/seccomp.h
new file mode 100644
index 0000000..5e97022
--- /dev/null
+++ b/include/asm-generic/seccomp.h
@@ -0,0 +1,28 @@
+ * include/asm-generic/seccomp.h
+ *
+ * Copyright (C) 2014 Linaro Limited
+ * Author: AKASHI Takahiro <takahiro.akashi@xxxxxxxxxx>
+ *
+ * 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.
+ */
+#include <asm-generic/unistd.h>
+#if defined(CONFIG_COMPAT) && !defined(__NR_seccomp_read_32)
+#define __NR_seccomp_read_32 __NR_read
+#define __NR_seccomp_write_32 __NR_write
+#define __NR_seccomp_exit_32 __NR_exit
+#define __NR_seccomp_sigreturn_32 __NR_rt_sigreturn
+#endif /* CONFIG_COMPAT && ! already defined */
+#define __NR_seccomp_read __NR_read
+#define __NR_seccomp_write __NR_write
+#define __NR_seccomp_exit __NR_exit
+#define __NR_seccomp_sigreturn __NR_rt_sigreturn

I don't like these names. __NR_seccomp_read sounds like the number of a
syscall called seccomp_read.

Also, shouldn't something be including this header? I'm confused.

Ah! Good catch. These names are correct (see kernel/seccomp.c's
mode1_syscalls and mode1_syscalls_32 arrays), but the location of this
change was unexpected. I was expecting this file to live in
arch/*/include/asm/seccomp.h, not in include/asm-generic/seccomp.h.

However, since it's always the same list, it might make sense to
consolidate them into a single place as a default to make arch porting

Yeah, that is why I put this file under include/asm-generic.

However, I think that should be a separate patch.

Do you mean that the code for all the existing archs should also be changed
to use this (common) header?

-Takahiro AKASHI


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