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Subject[PATCH (man-pages)] arch_prctl.2: Note new support on x86-32, ARCH_[GET|SET]_CPUID.
Date
Signed-off-by: Kyle Huey <khuey@kylehuey.com>
---
man2/arch_prctl.2 | 73 +++++++++++++++++++++++++++++++++++++++++++++----------
1 file changed, 60 insertions(+), 13 deletions(-)

diff --git a/man2/arch_prctl.2 b/man2/arch_prctl.2
index 989d369..c388797 100644
--- a/man2/arch_prctl.2
+++ b/man2/arch_prctl.2
@@ -22,7 +22,7 @@
.\" the source, must acknowledge the copyright and authors of this work.
.\" %%%LICENSE_END
.\"
-.TH ARCH_PRCTL 2 2015-02-21 "Linux" "Linux Programmer's Manual"
+.TH ARCH_PRCTL 2 2016-09-14 "Linux" "Linux Programmer's Manual"
.SH NAME
arch_prctl \- set architecture-specific thread state
.SH SYNOPSIS
@@ -31,8 +31,8 @@ arch_prctl \- set architecture-specific thread state
.br
.B #include <sys/prctl.h>
.sp
-.BI "int arch_prctl(int " code ", unsigned long " addr );
-.BI "int arch_prctl(int " code ", unsigned long *" addr );
+.BI "int arch_prctl(int " code ", unsigned long " arg2 );
+.BI "int arch_prctl(int " code ", unsigned long *" arg2 );
.fi
.SH DESCRIPTION
The
@@ -41,22 +41,47 @@ function sets architecture-specific process or thread state.
.I code
selects a subfunction
and passes argument
-.I addr
+.I arg2
to it;
-.I addr
+.I arg2
is interpreted as either an
.I "unsigned long"
for the "set" operations, or as an
.IR "unsigned long\ *" ,
for the "get" operations.
.LP
+Subfunctions for both x86-64 and x86-32 are:
+.TP
+.B ARCH_GET_CPUID " (since Linux 4.X)"
+Return the state of the flag determining whether the
+.I cpuid
+instruction can be executed by the process, in the
+.I unsigned long
+pointed to by
+.IR arg2 .
+.TP
+.B ARCH_SET_CPUID " (since Linux 4.X)"
+Set the state of the flag determining whether the
+.I cpuid
+instruction can be executed by the process. Pass
+.B ARCH_CPUID_ENABLE
+in
+.I arg2
+to allow it to be executed, or
+.B ARCH_CPUID_SIGSEGV
+to generate a
+.B SIGSEGV
+when the process tries to execute the
+.I cpuid
+instruction. This flag is propagated across fork and exec.
+.LP
Subfunctions for x86-64 are:
.TP
.B ARCH_SET_FS
Set the 64-bit base for the
.I FS
register to
-.IR addr .
+.IR arg2 .
.TP
.B ARCH_GET_FS
Return the 64-bit base value for the
@@ -64,13 +89,13 @@ Return the 64-bit base value for the
register of the current thread in the
.I unsigned long
pointed to by
-.IR addr .
+.IR arg2 .
.TP
.B ARCH_SET_GS
Set the 64-bit base for the
.I GS
register to
-.IR addr .
+.IR arg2 .
.TP
.B ARCH_GET_GS
Return the 64-bit base value for the
@@ -78,7 +103,7 @@ Return the 64-bit base value for the
register of the current thread in the
.I unsigned long
pointed to by
-.IR addr .
+.IR arg2 .
.SH RETURN VALUE
On success,
.BR arch_prctl ()
@@ -87,26 +112,48 @@ returns 0; on error, \-1 is returned, and
is set to indicate the error.
.SH ERRORS
.TP
+.B EACCES
+.I code
+is
+.B ARCH_SET_CPUID
+and
+.I arg2
+is
+.B ARCH_CPUID_ENABLE
+and cpuid was previously disabled with
+.B ARCH_CPUID_SIGSEGV
+and the
+.I no_new_privs
+bit is set on this thread.
+.TP
.B EFAULT
-.I addr
+.I arg2
points to an unmapped address or is outside the process address space.
.TP
.B EINVAL
.I code
is not a valid subcommand.
.TP
+.B EINVAL
+.I code
+is
+.B ARCH_SET_CPUID
+and
+.I cpuid
+faulting is not supported on this machine.
+.TP
.B EPERM
-.I addr
+.I arg2
is outside the process address space.
.\" .SH AUTHOR
.\" Man page written by Andi Kleen.
.SH CONFORMING TO
.BR arch_prctl ()
-is a Linux/x86-64 extension and should not be used in programs intended
+is a Linux/x86 extension and should not be used in programs intended
to be portable.
.SH NOTES
.BR arch_prctl ()
-is supported only on Linux/x86-64 for 64-bit programs currently.
+is supported only on Linux/x86 currently.

The 64-bit base changes when a new 32-bit segment selector is loaded.

--
2.7.4
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