Signed-off-by: Kyle Huey <khuey@xxxxxxxxxxxx> --- man2/arch_prctl.2 | 78 +++++++++++++++++++++++++++++++++++++++---------------- 1 file changed, 56 insertions(+), 22 deletions(-) diff --git a/man2/arch_prctl.2 b/man2/arch_prctl.2 index 678aada19..6c1d6f606 100644 --- a/man2/arch_prctl.2 +++ b/man2/arch_prctl.2 @@ -24,31 +24,52 @@ .\" .TH ARCH_PRCTL 2 2016-10-08 "Linux" "Linux Programmer's Manual" .SH NAME -arch_prctl \- set architecture-specific thread state +arch_prctl \- set architecture-specific process or thread state .SH SYNOPSIS .nf .B #include <asm/prctl.h> .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 " option ", unsigned long " arg2 ); +.BI "int arch_prctl(int " option ", unsigned long *" arg2 ); .fi .SH DESCRIPTION The .BR arch_prctl () function sets architecture-specific process or thread state. -.I code +.I option selects a subfunction and passes argument -.I addr +.I arg2 to it; -.I addr -is interpreted as either an -.I "unsigned long" -for the "set" operations, or as an -.IR "unsigned long\ *" , -for the "get" operations. +The interpretation of +.I arg2 +depends on which subfunction is invoked. +.LP +Subfunctions for both x86-64 and x86-32 are: +.TP +.B ARCH_GET_CPUID " (since Linux 4.12)" +Return the state of the flag determining whether the +.I cpuid +instruction can be executed by the process. +.IR arg2 +is ignored. +.TP +.B ARCH_SET_CPUID " (since Linux 4.12)" +Set the state of the flag determining whether the +.i cpuid +instruction can be executed by the process. +.IR arg2 +is interpreted as a boolean. This flag defaults to true (i.e. +.i cpuid +enabled). Pass 0 to disable the +.I cpuid +instruction or 1 to reenable it. If the value of the flag is 0 attempting to execute the +.I cpuid +instruction will generate a +.B SIGSEGV. +This flag is propagated across fork but reset on exec. .LP Subfunctions for x86-64 are: .TP @@ -56,7 +77,7 @@ Subfunctions for x86-64 are: 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 +85,13 @@ 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 @@ -78,35 +99,48 @@ 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 () -returns 0; on error, \-1 is returned, and +.BR ARCH_GET_CPUID +returns a non-negative value indicating the state of the +.I cpuid +enabled flag. All other +.I option +values return 0 on success. +On error, \-1 is returned, and .I errno is set to indicate the error. .SH ERRORS .TP .B EFAULT -.I addr +.I arg2 points to an unmapped address or is outside the process address space. .TP .B EINVAL -.I code +.I option is not a valid subcommand. .TP +.B ENODEV +.I option +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. -- 2.13.0 -- To unsubscribe from this list: send the line "unsubscribe linux-man" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
