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* [PATCH v2] prctl.2: Document Syscall User Dispatch
@ 2020-12-21 16:48 Gabriel Krisman Bertazi
  2020-12-21 18:15 ` Alejandro Colomar (man-pages)
  0 siblings, 1 reply; 2+ messages in thread
From: Gabriel Krisman Bertazi @ 2020-12-21 16:48 UTC (permalink / raw)
  To: alx.manpages, mtk.manpages; +Cc: linux-man, Gabriel Krisman Bertazi

Signed-off-by: Gabriel Krisman Bertazi <krisman@collabora.com>

---
Changes since v1:
(suggested by Alejandro Colomar)
  - Use semantic lines
  - Fix usage of .{B|I}R and .{B|I}
  - Don't format literals
  - Fix preferred spelling of userspace
  - Fix case of word
---
 man2/prctl.2 | 100 +++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 100 insertions(+)

diff --git a/man2/prctl.2 b/man2/prctl.2
index f25f05fdb593..1591354505b5 100644
--- a/man2/prctl.2
+++ b/man2/prctl.2
@@ -1533,6 +1533,78 @@ For more information, see the kernel source file
 (or
 .I Documentation/arm64/sve.txt
 before Linux 5.3).
+.TP
+.\" prctl PR_SET_SYSCALL_USER_DISPATCH
+.\" commit 1446e1df9eb183fdf81c3f0715402f1d7595d4
+.BR PR_SET_SYSCALL_USER_DISPATCH " (since Linux 5.11, x86 only)"
+.IP
+Configure the Syscall User Dispatch mechanism
+for the calling thread,
+to selective intercept system calls
+and dispatch them back to user space through
+.IR SIGSYS .
+.IP
+The current Syscall User Dispatch mode is selected via
+.IR arg2 ,
+which can either be set to
+.B PR_SYS_DISPATCH_ON
+to enable the feature,
+or to
+.B PR_SYS_DISPATCH_OFF
+to turn it off.
+.IP
+With
+.I arg2
+set to
+.BR PR_SYS_DISPATCH_ON ,
+.I arg3
+and
+.I arg4
+respectively identify the
+.I offset
+and
+.I length
+of a memory region in the process map
+from where system calls are always allowed to be executed,
+regardless of the switch variable.
+.I arg5
+points to a char-sized variable
+that is a fast switch to enable/disable the mechanism
+without invoking the kernel.
+The variable pointed by
+.I arg5
+can either be set to
+.B PR_SYS_DISPATCH_ON
+to enable the mechanism
+or to
+.B PR_SYS_DISPATCH_OFF
+to temporarily disable it.
+Any other value will fail the application
+with a
+.IR SIGSYS .
+.IP
+When a system call is intercepted,
+.I SIGSYS
+is raised with
+.I si_code
+set to
+.BR SYS_USER_DISPATCH .
+.IP
+When
+.I arg2
+is set to
+.BR PR_SYS_DISPATCH_OFF ,
+the remaining arguments must be set to 0.
+.IP
+The setting is not preserved across
+.BR fork (2),
+.BR clone (2)
+or
+.BR execve (2).
+.IP
+For more information,
+see the kernel source file
+.IR Documentation/admin-guide/syscall-user-dispatch.rst
 .\" prctl PR_SET_TAGGED_ADDR_CTRL
 .\" commit 63f0c60379650d82250f22e4cf4137ef3dc4f43d
 .TP
@@ -2000,6 +2072,14 @@ and
 .I arg3
 is an invalid address.
 .TP
+.B EFAULT
+.I option
+is
+.B PR_SET_SYSCALL_USER_DISPATCH
+and
+.I arg5
+has an invalid address.
+.TP
 .B EINVAL
 The value of
 .I option
@@ -2229,6 +2309,26 @@ is
 and SVE is not available on this platform.
 .TP
 .B EINVAL
+.I option is
+.B PR_SET_SYSCALL_USER_DISPATCH
+and one of the following is true:
+.RS
+.IP * 3
+.I arg2
+is
+.B PR_SYS_DISPATCH_OFF
+and remaining arguments are not 0;
+.IP * 3
+.I arg2
+is
+.B PR_SYS_DISPATCH_ON
+and the memory region provided is invalid;
+.IP * 3
+.I arg2
+is invalid.
+.RE
+.TP
+.B EINVAL
 .I option
 is
 .BR PR_SET_TAGGED_ADDR_CTRL
-- 
2.29.2


^ permalink raw reply related	[flat|nested] 2+ messages in thread
* Re: [PATCH v2] prctl.2: Document Syscall User Dispatch
  2020-12-21 16:48 [PATCH v2] prctl.2: Document Syscall User Dispatch Gabriel Krisman Bertazi
@ 2020-12-21 18:15 ` Alejandro Colomar (man-pages)
  0 siblings, 0 replies; 2+ messages in thread
From: Alejandro Colomar (man-pages) @ 2020-12-21 18:15 UTC (permalink / raw)
  To: Gabriel Krisman Bertazi, Michael Kerrisk (man-pages); +Cc: linux-man

Hi Gabriel,

Please, see a couple minor fixes below.

Thanks,

Alex

On 12/21/20 5:48 PM, Gabriel Krisman Bertazi wrote:
> Signed-off-by: Gabriel Krisman Bertazi <krisman@collabora.com>
> 
> ---
> Changes since v1:
> (suggested by Alejandro Colomar)
>   - Use semantic lines
>   - Fix usage of .{B|I}R and .{B|I}
>   - Don't format literals
>   - Fix preferred spelling of userspace
>   - Fix case of word
> ---
>  man2/prctl.2 | 100 +++++++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 100 insertions(+)
> 
> diff --git a/man2/prctl.2 b/man2/prctl.2
> index f25f05fdb593..1591354505b5 100644
> --- a/man2/prctl.2
> +++ b/man2/prctl.2
> @@ -1533,6 +1533,78 @@ For more information, see the kernel source file
>  (or
>  .I Documentation/arm64/sve.txt
>  before Linux 5.3).
> +.TP
> +.\" prctl PR_SET_SYSCALL_USER_DISPATCH
> +.\" commit 1446e1df9eb183fdf81c3f0715402f1d7595d4
> +.BR PR_SET_SYSCALL_USER_DISPATCH " (since Linux 5.11, x86 only)"
> +.IP
> +Configure the Syscall User Dispatch mechanism
> +for the calling thread,
> +to selective intercept system calls

s/selective/selectively/

> +and dispatch them back to user space through
> +.IR SIGSYS .
> +.IP
> +The current Syscall User Dispatch mode is selected via
> +.IR arg2 ,
> +which can either be set to
> +.B PR_SYS_DISPATCH_ON
> +to enable the feature,
> +or to
> +.B PR_SYS_DISPATCH_OFF
> +to turn it off.
> +.IP
> +With
> +.I arg2
> +set to
> +.BR PR_SYS_DISPATCH_ON ,
> +.I arg3
> +and
> +.I arg4
> +respectively identify the
> +.I offset
> +and
> +.I length
> +of a memory region in the process map
> +from where system calls are always allowed to be executed,
> +regardless of the switch variable.
> +.I arg5
> +points to a char-sized variable
> +that is a fast switch to enable/disable the mechanism
> +without invoking the kernel.
> +The variable pointed by
> +.I arg5
> +can either be set to
> +.B PR_SYS_DISPATCH_ON
> +to enable the mechanism
> +or to
> +.B PR_SYS_DISPATCH_OFF
> +to temporarily disable it.
> +Any other value will fail the application
> +with a
> +.IR SIGSYS .
> +.IP
> +When a system call is intercepted,
> +.I SIGSYS
> +is raised with
> +.I si_code
> +set to
> +.BR SYS_USER_DISPATCH .
> +.IP
> +When
> +.I arg2
> +is set to
> +.BR PR_SYS_DISPATCH_OFF ,
> +the remaining arguments must be set to 0.
> +.IP
> +The setting is not preserved across
> +.BR fork (2),
> +.BR clone (2)

.BR clone (2),

Oxford comma; see: d556548bf4907040c4c65705fc43f80de895afcf

> +or
> +.BR execve (2).
> +.IP
> +For more information,
> +see the kernel source file
> +.IR Documentation/admin-guide/syscall-user-dispatch.rst
>  .\" prctl PR_SET_TAGGED_ADDR_CTRL
>  .\" commit 63f0c60379650d82250f22e4cf4137ef3dc4f43d
>  .TP
> @@ -2000,6 +2072,14 @@ and
>  .I arg3
>  is an invalid address.
>  .TP
> +.B EFAULT
> +.I option
> +is
> +.B PR_SET_SYSCALL_USER_DISPATCH
> +and
> +.I arg5
> +has an invalid address.
> +.TP
>  .B EINVAL
>  The value of
>  .I option
> @@ -2229,6 +2309,26 @@ is
>  and SVE is not available on this platform.
>  .TP
>  .B EINVAL
> +.I option is
> +.B PR_SET_SYSCALL_USER_DISPATCH
> +and one of the following is true:
> +.RS
> +.IP * 3
> +.I arg2
> +is
> +.B PR_SYS_DISPATCH_OFF
> +and remaining arguments are not 0;
> +.IP * 3
> +.I arg2
> +is
> +.B PR_SYS_DISPATCH_ON
> +and the memory region provided is invalid;
> +.IP * 3
> +.I arg2
> +is invalid.
> +.RE
> +.TP
> +.B EINVAL
>  .I option
>  is
>  .BR PR_SET_TAGGED_ADDR_CTRL
> 

-- 
Alejandro Colomar
Linux man-pages comaintainer; https://www.kernel.org/doc/man-pages/
http://www.alejandro-colomar.es/

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2020-12-21 16:48 [PATCH v2] prctl.2: Document Syscall User Dispatch Gabriel Krisman Bertazi
2020-12-21 18:15 ` Alejandro Colomar (man-pages)

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