lkml.org 
[lkml]   [2016]   [Jul]   [4]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH] Syscall arguments are unsigned long (full registers)
From
Date
On July 4, 2016 1:13:21 PM PDT, "Tautschnig, Michael" <tautschn@amazon.co.uk> wrote:
>
>> On 4 Jul 2016, at 20:27, H. Peter Anvin <hpa@zytor.com> wrote:
>>
>> On July 4, 2016 6:52:58 AM PDT, "Tautschnig, Michael"
><tautschn@amazon.co.uk> wrote:
>>> All syscall arguments are passed in as types of the same byte size
>as
>>> unsigned long (width of full registers). Using a smaller type
>without a
>>> cast may result in losing bits of information. In all other
>instances
>>> apart from the ones fixed by the patch the code explicitly
>introduces
>>> type casts (using, e.g., SYSCALL_DEFINE1).
>>>
>>> While goto-cc reported these problems at build time, it is
>noteworthy
>>> that the calling conventions specified in the System V AMD64 ABI do
>>> ensure that parameters 1-6 are passed via registers, thus there is
>no
>>> implied risk of misaligned stack access.
>>>
>>>
>[...]
>>
>> Wrong. Syscall arguments aren't necessarily full registers, and on
>x86 truncation is already done by the callee, so we don't need any
>special handing. Some other architectures have other constraints.
>
>Ok - I'm assuming I have thus misunderstood
>eb974c62565072e10c1422eb3205f5b611dd99a1 ? Supposedly all those
>SYSCALL_DEFINEx are required for other architectures only?
>
>Best,
>Michael

That, and tracing.
--
Sent from my Android device with K-9 Mail. Please excuse brevity and formatting.

\
 
 \ /
  Last update: 2016-07-04 23:01    [W:0.032 / U:4.800 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site