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SubjectRe: [PATCH] Syscall arguments are unsigned long (full registers)
On July 4, 2016 1:13:21 PM PDT, "Tautschnig, Michael" <> wrote:
>> On 4 Jul 2016, at 20:27, H. Peter Anvin <> wrote:
>> On July 4, 2016 6:52:58 AM PDT, "Tautschnig, Michael"
><> wrote:
>>> All syscall arguments are passed in as types of the same byte size
>>> unsigned long (width of full registers). Using a smaller type
>without a
>>> cast may result in losing bits of information. In all other
>>> apart from the ones fixed by the patch the code explicitly
>>> type casts (using, e.g., SYSCALL_DEFINE1).
>>> While goto-cc reported these problems at build time, it is
>>> that the calling conventions specified in the System V AMD64 ABI do
>>> ensure that parameters 1-6 are passed via registers, thus there is
>>> 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?

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

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