> Yes, for regular function calls,
> but at least in the case of NetBSD,
> not for syscalls.
Those are the registers Linux uses for system calls on MIPS.
They are documented as such here:
https://www.man7.org/linux/man-pages/man2/syscall.2.html
> The second table shows the registers used
> to pa
> because the portable c api layer and syscall abi layer
> has a large enough gap that applications can break
> libc internals by doing raw syscalls.
I think that problem cannot really be fixed.
System call users just have to be aware of it.
It's true that using certain system calls can clobber l
> On Apr 9, 2024, at 9:48 PM, Matheus Afonso Martins Moreira via Gcc
> wrote:
>
> ...
> MIPS calling conventions work like this:
>
>> mips/n32,64 a0 a1 a2 a3 a4 a5
>> mips/o32a0 a1 a2 a3 ...
>> mips/o32args5-8 are passed on the stack
Yes, for regular function calls, but at least in
The 04/09/2024 23:59, Matheus Afonso Martins Moreira via Gcc wrote:
> > and using raw syscalls outside of the single runtime the
> > application is using is problematic (at least on linux).
>
> Why do you say they are problematic on Linux though? Please elaborate.
because the portable c api layer
> note: some syscalls / features don't work without asm
> (posix thread cancellation, vfork, signal return,..)
That's true. On the other hand, POSIX compliance
is not always a goal or a requirement.
> and using raw syscalls outside of the single runtime the
> application is using is problematic (
> I see systems making it more difficult for code to make syscalls,
> not easier.
That's true.
I think it's because other systems can afford to keep that ABI unstable.
Since Linux is an independently developed kernel, it _must_ be possible
to target the kernel directly with no user space compone
> Now the question comes is the argument long or some other type?
I believe so. Every library I've seen and the kernel itself uses long.
Other types just get typecasted to long. I think it's just supposed to
mean "register type" since all the arguments must be in registers.
> E.g. for some 32bit
> As noted by J. Wakely, you don't need to have one variant
> for each number of arguments.
Yes, he is right about that. I have already deleted
all the variants from my code since the variadic
builtin will be able to generate optimal code,
unlike a variadic C function.
> I assume you're talking a
The 04/08/2024 06:19, Matheus Afonso Martins Moreira via Gcc wrote:
> __builtin_linux_system_call(long n, ...)
...
> Calling these builtins will make GCC place all the parameters
> in the correct registers for the system call, emit the appropriate
> instruction for the target architecture and r
On 08-04-24 09:19, Matheus Afonso Martins Moreira via Gcc wrote:
+ It's becoming common
Despite being specific to the Linux kernel,
support for it is showing up in other systems.
FreeBSD implements limited support[4] for Linux ABIs.
Windows Subsystem fo
> On Apr 8, 2024, at 4:01 PM, Paul Iannetta via Gcc wrote:
>
> On Mon, Apr 08, 2024 at 11:26:40AM -0700, Andrew Pinski wrote:
>> On Mon, Apr 8, 2024 at 11:20 AM Paul Iannetta via Gcc
>> wrote:
>>> ...
>> Also do you sign or zero extend a 32bit argument for LP64 targets?
>> Right now it is no
On Mon, Apr 08, 2024 at 11:26:40AM -0700, Andrew Pinski wrote:
> On Mon, Apr 8, 2024 at 11:20 AM Paul Iannetta via Gcc wrote:
> >
> > Hi,
> >
> > On Mon, Apr 08, 2024 at 06:19:14AM -0300, Matheus Afonso Martins Moreira
> > via Gcc wrote:
> > > Hello! I'm a beginner when it comes to GCC developmen
On Mon, Apr 8, 2024 at 11:20 AM Paul Iannetta via Gcc wrote:
>
> Hi,
>
> On Mon, Apr 08, 2024 at 06:19:14AM -0300, Matheus Afonso Martins Moreira via
> Gcc wrote:
> > Hello! I'm a beginner when it comes to GCC development.
> > I want to learn how it works and start contributing.
> > Decided to st
Hi,
On Mon, Apr 08, 2024 at 06:19:14AM -0300, Matheus Afonso Martins Moreira via
Gcc wrote:
> Hello! I'm a beginner when it comes to GCC development.
> I want to learn how it works and start contributing.
> Decided to start by implementing something relatively simple
> but which would still be ve
On Mon, 8 Apr 2024, 13:00 Matheus Afonso Martins Moreira via Gcc, <
gcc@gcc.gnu.org> wrote:
>
> Compiler support for system calls help by eliminating the need for the
> system call stub functions traditionally provided by these C libraries.
> There's no need to link against the C libraries just fo
> There is quite a bit of variance in how the kernel is entered.
I assume you mean the vDSO. It is also documented and stable.
https://www.kernel.org/doc/html/latest/admin-guide/abi-stable.html#vdso
> Unless otherwise noted, the set of symbols with any given version
> and the ABI of those symbol
On Mon, 8 Apr 2024, Florian Weimer wrote:
> * Alexander Monakov:
>
> >> There is quite a bit of variance in how the kernel is entered. On
> >> x86-64, one once popular mechanism is longer present in widely-used
> >> kernels.
> >
> > I assume you're implicitly referencing the vsyscall mechanism
> What's the advantage of the _1, _2 etc. forms?
Now that you mention it... I don't believe there are any.
> The compiler knows how many arguments you're passing,
> why can't there just be one built-in handling all cases?
You're right about that.
When I started working on this I just mirrored t
* Alexander Monakov:
> On Mon, 8 Apr 2024, Florian Weimer via Gcc wrote:
>
>> * Matheus Afonso Martins Moreira via Gcc:
>>
>> > + It's stable
>> >
>> > This is one of the things which makes Linux unique
>> > in the operating system landscape: applications
>> > can target
On Mon, 8 Apr 2024, Florian Weimer via Gcc wrote:
> * Matheus Afonso Martins Moreira via Gcc:
>
> > + It's stable
> >
> > This is one of the things which makes Linux unique
> > in the operating system landscape: applications
> > can target the kernel directly. Unlike i
* Matheus Afonso Martins Moreira via Gcc:
> + It's stable
>
> This is one of the things which makes Linux unique
> in the operating system landscape: applications
> can target the kernel directly. Unlike in virtually
> every other operating system out there, the L
Hello,
On Mon, 8 Apr 2024 at 10:20, Matheus Afonso Martins Moreira via Gcc
wrote:
>
> I'd like to add GCC builtins for generating Linux system call
> code for all architectures supported by Linux.
>
> They would look like this:
>
> __builtin_linux_system_call(long n, ...)
> __builtin_linu
Hello! I'm a beginner when it comes to GCC development.
I want to learn how it works and start contributing.
Decided to start by implementing something relatively simple
but which would still be very useful for me: Linux builtins.
I sought help in the OFTC IRC channel and it was suggested
that I di
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