From Newsgroup: comp.os.linux.misc

vallor <vallor@vallor.earth> news:10h5kjp$3tql3$1@dont-email.me Mon, 08 Dec 2025 04:36:08 GMT in comp.os.linux.advocacy, wrote:

At Mon, 8 Dec 2025 02:32:39 -0000 (UTC), Gremlin <nobody@haph.org>
wrote:

vallor <vallor@vallor.earth> news:10h2u70$36bnl$1@dont-email.me Sun,
07 Dec 2025 04:01:36 GMT in comp.os.linux.advocacy, wrote:

At Wed, 3 Dec 2025 22:03:12 -0000 (UTC), Gremlin <nobody@haph.org>
wrote:

read_file: rem as the name implies, it reads bytes into a buffer.
:-) rem as with write_file, you need to predefine the dx register
for the rem buffer where you want the info stored. Like so:
dx=varptr(buffer(0)) rem if you don't, this routine will not work,
or will overwrite some rem other section of memory. And for virus
coding, this is very bad! :) rem cx register is how many bytes to
read :) if file_handle>4 then ax=&hex3f00 bx=file_handle
cx=bytesize int86(&hex21,ax,bx,cx,dx,na,na,na,na,na) bytesread=ax
endif return

Hey, just wanted to mention that Linux used to use int86(0x80,...)
for its own syscalls. In C, read(2) is the way to read into a
buffer, which would set up the syscall (call to interrupt 0x80). I
guess in DOS, C would set up the interrupt call similar to how you
show, and then call the interrupt.

I remember from writing elf binaries. <G> Fun and educational times.

Modern processors have an actual SYSCALL intrinsic, so no more
interrupt call to enter the kernel.

Windows API calls can still be used to enter the kernel. Modern CPUs
running a flavor of DOS still respect DOS interrupt calls when
running in 'real mode' kernel entrance. It's known as 'real mode' vs
'Protected mode and virtualization'

As for Linux, here's a c/p from google AI:

Yes, Linux absolutely uses interrupts and interrupt calls (like the
syscall instruction on modern CPUs) to allow user-space processes to
request kernel services, enabling privileged kernel access for tasks
like file I/O or process management, with specific mechanisms like
IRQs for hardware, `syscall` for system calls, and exceptions for
errors all transitioning the CPU to kernel mode (Ring 0) to execute
privileged code. Modern systems use efficient instructions like
syscall for system calls, but the core principle of interrupt-driven
transitions to kernel space for privileged operations remains
fundamental. ***

The 286 was the first to offer protected mode access. It was
significantly improved with the 386. Modern CPUs still offer real
mode as well. So, I'm not sure what you mean exactly by a modern CPU
in this instance? Or what you mean by no more interrupt call to enter
the kernel?

Exactly. "SYSCALL" is an opcode on x86_64 processors, and from
what I've read, it's faster than using an interrupt. (But don't
quote me on that. ;) )

Aha! Now I get what you meant. <G>

My main point, though, was the similarity of how DOS handled
things -- it's basically the old-style "syscall" (setting up
registers, maybe some stack, and then raising an interrupt),
even if it wasn't known as a "syscall".

Gotcha!
--
Liar, lawyer; mirror show me, what's the difference?
Kangaroo done hung the guilty with the innocent
Liar, lawyer; mirror for ya', what's the difference?
Kangaroo be stoned. He's guilty as the government

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From Newsgroup: comp.os.linux.misc

pothead <pothead@snakebite.com> news:10h7mil$fq1s$1@pothead.dont-email.me Mon, 08 Dec 2025 23:21:57 GMT in comp.os.linux.advocacy, wrote:

Way back in the dark ages I was fascinated by copy protection schemes
that were being used at the time and some of them used undocumented
INT 21h calls.

Yep! Did you ever see any of them rerouting any while they were in use? Sneaky bastages.

I found it interesting at the time even though I wasn't a hardcore
gamer.
Well, I did find Lounge Lizard Larry to be quite addictive.

<G> That series was fun!
Beat the pants off (no pun intended) of Where in the world is Carmen sandiego. --
Liar, lawyer; mirror show me, what's the difference?
Kangaroo done hung the guilty with the innocent
Liar, lawyer; mirror for ya', what's the difference?
Kangaroo be stoned. He's guilty as the government

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From Newsgroup: comp.os.linux.misc

On 2025-12-08 15:30, vallor wrote:

At Mon, 08 Dec 2025 04:36:08 +0000, vallor <vallor@vallor.earth> wrote:

At Mon, 8 Dec 2025 02:32:39 -0000 (UTC), Gremlin <nobody@haph.org> wrote: >>> vallor <vallor@vallor.earth> news:10h2u70$36bnl$1@dont-email.me Sun,

07 Dec 2025 04:01:36 GMT in comp.os.linux.advocacy, wrote:

At Wed, 3 Dec 2025 22:03:12 -0000 (UTC), Gremlin <nobody@haph.org> wrote:

...

Looked up the "syscall interrupt" on the net, discovered that it
used to be 0x80, but now newer processors use a new opcode,
"SYSCALL".

I asked google, got some answers and an AI summary:

The SYSCALL instruction (opcode 0F 05) is a fast, modern assembly instruction in 64-bit x86 systems used by applications (user-mode, Ring 3) to request services from the operating system kernel (kernel-mode, Ring 0). It efficiently transitions from user to kernel space by saving the return address (RIP) to the RCX register, flipping privilege levels, loading the kernel entry point from a Model Specific Register (MSR), and using the SYSRET instruction to return, replacing the slower INT 0x80 interrupt method for better performance, though security measures like KPTI add overhead.
How it works:

Initiation: A user program executes SYSCALL, often after placing a system call number in RAX and arguments in registers like RDI, RSI, RDX.
CPU Action:
Saves the address of the next instruction (RIP) into RCX.
Saves the RFLAGS into R11.
Loads a new RIP from a special kernel MSR, pointing to the kernel's system call entry code.
Changes privilege level from Ring 3 to Ring 0 (kernel mode).
Kernel Execution: The kernel runs, uses arguments, performs the requested service (e.g., file I/O, process management).
Return: The kernel uses the saved RCX and R11 to execute SYSRET, transitioning back to user mode, restoring registers, and resuming the user program.

Key aspects:

Performance: Much faster than the older INT 0x80 method, crucial for modern OS performance.
Registers: Uses specific registers (RAX for syscall number, RDI, RSI, RDX, R10, R8, R9 for arguments, RCX for return address).
Security: A vital part of OS security, creating a boundary between trusted kernel and untrusted user code.
Context: Part of the SYSCALL/SYSRET pair, optimized for 64-bit systems.

...and so forth.

--
Cheers, Carlos.
ES🇪🇸, EU🇪🇺;
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From Newsgroup: comp.os.linux.misc

On 2025-12-10, Gremlin <nobody@haph.org> wrote:

pothead <pothead@snakebite.com> news:10h7mil$fq1s$1@pothead.dont-email.me Mon,
08 Dec 2025 23:21:57 GMT in comp.os.linux.advocacy, wrote:

Way back in the dark ages I was fascinated by copy protection schemes
that were being used at the time and some of them used undocumented
INT 21h calls.

Yep! Did you ever see any of them rerouting any while they were in use? Sneaky
bastages.

I have heard something about that but personally I don't recall
experiencing it myself. It might explain why I sometimes had difficulties tracing what the code was doing. Expected vs actual results.

I found it interesting at the time even though I wasn't a hardcore
gamer.
Well, I did find Lounge Lizard Larry to be quite addictive.

<G> That series was fun!
Beat the pants off (no pun intended) of Where in the world is Carmen sandiego.

I never understood the fascination with that game.
Maybe I missed the point?
--
pothead
Give a Democrat a fish and he'll eat all day.
Teach a Democrat to fish and......
He'll steal your rod
Take your wallet
Assault the fish &
Blame Trump.

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From Newsgroup: comp.os.linux.misc

On Dec 10, 2025 at 11:13:25 AM MST, "pothead" wrote <10hcd85$1m977$1@pothead.dont-email.me>:

Give a Democrat a fish and he'll eat all day.
Teach a Democrat to fish and......
He'll steal your rod
Take your wallet
Assault the fish &
Blame Trump.

Your sig isn’t an argument; it’s a slogan that falls apart against basic facts. Blue states contribute more in federal taxes than they receive, Trump’s
record includes verified court rulings and fiscal mismanagement, and violent crime rates are generally higher per capita in Republican-led states. The joke relies on caricature and repetition rather than evidence, substituting
sneering for substance. Typical of White Nationalists.

While it contains no explicit racial language, it overlaps with common white supremacist rhetorical patterns. It frames an out-group as inherently criminal and parasitic, uses mockery and “just a joke” humor to deflect scrutiny, flattens millions of people into a single corrupt mass, and recasts grievances as moral righteousness. That’s the same toolbox extremist movements use to spread ideas indirectly – not by arguing facts, but by normalizing contempt.

You keep denying you tie yourself to such groups, but then you show you DO tie yourself to them.

Over and over and over.
--
It's impossible for someone who is at war with themselves to be at peace with you.
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From Newsgroup: comp.os.linux.misc

pothead <pothead@snakebite.com> news:10hcd85$1m977$1@pothead.dont-email.me
Wed, 10 Dec 2025 18:13:25 GMT in comp.os.linux.advocacy, wrote:

On 2025-12-10, Gremlin <nobody@haph.org> wrote:

pothead <pothead@snakebite.com>
news:10h7mil$fq1s$1@pothead.dont-email.me Mon, 08 Dec 2025 23:21:57 GMT
in comp.os.linux.advocacy, wrote:

Way back in the dark ages I was fascinated by copy protection schemes
that were being used at the time and some of them used undocumented
INT 21h calls.

Yep! Did you ever see any of them rerouting any while they were in use?
Sneaky bastages.

I have heard something about that but personally I don't recall
experiencing it myself. It might explain why I sometimes had
difficulties tracing what the code was doing. Expected vs actual
results.

I found it interesting at the time even though I wasn't a hardcore
gamer.
Well, I did find Lounge Lizard Larry to be quite addictive.

<G> That series was fun!
Beat the pants off (no pun intended) of Where in the world is Carmen
sandiego.

I never understood the fascination with that game.
Maybe I missed the point?

It was supposed to be a teaching aid for geography and reading comprehension. While it was somewhat succesful in both of those, as a whole, it was a lame
as frak game to spend any real time with.
--
Liar, lawyer; mirror show me, what's the difference?
Kangaroo done hung the guilty with the innocent
Liar, lawyer; mirror for ya', what's the difference?
Kangaroo be stoned. He's guilty as the government

--- Synchronet 3.21a-Linux NewsLink 1.2

From Newsgroup: comp.os.linux.misc

On 12/12/2025 6:44 pm, Gremlin wrote:

pothead <pothead@snakebite.com> news:10hcd85$1m977$1@pothead.dont-email.me Wed, 10 Dec 2025 18:13:25 GMT in comp.os.linux.advocacy, wrote:

On 2025-12-10, Gremlin <nobody@haph.org> wrote:

pothead <pothead@snakebite.com>
news:10h7mil$fq1s$1@pothead.dont-email.me Mon, 08 Dec 2025 23:21:57 GMT
in comp.os.linux.advocacy, wrote:

Way back in the dark ages I was fascinated by copy protection schemes
that were being used at the time and some of them used undocumented
INT 21h calls.

Yep! Did you ever see any of them rerouting any while they were in use?
Sneaky bastages.

I have heard something about that but personally I don't recall
experiencing it myself. It might explain why I sometimes had
difficulties tracing what the code was doing. Expected vs actual
results.

I found it interesting at the time even though I wasn't a hardcore
gamer.
Well, I did find Lounge Lizard Larry to be quite addictive.

Wasn't it "Leasuresuit Larry in the Land of the Lounge Lizards"!! (Did
all the Devs have a name beginning with 'L' or something??)
--
Daniel70
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From Newsgroup: comp.os.linux.misc

On 12/12/2025 11:39, Daniel70 wrote:

On 12/12/2025 6:44 pm, Gremlin wrote:

pothead <pothead@snakebite.com>
news:10hcd85$1m977$1@pothead.dont-email.me
Wed, 10 Dec 2025 18:13:25 GMT in comp.os.linux.advocacy, wrote:

On 2025-12-10, Gremlin <nobody@haph.org> wrote:

pothead <pothead@snakebite.com>
news:10h7mil$fq1s$1@pothead.dont-email.me Mon, 08 Dec 2025 23:21:57 GMT >>>> in comp.os.linux.advocacy, wrote:

Way back in the dark ages I was fascinated by copy protection schemes >>>>> that were being used at the time and some of them used undocumented
INT 21h calls.

Yep! Did you ever see any of them rerouting any while they were in use? >>>> Sneaky bastages.

I have heard something about that but personally I don't recall
experiencing it myself. It might explain why I sometimes had
difficulties tracing what the code was doing. Expected vs actual
results.

I found it interesting at the time even though I wasn't a hardcore
gamer.
Well, I did find Lounge Lizard Larry to be quite addictive.

Wasn't it "Leasuresuit Larry in the Land of the Lounge Lizards"!! (Did
all the Devs have a name beginning with 'L' or something??)

That was indeed the first one

And IIRC Leisure Suit Larry goes Looking for Love was another.

https://en.wikipedia.org/wiki/Leisure_Suit_Larry

Has more.
--
"A point of view can be a dangerous luxury when substituted for insight
and understanding".

Marshall McLuhan


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