linux-kernel - ptrace: Why does PTRACE_PEEKUSER not allow reading of FPU registers on x86?

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Message-ID: <01a401da64c3$0027ce60$00776b20$@gmail.com>
Date: Wed, 21 Feb 2024 12:39:23 -0000
From: <tartanllama@...il.com>
To: <linux-kernel@...r.kernel.org>
Subject: ptrace: Why does PTRACE_PEEKUSER not allow reading of FPU registers on x86?

Hey folks,

Looking at arch/x86/kernel/ptrace.c, I can see that reading with
PTRACE_PEEKUSER is only supported within the user::regs and user::u_debugreg
fields. What's the reason that reading from user::i387 is disallowed?

Thanks,
Sy Brand