| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Message-ID: <174461608607.31282.3975145232708711882.tip-bot2@tip-bot2>
Date: Mon, 14 Apr 2025 07:34:46 -0000
From: "tip-bot2 for Ingo Molnar" <tip-bot2@...utronix.de>
To: linux-tip-commits@...r.kernel.org
Cc: Ingo Molnar <mingo@...nel.org>, Andy Lutomirski <luto@...nel.org>,
Brian Gerst <brgerst@...il.com>, "Chang S. Bae" <chang.seok.bae@...el.com>,
Fenghua Yu <fenghua.yu@...el.com>, "H. Peter Anvin" <hpa@...or.com>,
Linus Torvalds <torvalds@...ux-foundation.org>,
Oleg Nesterov <oleg@...hat.com>, Peter Zijlstra <peterz@...radead.org>,
Uros Bizjak <ubizjak@...il.com>, x86@...nel.org, linux-kernel@...r.kernel.org
Subject: [tip: x86/merge] x86/fpu: Remove init_task FPU state dependencies,
add debugging warning for PF_KTHREAD tasks
The following commit has been merged into the x86/merge branch of tip:
Commit-ID: 22aafe3bcb67472effdea1ccf0df20280192bbaf
Gitweb: https://git.kernel.org/tip/22aafe3bcb67472effdea1ccf0df20280192bbaf
Author: Ingo Molnar <mingo@...nel.org>
AuthorDate: Wed, 09 Apr 2025 23:11:26 +02:00
Committer: Ingo Molnar <mingo@...nel.org>
CommitterDate: Mon, 14 Apr 2025 08:18:29 +02:00
x86/fpu: Remove init_task FPU state dependencies, add debugging warning for PF_KTHREAD tasks
init_task's FPU state initialization was a bit of a hack:
__x86_init_fpu_begin = .;
. = __x86_init_fpu_begin + 128*PAGE_SIZE;
__x86_init_fpu_end = .;
But the init task isn't supposed to be using the FPU context
in any case, so remove the hack and add in some debug warnings.
As Linus noted in the discussion, the init task (and other
PF_KTHREAD tasks) *can* use the FPU via kernel_fpu_begin()/_end(),
but they don't need the context area because their FPU use is not
preemptible or reentrant, and they don't return to user-space.
Signed-off-by: Ingo Molnar <mingo@...nel.org>
Cc: Andy Lutomirski <luto@...nel.org>
Cc: Brian Gerst <brgerst@...il.com>
Cc: Chang S. Bae <chang.seok.bae@...el.com>
Cc: Fenghua Yu <fenghua.yu@...el.com>
Cc: H. Peter Anvin <hpa@...or.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Oleg Nesterov <oleg@...hat.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Uros Bizjak <ubizjak@...il.com>
Link: https://lore.kernel.org/r/20250409211127.3544993-8-mingo@kernel.org
---
arch/x86/include/asm/processor.h | 6 +++++-
arch/x86/kernel/fpu/core.c | 15 +++++++++++----
arch/x86/kernel/fpu/init.c | 3 +--
arch/x86/kernel/fpu/xstate.c | 3 ---
arch/x86/kernel/vmlinux.lds.S | 4 ----
5 files changed, 17 insertions(+), 14 deletions(-)
diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
index b7f7c9c..eaa7214 100644
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -516,7 +516,11 @@ struct thread_struct {
#endif
};
-#define x86_task_fpu(task) ((struct fpu *)((void *)(task) + sizeof(*(task))))
+#ifdef CONFIG_X86_DEBUG_FPU
+extern struct fpu *x86_task_fpu(struct task_struct *task);
+#else
+# define x86_task_fpu(task) ((struct fpu *)((void *)(task) + sizeof(*(task))))
+#endif
/*
* X86 doesn't need any embedded-FPU-struct quirks:
diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c
index 4a21938..4d1a205 100644
--- a/arch/x86/kernel/fpu/core.c
+++ b/arch/x86/kernel/fpu/core.c
@@ -51,6 +51,16 @@ static DEFINE_PER_CPU(bool, in_kernel_fpu);
*/
DEFINE_PER_CPU(struct fpu *, fpu_fpregs_owner_ctx);
+#ifdef CONFIG_X86_DEBUG_FPU
+struct fpu *x86_task_fpu(struct task_struct *task)
+{
+ if (WARN_ON_ONCE(task->flags & PF_KTHREAD))
+ return NULL;
+
+ return (void *)task + sizeof(*task);
+}
+#endif
+
/*
* Can we use the FPU in kernel mode with the
* whole "kernel_fpu_begin/end()" sequence?
@@ -599,11 +609,9 @@ int fpu_clone(struct task_struct *dst, unsigned long clone_flags, bool minimal,
*
* This is safe because task_struct size is a multiple of cacheline size.
*/
- struct fpu *src_fpu = x86_task_fpu(current);
- struct fpu *dst_fpu = x86_task_fpu(dst);
+ struct fpu *dst_fpu = (void *)dst + sizeof(*dst);
BUILD_BUG_ON(sizeof(*dst) % SMP_CACHE_BYTES != 0);
- BUG_ON(!src_fpu);
/* The new task's FPU state cannot be valid in the hardware. */
dst_fpu->last_cpu = -1;
@@ -666,7 +674,6 @@ int fpu_clone(struct task_struct *dst, unsigned long clone_flags, bool minimal,
if (update_fpu_shstk(dst, ssp))
return 1;
- trace_x86_fpu_copy_src(src_fpu);
trace_x86_fpu_copy_dst(dst_fpu);
return 0;
diff --git a/arch/x86/kernel/fpu/init.c b/arch/x86/kernel/fpu/init.c
index da41a1d..16b6611 100644
--- a/arch/x86/kernel/fpu/init.c
+++ b/arch/x86/kernel/fpu/init.c
@@ -38,7 +38,7 @@ static void fpu__init_cpu_generic(void)
/* Flush out any pending x87 state: */
#ifdef CONFIG_MATH_EMULATION
if (!boot_cpu_has(X86_FEATURE_FPU))
- fpstate_init_soft(&x86_task_fpu(current)->fpstate->regs.soft);
+ ;
else
#endif
asm volatile ("fninit");
@@ -207,7 +207,6 @@ static void __init fpu__init_system_xstate_size_legacy(void)
fpu_kernel_cfg.default_size = size;
fpu_user_cfg.max_size = size;
fpu_user_cfg.default_size = size;
- fpstate_reset(x86_task_fpu(current));
}
/*
diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c
index 253da5a..4c771b9 100644
--- a/arch/x86/kernel/fpu/xstate.c
+++ b/arch/x86/kernel/fpu/xstate.c
@@ -870,9 +870,6 @@ void __init fpu__init_system_xstate(unsigned int legacy_size)
if (err)
goto out_disable;
- /* Reset the state for the current task */
- fpstate_reset(x86_task_fpu(current));
-
/*
* Update info used for ptrace frames; use standard-format size and no
* supervisor xstates:
diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S
index d9ca2d1..ccdc45e 100644
--- a/arch/x86/kernel/vmlinux.lds.S
+++ b/arch/x86/kernel/vmlinux.lds.S
@@ -181,10 +181,6 @@ SECTIONS
/* equivalent to task_pt_regs(&init_task) */
__top_init_kernel_stack = __end_init_stack - TOP_OF_KERNEL_STACK_PADDING - PTREGS_SIZE;
- __x86_init_fpu_begin = .;
- . = __x86_init_fpu_begin + 128*PAGE_SIZE;
- __x86_init_fpu_end = .;
-
#ifdef CONFIG_X86_32
/* 32 bit has nosave before _edata */
NOSAVE_DATA
Powered by blists - more mailing lists