From: Xin Li <xin3.li@intel.com>
To: linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-edac@vger.kernel.org, linux-hyperv@vger.kernel.org,
kvm@vger.kernel.org, xen-devel@lists.xenproject.org
Cc: Jonathan Corbet <corbet@lwn.net>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
Dave Hansen <dave.hansen@linux.intel.com>,
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Subject: [PATCH v9 16/36] x86/fred: Allow single-step trap and NMI when starting a new task
Date: Sun, 30 Jul 2023 23:32:57 -0700 [thread overview]
Message-ID: <20230731063317.3720-17-xin3.li@intel.com> (raw)
In-Reply-To: <20230731063317.3720-1-xin3.li@intel.com>
From: "H. Peter Anvin (Intel)" <hpa@zytor.com>
Entering a new task is logically speaking a return from a system call
(exec, fork, clone, etc.). As such, if ptrace enables single stepping
a single step exception should be allowed to trigger immediately upon
entering user space. This is not optional.
NMI should *never* be disabled in user space. As such, this is an
optional, opportunistic way to catch errors.
Allow single-step trap and NMI when starting a new task, thus once
the new task enters user space, single-step trap and NMI are both
enabled immediately.
Signed-off-by: H. Peter Anvin (Intel) <hpa@zytor.com>
Tested-by: Shan Kang <shan.kang@intel.com>
Signed-off-by: Xin Li <xin3.li@intel.com>
---
Changes since v8:
* Use high-order 48 bits above the lowest 16 bit SS only when FRED
is enabled (Thomas Gleixner).
---
arch/x86/kernel/process_64.c | 23 +++++++++++++++++------
1 file changed, 17 insertions(+), 6 deletions(-)
diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c
index 6d5fed29f552..0b47871a6141 100644
--- a/arch/x86/kernel/process_64.c
+++ b/arch/x86/kernel/process_64.c
@@ -56,6 +56,7 @@
#include <asm/resctrl.h>
#include <asm/unistd.h>
#include <asm/fsgsbase.h>
+#include <asm/fred.h>
#ifdef CONFIG_IA32_EMULATION
/* Not included via unistd.h */
#include <asm/unistd_32_ia32.h>
@@ -507,8 +508,18 @@ void x86_gsbase_write_task(struct task_struct *task, unsigned long gsbase)
static void
start_thread_common(struct pt_regs *regs, unsigned long new_ip,
unsigned long new_sp,
- unsigned int _cs, unsigned int _ss, unsigned int _ds)
+ u16 _cs, u16 _ss, u16 _ds)
{
+ /*
+ * Paranoia: High-order 48 bits above the lowest 16 bit SS are
+ * discarded by the legacy IRET instruction on all Intel, AMD,
+ * and Cyrix/Centaur/VIA CPUs, thus can be set unconditionally,
+ * even when FRED is not enabled. But we choose the safer side
+ * to use these bits only when FRED is enabled.
+ */
+ const unsigned long ssx_flags = cpu_feature_enabled(X86_FEATURE_FRED) ?
+ (FRED_SSX_SOFTWARE_INITIATED | FRED_SSX_NMI) : 0;
+
WARN_ON_ONCE(regs != current_pt_regs());
if (static_cpu_has(X86_BUG_NULL_SEG)) {
@@ -522,11 +533,11 @@ start_thread_common(struct pt_regs *regs, unsigned long new_ip,
loadsegment(ds, _ds);
load_gs_index(0);
- regs->ip = new_ip;
- regs->sp = new_sp;
- regs->cs = _cs;
- regs->ss = _ss;
- regs->flags = X86_EFLAGS_IF;
+ regs->ip = new_ip;
+ regs->sp = new_sp;
+ regs->csx = _cs;
+ regs->ssx = _ss | ssx_flags;
+ regs->flags = X86_EFLAGS_IF | X86_EFLAGS_FIXED;
}
void
--
2.34.1
next prev parent reply other threads:[~2023-07-31 7:03 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-07-31 6:32 [PATCH v9 00/36] x86: enable FRED for x86-64 Xin Li
2023-07-31 6:32 ` [PATCH v9 01/36] Documentation/x86/64: Add documentation for FRED Xin Li
2023-07-31 6:32 ` [PATCH v9 02/36] x86/fred: Add Kconfig option for FRED (CONFIG_X86_FRED) Xin Li
2023-07-31 6:32 ` [PATCH v9 03/36] x86/fred: Disable FRED support if CONFIG_X86_FRED is disabled Xin Li
2023-07-31 6:32 ` [PATCH v9 04/36] x86/cpufeatures: Add the cpu feature bit for FRED Xin Li
2023-07-31 6:32 ` [PATCH v9 05/36] x86/opcode: Add ERETU, ERETS instructions to x86-opcode-map Xin Li
2023-07-31 9:43 ` Masami Hiramatsu
2023-07-31 16:36 ` Li, Xin3
2023-07-31 6:32 ` [PATCH v9 06/36] x86/objtool: Teach objtool about ERETU and ERETS Xin Li
2023-07-31 6:32 ` [PATCH v9 07/36] x86/cpu: Add X86_CR4_FRED macro Xin Li
2023-07-31 6:32 ` [PATCH v9 08/36] x86/cpu: Add MSR numbers for FRED configuration Xin Li
2023-07-31 6:32 ` [PATCH v9 09/36] x86/fred: Make unions for the cs and ss fields in struct pt_regs Xin Li
2023-07-31 6:32 ` [PATCH v9 10/36] x86/fred: Add a new header file for FRED definitions Xin Li
2023-07-31 6:32 ` [PATCH v9 11/36] x86/fred: Reserve space for the FRED stack frame Xin Li
2023-07-31 6:32 ` [PATCH v9 12/36] x86/fred: Update MSR_IA32_FRED_RSP0 during task switch Xin Li
2023-07-31 6:32 ` [PATCH v9 13/36] x86/fred: Let ret_from_fork_asm() jmp to fred_exit_user when FRED is enabled Xin Li
2023-07-31 6:32 ` [PATCH v9 14/36] x86/fred: Disallow the swapgs instruction " Xin Li
2023-07-31 6:32 ` [PATCH v9 15/36] x86/fred: No ESPFIX needed " Xin Li
2023-07-31 6:32 ` Xin Li [this message]
2023-07-31 6:32 ` [PATCH v9 17/36] x86/fred: Define a common function type fred_handler Xin Li
2023-07-31 6:32 ` [PATCH v9 18/36] x86/fred: Add a page fault entry stub for FRED Xin Li
2023-07-31 6:33 ` [PATCH v9 19/36] x86/fred: Add a debug " Xin Li
2023-07-31 6:33 ` [PATCH v9 20/36] x86/fred: Add a NMI " Xin Li
2023-07-31 6:33 ` [PATCH v9 21/36] x86/fred: Add a machine check " Xin Li
2023-07-31 6:33 ` [PATCH v9 22/36] x86/fred: Add a double fault " Xin Li
2023-07-31 6:33 ` [PATCH v9 23/36] x86/entry: Remove idtentry_sysvec from entry_{32,64}.S Xin Li
2023-07-31 6:33 ` [PATCH v9 24/36] x86/idtentry: Incorporate definitions/declarations of the FRED external interrupt handler type Xin Li
2023-07-31 6:33 ` [PATCH v9 25/36] x86/traps: Add a system interrupt handler table for system interrupt dispatch Xin Li
2023-07-31 22:29 ` [PATCH v9 00/36] x86: enable FRED for x86-64 Sean Christopherson
2023-07-31 23:10 ` Li, Xin3
2023-07-31 23:17 ` Sean Christopherson
2023-07-31 23:56 ` Li, Xin3
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