From: "H. Peter Anvin (Intel)" <hpa@xxxxxxxxx>
Allow single-step trap and NMI when starting a new thread, thus once
the new thread returns to ring3, single-step trap and NMI are both
enabled immediately.
High-order 48 bits above the lowest 16 bit CS are discarded by the
legacy IRET instruction, thus can be set unconditionally, even when
FRED is not enabled.
Signed-off-by: H. Peter Anvin (Intel) <hpa@xxxxxxxxx>
Tested-by: Shan Kang <shan.kang@xxxxxxxxx>
Signed-off-by: Xin Li <xin3.li@xxxxxxxxx>
---
arch/x86/include/asm/fred.h | 11 +++++++++++
arch/x86/kernel/process_64.c | 13 +++++++------
2 files changed, 18 insertions(+), 6 deletions(-)
diff --git a/arch/x86/include/asm/fred.h b/arch/x86/include/asm/fred.h
index cd974edc8e8a..12449448e9bf 100644
--- a/arch/x86/include/asm/fred.h
+++ b/arch/x86/include/asm/fred.h
@@ -52,6 +52,14 @@
#define FRED_CSL_ALLOW_SINGLE_STEP _BITUL(25)
#define FRED_CSL_INTERRUPT_SHADOW _BITUL(24)
+/*
+ * High-order 48 bits above the lowest 16 bit CS are discarded by the
+ * legacy IRET instruction, thus can be set unconditionally, even when
+ * FRED is not enabled.
+ */
+#define CSL_PROCESS_START \
+ (FRED_CSL_ENABLE_NMI | FRED_CSL_ALLOW_SINGLE_STEP)
+
#ifndef __ASSEMBLY__
#include <linux/kernel.h>
@@ -115,6 +123,9 @@ void fred_setup_apic(void);
#else
#define cpu_init_fred_exceptions() BUG()
#define fred_setup_apic() BUG()
+
+#define CSL_PROCESS_START 0
+
#endif /* CONFIG_X86_FRED */
#endif /* ASM_X86_FRED_H */
diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c
index 2bea86073646..58addf3c78bb 100644
--- a/arch/x86/kernel/process_64.c
+++ b/arch/x86/kernel/process_64.c
@@ -55,6 +55,7 @@
#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>
@@ -506,7 +507,7 @@ 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)
{
WARN_ON_ONCE(regs != current_pt_regs());
@@ -521,11 +522,11 @@ 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 | CSL_PROCESS_START;
+ regs->ssx = _ss;
+ regs->flags = X86_EFLAGS_IF | X86_EFLAGS_FIXED;
}
void
--
2.34.1
