lkml.org 
[lkml]   [2021]   [Nov]   [26]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH V6 36/49] x86/entry: Implement the C version ist_paranoid_exit()
Date
From: Lai Jiangshan <laijs@linux.alibaba.com>

It implements the whole ASM version paranoid_exit().

No functional difference intended.

Signed-off-by: Lai Jiangshan <laijs@linux.alibaba.com>
---
arch/x86/entry/entry64.c | 41 +++++++++++++++++++++++++++++++++
arch/x86/include/asm/idtentry.h | 2 ++
2 files changed, 43 insertions(+)

diff --git a/arch/x86/entry/entry64.c b/arch/x86/entry/entry64.c
index dc0bd9dc6d48..63a6021a1f70 100644
--- a/arch/x86/entry/entry64.c
+++ b/arch/x86/entry/entry64.c
@@ -269,6 +269,29 @@ static __always_inline unsigned long ist_switch_to_kernel_gsbase(void)
return ret;
}

+static __always_inline void ist_restore_gsbase(unsigned long gsbase)
+{
+ /*
+ * Handle the three GSBASE cases.
+ *
+ * @gsbase contains the GSBASE related information depending
+ * on the availability of the FSGSBASE instructions:
+ *
+ * FSGSBASE @gsbase
+ * N 0 -> SWAPGS on exit
+ * 1 -> no SWAPGS on exit
+ *
+ * Y User space GSBASE, must be restored unconditionally
+ */
+ if (static_cpu_has(X86_FEATURE_FSGSBASE)) {
+ wrgsbase(gsbase);
+ return;
+ }
+
+ if (!gsbase)
+ native_swapgs();
+}
+
/*
* Switch and save CR3 in *@cr3 if PTI enabled. Return GSBASE related
* information in *@gsbase depending on the availability of the FSGSBASE
@@ -305,3 +328,21 @@ void ist_paranoid_entry(unsigned long *cr3, unsigned long *gsbase)
/* Handle GSBASE, store the return value in *@gsbase for exit. */
*gsbase = ist_switch_to_kernel_gsbase();
}
+
+/*
+ * "Paranoid" exit path from exception stack. This is invoked
+ * only on return from IST interrupts that came from kernel space.
+ *
+ * We may be returning to very strange contexts (e.g. very early
+ * in syscall entry), so checking for preemption here would
+ * be complicated. Fortunately, there's no good reason to try
+ * to handle preemption here.
+ */
+__visible __entry_text
+void ist_paranoid_exit(unsigned long cr3, unsigned long gsbase)
+{
+ /* Restore CR3 at first, it can use kernel GSBASE. */
+ ist_restore_cr3(cr3);
+ barrier();
+ ist_restore_gsbase(gsbase);
+}
diff --git a/arch/x86/include/asm/idtentry.h b/arch/x86/include/asm/idtentry.h
index f6efa21ec242..cf41901227ed 100644
--- a/arch/x86/include/asm/idtentry.h
+++ b/arch/x86/include/asm/idtentry.h
@@ -309,6 +309,8 @@ static __always_inline void __##func(struct pt_regs *regs)
#ifdef CONFIG_X86_64
__visible __entry_text
void ist_paranoid_entry(unsigned long *cr3, unsigned long *gsbase);
+__visible __entry_text
+void ist_paranoid_exit(unsigned long cr3, unsigned long gsbase);

/**
* DECLARE_IDTENTRY_IST - Declare functions for IST handling IDT entry points
--
2.19.1.6.gb485710b
\
 
 \ /
  Last update: 2021-11-26 11:40    [W:0.190 / U:9.320 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site