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Subject[PATCH V6 30/49] x86/entry: Add the C version ist_switch_to_kernel_cr3()
Date
From: Lai Jiangshan <laijs@linux.alibaba.com>

It switches the CR3 to kernel CR3 and returns the original CR3, and
the caller should save the return value.

It is the C version of SAVE_AND_SWITCH_TO_KERNEL_CR3.

Not functional difference intended.

Signed-off-by: Lai Jiangshan <laijs@linux.alibaba.com>
---
arch/x86/entry/entry64.c | 15 +++++++++++++++
1 file changed, 15 insertions(+)

diff --git a/arch/x86/entry/entry64.c b/arch/x86/entry/entry64.c
index 0dc63ae8153a..283bd685a275 100644
--- a/arch/x86/entry/entry64.c
+++ b/arch/x86/entry/entry64.c
@@ -35,8 +35,23 @@ static __always_inline void switch_to_kernel_cr3(void)
if (static_cpu_has(X86_FEATURE_PTI))
pti_switch_to_kernel_cr3(__native_read_cr3());
}
+
+static __always_inline unsigned long ist_switch_to_kernel_cr3(void)
+{
+ unsigned long cr3 = 0;
+
+ if (static_cpu_has(X86_FEATURE_PTI)) {
+ cr3 = __native_read_cr3();
+
+ if (cr3 & PTI_USER_PGTABLE_MASK)
+ pti_switch_to_kernel_cr3(cr3);
+ }
+
+ return cr3;
+}
#else
static __always_inline void switch_to_kernel_cr3(void) {}
+static __always_inline unsigned long ist_switch_to_kernel_cr3(void) { return 0; }
#endif

/*
--
2.19.1.6.gb485710b
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