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x86/syscall: Split IDT syscall setup code into idt_syscall_init()

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Because FRED uses the ring 3 FRED entrypoint for SYSCALL and SYSENTER and
ERETU is the only legit instruction to return to ring 3, there is NO need
to setup SYSCALL and SYSENTER MSRs for FRED, except the IA32_STAR MSR.

Split IDT syscall setup code into idt_syscall_init() to make it easy to
skip syscall setup code when FRED is enabled.

Suggested-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Xin Li <xin3.li@intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Tested-by: Shan Kang <shan.kang@intel.com>
Link: https://lore.kernel.org/r/20231205105030.8698-34-xin3.li@intel.com
This commit is contained in:
Xin Li 2023-12-05 02:50:22 -08:00 committed by Borislav Petkov (AMD)
parent 70d0fe5d09
commit 530dce278a
1 changed files with 10 additions and 3 deletions
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13
arch/x86/kernel/cpu/common.c
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@ -2066,10 +2066,8 @@ static void wrmsrl_cstar(unsigned long val)
wrmsrl(MSR_CSTAR, val);
}
/* May not be marked __init: used by software suspend */
void syscall_init(void)
static inline void idt_syscall_init(void)
{
wrmsr(MSR_STAR, 0, (__USER32_CS << 16) | __KERNEL_CS);
wrmsrl(MSR_LSTAR, (unsigned long)entry_SYSCALL_64);
if (ia32_enabled()) {
@ -2103,6 +2101,15 @@ void syscall_init(void)
X86_EFLAGS_AC|X86_EFLAGS_ID);
}
/* May not be marked __init: used by software suspend */
void syscall_init(void)
{
/* The default user and kernel segments */
wrmsr(MSR_STAR, 0, (__USER32_CS << 16) | __KERNEL_CS);
idt_syscall_init();
}
#else /* CONFIG_X86_64 */
#ifdef CONFIG_STACKPROTECTOR