diff options
| author | Ingo Molnar <mingo@kernel.org> | 2015-03-16 10:32:20 +0100 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2015-03-17 09:25:29 +0100 |
| commit | 8b6c0ab1a1296ef6922160fa27018f25c60b8940 (patch) | |
| tree | 274c64ca1d19d86bcd242129a43f2530844be919 /arch/x86/kernel/cpu/common.c | |
| parent | x86/asm/entry/32: Document the 32-bit SYSENTER "emergency stack" better (diff) | |
| download | linux-8b6c0ab1a1296ef6922160fa27018f25c60b8940.tar.xz linux-8b6c0ab1a1296ef6922160fa27018f25c60b8940.zip | |
x86/asm/entry: Document and clean up the enable_sep_cpu() and syscall32_cpu_init() functions
Clean up the flow and document the functions a bit better.
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Alexei Starovoitov <ast@plumgrid.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Will Drewry <wad@chromium.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'arch/x86/kernel/cpu/common.c')
| -rw-r--r-- | arch/x86/kernel/cpu/common.c | 42 |
1 files changed, 29 insertions, 13 deletions
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c index 7a3dfb1db78d..d79f139871e0 100644 --- a/arch/x86/kernel/cpu/common.c +++ b/arch/x86/kernel/cpu/common.c @@ -960,37 +960,53 @@ static void identify_cpu(struct cpuinfo_x86 *c) } #ifdef CONFIG_X86_64 -#ifdef CONFIG_IA32_EMULATION +# ifdef CONFIG_IA32_EMULATION /* May not be __init: called during resume */ static void syscall32_cpu_init(void) { - /* Load these always in case some future AMD CPU supports - SYSENTER from compat mode too. */ + /* + * Always load these, in case some future 64-bit CPU supports + * SYSENTER from compat mode too: + */ wrmsrl_safe(MSR_IA32_SYSENTER_CS, (u64)__KERNEL_CS); wrmsrl_safe(MSR_IA32_SYSENTER_ESP, 0ULL); wrmsrl_safe(MSR_IA32_SYSENTER_EIP, (u64)ia32_sysenter_target); wrmsrl(MSR_CSTAR, ia32_cstar_target); } -#endif /* CONFIG_IA32_EMULATION */ -#endif /* CONFIG_X86_64 */ +# endif +#endif +/* + * Set up the CPU state needed to execute SYSENTER/SYSEXIT instructions + * on 32-bit kernels: + */ #ifdef CONFIG_X86_32 void enable_sep_cpu(void) { - int cpu = get_cpu(); - struct tss_struct *tss = &per_cpu(cpu_tss, cpu); + struct tss_struct *tss; + int cpu; - if (!boot_cpu_has(X86_FEATURE_SEP)) { - put_cpu(); - return; - } + cpu = get_cpu(); + tss = &per_cpu(cpu_tss, cpu); + + if (!boot_cpu_has(X86_FEATURE_SEP)) + goto out; + + /* + * The struct::SS1 and tss_struct::SP1 fields are not used by the hardware, + * we cache the SYSENTER CS and ESP values there for easy access: + */ tss->x86_tss.ss1 = __KERNEL_CS; + wrmsr(MSR_IA32_SYSENTER_CS, tss->x86_tss.ss1, 0); + tss->x86_tss.sp1 = (unsigned long)tss + offsetofend(struct tss_struct, SYSENTER_stack); - wrmsr(MSR_IA32_SYSENTER_CS, __KERNEL_CS, 0); wrmsr(MSR_IA32_SYSENTER_ESP, tss->x86_tss.sp1, 0); - wrmsr(MSR_IA32_SYSENTER_EIP, (unsigned long) ia32_sysenter_target, 0); + + wrmsr(MSR_IA32_SYSENTER_EIP, (unsigned long)ia32_sysenter_target, 0); + +out: put_cpu(); } #endif |