diff options
| author | Jan Beulich <jbeulich@novell.com> | 2008-03-10 13:11:17 +0000 |
|---|---|---|
| committer | Ingo Molnar <mingo@elte.hu> | 2008-04-17 17:40:58 +0200 |
| commit | 5b0e508415a83989fe704b4718a1a214bc333ca7 (patch) | |
| tree | bf73f1e6b944c190441413cedfb49b05e04ffe6b | |
| parent | f694010185c429629ad5a65245da08103e611852 (diff) | |
| download | lwn-5b0e508415a83989fe704b4718a1a214bc333ca7.tar.gz lwn-5b0e508415a83989fe704b4718a1a214bc333ca7.zip | |
x86: prevent unconditional writes to DebugCtl MSR
Otherwise, enabling (or better, subsequent disabling) of single
stepping would cause a kernel oops on CPUs not having this MSR.
The patch could have been added a conditional to the MSR write in
user_disable_single_step(), but centralizing the updates seems safer
and (looking forward) better manageable.
Signed-off-by: Jan Beulich <jbeulich@novell.com>
Cc: Markus Metzger <markus.t.metzger@intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
| -rw-r--r-- | arch/x86/kernel/kprobes.c | 4 | ||||
| -rw-r--r-- | arch/x86/kernel/process_32.c | 4 | ||||
| -rw-r--r-- | arch/x86/kernel/process_64.c | 4 | ||||
| -rw-r--r-- | arch/x86/kernel/step.c | 2 | ||||
| -rw-r--r-- | include/asm-x86/processor.h | 9 |
5 files changed, 16 insertions, 7 deletions
diff --git a/arch/x86/kernel/kprobes.c b/arch/x86/kernel/kprobes.c index 34a591283f5d..1e3de7db9ad5 100644 --- a/arch/x86/kernel/kprobes.c +++ b/arch/x86/kernel/kprobes.c @@ -410,13 +410,13 @@ static void __kprobes set_current_kprobe(struct kprobe *p, struct pt_regs *regs, static void __kprobes clear_btf(void) { if (test_thread_flag(TIF_DEBUGCTLMSR)) - wrmsrl(MSR_IA32_DEBUGCTLMSR, 0); + update_debugctlmsr(0); } static void __kprobes restore_btf(void) { if (test_thread_flag(TIF_DEBUGCTLMSR)) - wrmsrl(MSR_IA32_DEBUGCTLMSR, current->thread.debugctlmsr); + update_debugctlmsr(current->thread.debugctlmsr); } static void __kprobes prepare_singlestep(struct kprobe *p, struct pt_regs *regs) diff --git a/arch/x86/kernel/process_32.c b/arch/x86/kernel/process_32.c index 9230ce060d09..ec05fb750dfc 100644 --- a/arch/x86/kernel/process_32.c +++ b/arch/x86/kernel/process_32.c @@ -564,12 +564,12 @@ __switch_to_xtra(struct task_struct *prev_p, struct task_struct *next_p, /* we clear debugctl to make sure DS * is not in use when we change it */ debugctl = 0; - wrmsrl(MSR_IA32_DEBUGCTLMSR, 0); + update_debugctlmsr(0); wrmsr(MSR_IA32_DS_AREA, next->ds_area_msr, 0); } if (next->debugctlmsr != debugctl) - wrmsr(MSR_IA32_DEBUGCTLMSR, next->debugctlmsr, 0); + update_debugctlmsr(next->debugctlmsr); if (test_tsk_thread_flag(next_p, TIF_DEBUG)) { set_debugreg(next->debugreg0, 0); diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c index 1ffce14cff6e..4f40272474dd 100644 --- a/arch/x86/kernel/process_64.c +++ b/arch/x86/kernel/process_64.c @@ -563,12 +563,12 @@ static inline void __switch_to_xtra(struct task_struct *prev_p, /* we clear debugctl to make sure DS * is not in use when we change it */ debugctl = 0; - wrmsrl(MSR_IA32_DEBUGCTLMSR, 0); + update_debugctlmsr(0); wrmsrl(MSR_IA32_DS_AREA, next->ds_area_msr); } if (next->debugctlmsr != debugctl) - wrmsrl(MSR_IA32_DEBUGCTLMSR, next->debugctlmsr); + update_debugctlmsr(next->debugctlmsr); if (test_tsk_thread_flag(next_p, TIF_DEBUG)) { loaddebug(next, 0); diff --git a/arch/x86/kernel/step.c b/arch/x86/kernel/step.c index 071ff4798236..92c20fee6781 100644 --- a/arch/x86/kernel/step.c +++ b/arch/x86/kernel/step.c @@ -148,7 +148,7 @@ static void write_debugctlmsr(struct task_struct *child, unsigned long val) if (child != current) return; - wrmsrl(MSR_IA32_DEBUGCTLMSR, val); + update_debugctlmsr(val); } /* diff --git a/include/asm-x86/processor.h b/include/asm-x86/processor.h index cc0268395ea2..40227c9bf51b 100644 --- a/include/asm-x86/processor.h +++ b/include/asm-x86/processor.h @@ -741,6 +741,15 @@ extern void switch_to_new_gdt(void); extern void cpu_init(void); extern void init_gdt(int cpu); +static inline void update_debugctlmsr(unsigned long debugctlmsr) +{ +#ifndef CONFIG_X86_DEBUGCTLMSR + if (boot_cpu_data.x86 < 6) + return; +#endif + wrmsrl(MSR_IA32_DEBUGCTLMSR, debugctlmsr); +} + /* * from system description table in BIOS. Mostly for MCA use, but * others may find it useful: |