diff options
| -rw-r--r-- | arch/i386/kernel/process.c | 29 | ||||
| -rw-r--r-- | arch/x86_64/kernel/process.c | 29 | ||||
| -rw-r--r-- | include/asm-i386/tlbflush.h | 12 | ||||
| -rw-r--r-- | include/asm-x86_64/tlbflush.h | 12 | ||||
| -rw-r--r-- | include/linux/seccomp.h | 10 |
5 files changed, 82 insertions, 10 deletions
diff --git a/arch/i386/kernel/process.c b/arch/i386/kernel/process.c index 5f8cfa6..ba243a4 100644 --- a/arch/i386/kernel/process.c +++ b/arch/i386/kernel/process.c @@ -617,6 +617,33 @@ handle_io_bitmap(struct thread_struct *next, struct tss_struct *tss) } /* + * This function selects if the context switch from prev to next + * has to tweak the TSC disable bit in the cr4. + */ +static inline void disable_tsc(struct task_struct *prev_p, + struct task_struct *next_p) +{ + struct thread_info *prev, *next; + + /* + * gcc should eliminate the ->thread_info dereference if + * has_secure_computing returns 0 at compile time (SECCOMP=n). + */ + prev = prev_p->thread_info; + next = next_p->thread_info; + + if (has_secure_computing(prev) || has_secure_computing(next)) { + /* slow path here */ + if (has_secure_computing(prev) && + !has_secure_computing(next)) { + write_cr4(read_cr4() & ~X86_CR4_TSD); + } else if (!has_secure_computing(prev) && + has_secure_computing(next)) + write_cr4(read_cr4() | X86_CR4_TSD); + } +} + +/* * switch_to(x,yn) should switch tasks from x to y. * * We fsave/fwait so that an exception goes off at the right time @@ -695,6 +722,8 @@ struct task_struct fastcall * __switch_to(struct task_struct *prev_p, struct tas if (unlikely(prev->io_bitmap_ptr || next->io_bitmap_ptr)) handle_io_bitmap(next, tss); + disable_tsc(prev_p, next_p); + return prev_p; } diff --git a/arch/x86_64/kernel/process.c b/arch/x86_64/kernel/process.c index 1d91271..7577f9d 100644 --- a/arch/x86_64/kernel/process.c +++ b/arch/x86_64/kernel/process.c @@ -482,6 +482,33 @@ out: } /* + * This function selects if the context switch from prev to next + * has to tweak the TSC disable bit in the cr4. + */ +static inline void disable_tsc(struct task_struct *prev_p, + struct task_struct *next_p) +{ + struct thread_info *prev, *next; + + /* + * gcc should eliminate the ->thread_info dereference if + * has_secure_computing returns 0 at compile time (SECCOMP=n). + */ + prev = prev_p->thread_info; + next = next_p->thread_info; + + if (has_secure_computing(prev) || has_secure_computing(next)) { + /* slow path here */ + if (has_secure_computing(prev) && + !has_secure_computing(next)) { + write_cr4(read_cr4() & ~X86_CR4_TSD); + } else if (!has_secure_computing(prev) && + has_secure_computing(next)) + write_cr4(read_cr4() | X86_CR4_TSD); + } +} + +/* * This special macro can be used to load a debugging register */ #define loaddebug(thread,r) set_debug(thread->debugreg ## r, r) @@ -599,6 +626,8 @@ struct task_struct *__switch_to(struct task_struct *prev_p, struct task_struct * } } + disable_tsc(prev_p, next_p); + return prev_p; } diff --git a/include/asm-i386/tlbflush.h b/include/asm-i386/tlbflush.h index f22fab0..ab216e1 100644 --- a/include/asm-i386/tlbflush.h +++ b/include/asm-i386/tlbflush.h @@ -22,16 +22,18 @@ */ #define __flush_tlb_global() \ do { \ - unsigned int tmpreg; \ + unsigned int tmpreg, cr4, cr4_orig; \ \ __asm__ __volatile__( \ - "movl %1, %%cr4; # turn off PGE \n" \ + "movl %%cr4, %2; # turn off PGE \n" \ + "movl %2, %1; \n" \ + "andl %3, %1; \n" \ + "movl %1, %%cr4; \n" \ "movl %%cr3, %0; \n" \ "movl %0, %%cr3; # flush TLB \n" \ "movl %2, %%cr4; # turn PGE back on \n" \ - : "=&r" (tmpreg) \ - : "r" (mmu_cr4_features & ~X86_CR4_PGE), \ - "r" (mmu_cr4_features) \ + : "=&r" (tmpreg), "=&r" (cr4), "=&r" (cr4_orig) \ + : "i" (~X86_CR4_PGE) \ : "memory"); \ } while (0) diff --git a/include/asm-x86_64/tlbflush.h b/include/asm-x86_64/tlbflush.h index 2e811ac..0617423 100644 --- a/include/asm-x86_64/tlbflush.h +++ b/include/asm-x86_64/tlbflush.h @@ -22,16 +22,18 @@ */ #define __flush_tlb_global() \ do { \ - unsigned long tmpreg; \ + unsigned long tmpreg, cr4, cr4_orig; \ \ __asm__ __volatile__( \ - "movq %1, %%cr4; # turn off PGE \n" \ + "movq %%cr4, %2; # turn off PGE \n" \ + "movq %2, %1; \n" \ + "andq %3, %1; \n" \ + "movq %1, %%cr4; \n" \ "movq %%cr3, %0; # flush TLB \n" \ "movq %0, %%cr3; \n" \ "movq %2, %%cr4; # turn PGE back on \n" \ - : "=&r" (tmpreg) \ - : "r" (mmu_cr4_features & ~X86_CR4_PGE), \ - "r" (mmu_cr4_features) \ + : "=&r" (tmpreg), "=&r" (cr4), "=&r" (cr4_orig) \ + : "i" (~X86_CR4_PGE) \ : "memory"); \ } while (0) diff --git a/include/linux/seccomp.h b/include/linux/seccomp.h index 3a2702b..dc89116 100644 --- a/include/linux/seccomp.h +++ b/include/linux/seccomp.h @@ -19,6 +19,11 @@ static inline void secure_computing(int this_syscall) __secure_computing(this_syscall); } +static inline int has_secure_computing(struct thread_info *ti) +{ + return unlikely(test_ti_thread_flag(ti, TIF_SECCOMP)); +} + #else /* CONFIG_SECCOMP */ #if (__GNUC__ > 2) @@ -28,6 +33,11 @@ static inline void secure_computing(int this_syscall) #endif #define secure_computing(x) do { } while (0) +/* static inline to preserve typechecking */ +static inline int has_secure_computing(struct thread_info *ti) +{ + return 0; +} #endif /* CONFIG_SECCOMP */ |