From: Miroslav Benes <mbenes@xxxxxxx> Update a task's patch state when returning from a system call or user space interrupt, or after handling a signal. This greatly increases the chances of a patch operation succeeding. If a task is I/O bound, it can be patched when returning from a system call. If a task is CPU bound, it can be patched when returning from an interrupt. If a task is sleeping on a to-be-patched function, the user can send SIGSTOP and SIGCONT to force it to switch. Since there are two ways the syscall can be restarted on return from a signal handling process, it is important to clear the flag before do_signal() is called. Otherwise we could miss the migration if we used SIGSTOP/SIGCONT procedure or fake signal to migrate patching blocking tasks. If we place our hook to sysc_work label in entry before TIF_SIGPENDING is evaluated we kill two birds with one stone. The task is correctly migrated in all return paths from a syscall. Signed-off-by: Miroslav Benes <mbenes@xxxxxxx> Signed-off-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx> --- arch/s390/include/asm/thread_info.h | 2 ++ arch/s390/kernel/entry.S | 31 ++++++++++++++++++++++++++++++- 2 files changed, 32 insertions(+), 1 deletion(-) diff --git a/arch/s390/include/asm/thread_info.h b/arch/s390/include/asm/thread_info.h index 4977668..646845e 100644 --- a/arch/s390/include/asm/thread_info.h +++ b/arch/s390/include/asm/thread_info.h @@ -56,6 +56,7 @@ int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src); #define TIF_SIGPENDING 1 /* signal pending */ #define TIF_NEED_RESCHED 2 /* rescheduling necessary */ #define TIF_UPROBE 3 /* breakpointed or single-stepping */ +#define TIF_PATCH_PENDING 4 /* pending live patching update */ #define TIF_31BIT 16 /* 32bit process */ #define TIF_MEMDIE 17 /* is terminating due to OOM killer */ @@ -74,6 +75,7 @@ int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src); #define _TIF_SIGPENDING _BITUL(TIF_SIGPENDING) #define _TIF_NEED_RESCHED _BITUL(TIF_NEED_RESCHED) #define _TIF_UPROBE _BITUL(TIF_UPROBE) +#define _TIF_PATCH_PENDING _BITUL(TIF_PATCH_PENDING) #define _TIF_31BIT _BITUL(TIF_31BIT) #define _TIF_SINGLE_STEP _BITUL(TIF_SINGLE_STEP) diff --git a/arch/s390/kernel/entry.S b/arch/s390/kernel/entry.S index 34ab7e8..9a15eac 100644 --- a/arch/s390/kernel/entry.S +++ b/arch/s390/kernel/entry.S @@ -47,7 +47,7 @@ STACK_SIZE = 1 << STACK_SHIFT STACK_INIT = STACK_SIZE - STACK_FRAME_OVERHEAD - __PT_SIZE _TIF_WORK = (_TIF_SIGPENDING | _TIF_NOTIFY_RESUME | _TIF_NEED_RESCHED | \ - _TIF_UPROBE) + _TIF_UPROBE | _TIF_PATCH_PENDING) _TIF_TRACE = (_TIF_SYSCALL_TRACE | _TIF_SYSCALL_AUDIT | _TIF_SECCOMP | \ _TIF_SYSCALL_TRACEPOINT) _CIF_WORK = (_CIF_MCCK_PENDING | _CIF_ASCE | _CIF_FPU) @@ -333,6 +333,11 @@ ENTRY(system_call) #endif TSTMSK __PT_FLAGS(%r11),_PIF_PER_TRAP jo .Lsysc_singlestep +#ifdef CONFIG_LIVEPATCH + TSTMSK __TI_flags(%r12),_TIF_PATCH_PENDING + jo .Lsysc_patch_pending # handle live patching just before + # signals and possible syscall restart +#endif TSTMSK __TI_flags(%r12),_TIF_SIGPENDING jo .Lsysc_sigpending TSTMSK __TI_flags(%r12),_TIF_NOTIFY_RESUME @@ -405,6 +410,16 @@ ENTRY(system_call) #endif # +# _TIF_PATCH_PENDING is set, call klp_update_patch_state +# +#ifdef CONFIG_LIVEPATCH +.Lsysc_patch_pending: + lg %r2,__LC_CURRENT # pass pointer to task struct + larl %r14,.Lsysc_return + jg klp_update_patch_state +#endif + +# # _PIF_PER_TRAP is set, call do_per_trap # .Lsysc_singlestep: @@ -654,6 +669,10 @@ ENTRY(io_int_handler) jo .Lio_mcck_pending TSTMSK __TI_flags(%r12),_TIF_NEED_RESCHED jo .Lio_reschedule +#ifdef CONFIG_LIVEPATCH + TSTMSK __TI_flags(%r12),_TIF_PATCH_PENDING + jo .Lio_patch_pending +#endif TSTMSK __TI_flags(%r12),_TIF_SIGPENDING jo .Lio_sigpending TSTMSK __TI_flags(%r12),_TIF_NOTIFY_RESUME @@ -700,6 +719,16 @@ ENTRY(io_int_handler) j .Lio_return # +# _TIF_PATCH_PENDING is set, call klp_update_patch_state +# +#ifdef CONFIG_LIVEPATCH +.Lio_patch_pending: + lg %r2,__LC_CURRENT # pass pointer to task struct + larl %r14,.Lio_return + jg klp_update_patch_state +#endif + +# # _TIF_SIGPENDING or is set, call do_signal # .Lio_sigpending: -- 2.7.4 -- To unsubscribe from this list: send the line "unsubscribe linux-s390" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
