From 222ee9087a730b1df08d09baed0d03626e67600f Mon Sep 17 00:00:00 2001 From: Vasily Gorbik Date: Wed, 27 Nov 2019 17:37:51 +0100 Subject: s390/unwind: start unwinding from reliable state A comment in arch/s390/include/asm/unwind.h says: > If 'first_frame' is not zero unwind_start skips unwind frames until it > reaches the specified stack pointer. > The end of the unwinding is indicated with unwind_done, this can be true > right after unwind_start, e.g. with first_frame!=0 that can not be found. > unwind_next_frame skips to the next frame. > Once the unwind is completed unwind_error() can be used to check if there > has been a situation where the unwinder could not correctly understand > the tasks call chain. With this change backchain unwinder now comply with behaviour described. As well as matches orc unwinder implementation. Now unwinder starts from reliable state, i.e. __unwind_start own stack frame is taken or stack frame generated by __switch_to (ksp) - both known to be valid. In case of pt_regs %r15 is better match for pt_regs psw, than sometimes random "sp" caller passed. Reviewed-by: Heiko Carstens Signed-off-by: Vasily Gorbik --- arch/s390/include/asm/unwind.h | 6 +++--- arch/s390/kernel/unwind_bc.c | 42 ++++++++++++++++++++++++++++-------------- 2 files changed, 31 insertions(+), 17 deletions(-) (limited to 'arch') diff --git a/arch/s390/include/asm/unwind.h b/arch/s390/include/asm/unwind.h index 5d6c8fe7a271..de9006b0cfeb 100644 --- a/arch/s390/include/asm/unwind.h +++ b/arch/s390/include/asm/unwind.h @@ -58,11 +58,11 @@ static inline bool unwind_error(struct unwind_state *state) static inline void unwind_start(struct unwind_state *state, struct task_struct *task, struct pt_regs *regs, - unsigned long sp) + unsigned long first_frame) { task = task ?: current; - sp = sp ?: get_stack_pointer(task, regs); - __unwind_start(state, task, regs, sp); + first_frame = first_frame ?: get_stack_pointer(task, regs); + __unwind_start(state, task, regs, first_frame); } static inline struct pt_regs *unwind_get_entry_regs(struct unwind_state *state) diff --git a/arch/s390/kernel/unwind_bc.c b/arch/s390/kernel/unwind_bc.c index c5ebb8a4cdd6..e1371cdf9fa5 100644 --- a/arch/s390/kernel/unwind_bc.c +++ b/arch/s390/kernel/unwind_bc.c @@ -105,13 +105,11 @@ out_stop: EXPORT_SYMBOL_GPL(unwind_next_frame); void __unwind_start(struct unwind_state *state, struct task_struct *task, - struct pt_regs *regs, unsigned long sp) + struct pt_regs *regs, unsigned long first_frame) { struct stack_info *info = &state->stack_info; - unsigned long *mask = &state->stack_mask; - bool reliable; struct stack_frame *sf; - unsigned long ip; + unsigned long ip, sp; memset(state, 0, sizeof(*state)); state->task = task; @@ -123,23 +121,28 @@ void __unwind_start(struct unwind_state *state, struct task_struct *task, return; } + /* Get the instruction pointer from pt_regs or the stack frame */ + if (regs) { + ip = regs->psw.addr; + sp = regs->gprs[15]; + } else if (task == current) { + sp = current_frame_address(); + } else { + sp = task->thread.ksp; + } + /* Get current stack pointer and initialize stack info */ - if (get_stack_info(sp, task, info, mask) != 0 || - !on_stack(info, sp, sizeof(struct stack_frame))) { + if (!update_stack_info(state, sp)) { /* Something is wrong with the stack pointer */ info->type = STACK_TYPE_UNKNOWN; state->error = true; return; } - /* Get the instruction pointer from pt_regs or the stack frame */ - if (regs) { - ip = READ_ONCE_NOCHECK(regs->psw.addr); - reliable = true; - } else { - sf = (struct stack_frame *) sp; + if (!regs) { + /* Stack frame is within valid stack */ + sf = (struct stack_frame *)sp; ip = READ_ONCE_NOCHECK(sf->gprs[8]); - reliable = false; } ip = ftrace_graph_ret_addr(state->task, &state->graph_idx, ip, NULL); @@ -147,6 +150,17 @@ void __unwind_start(struct unwind_state *state, struct task_struct *task, /* Update unwind state */ state->sp = sp; state->ip = ip; - state->reliable = reliable; + state->reliable = true; + + if (!first_frame) + return; + /* Skip through the call chain to the specified starting frame */ + while (!unwind_done(state)) { + if (on_stack(&state->stack_info, first_frame, sizeof(struct stack_frame))) { + if (state->sp >= first_frame) + break; + } + unwind_next_frame(state); + } } EXPORT_SYMBOL_GPL(__unwind_start); -- cgit v1.2.3-59-g8ed1b