From 97806dfb6f3838ee4b7bc69e6f160d83eadbc74a Mon Sep 17 00:00:00 2001 From: Vasily Gorbik Date: Fri, 22 Nov 2019 15:58:42 +0100 Subject: s390/unwind: make reuse_sp default when unwinding pt_regs Currently unwinder yields 2 entries when pt_regs are met: sp="address of pt_regs itself" ip=pt_regs->psw sp=pt_regs->gprs[15] ip="r14 from stack frame pointed by pt_regs->gprs[15]" And neither of those 2 states (combination of sp and ip) ever happened. reuse_sp has been introduced by commit a1d863ac3e10 ("s390/unwind: fix mixing regs and sp"). reuse_sp=true makes unwinder keen to produce the following result, when pt_regs are given (as an arg to unwind_start): sp=pt_regs->gprs[15] ip=pt_regs->psw sp=pt_regs->gprs[15] ip="r14 from stack frame pointed by pt_regs->gprs[15]" The first state is an actual state in which a task was when pt_regs were collected. The second state is marked unreliable and is for debugging purposes to cover the case when a task has been interrupted in between stack frame allocation and writing back_chain - in this case r14 might show an actual caller. Make unwinder behaviour enabled via reuse_sp=true default and drop the special case handling. Reviewed-by: Heiko Carstens Signed-off-by: Vasily Gorbik --- arch/s390/include/asm/unwind.h | 1 - arch/s390/kernel/unwind_bc.c | 21 +++++++-------------- 2 files changed, 7 insertions(+), 15 deletions(-) (limited to 'arch') diff --git a/arch/s390/include/asm/unwind.h b/arch/s390/include/asm/unwind.h index a2d8dd766987..5d6c8fe7a271 100644 --- a/arch/s390/include/asm/unwind.h +++ b/arch/s390/include/asm/unwind.h @@ -35,7 +35,6 @@ struct unwind_state { struct task_struct *task; struct pt_regs *regs; unsigned long sp, ip; - bool reuse_sp; int graph_idx; bool reliable; bool error; diff --git a/arch/s390/kernel/unwind_bc.c b/arch/s390/kernel/unwind_bc.c index fd90b6e21663..ac6cfab567d1 100644 --- a/arch/s390/kernel/unwind_bc.c +++ b/arch/s390/kernel/unwind_bc.c @@ -46,16 +46,7 @@ bool unwind_next_frame(struct unwind_state *state) regs = state->regs; if (unlikely(regs)) { - if (state->reuse_sp) { - sp = state->sp; - state->reuse_sp = false; - } else { - sp = READ_ONCE_NOCHECK(regs->gprs[15]); - if (unlikely(outside_of_stack(state, sp))) { - if (!update_stack_info(state, sp)) - goto out_err; - } - } + sp = state->sp; sf = (struct stack_frame *) sp; ip = READ_ONCE_NOCHECK(sf->gprs[8]); reliable = false; @@ -81,6 +72,11 @@ bool unwind_next_frame(struct unwind_state *state) if (READ_ONCE_NOCHECK(regs->psw.mask) & PSW_MASK_PSTATE) goto out_stop; ip = READ_ONCE_NOCHECK(regs->psw.addr); + sp = READ_ONCE_NOCHECK(regs->gprs[15]); + if (unlikely(outside_of_stack(state, sp))) { + if (!update_stack_info(state, sp)) + goto out_err; + } reliable = true; } } @@ -107,7 +103,7 @@ void __unwind_start(struct unwind_state *state, struct task_struct *task, { struct stack_info *info = &state->stack_info; unsigned long *mask = &state->stack_mask; - bool reliable, reuse_sp; + bool reliable; struct stack_frame *sf; unsigned long ip; @@ -134,12 +130,10 @@ void __unwind_start(struct unwind_state *state, struct task_struct *task, if (regs) { ip = READ_ONCE_NOCHECK(regs->psw.addr); reliable = true; - reuse_sp = true; } else { sf = (struct stack_frame *) sp; ip = READ_ONCE_NOCHECK(sf->gprs[8]); reliable = false; - reuse_sp = false; } ip = ftrace_graph_ret_addr(state->task, &state->graph_idx, ip, NULL); @@ -148,6 +142,5 @@ void __unwind_start(struct unwind_state *state, struct task_struct *task, state->sp = sp; state->ip = ip; state->reliable = reliable; - state->reuse_sp = reuse_sp; } EXPORT_SYMBOL_GPL(__unwind_start); -- cgit v1.2.3