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97806dfb6f
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 a1d863ac3e ("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 <heiko.carstens@de.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
83 lines
2.8 KiB
C
83 lines
2.8 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef _ASM_S390_UNWIND_H
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#define _ASM_S390_UNWIND_H
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#include <linux/sched.h>
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#include <linux/ftrace.h>
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#include <asm/ptrace.h>
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#include <asm/stacktrace.h>
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/*
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* To use the stack unwinder it has to be initialized with unwind_start.
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* There four combinations for task and regs:
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* 1) task==NULL, regs==NULL: the unwind starts for the task that is currently
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* running, sp/ip picked up from the CPU registers
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* 2) task==NULL, regs!=NULL: the unwind starts from the sp/ip found in
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* the struct pt_regs of an interrupt frame for the current task
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* 3) task!=NULL, regs==NULL: the unwind starts for an inactive task with
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* the sp picked up from task->thread.ksp and the ip picked up from the
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* return address stored by __switch_to
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* 4) task!=NULL, regs!=NULL: the sp/ip are picked up from the interrupt
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* frame 'regs' of a inactive task
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* If 'first_frame' is not zero unwind_start skips unwind frames until it
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* reaches the specified stack pointer.
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* The end of the unwinding is indicated with unwind_done, this can be true
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* right after unwind_start, e.g. with first_frame!=0 that can not be found.
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* unwind_next_frame skips to the next frame.
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* Once the unwind is completed unwind_error() can be used to check if there
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* has been a situation where the unwinder could not correctly understand
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* the tasks call chain.
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*/
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struct unwind_state {
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struct stack_info stack_info;
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unsigned long stack_mask;
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struct task_struct *task;
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struct pt_regs *regs;
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unsigned long sp, ip;
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int graph_idx;
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bool reliable;
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bool error;
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};
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void __unwind_start(struct unwind_state *state, struct task_struct *task,
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struct pt_regs *regs, unsigned long first_frame);
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bool unwind_next_frame(struct unwind_state *state);
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unsigned long unwind_get_return_address(struct unwind_state *state);
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static inline bool unwind_done(struct unwind_state *state)
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{
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return state->stack_info.type == STACK_TYPE_UNKNOWN;
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}
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static inline bool unwind_error(struct unwind_state *state)
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{
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return state->error;
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}
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static inline void unwind_start(struct unwind_state *state,
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struct task_struct *task,
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struct pt_regs *regs,
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unsigned long sp)
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{
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task = task ?: current;
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sp = sp ?: get_stack_pointer(task, regs);
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__unwind_start(state, task, regs, sp);
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}
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static inline struct pt_regs *unwind_get_entry_regs(struct unwind_state *state)
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{
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return unwind_done(state) ? NULL : state->regs;
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}
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#define unwind_for_each_frame(state, task, regs, first_frame) \
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for (unwind_start(state, task, regs, first_frame); \
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!unwind_done(state); \
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unwind_next_frame(state))
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static inline void unwind_init(void) {}
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static inline void unwind_module_init(struct module *mod, void *orc_ip,
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size_t orc_ip_size, void *orc,
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size_t orc_size) {}
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#endif /* _ASM_S390_UNWIND_H */
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