unwind-libdw: use the mmap_notify subsystem
The unwind subsystem uses the mmap_cache subsystem even it uses
unwind-libdw as backend. unwind-libdw doesn't need the full set of the
mmap_cache subsystem; libdw has a feature for caching a memory
mapping.
This commit does three things.
(1) Make the unwind subsystem not use the mmap_cache subsystem.
The unwind subsystem never concern the memory mapping of the target.
It becomes a thin layer.
(2) Make unwind-libunwind use the mmap_cache subsystem directly.
(3) Make unwind-libdw use the mmap_notify subsystem to know when it
should call dwfl_linux_proc_report/dwfl_report_end for updating the
cache.
Here is a subsystem structure that this patch
introduces:
+-------------------------------------+
| unwind subsys |
+------------------+------------------+
| unwind-libunwind | unwind-libdw |
+------------------+------------------+
| mmap_cache | |
+------------------+ |
| mmap_notify |
+-------------------------------------+
| syscall |
+-------------------------------------+
mmap/munmap/mprotect/brk...
* unwind.c: Don't include "mmap_cache.h".
(unwind_init): Don't call mmap_cache_enable.
(unwind_tcb_print, unwind_tcb_capture): Don't call mmap_cache related
functions, just invoke unwinder.tcb_walk.
* unwind.h (struct unwind_unwinder_t): Remove tcb_flush_cache field.
* unwind-libdw.c: Include "mmap_notify.h" instead of "mmap_cache.h".
(struct ctx): Add last_proc_updating field to record the generation
of memory mapping that is cached by dwfl_linux_proc_report
and dwfl_report_end.
(mapping_generation): A variable counting how many times the memory
mapping of targets has been changed.
(updating_mapping_generation): New utility function for updating
mapping_generation.
(init): New function for registering updating_mapping_generation
in the mmap_notify subsystem as a callback function.
(tcb_init): Initialize ctx::last_proc_updating.
(tcb_flush_cache): Rename to flush_cache_maybe. Rebuild the cache data
only if the data is stale.
(tcb_walk): Call flush_cache_maybe for avoiding referring staled cache data.
(unwinder): Set init function, remove tcb_flush_cache field.
* unwind-libunwind.c (init): Enable the mmap_cache subsystem.
(tcb_walk): Call mmap_cache_rebuild_if_invalid and unw_flush_cache for
updating the cache of the memory mapping before walking the stack.
(tcb_walk): Rename to walk.
(unwinder): Remove tcb_flush_cache field.
Signed-off-by: Masatake YAMATO <yamato@redhat.com>
This commit is contained in:
Masatake YAMATO
parent
e09c6c88aa
commit
840bb0acb5
@ -36,13 +36,28 @@
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#include "defs.h"
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#include "unwind.h"
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#include "mmap_cache.h"
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#include "mmap_notify.h"
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#include <elfutils/libdwfl.h>
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struct ctx {
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Dwfl *dwfl;
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unsigned int last_proc_updating;
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};
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static unsigned int mapping_generation;
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static void
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update_mapping_generation(struct tcb *tcp, void *unused)
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{
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mapping_generation++;
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}
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static void
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init(void)
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{
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mmap_notify_register_client(update_mapping_generation, NULL);
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}
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static void *
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tcb_init(struct tcb *tcp)
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{
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@ -74,6 +89,7 @@ tcb_init(struct tcb *tcp)
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struct ctx *ctx = xmalloc(sizeof(*ctx));
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ctx->dwfl = dwfl;
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ctx->last_proc_updating = 0;
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return ctx;
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}
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@ -87,6 +103,31 @@ tcb_fin(struct tcb *tcp)
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}
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}
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static void
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flush_cache_maybe(struct tcb *tcp)
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{
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struct ctx *ctx = tcp->unwind_ctx;
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if (!ctx)
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return;
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if (ctx->last_proc_updating == mapping_generation)
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return;
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int r = dwfl_linux_proc_report(ctx->dwfl, tcp->pid);
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if (r < 0)
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error_msg("dwfl_linux_proc_report returned an error"
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" for pid %d: %s", tcp->pid, dwfl_errmsg(-1));
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else if (r > 0)
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error_msg("dwfl_linux_proc_report returned an error"
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" for pid %d", tcp->pid);
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else if (dwfl_report_end(ctx->dwfl, NULL, NULL) != 0)
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error_msg("dwfl_report_end returned an error"
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" for pid %d: %s", tcp->pid, dwfl_errmsg(-1));
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ctx->last_proc_updating = mapping_generation;
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}
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struct frame_user_data {
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unwind_call_action_fn call_action;
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unwind_error_action_fn error_action;
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@ -150,6 +191,9 @@ tcb_walk(struct tcb *tcp,
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.data = data,
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.stack_depth = 256,
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};
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flush_cache_maybe(tcp);
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int r = dwfl_getthread_frames(ctx->dwfl, tcp->pid, frame_callback,
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&user_data);
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if (r)
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@ -158,31 +202,10 @@ tcb_walk(struct tcb *tcp,
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0);
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}
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static void
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tcb_flush_cache(struct tcb *tcp)
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{
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struct ctx *ctx = tcp->unwind_ctx;
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if (!ctx)
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return;
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int r = dwfl_linux_proc_report(ctx->dwfl, tcp->pid);
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if (r < 0)
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error_msg("dwfl_linux_proc_report returned an error"
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" for pid %d: %s", tcp->pid, dwfl_errmsg(-1));
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else if (r > 0)
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error_msg("dwfl_linux_proc_report returned an error"
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" for pid %d", tcp->pid);
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else if (dwfl_report_end(ctx->dwfl, NULL, NULL) != 0)
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error_msg("dwfl_report_end returned an error"
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" for pid %d: %s", tcp->pid, dwfl_errmsg(-1));
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}
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const struct unwind_unwinder_t unwinder = {
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.name = "libdw",
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.init = NULL,
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.init = init,
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.tcb_init = tcb_init,
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.tcb_fin = tcb_fin,
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.tcb_walk = tcb_walk,
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.tcb_flush_cache = tcb_flush_cache,
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};
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@ -36,6 +36,8 @@ static unw_addr_space_t libunwind_as;
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static void
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init(void)
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{
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mmap_cache_enable();
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libunwind_as = unw_create_addr_space(&_UPT_accessors, 0);
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if (!libunwind_as)
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error_msg_and_die("failed to create address space"
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@ -125,10 +127,10 @@ print_stack_frame(struct tcb *tcp,
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}
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static void
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tcb_walk(struct tcb *tcp,
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unwind_call_action_fn call_action,
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unwind_error_action_fn error_action,
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void *data)
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walk(struct tcb *tcp,
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unwind_call_action_fn call_action,
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unwind_error_action_fn error_action,
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void *data)
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{
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char *symbol_name;
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size_t symbol_name_size = 40;
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@ -159,9 +161,27 @@ tcb_walk(struct tcb *tcp,
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}
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static void
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tcb_flush_cache(struct tcb *tcp)
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tcb_walk(struct tcb *tcp,
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unwind_call_action_fn call_action,
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unwind_error_action_fn error_action,
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void *data)
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{
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unw_flush_cache(libunwind_as, 0, 0);
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switch (mmap_cache_rebuild_if_invalid(tcp, __func__)) {
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case MMAP_CACHE_REBUILD_RENEWED:
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/*
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* Rebuild the unwinder internal cache.
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* Called when mmap cache subsystem detects a
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* change of tracee memory mapping.
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*/
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unw_flush_cache(libunwind_as, 0, 0);
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ATTRIBUTE_FALLTHROUGH;
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case MMAP_CACHE_REBUILD_READY:
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walk(tcp, call_action, error_action, data);
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break;
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default:
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/* Do nothing */
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;
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}
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}
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const struct unwind_unwinder_t unwinder = {
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@ -170,5 +190,4 @@ const struct unwind_unwinder_t unwinder = {
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.tcb_init = tcb_init,
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.tcb_fin = tcb_fin,
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.tcb_walk = tcb_walk,
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.tcb_flush_cache = tcb_flush_cache,
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};
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34
unwind.c
34
unwind.c
@ -26,7 +26,6 @@
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*/
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#include "defs.h"
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#include "mmap_cache.h"
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#include "unwind.h"
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#ifdef USE_DEMANGLE
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@ -59,7 +58,6 @@ unwind_init(void)
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{
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if (unwinder.init)
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unwinder.init();
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mmap_cache_enable();
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}
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void
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@ -296,19 +294,8 @@ unwind_tcb_print(struct tcb *tcp)
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debug_func_msg("head: tcp=%p, queue=%p",
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tcp, tcp->unwind_queue->head);
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queue_print(tcp->unwind_queue);
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} else switch (mmap_cache_rebuild_if_invalid(tcp, __func__)) {
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case MMAP_CACHE_REBUILD_RENEWED:
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unwinder.tcb_flush_cache(tcp);
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ATTRIBUTE_FALLTHROUGH;
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case MMAP_CACHE_REBUILD_READY:
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debug_func_msg("walk: tcp=%p, queue=%p",
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tcp, tcp->unwind_queue->head);
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unwinder.tcb_walk(tcp, print_call_cb, print_error_cb, NULL);
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break;
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default:
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/* Do nothing */
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;
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}
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} else
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unwinder.tcb_walk(tcp, print_call_cb, print_error_cb, NULL);
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}
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/*
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@ -325,19 +312,10 @@ unwind_tcb_capture(struct tcb *tcp)
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#endif
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if (tcp->unwind_queue->head)
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error_msg_and_die("bug: unprinted entries in queue");
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switch (mmap_cache_rebuild_if_invalid(tcp, __func__)) {
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case MMAP_CACHE_REBUILD_RENEWED:
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unwinder.tcb_flush_cache(tcp);
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ATTRIBUTE_FALLTHROUGH;
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case MMAP_CACHE_REBUILD_READY:
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unwinder.tcb_walk(tcp, queue_put_call, queue_put_error,
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tcp->unwind_queue);
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debug_func_msg("tcp=%p, queue=%p",
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else {
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debug_func_msg("walk: tcp=%p, queue=%p",
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tcp, tcp->unwind_queue->head);
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break;
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default:
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/* Do nothing */
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;
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unwinder.tcb_walk(tcp, queue_put_call, queue_put_error,
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tcp->unwind_queue);
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}
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}
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6
unwind.h
6
unwind.h
@ -63,12 +63,6 @@ struct unwind_unwinder_t {
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unwind_call_action_fn,
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unwind_error_action_fn,
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void *);
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/*
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* Rebuild the unwinder internal cache. Called when mmap cache
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* subsystem detects a change of tracee memory mapping.
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*/
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void (*tcb_flush_cache)(struct tcb *);
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};
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extern const struct unwind_unwinder_t unwinder;
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