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fix: Cache binary images to be used for crashes (#2939)
During crashes we use 2 async-signal-unsafe functions _dyld_get_image_header and _dyld_get_image_name. This may lead to a crash report not being properly saved to disk. This proposal will cache binary images during runtime and use it when the app crashes. Co-authored-by: Andrew McKnight <andrew.mcknight@sentry.io> Co-authored-by: Philipp Hofmann <philipp.hofmann@sentry.io>
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180 changes: 180 additions & 0 deletions
180
Sources/SentryCrash/Recording/SentryCrashBinaryImageCache.c
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,180 @@ | ||
| #include "SentryCrashBinaryImageCache.h" | ||
| #include "SentryCrashDynamicLinker.h" | ||
| #include <mach-o/dyld.h> | ||
| #include <pthread.h> | ||
| #include <stdio.h> | ||
| #include <stdlib.h> | ||
| #include <string.h> | ||
| #include <unistd.h> | ||
|
|
||
| #if TEST || TESTCI | ||
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| typedef void (*SentryRegisterImageCallback)(const struct mach_header *mh, intptr_t vmaddr_slide); | ||
| typedef void (*SentryRegisterFunction)(SentryRegisterImageCallback function); | ||
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| static SentryRegisterFunction _sentry_register_func_for_add_image | ||
| = &_dyld_register_func_for_add_image; | ||
| static SentryRegisterFunction _sentry_register_func_for_remove_image | ||
| = &_dyld_register_func_for_remove_image; | ||
|
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| static void (*SentryWillAddImageCallback)(void) = NULL; | ||
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| void | ||
| sentry_setRegisterFuncForAddImage(SentryRegisterFunction addFunction) | ||
| { | ||
| _sentry_register_func_for_add_image = addFunction; | ||
| } | ||
|
|
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| void | ||
| sentry_setRegisterFuncForRemoveImage(SentryRegisterFunction removeFunction) | ||
| { | ||
| _sentry_register_func_for_remove_image = removeFunction; | ||
| } | ||
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| void | ||
| sentry_setFuncForBeforeAdd(void (*callback)(void)) | ||
| { | ||
| SentryWillAddImageCallback = callback; | ||
| } | ||
|
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| void | ||
| sentry_resetFuncForAddRemoveImage(void) | ||
| { | ||
| _sentry_register_func_for_add_image = &_dyld_register_func_for_add_image; | ||
| _sentry_register_func_for_remove_image = &_dyld_register_func_for_remove_image; | ||
| } | ||
|
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| # define sentry_dyld_register_func_for_add_image(CALLBACK) \ | ||
| _sentry_register_func_for_add_image(CALLBACK); | ||
| # define sentry_dyld_register_func_for_remove_image(CALLBACK) \ | ||
| _sentry_register_func_for_remove_image(CALLBACK); | ||
| # define _will_add_image() \ | ||
| if (SentryWillAddImageCallback) \ | ||
| SentryWillAddImageCallback(); | ||
| #else | ||
| # define sentry_dyld_register_func_for_add_image(CALLBACK) \ | ||
| _dyld_register_func_for_add_image(CALLBACK) | ||
| # define sentry_dyld_register_func_for_remove_image(CALLBACK) \ | ||
| _dyld_register_func_for_remove_image(CALLBACK) | ||
| # define _will_add_image() | ||
| #endif | ||
|
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| typedef struct SentryCrashBinaryImageNode { | ||
| SentryCrashBinaryImage image; | ||
| bool available; | ||
| struct SentryCrashBinaryImageNode *next; | ||
| } SentryCrashBinaryImageNode; | ||
|
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| static SentryCrashBinaryImageNode rootNode = { 0 }; | ||
| static SentryCrashBinaryImageNode *tailNode = NULL; | ||
| static pthread_mutex_t binaryImagesMutex = PTHREAD_MUTEX_INITIALIZER; | ||
|
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| static void | ||
| binaryImageAdded(const struct mach_header *header, intptr_t slide) | ||
| { | ||
| if (tailNode == NULL) { | ||
| return; | ||
| } | ||
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| Dl_info info; | ||
| if (!dladdr(header, &info) || info.dli_fname == NULL) { | ||
| return; | ||
| } | ||
|
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| SentryCrashBinaryImage binaryImage = { 0 }; | ||
| if (!sentrycrashdl_getBinaryImageForHeader( | ||
| (const void *)header, info.dli_fname, &binaryImage, false)) { | ||
| return; | ||
| } | ||
|
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| SentryCrashBinaryImageNode *newNode = malloc(sizeof(SentryCrashBinaryImageNode)); | ||
| newNode->available = true; | ||
| newNode->image = binaryImage; | ||
| newNode->next = NULL; | ||
| _will_add_image(); | ||
| pthread_mutex_lock(&binaryImagesMutex); | ||
| // Recheck tailNode as it could be null when | ||
| // stopped from another thread. | ||
| if (tailNode != NULL) { | ||
| tailNode->next = newNode; | ||
| tailNode = tailNode->next; | ||
| } else { | ||
| free(newNode); | ||
| } | ||
| pthread_mutex_unlock(&binaryImagesMutex); | ||
| } | ||
|
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| static void | ||
| binaryImageRemoved(const struct mach_header *header, intptr_t slide) | ||
| { | ||
| SentryCrashBinaryImageNode *nextNode = &rootNode; | ||
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| while (nextNode != NULL) { | ||
| if (nextNode->image.address == (uint64_t)header) { | ||
| nextNode->available = false; | ||
| break; | ||
| } | ||
| nextNode = nextNode->next; | ||
| } | ||
| } | ||
|
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| void | ||
| sentrycrashbic_iterateOverImages(sentrycrashbic_imageIteratorCallback callback, void *context) | ||
| { | ||
| /** | ||
| We can't use locks here because this is meant to be used during crashes, | ||
| where we can't use async unsafe functions. In order to avoid potential problems, | ||
| we choose an approach that doesn't remove nodes from the list. | ||
| */ | ||
| SentryCrashBinaryImageNode *nextNode = &rootNode; | ||
|
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| // If tailNode is null it means the cache was stopped, therefore we end the iteration. | ||
| // This will minimize any race condition effect without the need for locks. | ||
| while (nextNode != NULL && tailNode != NULL) { | ||
| if (nextNode->available) { | ||
| callback(&nextNode->image, context); | ||
| } | ||
| nextNode = nextNode->next; | ||
| } | ||
| } | ||
|
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| void | ||
| sentrycrashbic_startCache(void) | ||
| { | ||
| pthread_mutex_lock(&binaryImagesMutex); | ||
| if (tailNode != NULL) { | ||
| // Already initialized | ||
| pthread_mutex_unlock(&binaryImagesMutex); | ||
| return; | ||
| } | ||
| tailNode = &rootNode; | ||
| rootNode.next = NULL; | ||
| pthread_mutex_unlock(&binaryImagesMutex); | ||
|
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| // During a call to _dyld_register_func_for_add_image() the callback func is called for every | ||
| // existing image | ||
| sentry_dyld_register_func_for_add_image(&binaryImageAdded); | ||
| sentry_dyld_register_func_for_remove_image(&binaryImageRemoved); | ||
| } | ||
|
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| void | ||
| sentrycrashbic_stopCache(void) | ||
| { | ||
| pthread_mutex_lock(&binaryImagesMutex); | ||
| if (tailNode == NULL) { | ||
| pthread_mutex_unlock(&binaryImagesMutex); | ||
| return; | ||
| } | ||
|
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| SentryCrashBinaryImageNode *node = rootNode.next; | ||
| rootNode.next = NULL; | ||
| tailNode = NULL; | ||
|
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| while (node != NULL) { | ||
| SentryCrashBinaryImageNode *nextNode = node->next; | ||
| free(node); | ||
| node = nextNode; | ||
| } | ||
|
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| pthread_mutex_unlock(&binaryImagesMutex); | ||
| } |
22 changes: 22 additions & 0 deletions
22
Sources/SentryCrash/Recording/SentryCrashBinaryImageCache.h
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,22 @@ | ||
| #ifndef SentryCrashBinaryImageCache_h | ||
| #define SentryCrashBinaryImageCache_h | ||
|
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| #include "SentryCrashDynamicLinker.h" | ||
| #include <stdio.h> | ||
|
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| typedef void (*sentrycrashbic_imageIteratorCallback)(SentryCrashBinaryImage *, void *context); | ||
|
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| void sentrycrashbic_iterateOverImages(sentrycrashbic_imageIteratorCallback index, void *context); | ||
|
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| /** | ||
| * Starts the cache that will monitor binary image being loaded or removed. | ||
| */ | ||
| void sentrycrashbic_startCache(void); | ||
|
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| /** | ||
| * Stops the cache from monitoring binary image being loaded or removed. | ||
| * This will also clean the cache. | ||
| */ | ||
| void sentrycrashbic_stopCache(void); | ||
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| #endif /* SentryCrashBinaryImageCache_h */ |
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