[lldb-dev] [LLVMdev] Proposal: ASan debugging API

[Kostya Serebryany]

The overall idea makes sense, especially if there is a real interest from
gdb/lldb users.
So far __asan_describe_address was the only thing that anyone requested,
but we could be proactive too.
Please send patches as usual, with tests (compiler-rt/test/asan/TestCases),
and preferably in small chunks.

--kcc


On Thu, Jul 10, 2014 at 6:28 AM, Chandler Carruth <chandlerc at google.com>
wrote:

> Should probably involve the LLDB developers as well here.
>
>
> On Wed, Jul 9, 2014 at 6:13 PM, Kuba Břečka <kuba.brecka at gmail.com> wrote:
>
>> Hi,
>>
>> I would like to improve the debugging experience for ASan. The idea is to
>> have a couple of useful commands in LLDB (probably implemented as Python
>> scripts) that could help the user when they are debugging an ASan-enabled
>> binary. We already have some debugging API (asan_interface.h):
>>
>>     // Print the description of addr (useful when debugging in gdb).
>>     void __asan_describe_address(void *addr);
>>
>> What I'd like to have is a few more API on the ASan/compiler-rt side to
>> query various information that ASan can provide, both about an error report
>> and about general addresses, something like:
>>
>>     // Useful for calling from a debugger to get information about an
>> error.
>>     // If an error has been (or is beign) reported, returns the pc, bp,
>> sp,
>>     // address, access type, access type and bug description, and the
>> return
>>     // value of the function is 1. If no error occurred yet, returns 0.
>>     int __asan_get_report_data(void **pc, void **bp, void **sp, void
>> **addr,
>>                                int *is_write, size_t *access_size,
>>                                char **bug_description);
>>
>>     // Address/memory type from ASan's point of view.
>>     typedef enum {
>>       __ADDRESS_TYPE_UNKNOWN,
>>       __ADDRESS_TYPE_SHADOW_LOW,
>>       __ADDRESS_TYPE_SHADOW_GAP,
>>       __ADDRESS_TYPE_SHADOW_HIGH,
>>       __ADDRESS_TYPE_GLOBAL,
>>       __ADDRESS_TYPE_STACK,
>>       __ADDRESS_TYPE_HEAP,
>>     } asan_address_type;
>>
>>     // Useful for calling from the debugger to get information about a
>> pointer.
>>     // Return one of the __ADDRESS_TYPE_* enum values. If global or
>> stack, tries
>>     // to also return the variable name, address and size. If heap, tries
>> to
>>     // return the chunk address and size.
>>     int __asan_get_address_type(void *addr, char **region_name,
>>                                 void **region_address, size_t
>> *region_size);
>>
>>     // Useful for calling from the debugger to get the allocation stack
>> trace
>>     // and thread ID for a heap address. Returns 1 on success, 0 on error.
>>     int __asan_get_alloc_stack(void *addr, void **trace, size_t
>> *frame_count,
>>                                void **top_frame_bp, int *thread_id);
>>
>>     // Useful for calling from the debugger to get the free stack trace
>>     // and thread ID for a heap address. Returns 1 on success, 0 on error.
>>     int __asan_get_free_stack(void *addr, void **trace, size_t
>> *frame_count,
>>                               void **top_frame_bp, int *thread_id);
>>
>>     // Useful for calling from the debugger to get the current shadow
>> memory
>>     // mapping.
>>     void __asan_get_shadow_mapping(size_t *shadow_scale, size_t
>> *shadow_offset);
>> Hi,
>>
>> I would like to improve the debugging experience for ASan. The idea is to
>> have a couple of useful commands in LLDB (probably implemented as Python
>> scripts) that could help the user when they are debugging an ASan-enabled
>> binary. We already have some debugging API (asan_interface.h):
>>
>>     // Print the description of addr (useful when debugging in gdb).
>>     void __asan_describe_address(void *addr);
>>
>> What I'd like to have is a few more API to query various information that
>> ASan can provide, both about an error report and about general addresses,
>> something like:
>>
>>     // Useful for calling from a debugger to get information about an
>> error.
>>     // If an error has been (or is being) reported, returns the pc, bp,
>> sp,
>>     // address, access type, access type and bug description, and the
>> return
>>     // value of the function is 1. If no error occurred yet, returns 0.
>>     int __asan_get_report_data(void **pc, void **bp, void **sp, void
>> **addr,
>>                                int *is_write, size_t *access_size,
>>                                char **bug_description);
>>
>>     // Address/memory type from ASan's point of view.
>>     typedef enum {
>>       __ADDRESS_TYPE_UNKNOWN,
>>       __ADDRESS_TYPE_SHADOW_LOW,
>>       __ADDRESS_TYPE_SHADOW_GAP,
>>       __ADDRESS_TYPE_SHADOW_HIGH,
>>       __ADDRESS_TYPE_GLOBAL,
>>       __ADDRESS_TYPE_STACK,
>>       __ADDRESS_TYPE_HEAP,
>>     } asan_address_type;
>>
>>     // Useful for calling from the debugger to get information about a
>> pointer.
>>     // Return one of the __ADDRESS_TYPE_* enum values. If global or
>> stack, tries
>>     // to also return the variable name, address and size. If heap, tries
>> to
>>     // return the chunk address and size.
>>     int __asan_get_address_type(void *addr, char **region_name,
>>                                 void **region_address, size_t
>> *region_size);
>>
>>     // Useful for calling from the debugger to get the allocation stack
>> trace
>>     // and thread ID for a heap address. Returns 1 on success, 0 on error.
>>     int __asan_get_alloc_stack(void *addr, void **trace, size_t
>> *frame_count,
>>                                void **top_frame_bp, int *thread_id);
>>
>>     // Useful for calling from the debugger to get the free stack trace
>>     // and thread ID for a heap address. Returns 1 on success, 0 on error.
>>     int __asan_get_free_stack(void *addr, void **trace, size_t
>> *frame_count,
>>                               void **top_frame_bp, int *thread_id);
>>
>>     // Useful for calling from the debugger to get the current shadow
>> memory
>>     // mapping.
>>     void __asan_get_shadow_mapping(size_t *shadow_scale, size_t
>> *shadow_offset);
>>
>> The information that this API would provide is currently only available
>> in the textual form in ASan reports. Having an API to provide it would
>> enable implementation of various tools/script for LLDB and GDB.
>>
>> Kuba
>>
>>
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>> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
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>>
>>
>
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