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Bug#51817: incorrect assumption: thd->query at 0x2ab2a8360360 is an invalid pointer

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The problem is that the logic which checks if a pointer is
valid relies on a poor heuristic based on the start and end
addresses of the data segment and heap.

Apart from miscalculating the heap bounds, this approach also
suffers from the fact that memory can come from places other
than the heap. See Bug#58528 for a more detailed explanation.

On Linux, the solution is to access the process's memory
through /proc/self/task/<tid>/mem, which allows for retrieving
the contents of pages within the virtual address space of
the calling process. If a address range is not mapped, a
input/output error is returned.

client/mysqltest.cc:
  Use new interface to my_safe_print_str.
include/my_stacktrace.h:
  Drop name from my_safe_print_str.
mysys/stacktrace.c:
  Access the process's memory through a file descriptor and
  dump the contents of the memory range. The file descriptor
  offset is equivalent to a offset into the address space.
  
  Do not print the name of the variable associated with the
  address. It can be better accomplished at a higher level.
sql/mysqld.cc:
  Put the variable dumping information within its own newline block.
  Use symbolic names which better convey information to the user.
This commit is contained in:
Davi Arnaut
2010-11-26 19:59:10 -02:00
parent 2bdeabe78b
commit d5e928959e
4 changed files with 112 additions and 18 deletions
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2
include/my_stacktrace.h
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@@ -47,7 +47,7 @@ C_MODE_START
#if defined(HAVE_STACKTRACE) || defined(HAVE_BACKTRACE)
void my_init_stacktrace();
void my_print_stacktrace(uchar* stack_bottom, ulong thread_stack);
void my_safe_print_str(const char* name, const char* val, int max_len);
void my_safe_print_str(const char* val, int max_len);
void my_write_core(int sig);
#if BACKTRACE_DEMANGLE
char *my_demangle(const char *mangled_name, int *status);