guminterceptor: add alt stack support #826
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This commit adds a new public API to gum to configure the size of an alternate stack to use for hooking. If the configuration is set, then when an interceptor is triggered, it will switch to this stack after the trampoline but before executing the handler. This is needed to support go or programs which do not have large and mutable thread stacks. One note is that only x86_64 support has initially been added, and that it only applies for entry invocation listeners. Exit invocation listeners are not supported because they still would not work with go out-of-the-box because go doesn't like junk being added to call stacks.
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One question I have is how best to test this in CI. Locally I changed the default value the stack size to enable the alternate stack switching and I observed the tests passing. Ideally we could run the interceptor suite twice -- once on the local stack and once on the switched stack. Any pointers on how best to do this would be great. |
| // Switch to the new stack and call the function with arguments | ||
| asm volatile ( | ||
| "movq %%rsp, %%rbx\n" // Save the current stack pointer | ||
| "movq %0, %%rsp\n" // Set the new stack pointer |
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I suppose this may be too late in some cases, as we've already used quite some stack space for saving registers?
| @@ -1782,7 +1897,7 @@ gum_function_context_fixup_cpu_context (GumFunctionContext * function_ctx, | |||
| } | |||
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| static InterceptorThreadContext * | |||
| get_interceptor_thread_context (void) | |||
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This is incorrect; in C (unlike C++), (void) means "no arguments", whereas () means "0 or more arguments".
| @@ -84,6 +84,13 @@ GUM_API void gum_interceptor_with_lock_held (GumInterceptor * self, | |||
| GumInterceptorLockedFunc func, gpointer user_data); | |||
| GUM_API gboolean gum_interceptor_is_locked (GumInterceptor * self); | |||
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| // Configure the alternate stack for the interceptor. The alternate stack is | |||
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Style nitpick: Only C-style comments should be used.
| @@ -1939,9 +2054,16 @@ interceptor_thread_context_new (void) | |||
| context->stack = g_array_sized_new (FALSE, TRUE, | |||
| sizeof (GumInvocationStackEntry), GUM_MAX_CALL_DEPTH); | |||
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Style nitpick: For consistency, two or more consecutive blank lines shouldn't be used.
| @@ -1919,7 +2034,7 @@ gum_interceptor_replacement_invocation_backend = | |||
| }; | |||
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| static InterceptorThreadContext * | |||
| interceptor_thread_context_new (void) | |||
| @@ -27,6 +27,10 @@ | |||
| # define GUM_INTERCEPTOR_CODE_SLICE_SIZE 256 | |||
| #endif | |||
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| #if defined(__x86_64__) | |||
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| #if defined(__x86_64__) | |
| #if defined (HAVE_I386) && GLIB_SIZEOF_VOID_P == 8 |
(For consistency.)
Should also check that GCC or Clang is used, as MSVC doesn't support the inline assembly syntax.
This commit adds a new public API to gum to configure the size of an alternate stack to use for hooking. If the configuration is set, then when an interceptor is triggered, it will switch to this stack after the trampoline but before executing the handler. This is needed to support go or programs which do not have large and mutable thread stacks.
One note is that only x86_64 support has initially been added, and that it only applies for entry invocation listeners. Exit invocation listeners are not supported because they still would not work with go out-of-the-box because go doesn't like junk being added to call stacks.