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. |
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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.