PTRACE_O_TRACESYSGOOD flag is interpreted as part of a signal #550
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@chaosagent thanks for the report. What's the platform / architecture this happens on? |
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This only happens on Linux, and I can confirm it happens on x86_64, but the Linux man page says that it might not work on all platforms. The name of the flag is PTRACE_O_TRACESYSGOOD btw; I'll changethe issue title to reflect. |
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geofft
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Mar 28, 2017
The recommended way to trace syscalls with ptrace is to set the PTRACE_O_TRACESYSGOOD option, to distinguish syscall stops from receiving an actual SIGTRAP. In C, this would cause WSTOPSIG to return SIGTRAP | 0x80, but nix wants to parse that as an actual signal. Add another wait status type for syscall stops (in the language of the ptrace(2) manpage, "PTRACE_EVENT stops" and "Syscall-stops" are different things), and mask out bit 0x80 from signals before trying to parse it. Closes nix-rust#550
geofft
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Apr 17, 2017
The recommended way to trace syscalls with ptrace is to set the PTRACE_O_TRACESYSGOOD option, to distinguish syscall stops from receiving an actual SIGTRAP. In C, this would cause WSTOPSIG to return SIGTRAP | 0x80, but nix wants to parse that as an actual signal. Add another wait status type for syscall stops (in the language of the ptrace(2) manpage, "PTRACE_EVENT stops" and "Syscall-stops" are different things), and mask out bit 0x80 from signals before trying to parse it. Closes nix-rust#550
geofft
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Jun 20, 2017
The recommended way to trace syscalls with ptrace is to set the PTRACE_O_TRACESYSGOOD option, to distinguish syscall stops from receiving an actual SIGTRAP. In C, this would cause WSTOPSIG to return SIGTRAP | 0x80, but nix wants to parse that as an actual signal. Add another wait status type for syscall stops (in the language of the ptrace(2) manpage, "PTRACE_EVENT stops" and "Syscall-stops" are different things), and mask out bit 0x80 from signals before trying to parse it. Closes nix-rust#550
geofft
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Jul 19, 2017
The recommended way to trace syscalls with ptrace is to set the PTRACE_O_TRACESYSGOOD option, to distinguish syscall stops from receiving an actual SIGTRAP. In C, this would cause WSTOPSIG to return SIGTRAP | 0x80, but nix wants to parse that as an actual signal. Add another wait status type for syscall stops (in the language of the ptrace(2) manpage, "PTRACE_EVENT stops" and "Syscall-stops" are different things), and mask out bit 0x80 from signals before trying to parse it. Closes nix-rust#550
geofft
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Jul 19, 2017
The recommended way to trace syscalls with ptrace is to set the PTRACE_O_TRACESYSGOOD option, to distinguish syscall stops from receiving an actual SIGTRAP. In C, this would cause WSTOPSIG to return SIGTRAP | 0x80, but nix wants to parse that as an actual signal. Add another wait status type for syscall stops (in the language of the ptrace(2) manpage, "PTRACE_EVENT stops" and "Syscall-stops" are different things), and mask out bit 0x80 from signals before trying to parse it. Closes nix-rust#550
geofft
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Jul 21, 2017
The recommended way to trace syscalls with ptrace is to set the PTRACE_O_TRACESYSGOOD option, to distinguish syscall stops from receiving an actual SIGTRAP. In C, this would cause WSTOPSIG to return SIGTRAP | 0x80, but nix wants to parse that as an actual signal. Add another wait status type for syscall stops (in the language of the ptrace(2) manpage, "PTRACE_EVENT stops" and "Syscall-stops" are different things), and mask out bit 0x80 from signals before trying to parse it. Closes nix-rust#550
geofft
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Jul 21, 2017
The recommended way to trace syscalls with ptrace is to set the PTRACE_O_TRACESYSGOOD option, to distinguish syscall stops from receiving an actual SIGTRAP. In C, this would cause WSTOPSIG to return SIGTRAP | 0x80, but nix wants to parse that as an actual signal. Add another wait status type for syscall stops (in the language of the ptrace(2) manpage, "PTRACE_EVENT stops" and "Syscall-stops" are different things), and mask out bit 0x80 from signals before trying to parse it. Closes nix-rust#550
geofft
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Jul 21, 2017
The recommended way to trace syscalls with ptrace is to set the PTRACE_O_TRACESYSGOOD option, to distinguish syscall stops from receiving an actual SIGTRAP. In C, this would cause WSTOPSIG to return SIGTRAP | 0x80, but nix wants to parse that as an actual signal. Add another wait status type for syscall stops (in the language of the ptrace(2) manpage, "PTRACE_EVENT stops" and "Syscall-stops" are different things), and mask out bit 0x80 from signals before trying to parse it. Closes nix-rust#550
bors bot
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Jul 21, 2017
566: Add WaitStatus::PtraceSyscall for use with PTRACE_O_TRACESYSGOOD r=asomers The recommended way to trace syscalls with ptrace is to set the PTRACE_O_TRACESYSGOOD option, to distinguish syscall stops from receiving an actual SIGTRAP. In C, this would cause WSTOPSIG to return SIGTRAP | 0x80, but nix wants to parse that as an actual signal. Add another wait status type for syscall stops (in the language of the ptrace(2) manpage, "PTRACE_EVENT stops" and "Syscall-stops" are different things), and mask out bit 0x80 from signals before trying to parse it. Closes #550
marmistrz
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Jul 25, 2017
The recommended way to trace syscalls with ptrace is to set the PTRACE_O_TRACESYSGOOD option, to distinguish syscall stops from receiving an actual SIGTRAP. In C, this would cause WSTOPSIG to return SIGTRAP | 0x80, but nix wants to parse that as an actual signal. Add another wait status type for syscall stops (in the language of the ptrace(2) manpage, "PTRACE_EVENT stops" and "Syscall-stops" are different things), and mask out bit 0x80 from signals before trying to parse it. Closes nix-rust#550
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In sys::wait, if waitpid returns a status originating from ptrace and PTRACE_O_TRACESYSGOOD is set, the seventh (0x80) bit of the status will be flipped. This causes status parsing to fail.
The flag technically isn't a ptrace event either, but I feel like that would be the best place to put it. Alternatively, a TRACESYSGOOD-status could be its own unique kind of status, or a boolean entry could be added in WaitStatus::Stopped to mark it.
I've opened a pull request simply ignoring the bit for now (#549)
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