PTRACE_O_TRACEEXIT, PTRACE_O_TRACEEXEC

[kimjs29]

I am testing Swift on WSL.

Swift REPL uses LLVM's LLDB which calls ptrace(PTRACE_SETOPTIONS,...).

ptrace on WSL accepts PTRACE_O_TRACECLONE, but not PTRACE_O_TRACEEXIT nor PTRACE_O_TRACEEXEC.

The test code is as follows:

#include <unistd.h>
#include <stdlib.h>
#include <sys/ptrace.h>

int main()
{
    long data = PTRACE_O_TRACECLONE|PTRACE_O_TRACEEXEC|PTRACE_O_TRACEEXIT;

    pid_t child = fork();
    if (child == 0) {
        ptrace(PTRACE_TRACEME, 0, NULL, NULL);
        execl("/bin/echo", "echo", NULL);
    }
    wait(NULL);
    if (ptrace(PTRACE_SETOPTIONS, child, NULL, (void*)data) == -1)
        perror("ptrace error");
}

On Ubuntu LTS 14.04, the test code does not generate errors.
On WSL Build 14367, the test code produces an "Invalid argument" error with PTRACE_O_TRACEEXEC or PTRACE_O_TRACEEXIT suboptions.

[kimjs29]

I met another similar case with PTRACE_GETREGSET option.

#include <unistd.h>
#include <stdlib.h>
#include <sys/ptrace.h>
#include <linux/uio.h>

int main()
{
    long regs[27];
    struct iovec iov = { regs, sizeof(regs) };
    pid_t child = fork();
    if (child == 0) {
        ptrace(PTRACE_TRACEME, 0, NULL, NULL);
        execl("/bin/echo", "echo", NULL);
    }
    wait(NULL);
    if (ptrace(PTRACE_GETREGSET, child, 1, &iov) == -1)
        perror("ptrace error");
}

[cbuschardt]

I met yet another case with PTRACE_TRACEME reporting EPERM on Creator's Update. This blocks lldb from functioning.

[sunilmut]

@SvenGroot recently added support for PTRACE_O_TRACEEXIT and PTRACE_GETREGSET. Support for PTRACE_O_TRACEEXEC exists in Creators Update (build 15063). So, I am going to mark this as "fixinbound".

[therealkenc]

💯 Sven.

[therealkenc]

PTRACE_SYSEMU for the win, BTW. It is being tracked in awkwardly titled #1692.

[sunilmut]

Support for PTRACE_O_TRACEEXIT, TRACE_GETFPREGS and PTRACE_GETREGSET has come in the Insider build 16251