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* selftests/powerpc: New PTRACE_SYSEMU testBreno Leitao2018-10-031-0/+228
This patch adds a new test for the new PTRACE_SYSEMU ptrace request. This test also relies on PTRACE_GETREGS and PTRACE_SETREGS requests to run properly, since the trace instruction (gettid() syscall) is being modified at run-time (by PTRACE_SETREGS) and re-executed three times. PTRACE_GETREGS is being used to check that the registers are still sane. This test basically creates a child process that executes syscalls and the parent process check if it is being traced appropriately. The parent process guarantees that the SYSCALLs are being traced, with PTRACE_SYSEMU, and ptrace stops the child application before a syscall is executed. The way the tests validates it, is by guaranteeing that the system calls arguments, as argv[0] (r3) which is the same register that will have the syscall return value on powerpc, are not being corrupted on PTRACE_SYSEMU with a return value, i.e, it continues to have the current arguments instead, meaning that the registers where not clobbered. This test is basically the same test for x86 located at tools/testing/selftests/x86/ptrace_syscall.c, limited to test PTRACE_SYSEMU request, and ported to PowerPC. Signed-off-by: Breno Leitao <leitao@debian.org> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>