On 21/12/2015 11:13, Richard Weinberger wrote: > Am 21.12.2015 um 10:23 schrieb Mickaël Salaün: >>>>> Doesn't this break the support for changing syscall numbers using >>>>> PTRACE_SETREGS? >>>> >>>> The logic is unchanged except updating the UPT_SYSCALL_NR before >>>> syscall_trace_enter(). I did my last tests with the x86_32 subarchitecture >>>> and all tests (from selftest/seccomp), including PTRACE_SETREGS for >>>> syscall numbers tests, passed. However, 2 of this tests still fail for >>>> x86_64 (only). >>> >>> No, the logic is different. >>> syscall_trace_enter(regs) enters the ptrace() path and here registers can >>> be changed. >>> Hence "syscall = UPT_SYSCALL_NR(r);" will see the old syscall number. >>> UPT_SYSCALL_NR() returns the syscall number before the ptrace() path... >> >> The thing is, PTRACE_SETREGS give access to *orig_ax* in the >> user_regs_struct from arch/x86/include/asm/user_*.h and selftest/seccomp >> only update this (virtual) register, not the EAX/RAX. Am I missing something? > > Sorry, meant orig... > > Please see the attached program. It proves that your patch is breaking stuff. > The test is extracted from UML's selftests.
OK, I found the origin of this misunderstanding. On x86_32, PTRACE_SETREGS set regs->syscall when updating orig_eax, which is not the case on x86_64, hence the difference of behavior. I fixed this bug in the v2 series. The ptsc test and all the seccomp tests pass for 32 and 64 bits! Where can we find the UML selftests? Thanks, Mickaël
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