Hi Fotios, On 2/27/23 20:19, Φώτης Βαλασιάδης wrote: > Hi Alex! > > Is that good enough? > Yep. Patch applied. Thanks! Alex On 2/27/23 20:17, Fotios Valasiadis wrote: > Document the role of PTRACE_O_TRACESYSGOOD option in connection with > PTRACE_GET_SYSCALL_INFO. > > Came upon this after writing a test program using PTRACE_GET_SYSCALL_INFO. > After failing to find what's wrong I posted a StackOverflow question > which you can find right here: > <https://stackoverflow.com/questions/72410182/ptrace-get-syscall-info-always-returns-info-op-as-ptrace-syscall-info-none> > > Nate Eldredge found out what happens by looking into the kernel's source > code, here is a link to the relevant part > <https://github.com/torvalds/linux/blob/8291eaafed36f575f23951f3ce18407f480e9ecf/kernel/ptrace.c#L1018> > > In the code it can be seen that in case of system call entry or > exit stops, the union is filled if and only if the signal matches > "SIGTRAP | 0x80", a signal which is only sent if the PTRACE_O_TRACESYSGOOD > option is set. You can read about that in the PTRACE_O_TRACESYSGOOD > section of ptrace(2)'s manual. > > Complements: fc91449cb "ptrace.2: Document PTRACE_GET_SYSCALL_INFO" > Cowritten-by: Dmitry V. Levin <ldv@xxxxxxxxx> > Signed-off-by: Dmitry V. Levin <ldv@xxxxxxxxx> > Signed-off-by: Fotios Valasiadis <fvalasiad@xxxxxxxxx> > Acked-by: Nate Eldredge <nate@xxxxxxxxxxxxxxxxxxxx> > Cc: Elvira Khabirova <lineprinter0@xxxxxxxxx> > Signed-off-by: Alejandro Colomar <alx@xxxxxxxxxx> > --- > man2/ptrace.2 | 9 +++++++++ > 1 file changed, 9 insertions(+) > > diff --git a/man2/ptrace.2 b/man2/ptrace.2 > index 55d9fd36d..9737b3825 100644 > --- a/man2/ptrace.2 > +++ b/man2/ptrace.2 > @@ -1111,6 +1111,15 @@ stop. > .B PTRACE_SYSCALL_INFO_NONE > No component of the union contains relevant information. > .RE > +.IP > +In case of system call entry or exit stops, > +the data returned by > +.B PTRACE_GET_SYSCALL_INFO > +is limited to type > +.B PTRACE_SYSCALL_INFO_NONE > +unless > +.B PTRACE_O_TRACESYSGOOD > +option is set before the corresponding system call stop has occurred. > .\" > .SS Death under ptrace > When a (possibly multithreaded) process receives a killing signal -- <http://www.alejandro-colomar.es/> GPG key fingerprint: A9348594CE31283A826FBDD8D57633D441E25BB5
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