Re: git: 6e66030c4c05 - main - linux: implement PTRACE_EVENT_EXEC
- In reply to: Edward Tomasz Napierala : "git: 6e66030c4c05 - main - linux: implement PTRACE_EVENT_EXEC"
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Date: Sat, 23 Oct 2021 22:12:34 UTC
On Sat, Oct 23, 2021 at 06:46:34PM +0000, Edward Tomasz Napierala wrote: > The branch main has been updated by trasz: > > URL: https://cgit.FreeBSD.org/src/commit/?id=6e66030c4c05331f9b0adf87c31f2f233dd3ae1f > > commit 6e66030c4c05331f9b0adf87c31f2f233dd3ae1f > Author: Edward Tomasz Napierala <trasz@FreeBSD.org> > AuthorDate: 2021-10-23 18:13:14 +0000 > Commit: Edward Tomasz Napierala <trasz@FreeBSD.org> > CommitDate: 2021-10-23 18:46:26 +0000 > > linux: implement PTRACE_EVENT_EXEC > > This fixes strace(1) from Ubuntu Focal. > > Reviewed By: jhb > Sponsored By: EPSRC > Differential Revision: https://reviews.freebsd.org/D32367 > --- > sys/amd64/linux/linux_ptrace.c | 9 +++++++-- > sys/kern/subr_syscall.c | 12 ++++++++++++ > 2 files changed, 19 insertions(+), 2 deletions(-) > > diff --git a/sys/amd64/linux/linux_ptrace.c b/sys/amd64/linux/linux_ptrace.c > index 37f136856ef0..d7dffc92dd11 100644 > --- a/sys/amd64/linux/linux_ptrace.c > +++ b/sys/amd64/linux/linux_ptrace.c > @@ -71,6 +71,7 @@ __FBSDID("$FreeBSD$"); > #define LINUX_PTRACE_SEIZE 0x4206 > #define LINUX_PTRACE_GET_SYSCALL_INFO 0x420e > > +#define LINUX_PTRACE_EVENT_EXEC 4 > #define LINUX_PTRACE_EVENT_EXIT 6 > > #define LINUX_PTRACE_O_TRACESYSGOOD 1 > @@ -151,8 +152,12 @@ linux_ptrace_status(struct thread *td, pid_t pid, int status) > lwpinfo.pl_flags & PL_FLAG_SCE) > status |= (LINUX_SIGTRAP | 0x80) << 8; > if ((pem->ptrace_flags & LINUX_PTRACE_O_TRACESYSGOOD) && > - lwpinfo.pl_flags & PL_FLAG_SCX) > - status |= (LINUX_SIGTRAP | 0x80) << 8; > + lwpinfo.pl_flags & PL_FLAG_SCX) { > + if (lwpinfo.pl_flags & PL_FLAG_EXEC) > + status |= (LINUX_SIGTRAP | LINUX_PTRACE_EVENT_EXEC << 8) << 8; > + else > + status |= (LINUX_SIGTRAP | 0x80) << 8; > + } > if ((pem->ptrace_flags & LINUX_PTRACE_O_TRACEEXIT) && > lwpinfo.pl_flags & PL_FLAG_EXITED) > status |= (LINUX_SIGTRAP | LINUX_PTRACE_EVENT_EXIT << 8) << 8; > diff --git a/sys/kern/subr_syscall.c b/sys/kern/subr_syscall.c > index ada2053bc87c..fab67a68b0a3 100644 > --- a/sys/kern/subr_syscall.c > +++ b/sys/kern/subr_syscall.c > @@ -254,6 +254,18 @@ syscallret(struct thread *td) > if (__predict_false(traced || > (td->td_dbgflags & (TDB_EXEC | TDB_FORK)) != 0)) { > PROC_LOCK(p); > + /* > + * Linux debuggers expect an additional stop for exec, > + * between the usual syscall entry and exit. Raise > + * the exec event now and then clear TDB_EXEC so that > + * the next stop is reported as a syscall exit by > + * linux_ptrace_status(). > + */ > + if ((td->td_dbgflags & TDB_EXEC) != 0 && > + SV_PROC_ABI(td->td_proc) == SV_ABI_LINUX) { > + ptracestop(td, SIGTRAP, NULL); > + td->td_dbgflags &= ~TDB_EXEC; > + } > /* > * If tracing the execed process, trap to the debugger > * so that breakpoints can be set before the program You committed before we finished the discussion. In fact I do not think it is right. Now it generates spurious stop for FreeBSD native debugger, and probably de-synchronize SCX/SCE pairing for it as well. In other words, you need to generate this stop based on ABI of the debugger, not debuggeeeeee.