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libproc: Add support for some proc_attach() flags.

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This change adds some handling for the equivalent of Solaris' PGRAB_*
flags. In particular, support for PGRAB_RDONLY is needed to avoid a
nasty deadlock: dtrace(1) may otherwise stop the master process for its
pseudo-terminal and end up blocking while writing to standard output.
This commit is contained in:
Mark Johnston 2016-12-06 04:22:38 +00:00
parent c156354ff8
commit b043b5dc6b
5 changed files with 39 additions and 25 deletions
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3
cddl/compat/opensolaris/include/libproc.h
View File

@ -38,9 +38,6 @@
#define PR_RLC 0x0001
#define PR_KLC 0x0002
#define PGRAB_RDONLY O_RDONLY
#define PGRAB_FORCE 0
#include_next <libproc.h>
#endif

3
cddl/lib/libdtrace/libproc_compat.h
View File

@ -34,6 +34,9 @@
* Functions sorted alphabetically.
*/
#define PR_LMID_EVERY 0
#define PGRAB_RDONLY PATTACH_RDONLY
#define PGRAB_FORCE PATTACH_FORCE
#define Psetrun(p, a1, a2) proc_continue((p))
#define Pxlookup_by_addr(p, a, n, s, sym, i) \
proc_addr2sym(p, a, n, s, sym)

5
lib/libproc/libproc.h
View File

@ -50,6 +50,11 @@ typedef void (*proc_child_func)(void *);
#define PS_DEAD 5
#define PS_LOST 6
/* Flags for proc_attach(). */
#define PATTACH_FORCE 0x01
#define PATTACH_RDONLY 0x02
#define PATTACH_NOSTOP 0x04
/* Reason values for proc_detach(). */
#define PRELEASE_HANG 1
#define PRELEASE_KILL 2

41
lib/libproc/proc_create.c
View File

@ -127,7 +127,7 @@ proc_attach(pid_t pid, int flags, struct proc_handle **pphdl)
struct proc_handle *phdl;
int error, status;
if (pid == 0 || pid == getpid())
if (pid == 0 || (pid == getpid() && (flags & PATTACH_RDONLY) == 0))
return (EINVAL);
if (elf_version(EV_CURRENT) == EV_NONE)
return (ENOENT);
@ -140,27 +140,32 @@ proc_attach(pid_t pid, int flags, struct proc_handle **pphdl)
if (error != 0)
goto out;
if (ptrace(PT_ATTACH, proc_getpid(phdl), 0, 0) != 0) {
error = errno;
DPRINTF("ERROR: cannot ptrace child process %d", pid);
goto out;
}
if ((flags & PATTACH_RDONLY) == 0) {
if (ptrace(PT_ATTACH, proc_getpid(phdl), 0, 0) != 0) {
error = errno;
DPRINTF("ERROR: cannot ptrace child process %d", pid);
goto out;
}
/* Wait for the child process to stop. */
if (waitpid(pid, &status, WUNTRACED) == -1) {
error = errno;
DPRINTF("ERROR: child process %d didn't stop as expected", pid);
goto out;
}
/* Wait for the child process to stop. */
if (waitpid(pid, &status, WUNTRACED) == -1) {
error = errno;
DPRINTF("ERROR: child process %d didn't stop as expected", pid);
goto out;
}
/* Check for an unexpected status. */
if (!WIFSTOPPED(status))
DPRINTFX("ERROR: child process %d status 0x%x", pid, status);
else
phdl->status = PS_STOP;
/* Check for an unexpected status. */
if (!WIFSTOPPED(status))
DPRINTFX("ERROR: child process %d status 0x%x", pid, status);
else
phdl->status = PS_STOP;
if ((flags & PATTACH_NOSTOP) != 0)
proc_continue(phdl);
}
out:
if (error && phdl != NULL) {
if (error != 0 && phdl != NULL) {
proc_free(phdl);
phdl = NULL;
}

12
lib/libproc/proc_util.c
View File

@ -87,21 +87,25 @@ proc_detach(struct proc_handle *phdl, int reason)
if (phdl == NULL)
return (EINVAL);
if (reason == PRELEASE_HANG)
return (EINVAL);
if (reason == PRELEASE_KILL) {
kill(proc_getpid(phdl), SIGKILL);
return (0);
goto free;
}
if ((phdl->flags & PATTACH_RDONLY) != 0)
goto free;
pid = proc_getpid(phdl);
if (ptrace(PT_DETACH, pid, 0, 0) != 0 && errno == ESRCH)
return (0);
goto free;
if (errno == EBUSY) {
kill(pid, SIGSTOP);
waitpid(pid, &status, WUNTRACED);
ptrace(PT_DETACH, pid, 0, 0);
kill(pid, SIGCONT);
return (0);
}
free:
proc_free(phdl);
return (0);
}