[PATCH v15 3/4] Introduce upoken function and expose it to Lua scripts
Victor Krapivensky
krapivenskiy.va at phystech.edu
Wed Sep 20 16:42:51 UTC 2017
* configure.ac: check for process_vm_writev's availability.
* defs.h: Add declaration for upoken.
* luajit.h (func_upoke): New wrapper function.
(init_luajit): Expose it as strace.C.upoke.
* luajit_lib.lua (write_obj): New function.
* strace.1 (LUA SCRIPTING): Describe new functions.
* ucopy.c (process_vm_writev_not_supported): New global flag.
(strace_process_vm_writev): New function.
(vm_write_mem): Likewise.
(partial_poke): Likewise.
(upoken_peekpoke): Likewise.
(upoken): Likewise.
---
configure.ac | 1 +
defs.h | 3 +
luajit.h | 8 +++
luajit_lib.lua | 4 ++
strace.1.in | 30 ++++++++++
ucopy.c | 177 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
6 files changed, 223 insertions(+)
diff --git a/configure.ac b/configure.ac
index 2c166403..f1b81aeb 100644
--- a/configure.ac
+++ b/configure.ac
@@ -282,6 +282,7 @@ AC_CHECK_FUNCS(m4_normalize([
prctl
preadv
process_vm_readv
+ process_vm_writev
pwritev
readahead
signalfd
diff --git a/defs.h b/defs.h
index ec14cd84..db034cfa 100644
--- a/defs.h
+++ b/defs.h
@@ -429,6 +429,9 @@ umovestr(struct tcb *, kernel_ulong_t addr, unsigned int len, char *laddr);
extern int upeek(int pid, unsigned long, kernel_ulong_t *);
extern int upoke(int pid, unsigned long, kernel_ulong_t);
+extern int upoken(struct tcb *, kernel_ulong_t addr, unsigned int len,
+ const void *laddr);
+
extern bool
print_array(struct tcb *,
kernel_ulong_t start_addr,
diff --git a/luajit.h b/luajit.h
index a707446f..f01505ec 100644
--- a/luajit.h
+++ b/luajit.h
@@ -95,6 +95,12 @@ func_umove_str(kernel_ulong_t addr, size_t len, char *laddr)
return current_tcp ? umovestr(current_tcp, addr, len, laddr) : -1;
}
+static int
+func_upoke(kernel_ulong_t addr, size_t len, const void *laddr)
+{
+ return current_tcp ? upoken(current_tcp, addr, len, laddr) : -1;
+}
+
static bool
func_path_match(const char **set, size_t nset)
{
@@ -267,6 +273,8 @@ init_luajit(const char *scriptfile)
kernel_ulong_t, size_t, void *);
EXPOSE_FUNC(int, func_umove_str, "umove_str",
kernel_ulong_t, size_t, char *);
+ EXPOSE_FUNC(int, func_upoke, "upoke",
+ kernel_ulong_t, size_t, const void *);
EXPOSE_FUNC(bool, func_path_match, "path_match",
const char **, size_t);
diff --git a/luajit_lib.lua b/luajit_lib.lua
index e3710627..018b829e 100644
--- a/luajit_lib.lua
+++ b/luajit_lib.lua
@@ -351,6 +351,10 @@ function strace.read_path(addr)
return strace.read_str(addr, strace.path_max - 1, strace.path_max)
end
+function strace.write_obj(addr, obj)
+ return call_ufunc_on(strace.C.upoke, addr, obj) == 0
+end
+
local function parse_when(when)
if type(when) == 'table' then
return unpack(when)
diff --git a/strace.1.in b/strace.1.in
index a48f3cf2..04739084 100644
--- a/strace.1.in
+++ b/strace.1.in
@@ -1002,6 +1002,20 @@ Note: there is no guarantee it won't overwrite some bytes in \fIladdr\fR after
terminating NUL (but, of course, it never writes past
.IR laddr[len-1] ).
.TP
+\fIstatus\fR = \fBstrace.C.upoke\fR(\fIaddr\fR, \fIlen\fR, \fIladdr\fR)
+C type:
+.B int (*)(kernel_ulong_t, size_t, const void *)
+.IP
+Copies ("pokes")
+.I len
+bytes of data from the local address
+.I laddr
+to the address
+.I addr
+of the current tracee process' address space.
+.IP
+Returns 0 on success and \-1 on failure.
+.TP
\fIstatus\fR = \fBstrace.C.path_match\fR(\fIset\fR, \fInset\fR)
C type:
.B bool (*)(const char **, size_t)
@@ -1435,6 +1449,22 @@ Returns a Lua string on success and
.B nil
and an error message string on failure.
.TP
+\fIstatus\fR = \fBstrace.write_obj\fR(\fIaddr\fR, \fIobj\fR)
+Writes a FFI cdata object
+.I obj
+to the address
+.I addr
+of the current tracee process's address space.
+.IP
+Returns
+.B true
+on success and
+.B false
+on failure.
+.IP
+See the note for
+.BR strace.read_obj .
+.TP
\fIstatus\fR = \fBstrace.hook\fR(\fIscname\fR, \fIwhen\fR, \fIcb\fR)
.TQ
\fIstatus\fR = \fBstrace.hook_class\fR(\fIclsname\fR, \fIwhen\fR, \fIcb\fR)
diff --git a/ucopy.c b/ucopy.c
index c3be4170..7f4e99ce 100644
--- a/ucopy.c
+++ b/ucopy.c
@@ -40,6 +40,7 @@
#include "ptrace.h"
static bool process_vm_readv_not_supported;
+static bool process_vm_writev_not_supported;
#ifndef HAVE_PROCESS_VM_READV
/*
@@ -61,6 +62,19 @@ static ssize_t strace_process_vm_readv(pid_t pid,
# define process_vm_readv strace_process_vm_readv
#endif /* !HAVE_PROCESS_VM_READV */
+#ifndef HAVE_PROCESS_VM_WRITEV
+/* The same goes for process_vm_writev(). */
+static ssize_t strace_process_vm_writev(pid_t pid, const struct iovec *lvec,
+ unsigned long liovcnt,
+ const struct iovec *rvec,
+ unsigned long riovcnt,
+ unsigned long flags)
+{
+ return syscall(__NR_process_vm_writev, (long)pid, lvec, liovcnt, rvec,
+ riovcnt, flags);
+}
+#endif /* !HAVE_PROCESS_VM_WRITEV */
+
static ssize_t
vm_read_mem(const pid_t pid, void *const laddr,
const kernel_ulong_t raddr, const size_t len)
@@ -90,6 +104,35 @@ vm_read_mem(const pid_t pid, void *const laddr,
return rc;
}
+static ssize_t
+vm_write_mem(const pid_t pid, const void *const laddr,
+ const kernel_ulong_t raddr, const size_t len)
+{
+ const unsigned long truncated_raddr = raddr;
+
+#if SIZEOF_LONG < SIZEOF_KERNEL_LONG_T
+ if (raddr != (kernel_ulong_t) truncated_raddr) {
+ errno = EIO;
+ return -1;
+ }
+#endif
+
+ const struct iovec local = {
+ .iov_base = (void *) laddr,
+ .iov_len = len
+ };
+ const struct iovec remote = {
+ .iov_base = (void *) truncated_raddr,
+ .iov_len = len
+ };
+
+ const ssize_t rc = process_vm_writev(pid, &local, 1, &remote, 1, 0);
+ if (rc < 0 && errno == ENOSYS)
+ process_vm_writev_not_supported = true;
+
+ return rc;
+}
+
static bool
tracee_addr_is_invalid(kernel_ulong_t addr)
{
@@ -324,3 +367,137 @@ umovestr(struct tcb *const tcp, kernel_ulong_t addr, unsigned int len,
return 0;
}
+
+static bool
+partial_poke(int pid, kernel_ulong_t addr, unsigned int len, const void *laddr,
+ unsigned int off)
+{
+ union {
+ long val;
+ char x[sizeof(long)];
+ } u;
+ errno = 0;
+ u.val = ptrace(PTRACE_PEEKDATA, pid, addr, 0);
+ switch (errno) {
+ case 0:
+ break;
+ case ESRCH: case EINVAL:
+ /* these could be seen if the process is gone */
+ return false;
+ case EFAULT: case EIO: case EPERM:
+ /* address space is inaccessible */
+ return false;
+ default:
+ /* all the rest is strange and should be reported */
+ perror_msg("partial_poke: PTRACE_PEEKDATA pid:%d @0x%" PRI_klx,
+ pid, addr);
+ return false;
+ }
+
+ memcpy(u.x + off, laddr, len);
+
+ /* now write it back */
+ if (ptrace(PTRACE_POKEDATA, pid, addr, u.val) < 0) {
+ switch (errno) {
+ case ESRCH: case EINVAL:
+ /* these could be seen if the process is gone */
+ return false;
+ case EFAULT: case EIO: case EPERM:
+ /* address space is inaccessible, or write is prohibited */
+ return false;
+ default:
+ /* all the rest is strange and should be reported */
+ perror_msg("partial_poke: PTRACE_POKEDATA pid:%d @0x%" PRI_klx,
+ pid, addr);
+ return false;
+ }
+ }
+
+ return true;
+}
+
+static int
+upoken_peekpoke(struct tcb *tcp, kernel_ulong_t addr, unsigned int len,
+ const void *const our_addr)
+{
+ const char *laddr = our_addr;
+ int pid = tcp->pid;
+
+ if (addr & (sizeof(long) - 1)) {
+ /* addr not a multiple of sizeof(long) */
+ unsigned n = addr & (sizeof(long) - 1); /* residue */
+ addr &= -sizeof(long); /* aligned address */
+ unsigned m = MIN(sizeof(long) - n, len);
+ if (!partial_poke(pid, addr, m, laddr, n))
+ return -1;
+ addr += sizeof(long);
+ laddr += m;
+ len -= m;
+ }
+
+ while (len >= sizeof(long)) {
+ if (ptrace(PTRACE_POKEDATA, pid, addr, * (const long *) laddr) < 0) {
+ switch (errno) {
+ case ESRCH: case EINVAL:
+ /* these could be seen if the process is gone */
+ return -1;
+ case EFAULT: case EIO: case EPERM:
+ /* address space is inaccessible, or write is prohibited */
+ return -1;
+ default:
+ /* all the rest is strange and should be reported */
+ perror_msg("upoken_peekpoke: PTRACE_POKEDATA pid:%d @0x%" PRI_klx,
+ pid, addr);
+ return -1;
+ }
+ }
+ addr += sizeof(long);
+ laddr += sizeof(long);
+ len -= sizeof(long);
+ }
+
+ if (len) {
+ if (!partial_poke(pid, addr, len, laddr, 0))
+ return -1;
+ }
+
+ return 0;
+}
+
+int
+upoken(struct tcb *tcp, kernel_ulong_t addr, unsigned int len,
+ const void *const our_addr)
+{
+ if (!len)
+ return 0;
+ if (tracee_addr_is_invalid(addr))
+ return -1;
+
+ if (process_vm_writev_not_supported)
+ return upoken_peekpoke(tcp, addr, len, our_addr);
+
+ int r = vm_write_mem(tcp->pid, our_addr, addr, len);
+ if ((unsigned int) r == len)
+ return 0;
+ if (r >= 0) {
+ error_msg("upoken: short write (%u < %u) @0x%" PRI_klx,
+ (unsigned int) r, len, addr);
+ return -1;
+ }
+ switch (errno) {
+ case ENOSYS:
+ case EPERM:
+ /* try PTRACE_PEEKDATA/PTRACE_POKEDATA */
+ return upoken_peekpoke(tcp, addr, len, our_addr);
+ case ESRCH:
+ /* the process is gone */
+ return -1;
+ case EFAULT: case EIO:
+ /* address space is inaccessible */
+ return -1;
+ default:
+ /* all the rest is strange and should be reported */
+ perror_msg("process_vm_writev");
+ return -1;
+ }
+}
--
2.11.0
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