Add writev syscall

Author: Matthieu Morel

Makefile

@@ -34,6 +34,7 @@ EXAMPLE_PROGRAMS += $(EXAMPLE_DST)/madvise
 EXAMPLE_PROGRAMS += $(EXAMPLE_DST)/chdir
 EXAMPLE_PROGRAMS += $(EXAMPLE_DST)/mkdir
 EXAMPLE_PROGRAMS += $(EXAMPLE_DST)/rmdir
+EXAMPLE_PROGRAMS += $(EXAMPLE_DST)/writev
 
 .PHONY: example-programs
 example-programs: $(EXAMPLE_PROGRAMS)

example-programs/writev.c

@@ -0,0 +1,29 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/uio.h>
+#include <unistd.h>
+
+int main(int argc, char *const argv[])
+{
+  // example taken from man for writev(2):
+  char *str0 = "hello ";
+  char *str1 = "world\n";
+  struct iovec iov[2];
+  ssize_t nwritten;
+
+  iov[0].iov_base = str0;
+  iov[0].iov_len = strlen(str0);
+  iov[1].iov_base = str1;
+  iov[1].iov_len = strlen(str1);
+
+  nwritten = writev(STDOUT_FILENO, iov, 2);
+  printf("%ld\n", nwritten);
+  printf("%p\n", iov[0].iov_base);
+  printf("%p\n", iov[1].iov_base);
+
+  if (nwritten == -1) {
+    perror("writev");
+  }
+  return nwritten;
+}

src/System/Hatrace.hs

@@ -40,6 +40,8 @@ module System.Hatrace
   , SyscallExitDetails_faccessat(..)
   , SyscallEnterDetails_write(..)
   , SyscallExitDetails_write(..)
+  , SyscallEnterDetails_writev(..)
+  , SyscallExitDetails_writev(..)
   , SyscallEnterDetails_read(..)
   , SyscallExitDetails_read(..)
   , SyscallEnterDetails_close(..)
@@ -193,7 +195,7 @@ import           Foreign.Marshal.Alloc (alloca)
 import           Foreign.Marshal.Array (withArray)
 import qualified Foreign.Marshal.Array (peekArray)
 import           Foreign.Marshal.Utils (withMany)
-import           Foreign.Ptr (castPtr, Ptr, nullPtr, wordPtrToPtr)
+import           Foreign.Ptr (castPtr, Ptr, nullPtr, wordPtrToPtr, intPtrToPtr)
 import           Foreign.Storable (Storable, peekByteOff, sizeOf)
 import           GHC.Stack (HasCallStack, callStack, getCallStack, prettySrcLoc)
 import           System.Directory (canonicalizePath, doesFileExist, findExecutable)
@@ -1813,6 +1815,26 @@ instance SyscallExitFormatting SyscallExitDetails_rmdir where
   syscallExitToFormatted SyscallExitDetails_rmdir{ enterDetail } =
     (syscallEnterToFormatted enterDetail, NoReturn)
 
+data SyscallEnterDetails_writev = SyscallEnterDetails_writev
+  { fd :: CInt
+  , count :: CSize
+  -- Peeked details
+  , iovs :: [IovecStruct]
+  , bufContents :: [ByteString]
+  } deriving (Eq, Ord, Show)
+
+instance SyscallEnterFormatting SyscallEnterDetails_writev where
+  syscallEnterToFormatted SyscallEnterDetails_writev{ fd, iovs, bufContents, count } =
+    FormattedSyscall "writev" [formatArg fd, argPlaceholder "*iovec", formatArg iovs, formatArg bufContents, formatArg count]
+
+data SyscallExitDetails_writev = SyscallExitDetails_writev
+  { enterDetail :: SyscallEnterDetails_writev
+  , writtenCount :: CSize
+  } deriving (Eq, Ord, Show)
+
+instance SyscallExitFormatting SyscallExitDetails_writev where
+  syscallExitToFormatted SyscallExitDetails_writev{ enterDetail, writtenCount  } =
+    (syscallEnterToFormatted enterDetail, formatReturn writtenCount)
 
 data DetailedSyscallEnter
   = DetailedSyscallEnter_open SyscallEnterDetails_open
@@ -1823,6 +1845,7 @@ data DetailedSyscallEnter
   | DetailedSyscallEnter_access SyscallEnterDetails_access
   | DetailedSyscallEnter_faccessat SyscallEnterDetails_faccessat
   | DetailedSyscallEnter_write SyscallEnterDetails_write
+  | DetailedSyscallEnter_writev SyscallEnterDetails_writev
   | DetailedSyscallEnter_read SyscallEnterDetails_read
   | DetailedSyscallEnter_execve SyscallEnterDetails_execve
   | DetailedSyscallEnter_close SyscallEnterDetails_close
@@ -1885,6 +1908,7 @@ data DetailedSyscallExit
   | DetailedSyscallExit_access SyscallExitDetails_access
   | DetailedSyscallExit_faccessat SyscallExitDetails_faccessat
   | DetailedSyscallExit_write SyscallExitDetails_write
+  | DetailedSyscallExit_writev SyscallExitDetails_writev
   | DetailedSyscallExit_read SyscallExitDetails_read
   | DetailedSyscallExit_execve SyscallExitDetails_execve
   | DetailedSyscallExit_close SyscallExitDetails_close
@@ -2043,6 +2067,17 @@ getSyscallEnterDetails syscall syscallArgs pid = let proc = TracedProcess pid in
       , count = fromIntegral count
       , bufContents
       }
+  Syscall_writev -> do
+    let SyscallArgs{ arg0 = fd, arg1 = iovPtr, arg2 = iovcnt } = syscallArgs
+        n = fromIntegral $ min iovcnt $ fromIntegral (maxBound :: Int)
+    iovs <- peekArray (TracedProcess pid) n (word64ToPtr iovPtr :: Ptr IovecStruct)
+    contents <- mapM (\IovecStruct{ iov_base = base, iov_len = len } -> peekBytes proc (intPtrToPtr $ fromIntegral base) (fromIntegral len)) iovs
+    pure $ DetailedSyscallEnter_writev $ SyscallEnterDetails_writev
+      { fd = fromIntegral fd
+      , iovs = iovs
+      , count = fromIntegral iovcnt
+      , bufContents = contents
+      }
   Syscall_read -> do
     let SyscallArgs{ arg0 = fd, arg1 = bufAddr, arg2 = count } = syscallArgs
     let bufPtr = word64ToPtr bufAddr
@@ -2577,6 +2612,11 @@ getSyscallExitDetails detailedSyscallEnter result pid =
         pure $ DetailedSyscallExit_write $
           SyscallExitDetails_write{ enterDetail, writtenCount = fromIntegral result }
 
+    DetailedSyscallEnter_writev
+      enterDetail@SyscallEnterDetails_writev{} -> do
+        pure $ DetailedSyscallExit_writev $
+          SyscallExitDetails_writev{ enterDetail, writtenCount = fromIntegral result }
+
     DetailedSyscallEnter_access
       enterDetail@SyscallEnterDetails_access{} -> do
         pure $ DetailedSyscallExit_access $
@@ -2880,7 +2920,9 @@ peekArray pid size ptr
       let (tmpPtr, _, _) = BSI.toForeignPtr arrayBytes
       withForeignPtr tmpPtr (\p -> Foreign.Marshal.Array.peekArray size (castPtr p))
       where
-        elemSize = sizeOf ptr
+        elemSize = sizeOf (valueOf ptr)
+        valueOf :: Ptr a -> a
+        valueOf = undefined
 
 readPipeFds :: CPid -> Ptr CInt -> IO (CInt, CInt)
 readPipeFds pid pipefd = do
@@ -3277,6 +3319,8 @@ formatSyscallEnter enterDetails =
 
         DetailedSyscallEnter_write details -> syscallEnterToFormatted details
 
+        DetailedSyscallEnter_writev details -> syscallEnterToFormatted details
+
         DetailedSyscallEnter_read details -> syscallEnterToFormatted details
 
         DetailedSyscallEnter_close details -> syscallEnterToFormatted details
@@ -3430,6 +3474,8 @@ formatDetailedSyscallExit detailedExit handleUnimplemented =
 
     DetailedSyscallExit_write details -> formatDetails details
 
+    DetailedSyscallExit_writev details -> formatDetails details
+
     DetailedSyscallExit_read details -> formatDetails details
 
     DetailedSyscallExit_close details -> formatDetails details

src/System/Hatrace/Format.hs

@@ -26,7 +26,7 @@ import qualified Data.Text.Encoding.Error as TE
 import           Data.Time.Clock.POSIX (posixSecondsToUTCTime)
 import           Data.Void (Void)
 import           Data.Word (Word64)
-import           Foreign.C.Types (CShort(..), CUShort(..), CInt(..), CUInt(..), CLong(..), CULong(..), CSize(..), CTime(..))
+import           Foreign.C.Types (CShort(..), CUShort(..), CInt(..), CUInt(..), CLong(..), CULong(..), CSize(..), CTime(..), CUIntPtr)
 import           Foreign.Ptr (Ptr, nullPtr, ptrToIntPtr)
 import           System.Posix.Types (CMode(..), CPid(..), CUid(..), CGid(..))
 
@@ -98,6 +98,9 @@ instance ArgFormatting CTime where
 instance ArgFormatting (Ptr Void) where
   formatArg = formatPtrArg "void"
 
+instance ArgFormatting CUIntPtr where
+  formatArg = IntegerArg . fromIntegral
+
 formatPtrArg :: String -> Ptr a -> FormattedArg
 formatPtrArg type_ p
   | p == nullPtr = FixedStringArg "NULL"

src/System/Hatrace/Types.hsc

@@ -59,14 +59,15 @@ module System.Hatrace.Types
   , RLimitType(..)
   , ResourceType(..)
   , RLimitStruct(..)
+  , IovecStruct(..)
   ) where
 
 import           Control.Monad (filterM)
 import           Data.Bits
 import           Data.List (intercalate)
 import           Data.Map (lookup)
 import           Data.Maybe (catMaybes)
-import           Foreign.C.Types (CShort(..), CUShort(..), CInt(..), CUInt(..), CLong(..), CULong(..))
+import           Foreign.C.Types (CShort(..), CUShort(..), CInt(..), CUInt(..), CLong(..), CULong(..), CUIntPtr(..))
 import           Foreign.Marshal (copyBytes)
 import           Foreign.Marshal.Array (peekArray, pokeArray)
 import           Foreign.Ptr (plusPtr, castPtr)
@@ -1729,3 +1730,23 @@ $(deriveEnumTypeClasses ''RLimitType
   , ('ResourceRTPrio, (#const RLIMIT_RTPRIO), "RLIMIT_RTPRIO")
   , ('ResourceRTTime, (#const RLIMIT_RTTIME), "RLIMIT_RTTIME")
   ])
+
+data IovecStruct = IovecStruct
+  { iov_base :: CUIntPtr  -- ^ Starting address
+  , iov_len :: CULong -- ^ Number of bytes to transfer
+  }  deriving (Eq, Ord, Show)
+
+instance ArgFormatting IovecStruct where
+  formatArg  (IovecStruct {..}) =
+    StructArg [("iov_base", formatArg iov_base), ("iov_len", formatArg iov_len)]
+
+instance Storable IovecStruct where
+  sizeOf _ = #{size struct iovec}
+  alignment _ = #{alignment struct iovec}
+  peek p = do
+    iov_base <- #{peek struct iovec, iov_base} p
+    iov_len <- #{peek struct iovec, iov_len} p
+    return IovecStruct{..}
+  poke p IovecStruct{..} = do
+    #{poke struct iovec, iov_base} p iov_base
+    #{poke struct iovec, iov_len} p iov_len

test/HatraceSpec.hs

@@ -12,6 +12,7 @@ import           Control.Monad.IO.Class (liftIO)
 import           Control.Monad.IO.Unlift (MonadUnliftIO)
 import           Data.ByteString (ByteString)
 import qualified Data.ByteString as BS
+import qualified Data.ByteString.Char8 as B8
 import           Data.Conduit
 import qualified Data.Conduit.Combinators as CC
 import qualified Data.Conduit.List as CL
@@ -116,6 +117,41 @@ spec = before_ assertNoChildren $ do
         exitCode `shouldSatisfy` \x ->
           x `elem` [ExitFailure 11, ExitFailure (128+11)]
 
+  describe "writev" $ do
+    it "cant peek correct values of struct iov and number of byte written" $ do
+      callProcess "make" ["--quiet", "example-programs-build/writev"]
+
+      argv <- procToArgv "example-programs-build/writev" []
+      (exitCode, events) <-
+          sourceTraceForkExecvFullPathWithSink argv $
+            syscallExitDetailsOnlyConduit .| CL.consume
+      exitCode `shouldBe` ExitSuccess
+
+      let [(stdinReads, (iov1:iov2:_), writtenCount_)] =
+              [ (bufContents, iovs, writtenCount)
+              | (_pid
+                , Right (
+                    DetailedSyscallExit_writev
+                      SyscallExitDetails_writev
+                        { enterDetail = SyscallEnterDetails_writev{ fd = 1, bufContents, iovs }
+                        , writtenCount
+                        }
+                    )
+                ) <- events
+              ]
+      -- The example program prints out some expected values, we retrieve them relying on the write syscall
+      let (expectedCount:expectedVect1:expectedVect2:_) = [ bufContents |
+                 (_pid, Right (
+                          DetailedSyscallExit_write
+                            SyscallExitDetails_write{ enterDetail = SyscallEnterDetails_write { bufContents } }
+                          )
+                 ) <- events
+                 ]
+      stdinReads `shouldBe` ["hello ", "world\n"]
+      fromIntegral writtenCount_ `shouldBe` (read (B8.unpack expectedCount) :: Int)
+      fromIntegral (iov_base iov1) `shouldBe` (read (B8.unpack expectedVect1) :: Int)
+      fromIntegral (iov_base iov2) `shouldBe` (read (B8.unpack expectedVect2) :: Int)
+
   describe "sourceRawTraceForkExecvFullPathWithSink" $ do
 
     it "lets the process finish if the sink exits early" $ do