| Message ID | 20190913145100.303433-6-anthony.perard@citrix.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | OvmfPkg/XenBusDxe: Fix ExitBootServices handler to avoid allocation | expand |
On 09/13/19 16:50, Anthony PERARD wrote: > When doing an action with a path and subpath in the xenstore, > XenStoreJoin is called to generate "$path/$subpath". But this function > do an allocation of memory which isn't necessary. Instead we will > construct the path with WRITE_REQUEST and data used to generate the > path will be copied directly to the xenstore shared ring. > > Also change WRITE_REQUEST.Len type, it only contain sizes and doesn't > need to be exactly 32bits. > > Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=2190 > Signed-off-by: Anthony PERARD <anthony.perard@citrix.com> > --- > OvmfPkg/XenBusDxe/XenStore.c | 78 +++++++++++++++++++++--------------- > 1 file changed, 46 insertions(+), 32 deletions(-) > > diff --git a/OvmfPkg/XenBusDxe/XenStore.c b/OvmfPkg/XenBusDxe/XenStore.c > index 7b71dc156d..ca7be12d68 100644 > --- a/OvmfPkg/XenBusDxe/XenStore.c > +++ b/OvmfPkg/XenBusDxe/XenStore.c > @@ -53,7 +53,7 @@ > > typedef struct { > CONST VOID *Data; > - UINT32 Len; > + UINTN Len; > } WRITE_REQUEST; > > /* Register callback to watch subtree (node) in the XenStore. */ > @@ -260,6 +260,35 @@ XenStoreFindWatch ( > return NULL; > } > > +/** > + Fill the first three slots of a WRITE_REQUEST array. > + > + When those three slots are concatenated to generate a string, the resulting > + string will be "$Path\0" or "$Path/$SubPath\0" if SubPath is provided. > +**/ > +STATIC > +VOID > +XenStorePrepareWriteRequest ( > + IN OUT WRITE_REQUEST *WriteRequest, > + IN CONST CHAR8 *Path, > + IN CONST CHAR8 *SubPath OPTIONAL > + ) > +{ > + SetMem(WriteRequest, 3 * sizeof (WRITE_REQUEST), 0); (1) ZeroMem() is more idiomatic. Also, please insert a space before the opening paren. > + WriteRequest[0].Data = Path; > + WriteRequest[0].Len = AsciiStrSize (Path); > + if (SubPath != NULL && SubPath[0] != '\0') { > + // > + // Remove the \0 from the first part of the request. > + // > + WriteRequest[0].Len--; > + WriteRequest[1].Data = "/"; > + WriteRequest[1].Len = 1; > + WriteRequest[2].Data = SubPath; > + WriteRequest[2].Len = AsciiStrSize (SubPath); > + } > +} > + So this suggests that only the last element in the array should point to a NUL-terminated string. Strings pointed-to by earlier elements in the array should not be NUL-terminated. Is that correct? > // > // Public Utility Functions > // API comments for these methods can be found in XenStore.h > @@ -842,6 +871,7 @@ XenStoreTalkv ( > @param Transaction The transaction to use for this request. > @param RequestType The type of message to send. > @param Body The body of the request. > + @param SubPath If !NULL and not "", "/$SubPath" is append to Body. > @param LenPtr The returned length of the reply. > @param Result The returned body of the reply. > > @@ -854,16 +884,16 @@ XenStoreSingle ( > IN CONST XENSTORE_TRANSACTION *Transaction, > IN enum xsd_sockmsg_type RequestType, > IN CONST CHAR8 *Body, > + IN CONST CHAR8 *SubPath OPTIONAL, > OUT UINT32 *LenPtr OPTIONAL, > OUT VOID **Result OPTIONAL > ) > { > - WRITE_REQUEST WriteRequest; > + WRITE_REQUEST WriteRequest[3]; > > - WriteRequest.Data = (VOID *) Body; > - WriteRequest.Len = (UINT32)AsciiStrSize (Body); > + XenStorePrepareWriteRequest (WriteRequest, Body, SubPath); > > - return XenStoreTalkv (Transaction, RequestType, &WriteRequest, 1, > + return XenStoreTalkv (Transaction, RequestType, WriteRequest, 3, > LenPtr, Result); (2) It would be slightly more idiomatic to pass ARRAY_SIZE (WriteRequest) in place of the naked 3. > } > > @@ -1113,15 +1143,12 @@ XenStoreListDirectory ( > OUT CONST CHAR8 ***DirectoryListPtr > ) > { > - CHAR8 *Path; > CHAR8 *TempStr; > UINT32 Len = 0; > XENSTORE_STATUS Status; > > - Path = XenStoreJoin (DirectoryPath, Node); > - Status = XenStoreSingle (Transaction, XS_DIRECTORY, Path, &Len, > + Status = XenStoreSingle (Transaction, XS_DIRECTORY, DirectoryPath, Node, &Len, > (VOID **) &TempStr); > - FreePool (Path); > if (Status != XENSTORE_STATUS_SUCCESS) { > return Status; > } > @@ -1160,13 +1187,11 @@ XenStoreRead ( > OUT VOID **Result > ) > { > - CHAR8 *Path; > VOID *Value; > XENSTORE_STATUS Status; > > - Path = XenStoreJoin (DirectoryPath, Node); > - Status = XenStoreSingle (Transaction, XS_READ, Path, LenPtr, &Value); > - FreePool (Path); > + Status = XenStoreSingle (Transaction, XS_READ, DirectoryPath, Node, > + LenPtr, &Value); (3) Indentation. > if (Status != XENSTORE_STATUS_SUCCESS) { > return Status; > } > @@ -1183,21 +1208,13 @@ XenStoreWrite ( > IN CONST CHAR8 *Str > ) > { > - CHAR8 *Path; > - WRITE_REQUEST WriteRequest[2]; > - XENSTORE_STATUS Status; > + WRITE_REQUEST WriteRequest[4]; > > - Path = XenStoreJoin (DirectoryPath, Node); > + XenStorePrepareWriteRequest (WriteRequest, DirectoryPath, Node); > + WriteRequest[3].Data = Str; > + WriteRequest[3].Len = AsciiStrLen (Str); Now we have two strings, pointed-to by elements in the array, that are NUL-terminated: the element at offset 2, and the one at offset 3. Is that intentional? Is that part of the message framing? Hmmm... From the original code: > > - WriteRequest[0].Data = (VOID *) Path; > - WriteRequest[0].Len = (UINT32)AsciiStrSize (Path); > - WriteRequest[1].Data = (VOID *) Str; > - WriteRequest[1].Len = (UINT32)AsciiStrLen (Str); That seems to be the case. I guess the first run (offsets 0 through 2) is parsed until the first NUL is encountered, for "path", then the second run (3 and onwards) is parsed until the second NUL for "data". Sounds plausible; OK. > - > - Status = XenStoreTalkv (Transaction, XS_WRITE, WriteRequest, 2, NULL, NULL); > - FreePool (Path); > - > - return Status; > + return XenStoreTalkv (Transaction, XS_WRITE, WriteRequest, 4, NULL, NULL); (4) Please use ARRAY_SIZE(); it's more robust. > } > > XENSTORE_STATUS > @@ -1207,12 +1224,9 @@ XenStoreRemove ( > IN CONST CHAR8 *Node > ) > { > - CHAR8 *Path; > XENSTORE_STATUS Status; > > - Path = XenStoreJoin (DirectoryPath, Node); > - Status = XenStoreSingle (Transaction, XS_RM, Path, NULL, NULL); > - FreePool (Path); > + Status = XenStoreSingle (Transaction, XS_RM, DirectoryPath, Node, NULL, NULL); > > return Status; > } > @@ -1226,7 +1240,7 @@ XenStoreTransactionStart ( > XENSTORE_STATUS Status; > > Status = XenStoreSingle (XST_NIL, XS_TRANSACTION_START, "", NULL, > - (VOID **) &IdStr); > + NULL, (VOID **) &IdStr); (5) Indentation. > if (Status == XENSTORE_STATUS_SUCCESS) { > Transaction->Id = (UINT32)AsciiStrDecimalToUintn (IdStr); > FreePool (IdStr); > @@ -1246,7 +1260,7 @@ XenStoreTransactionEnd ( > AbortStr[0] = Abort ? 'F' : 'T'; > AbortStr[1] = '\0'; > > - return XenStoreSingle (Transaction, XS_TRANSACTION_END, AbortStr, NULL, NULL); > + return XenStoreSingle (Transaction, XS_TRANSACTION_END, AbortStr, NULL, NULL, NULL); > } > > XENSTORE_STATUS > With the above addressed: Reviewed-by: Laszlo Ersek <lersek@redhat.com>
On 09/16/19 17:39, Laszlo Ersek wrote: > On 09/13/19 16:50, Anthony PERARD wrote: >> When doing an action with a path and subpath in the xenstore, >> XenStoreJoin is called to generate "$path/$subpath". But this function >> do an allocation of memory which isn't necessary. Instead we will >> construct the path with WRITE_REQUEST and data used to generate the >> path will be copied directly to the xenstore shared ring. >> >> Also change WRITE_REQUEST.Len type, it only contain sizes and doesn't >> need to be exactly 32bits. >> >> Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=2190 >> Signed-off-by: Anthony PERARD <anthony.perard@citrix.com> >> --- >> OvmfPkg/XenBusDxe/XenStore.c | 78 +++++++++++++++++++++--------------- >> 1 file changed, 46 insertions(+), 32 deletions(-) >> >> diff --git a/OvmfPkg/XenBusDxe/XenStore.c b/OvmfPkg/XenBusDxe/XenStore.c >> index 7b71dc156d..ca7be12d68 100644 >> --- a/OvmfPkg/XenBusDxe/XenStore.c >> +++ b/OvmfPkg/XenBusDxe/XenStore.c >> @@ -53,7 +53,7 @@ >> >> typedef struct { >> CONST VOID *Data; >> - UINT32 Len; >> + UINTN Len; >> } WRITE_REQUEST; >> >> /* Register callback to watch subtree (node) in the XenStore. */ >> @@ -260,6 +260,35 @@ XenStoreFindWatch ( >> return NULL; >> } >> >> +/** >> + Fill the first three slots of a WRITE_REQUEST array. >> + >> + When those three slots are concatenated to generate a string, the resulting >> + string will be "$Path\0" or "$Path/$SubPath\0" if SubPath is provided. >> +**/ >> +STATIC >> +VOID >> +XenStorePrepareWriteRequest ( >> + IN OUT WRITE_REQUEST *WriteRequest, (6) I think this could be just OUT -- we start by zeroing it out. >> + IN CONST CHAR8 *Path, >> + IN CONST CHAR8 *SubPath OPTIONAL >> + ) >> +{ >> + SetMem(WriteRequest, 3 * sizeof (WRITE_REQUEST), 0); Thanks Laszlo
diff --git a/OvmfPkg/XenBusDxe/XenStore.c b/OvmfPkg/XenBusDxe/XenStore.c index 7b71dc156d..ca7be12d68 100644 --- a/OvmfPkg/XenBusDxe/XenStore.c +++ b/OvmfPkg/XenBusDxe/XenStore.c @@ -53,7 +53,7 @@ typedef struct { CONST VOID *Data; - UINT32 Len; + UINTN Len; } WRITE_REQUEST; /* Register callback to watch subtree (node) in the XenStore. */ @@ -260,6 +260,35 @@ XenStoreFindWatch ( return NULL; } +/** + Fill the first three slots of a WRITE_REQUEST array. + + When those three slots are concatenated to generate a string, the resulting + string will be "$Path\0" or "$Path/$SubPath\0" if SubPath is provided. +**/ +STATIC +VOID +XenStorePrepareWriteRequest ( + IN OUT WRITE_REQUEST *WriteRequest, + IN CONST CHAR8 *Path, + IN CONST CHAR8 *SubPath OPTIONAL + ) +{ + SetMem(WriteRequest, 3 * sizeof (WRITE_REQUEST), 0); + WriteRequest[0].Data = Path; + WriteRequest[0].Len = AsciiStrSize (Path); + if (SubPath != NULL && SubPath[0] != '\0') { + // + // Remove the \0 from the first part of the request. + // + WriteRequest[0].Len--; + WriteRequest[1].Data = "/"; + WriteRequest[1].Len = 1; + WriteRequest[2].Data = SubPath; + WriteRequest[2].Len = AsciiStrSize (SubPath); + } +} + // // Public Utility Functions // API comments for these methods can be found in XenStore.h @@ -842,6 +871,7 @@ XenStoreTalkv ( @param Transaction The transaction to use for this request. @param RequestType The type of message to send. @param Body The body of the request. + @param SubPath If !NULL and not "", "/$SubPath" is append to Body. @param LenPtr The returned length of the reply. @param Result The returned body of the reply. @@ -854,16 +884,16 @@ XenStoreSingle ( IN CONST XENSTORE_TRANSACTION *Transaction, IN enum xsd_sockmsg_type RequestType, IN CONST CHAR8 *Body, + IN CONST CHAR8 *SubPath OPTIONAL, OUT UINT32 *LenPtr OPTIONAL, OUT VOID **Result OPTIONAL ) { - WRITE_REQUEST WriteRequest; + WRITE_REQUEST WriteRequest[3]; - WriteRequest.Data = (VOID *) Body; - WriteRequest.Len = (UINT32)AsciiStrSize (Body); + XenStorePrepareWriteRequest (WriteRequest, Body, SubPath); - return XenStoreTalkv (Transaction, RequestType, &WriteRequest, 1, + return XenStoreTalkv (Transaction, RequestType, WriteRequest, 3, LenPtr, Result); } @@ -1113,15 +1143,12 @@ XenStoreListDirectory ( OUT CONST CHAR8 ***DirectoryListPtr ) { - CHAR8 *Path; CHAR8 *TempStr; UINT32 Len = 0; XENSTORE_STATUS Status; - Path = XenStoreJoin (DirectoryPath, Node); - Status = XenStoreSingle (Transaction, XS_DIRECTORY, Path, &Len, + Status = XenStoreSingle (Transaction, XS_DIRECTORY, DirectoryPath, Node, &Len, (VOID **) &TempStr); - FreePool (Path); if (Status != XENSTORE_STATUS_SUCCESS) { return Status; } @@ -1160,13 +1187,11 @@ XenStoreRead ( OUT VOID **Result ) { - CHAR8 *Path; VOID *Value; XENSTORE_STATUS Status; - Path = XenStoreJoin (DirectoryPath, Node); - Status = XenStoreSingle (Transaction, XS_READ, Path, LenPtr, &Value); - FreePool (Path); + Status = XenStoreSingle (Transaction, XS_READ, DirectoryPath, Node, + LenPtr, &Value); if (Status != XENSTORE_STATUS_SUCCESS) { return Status; } @@ -1183,21 +1208,13 @@ XenStoreWrite ( IN CONST CHAR8 *Str ) { - CHAR8 *Path; - WRITE_REQUEST WriteRequest[2]; - XENSTORE_STATUS Status; + WRITE_REQUEST WriteRequest[4]; - Path = XenStoreJoin (DirectoryPath, Node); + XenStorePrepareWriteRequest (WriteRequest, DirectoryPath, Node); + WriteRequest[3].Data = Str; + WriteRequest[3].Len = AsciiStrLen (Str); - WriteRequest[0].Data = (VOID *) Path; - WriteRequest[0].Len = (UINT32)AsciiStrSize (Path); - WriteRequest[1].Data = (VOID *) Str; - WriteRequest[1].Len = (UINT32)AsciiStrLen (Str); - - Status = XenStoreTalkv (Transaction, XS_WRITE, WriteRequest, 2, NULL, NULL); - FreePool (Path); - - return Status; + return XenStoreTalkv (Transaction, XS_WRITE, WriteRequest, 4, NULL, NULL); } XENSTORE_STATUS @@ -1207,12 +1224,9 @@ XenStoreRemove ( IN CONST CHAR8 *Node ) { - CHAR8 *Path; XENSTORE_STATUS Status; - Path = XenStoreJoin (DirectoryPath, Node); - Status = XenStoreSingle (Transaction, XS_RM, Path, NULL, NULL); - FreePool (Path); + Status = XenStoreSingle (Transaction, XS_RM, DirectoryPath, Node, NULL, NULL); return Status; } @@ -1226,7 +1240,7 @@ XenStoreTransactionStart ( XENSTORE_STATUS Status; Status = XenStoreSingle (XST_NIL, XS_TRANSACTION_START, "", NULL, - (VOID **) &IdStr); + NULL, (VOID **) &IdStr); if (Status == XENSTORE_STATUS_SUCCESS) { Transaction->Id = (UINT32)AsciiStrDecimalToUintn (IdStr); FreePool (IdStr); @@ -1246,7 +1260,7 @@ XenStoreTransactionEnd ( AbortStr[0] = Abort ? 'F' : 'T'; AbortStr[1] = '\0'; - return XenStoreSingle (Transaction, XS_TRANSACTION_END, AbortStr, NULL, NULL); + return XenStoreSingle (Transaction, XS_TRANSACTION_END, AbortStr, NULL, NULL, NULL); } XENSTORE_STATUS
When doing an action with a path and subpath in the xenstore, XenStoreJoin is called to generate "$path/$subpath". But this function do an allocation of memory which isn't necessary. Instead we will construct the path with WRITE_REQUEST and data used to generate the path will be copied directly to the xenstore shared ring. Also change WRITE_REQUEST.Len type, it only contain sizes and doesn't need to be exactly 32bits. Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=2190 Signed-off-by: Anthony PERARD <anthony.perard@citrix.com> --- OvmfPkg/XenBusDxe/XenStore.c | 78 +++++++++++++++++++++--------------- 1 file changed, 46 insertions(+), 32 deletions(-)