define full PCI Express capability struct (#289)

Define the full-size capability as defined in the specification.
Previously, we were defining the structure as in the form used by PCI Express
Integrated Endpoints. It's reasonable to assume, however, that a vfio-user
device is a normal PCI Express Endpoint connected over a Link.

We'll go further, and define the whole structure, including the slot registers
at the end that are usually only used for Ports.

The presumption here is that it can't hurt to use the larger size: the only way
a client could care is if it presumed the next capability was at a particular
offset from this one, and we must hope nothing is that silly.

This also corrects a buffer overflow: cap_size() in fact disagreed with the
original size of our struct pxcap (found via clang's address sanitizer).

Signed-off-by: John Levon <john.levon@nutanix.com
Reviewed-by: Thanos Makatos <thanos.makatos@nutanix.com>

1 files changed, 116 insertions, 5 deletions

diff --git a/include/pci_caps/px.h b/include/pci_caps/px.h
index 6b1c364..ca564fc 100644
--- a/include/pci_caps/px.h
+++ b/include/pci_caps/px.h
@@ -107,6 +107,36 @@ struct pxls {
 } __attribute__((packed));
 _Static_assert(sizeof(struct pxls) == 0x2, "bad PXLS size");
 
+struct pxscap {
+    unsigned int stuff:32;
+} __attribute__((packed));
+_Static_assert(sizeof(struct pxscap) == 0x4, "bad PXSCAP size");
+
+struct pxsc {
+    unsigned int stuff:16;
+} __attribute__((packed));
+_Static_assert(sizeof(struct pxsc) == 0x2, "bad PXSC size");
+
+struct pxss {
+    unsigned int stuff:16;
+} __attribute__((packed));
+_Static_assert(sizeof(struct pxss) == 0x2, "bad PXSS size");
+
+struct pxrc {
+    unsigned int stuff:16;
+} __attribute__((packed));
+_Static_assert(sizeof(struct pxrc) == 0x2, "bad PXRC size");
+
+struct pxrcap {
+    unsigned int stuff:16;
+} __attribute__((packed));
+_Static_assert(sizeof(struct pxrcap) == 0x2, "bad PXRCAP size");
+
+struct pxrs {
+    unsigned int stuff:32;
+} __attribute__((packed));
+_Static_assert(sizeof(struct pxrs) == 0x4, "bad PXRS size");
+
 struct pxdcap2 {
     unsigned int ctrs:4;
     unsigned int ctds:1;
@@ -131,25 +161,106 @@ struct pxdc2 {
 } __attribute__((packed));
 _Static_assert(sizeof(struct pxdc2) == 0x2, "bad PXDC2 size");
 
+struct pxds2 {
+    unsigned int stuff:16;
+} __attribute__((packed));
+_Static_assert(sizeof(struct pxds2) == 0x2, "bad PXDS2 size");
+
+struct pxlcap2 {
+    unsigned int stuff:32;
+} __attribute__((packed));
+_Static_assert(sizeof(struct pxlcap2) == 0x4, "bad PXLCAP2 size");
+
+struct pxlc2 {
+    unsigned int stuff:16;
+} __attribute__((packed));
+_Static_assert(sizeof(struct pxlc2) == 0x2, "bad PXLC2 size");
+
+struct pxls2 {
+    unsigned int stuff:16;
+} __attribute__((packed));
+_Static_assert(sizeof(struct pxls2) == 0x2, "bad PXLS2 size");
+
+struct pxscap2 {
+    unsigned int stuff:32;
+} __attribute__((packed));
+_Static_assert(sizeof(struct pxscap2) == 0x4, "bad PXSCAP2 size");
+
+struct pxsc2 {
+    unsigned int stuff:16;
+} __attribute__((packed));
+_Static_assert(sizeof(struct pxsc2) == 0x2, "bad PXSC2 size");
+
+struct pxss2 {
+    unsigned int stuff:16;
+} __attribute__((packed));
+_Static_assert(sizeof(struct pxss2) == 0x2, "bad PXSS2 size");
+
 /*
- * TODO the definition of this struct varies, check PCI Express 2.1
- * specification. Maybe we should only define the idividual registers but not
- * the whole struct.
+ * PCI_CAP_EXP_ENDPOINT_SIZEOF_V2 from pci_regs.h is a false friend: earlier
+ * kernel versions defined the size as if the device was a Root Complex
+ * Integrated Endpoint (size 0x2c).
+ *
+ * Regardless, we define the full structure anyway.
+ */
+#define VFIO_USER_PCI_CAP_EXP_SIZEOF (0x3c)
+
+/*
+ * PCI Express capability, defined in PCI Express 7.8.
+ *
+ * The relevant fields and size of this capability varies depending upon the
+ * type. While we can expect, at least for now, all users to implement a PCI
+ * Express Endpoint, we'll define the entire struct, on the presumption that
+ * there is no issue with having additional space in the capability.
  */
 struct pxcap {
     struct cap_hdr hdr;
+    /* PCI Express Capabilities Register */
     struct pxcaps pxcaps;
+    /* Device Capabilities */
     struct pxdcap pxdcap;
+    /* Device Control */
     union pxdc pxdc;
+    /* Device Status */
     struct pxds pxds;
+    /* Link Capabilities */
     struct pxlcap pxlcap;
+    /* Link Control */
     struct pxlc pxlc;
+    /* Link Status */
     struct pxls pxls;
-    uint8_t pad[0x10];
+    /* Slot Capabilities */
+    struct pxscap pxscap;
+    /* Slot Control */
+    struct pxsc pxsc;
+    /* Slot Status */
+    struct pxss pxss;
+    /* Root Control */
+    struct pxrc pxrc;
+    /* Root Capabilities */
+    struct pxrcap pxrcap;
+    /* Root Status */
+    struct pxrs pxrs;
+    /* Device Capabilities 2 */
     struct pxdcap2 pxdcap2;
+    /* Device Control 2 */
     struct pxdc2 pxdc2;
+    /* Device Status 2 */
+    struct pxds2 pxds2;
+    /* Link Capabilities 2 */
+    struct pxlcap2 pxlcap2;
+    /* Link Control 2 */
+    struct pxlc2 pxlc2;
+    /* Link Status 2 */
+    struct pxls2 pxls2;
+    /* Slot Capabilities 2 */
+    struct pxscap2 pxscap2;
+    /* Slot Control 2 */
+    struct pxsc2 pxsc2;
+    /* Slot Status 2 */
+    struct pxss2 pxss2;
 } __attribute__((packed));
-_Static_assert(sizeof(struct pxcap) == 0x2a,
+_Static_assert(sizeof(struct pxcap) == VFIO_USER_PCI_CAP_EXP_SIZEOF,
 		"bad PCI Express Capability size");
 _Static_assert(offsetof(struct pxcap, hdr) == 0, "bad offset");