Cleanup in nvdebug_entry.c

- Fix pointer corruption when `compat_ops()` is called more than
  once on the same struct.
- Add support for detecting Jetson Orin on newer releases of L4T.
- Reorder some initialization steps such that the order matches for
  both PCIe- and platform-bus devices.
- Remove a duplicate check in `nvdebug_exit()`.

Tested on ga10b (Jetson Orin) with L4T r36.3.

1 files changed, 23 insertions, 13 deletions

diff --git a/nvdebug_entry.c b/nvdebug_entry.c
index 1f9e1c9..5f99976 100644
--- a/nvdebug_entry.c
+++ b/nvdebug_entry.c
@@ -25,9 +25,9 @@ MODULE_DESCRIPTION("A scheduling debugging module for NVIDIA GPUs");
 // runlist_procfs.c
 extern struct file_operations runlist_file_ops;
 extern struct file_operations preempt_tsg_file_ops;
-extern struct file_operations resubmit_runlist_file_ops;
 extern struct file_operations disable_channel_file_ops;
 extern struct file_operations enable_channel_file_ops;
+extern struct file_operations resubmit_runlist_file_ops;
 extern struct file_operations switch_to_tsg_file_ops;
 // device_info_procfs.c
 extern struct file_operations device_info_file_ops;
@@ -46,15 +46,22 @@ extern struct bus_type platform_bus_type;
 // As file_operations is larger than proc_ops, we can overwrite the memory
 // backing the file_operations struct to follow the proc_ops layout, and then
 // cast on newer kernels.
+// We use the last byte of the file_operations struct to flag that the memory
+// layout has been rearranged.
 #if LINUX_VERSION_CODE >= KERNEL_VERSION(5,6,0)
 const struct proc_ops* compat_ops(const struct file_operations* ops) {
         struct proc_ops new_ops = {};
+        // Don't re-layout if it's already been done
+        if (*((uint8_t*)(ops + 1) - 1))
+                return (struct proc_ops*)ops;
         new_ops.proc_open = ops->open;
         new_ops.proc_read = ops->read;
         new_ops.proc_write = ops->write;
         new_ops.proc_lseek = ops->llseek;
         new_ops.proc_release = ops->release;
         memcpy((void*)ops, &new_ops, sizeof(new_ops));
+        // Flag re-layout as complete in last byte of structure
+        *((uint8_t*)(ops + 1) - 1) = 1;
         return (struct proc_ops*)ops;
 }
 #else
@@ -89,6 +96,9 @@ int probe_and_cache_devices(void) {
         };
         int i = 0;
         // Search the platform bus for the first device that matches our name
+        // Search for embedded GPU on Jetson (generic name starting around L4T 36.3)
+        while (!dev && (temp_dev = bus_find_device_by_name(&platform_bus_type, dev, "17000000.gpu")))
+                dev = temp_dev;
         // Search for GA10B (Jetson Orin)
         while (!dev && (temp_dev = bus_find_device_by_name(&platform_bus_type, dev, "17000000.ga10b")))
                 dev = temp_dev;
@@ -112,15 +122,15 @@ int probe_and_cache_devices(void) {
                 if (ids.raw == -1)
                         return -EADDRNOTAVAIL;
                 g_nvdebug_state[i].chip_id = ids.chip_id;
-                g_nvdebug_state[i].pcid = NULL;
                 g_nvdebug_state[i].bar3 = NULL;
+                g_nvdebug_state[i].pcid = NULL;
                 g_nvdebug_state[i].dev = dev;
                 printk(KERN_INFO "[nvdebug] Chip ID %x (architecture %s) detected on platform bus and initialized.",
                        ids.chip_id, ARCH2NAME(ids.architecture));
                 i++;
         }
         // Search the PCI bus and iterate through all matches
-        // FIXME: State rollback
+        // FIXME: Undo the pci_iomap() if this fails
         while ((pcid = pci_get_dev_by_id(&query, pcid)) && i < NVDEBUG_MAX_DEVICES) {
                 mc_boot_0_t ids;
                 g_nvdebug_state[i].g = NULL;
@@ -130,20 +140,20 @@ int probe_and_cache_devices(void) {
                         pci_err(pcid, "[nvdebug] Unable to map BAR0 on this GPU\n");
                         return -EADDRNOTAVAIL;
                 }
+                ids.raw = nvdebug_readl(&g_nvdebug_state[i], NV_MC_BOOT_0);
+                if (ids.raw == -1) {
+                        pci_err(pcid, "[nvdebug] Unable to read config from Master Controller on this GPU\n");
+                        return -EADDRNOTAVAIL;
+                }
+                g_nvdebug_state[i].chip_id = ids.chip_id;
                 // Map BAR3 (CPU-accessible mappings of GPU DRAM)
                 g_nvdebug_state[i].bar3 = pci_iomap(pcid, 3, 0);
-                // Try mapping only the lower half of BAR3 on fail
+                // XXX: Try mapping only the lower half of BAR3 on fail
                 // (vesafb may map the top half for display)
                 if (!g_nvdebug_state[i].bar3)
                         g_nvdebug_state[i].bar3 = pci_iomap(pcid, 3, pci_resource_len(pcid, 3)/2);
                 g_nvdebug_state[i].pcid = pcid;
                 g_nvdebug_state[i].dev = &pcid->dev;
-                ids.raw = nvdebug_readl(&g_nvdebug_state[i], NV_MC_BOOT_0);
-                if (ids.raw == -1) {
-                        pci_err(pcid, "[nvdebug] Unable to read config from Master Controller on this GPU\n");
-                        return -EADDRNOTAVAIL;
-                }
-                g_nvdebug_state[i].chip_id = ids.chip_id;
                 printk(KERN_INFO "[nvdebug] Chip ID %x (architecture %s) detected on PCI bus and initialized.",
                        ids.chip_id, ARCH2NAME(ids.architecture));
 #if INTERRUPT_DEBUG
@@ -397,12 +407,12 @@ static void __exit nvdebug_exit(void) {
                 char device_id[7];
                 snprintf(device_id, 7, "gpu%d", g_nvdebug_devices);
                 remove_proc_subtree(device_id, NULL);
-                // Free BAR mappings for PCIe devices
                 g = &g_nvdebug_state[g_nvdebug_devices];
+                // Free BAR mappings for PCIe devices
                 if (g && g->pcid) {
-                        if (g && g->regs)
+                        if (g->regs)
                                 pci_iounmap(g->pcid, g->regs);
-                        if (g && g->bar2)
+                        if (g->bar2)
                                 pci_iounmap(g->pcid, g->bar2);
 #if INTERRUPT_DEBUG
                         free_irq(g->pcid->irq, g->pcid);