remoteproc: Add remote processor coredump support

As the remoteproc framework restarts the remote processor after a fatal
event, it's useful to be able to acquire a coredump of the remote
processor's state, for post mortem debugging.

This patch introduces a mechanism for extracting the memory contents
after the remote has stopped and before the restart sequence has begun
in the recovery path. The remoteproc framework builds the core dump in
memory and use devcoredump to expose this to user space.

Signed-off-by: Sarangdhar Joshi <spjoshi@codeaurora.org>
[bjorn: Use vmalloc instead of composing the ELF on the fly]
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>

2 files changed, 129 insertions, 0 deletions

diff --git a/drivers/remoteproc/Kconfig b/drivers/remoteproc/Kconfig
index b609e1d..3e4bca7 100644
--- a/drivers/remoteproc/Kconfig
+++ b/drivers/remoteproc/Kconfig
@@ -6,6 +6,7 @@ config REMOTEPROC
 	select CRC32
 	select FW_LOADER
 	select VIRTIO
+	select WANT_DEV_COREDUMP
 	help
 	  Support for remote processors (such as DSP coprocessors). These
 	  are mainly used on embedded systems.
diff --git a/drivers/remoteproc/remoteproc_core.c b/drivers/remoteproc/remoteproc_core.c
index 4170dfb..5af7547 100644
--- a/drivers/remoteproc/remoteproc_core.c
+++ b/drivers/remoteproc/remoteproc_core.c
@@ -33,6 +33,7 @@
 #include <linux/firmware.h>
 #include <linux/string.h>
 #include <linux/debugfs.h>
+#include <linux/devcoredump.h>
 #include <linux/remoteproc.h>
 #include <linux/iommu.h>
 #include <linux/idr.h>
@@ -802,6 +803,20 @@ static void rproc_remove_subdevices(struct rproc *rproc)
 }
 
 /**
+ * rproc_coredump_cleanup() - clean up dump_segments list
+ * @rproc: the remote processor handle
+ */
+static void rproc_coredump_cleanup(struct rproc *rproc)
+{
+	struct rproc_dump_segment *entry, *tmp;
+
+	list_for_each_entry_safe(entry, tmp, &rproc->dump_segments, node) {
+		list_del(&entry->node);
+		kfree(entry);
+	}
+}
+
+/**
  * rproc_resource_cleanup() - clean up and free all acquired resources
  * @rproc: rproc handle
  *
@@ -848,6 +863,8 @@ static void rproc_resource_cleanup(struct rproc *rproc)
 	/* clean up remote vdev entries */
 	list_for_each_entry_safe(rvdev, rvtmp, &rproc->rvdevs, node)
 		kref_put(&rvdev->refcount, rproc_vdev_release);
+
+	rproc_coredump_cleanup(rproc);
 }
 
 static int rproc_start(struct rproc *rproc, const struct firmware *fw)
@@ -1018,6 +1035,113 @@ static int rproc_stop(struct rproc *rproc)
 }
 
 /**
+ * rproc_coredump_add_segment() - add segment of device memory to coredump
+ * @rproc:	handle of a remote processor
+ * @da:		device address
+ * @size:	size of segment
+ *
+ * Add device memory to the list of segments to be included in a coredump for
+ * the remoteproc.
+ *
+ * Return: 0 on success, negative errno on error.
+ */
+int rproc_coredump_add_segment(struct rproc *rproc, dma_addr_t da, size_t size)
+{
+	struct rproc_dump_segment *segment;
+
+	segment = kzalloc(sizeof(*segment), GFP_KERNEL);
+	if (!segment)
+		return -ENOMEM;
+
+	segment->da = da;
+	segment->size = size;
+
+	list_add_tail(&segment->node, &rproc->dump_segments);
+
+	return 0;
+}
+EXPORT_SYMBOL(rproc_coredump_add_segment);
+
+/**
+ * rproc_coredump() - perform coredump
+ * @rproc:	rproc handle
+ *
+ * This function will generate an ELF header for the registered segments
+ * and create a devcoredump device associated with rproc.
+ */
+static void rproc_coredump(struct rproc *rproc)
+{
+	struct rproc_dump_segment *segment;
+	struct elf32_phdr *phdr;
+	struct elf32_hdr *ehdr;
+	size_t data_size;
+	size_t offset;
+	void *data;
+	void *ptr;
+	int phnum = 0;
+
+	if (list_empty(&rproc->dump_segments))
+		return;
+
+	data_size = sizeof(*ehdr);
+	list_for_each_entry(segment, &rproc->dump_segments, node) {
+		data_size += sizeof(*phdr) + segment->size;
+
+		phnum++;
+	}
+
+	data = vmalloc(data_size);
+	if (!data)
+		return;
+
+	ehdr = data;
+
+	memset(ehdr, 0, sizeof(*ehdr));
+	memcpy(ehdr->e_ident, ELFMAG, SELFMAG);
+	ehdr->e_ident[EI_CLASS] = ELFCLASS32;
+	ehdr->e_ident[EI_DATA] = ELFDATA2LSB;
+	ehdr->e_ident[EI_VERSION] = EV_CURRENT;
+	ehdr->e_ident[EI_OSABI] = ELFOSABI_NONE;
+	ehdr->e_type = ET_CORE;
+	ehdr->e_machine = EM_NONE;
+	ehdr->e_version = EV_CURRENT;
+	ehdr->e_entry = rproc->bootaddr;
+	ehdr->e_phoff = sizeof(*ehdr);
+	ehdr->e_ehsize = sizeof(*ehdr);
+	ehdr->e_phentsize = sizeof(*phdr);
+	ehdr->e_phnum = phnum;
+
+	phdr = data + ehdr->e_phoff;
+	offset = ehdr->e_phoff + sizeof(*phdr) * ehdr->e_phnum;
+	list_for_each_entry(segment, &rproc->dump_segments, node) {
+		memset(phdr, 0, sizeof(*phdr));
+		phdr->p_type = PT_LOAD;
+		phdr->p_offset = offset;
+		phdr->p_vaddr = segment->da;
+		phdr->p_paddr = segment->da;
+		phdr->p_filesz = segment->size;
+		phdr->p_memsz = segment->size;
+		phdr->p_flags = PF_R | PF_W | PF_X;
+		phdr->p_align = 0;
+
+		ptr = rproc_da_to_va(rproc, segment->da, segment->size);
+		if (!ptr) {
+			dev_err(&rproc->dev,
+				"invalid coredump segment (%pad, %zu)\n",
+				&segment->da, segment->size);
+			memset(data + offset, 0xff, segment->size);
+		} else {
+			memcpy(data + offset, ptr, segment->size);
+		}
+
+		offset += phdr->p_filesz;
+		phdr++;
+	}
+
+	dev_coredumpv(&rproc->dev, data, data_size, GFP_KERNEL);
+}
+
+/**
  * rproc_trigger_recovery() - recover a remoteproc
  * @rproc: the remote processor
  *
@@ -1043,6 +1167,9 @@ int rproc_trigger_recovery(struct rproc *rproc)
 	if (ret)
 		goto unlock_mutex;
 
+	/* generate coredump */
+	rproc_coredump(rproc);
+
 	/* load firmware */
 	ret = request_firmware(&firmware_p, rproc->firmware, dev);
 	if (ret < 0) {
@@ -1443,6 +1570,7 @@ struct rproc *rproc_alloc(struct device *dev, const char *name,
 	INIT_LIST_HEAD(&rproc->traces);
 	INIT_LIST_HEAD(&rproc->rvdevs);
 	INIT_LIST_HEAD(&rproc->subdevs);
+	INIT_LIST_HEAD(&rproc->dump_segments);
 
 	INIT_WORK(&rproc->crash_handler, rproc_crash_handler_work);