[PATCH 6/6] powerpc/pseries: Add papr-platform-dump character driver for dump retrieval
Haren Myneni
haren at linux.ibm.com
Sun Jan 5 07:46:50 AEDT 2025
ibm,platform-dump RTAS call in combination with writable mapping
/dev/mem is issued to collect platform dump from the hypervisor
and may need multiple calls to get the complete dump. The current
implementation uses rtas_platform_dump() API provided by librtas
library to issue these HCALLs. But /dev/mem access by the user
space is prohibited under system lockdown.
The solution should be to restrict access to RTAS function in user
space and provide kernel interfaces to collect dump. This patch
adds papr-platform-dump character driver and expose standard
interfaces such as open / ioctl/ read to user space in ways that
are compatible with lockdown.
PAPR (7.3.3.4.1 ibm,platform-dump) provides a method to obtain
the complete dump:
- Each dump will be identified by ID called dump tag.
- A sequence of RTAS calls have to be issued until retrieve the
complete dump. The hypervisor expects the first RTAS call with
the sequence 0 and the subsequent calls with the sequence
number returned from the previous calls.
- The hypervisor returns "dump complete" status once the complete
dump is retrieved. But expects one more RTAS call from the
partition with the NULL buffer to invalidate dump which means
the dump will be removed in the hypervisor.
- Sequence of calls are allowed with different dump IDs at the
same time but not with the same dump ID.
Expose these interfaces to user space with a /dev/papr-platform-dump
character device using the following programming model:
int devfd = open("/dev/papr-platform-dump", O_RDONLY);
int fd = ioctl(devfd,PAPR_PLATFORM_DUMP_IOC_CREATE_HANDLE, &dump_id)
- Restrict user space to access with the same dump ID.
Typically we do not expect user space requests the dump
again for the same dump ID.
char *buf = malloc(size);
length = read(fd, buf, size);
- size should be minimum 1K based on PAPR and <= 4K based
on RTAS work area size. It will be restrict to RTAS work
area size. Using 4K work area based on the current
implementation in librtas library
- Each read call issue RTAS call to get the data based on
the size requirement and returns bytes returned from the
hypervisor
- If the previous HCALL returns dump complete status, the
next read returns 0 like EOF.
ret = ioctl(PAPR_PLATFORM_DUMP_IOC_INVALIDATE, &dump_id)
- RTAS call with NULL buffer to invalidates the dump.
The read API should use the file descriptor obtained from ioctl
based on dump ID so that gets dump contents for the corresponding
dump ID. Implemented support in librtas (rtas_platform_dump()) for
this new ABI to support system lockdown.
Signed-off-by: Haren Myneni <haren at linux.ibm.com>
---
.../include/uapi/asm/papr-platform-dump.h | 15 +
arch/powerpc/platforms/pseries/Makefile | 1 +
.../platforms/pseries/papr-platform-dump.c | 408 ++++++++++++++++++
3 files changed, 424 insertions(+)
create mode 100644 arch/powerpc/include/uapi/asm/papr-platform-dump.h
create mode 100644 arch/powerpc/platforms/pseries/papr-platform-dump.c
diff --git a/arch/powerpc/include/uapi/asm/papr-platform-dump.h b/arch/powerpc/include/uapi/asm/papr-platform-dump.h
new file mode 100644
index 000000000000..3a0f152e3ce8
--- /dev/null
+++ b/arch/powerpc/include/uapi/asm/papr-platform-dump.h
@@ -0,0 +1,15 @@
+/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
+#ifndef _UAPI_PAPR_PLATFORM_DUMP_H_
+#define _UAPI_PAPR_PLATFORM_DUMP_H_
+
+#include <asm/ioctl.h>
+#include <asm/papr-miscdev.h>
+
+/*
+ * ioctl for /dev/papr-platform-dump. Returns a VPD handle fd corresponding to
+ * the location code.
+ */
+#define PAPR_PLATFORM_DUMP_IOC_CREATE_HANDLE _IOW(PAPR_MISCDEV_IOC_ID, 6, __u64)
+#define PAPR_PLATFORM_DUMP_IOC_INVALIDATE _IOW(PAPR_MISCDEV_IOC_ID, 7, __u64)
+
+#endif /* _UAPI_PAPR_PLATFORM_DUMP_H_ */
diff --git a/arch/powerpc/platforms/pseries/Makefile b/arch/powerpc/platforms/pseries/Makefile
index e1db61877bb9..c82c94e0a73c 100644
--- a/arch/powerpc/platforms/pseries/Makefile
+++ b/arch/powerpc/platforms/pseries/Makefile
@@ -4,6 +4,7 @@ ccflags-$(CONFIG_PPC_PSERIES_DEBUG) += -DDEBUG
obj-y := lpar.o hvCall.o nvram.o reconfig.o \
of_helpers.o rtas-work-area.o papr-sysparm.o \
papr-rtas-common.o papr-vpd.o papr-indices.o \
+ papr-platform-dump.o \
setup.o iommu.o event_sources.o ras.o \
firmware.o power.o dlpar.o mobility.o rng.o \
pci.o pci_dlpar.o eeh_pseries.o msi.o \
diff --git a/arch/powerpc/platforms/pseries/papr-platform-dump.c b/arch/powerpc/platforms/pseries/papr-platform-dump.c
new file mode 100644
index 000000000000..a78a20ec983e
--- /dev/null
+++ b/arch/powerpc/platforms/pseries/papr-platform-dump.c
@@ -0,0 +1,408 @@
+// SPDX-License-Identifier: GPL-2.0-only
+
+#define pr_fmt(fmt) "papr-platform-dump: " fmt
+
+#include <linux/anon_inodes.h>
+#include <linux/file.h>
+#include <linux/fs.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/miscdevice.h>
+#include <asm/machdep.h>
+#include <asm/rtas-work-area.h>
+#include <asm/rtas.h>
+#include <uapi/asm/papr-platform-dump.h>
+
+/*
+ * Function-specific return values for ibm,platform-dump, derived from
+ * PAPR+ v2.13 7.3.3.4.1 "ibm,platform-dump RTAS Call".
+ */
+#define RTAS_IBM_PLATFORM_DUMP_COMPLETE 0 /* Complete dump retrieved. */
+#define RTAS_IBM_PLATFORM_DUMP_CONTINUE 1 /* Continue dump */
+#define RTAS_NOT_AUTHORIZED -9002 /* Not Authorized */
+
+#define RTAS_IBM_PLATFORM_DUMP_START 2 /* Linux status to start dump */
+
+/**
+ * struct ibm_platform_dump_params - Parameters (in and out) for
+ * ibm,platform-dump
+ * @work_area: In: work area buffer for results.
+ * @buf_length: In: work area buffer length in bytes
+ * @dump_tag_hi: In: Most-significant 32 bits of a Dump_Tag representing
+ * an id of the dump being processed.
+ * @dump_tag_lo: In: Least-significant 32 bits of a Dump_Tag representing
+ * an id of the dump being processed.
+ * @sequence_hi: In: Sequence number in most-significant 32 bits.
+ * Out: Next sequence number in most-significant 32 bits.
+ * @sequence_lo: In: Sequence number in Least-significant 32 bits
+ * Out: Next sequence number in Least-significant 32 bits.
+ * @bytes_ret_hi: Out: Bytes written in most-significant 32 bits.
+ * @bytes_ret_lo: Out: Bytes written in Least-significant 32 bits.
+ * @status: Out: RTAS call status.
+ * @list: Maintain the list of dumps are in progress. Can
+ * retrieve multiple dumps with different dump IDs at
+ * the same time but not with the same dump ID. This list
+ * is used to determine whether the dump for the same ID
+ * is in progress.
+ */
+struct ibm_platform_dump_params {
+ struct rtas_work_area *work_area;
+ u32 buf_length;
+ u32 dump_tag_hi;
+ u32 dump_tag_lo;
+ u32 sequence_hi;
+ u32 sequence_lo;
+ u32 bytes_ret_hi;
+ u32 bytes_ret_lo;
+ s32 status;
+ struct list_head list;
+};
+
+/*
+ * Multiple dumps with different dump IDs can be retrieved at the same
+ * time, but not with dame dump ID. platform_dump_list_mutex and
+ * platform_dump_list are used to prevent this behavior.
+ */
+static DEFINE_MUTEX(platform_dump_list_mutex);
+static LIST_HEAD(platform_dump_list);
+
+/**
+ * rtas_ibm_platform_dump() - Call ibm,platform-dump to fill a work area
+ * buffer.
+ * @params: See &struct ibm_platform_dump_params.
+ * @buf_addr: Address of dump buffer (work_area)
+ * @buf_length: Length of the buffer in bytes (min. 1024)
+ *
+ * Calls ibm,platform-dump until it errors or successfully deposits data
+ * into the supplied work area. Handles RTAS retry statuses. Maps RTAS
+ * error statuses to reasonable errno values.
+ *
+ * Can request multiple dumps with different dump IDs at the same time,
+ * but not with the same dump ID which is prevented with the check in
+ * the ioctl code (papr_platform_dump_create_handle()).
+ *
+ * The caller should inspect @params.status to determine whether more
+ * calls are needed to complete the sequence.
+ *
+ * Context: May sleep.
+ * Return: -ve on error, 0 for dump complete and 1 for continue dump
+ */
+static int rtas_ibm_platform_dump(struct ibm_platform_dump_params *params,
+ phys_addr_t buf_addr, u32 buf_length)
+{
+ u32 rets[4];
+ s32 fwrc;
+ int ret = 0;
+
+ do {
+ fwrc = rtas_call(rtas_function_token(RTAS_FN_IBM_PLATFORM_DUMP),
+ 6, 5,
+ rets,
+ params->dump_tag_hi,
+ params->dump_tag_lo,
+ params->sequence_hi,
+ params->sequence_lo,
+ buf_addr,
+ buf_length);
+ } while (rtas_busy_delay(fwrc));
+
+ switch (fwrc) {
+ case RTAS_HARDWARE_ERROR:
+ ret = -EIO;
+ break;
+ case RTAS_NOT_AUTHORIZED:
+ ret = -EPERM;
+ break;
+ case RTAS_IBM_PLATFORM_DUMP_CONTINUE:
+ case RTAS_IBM_PLATFORM_DUMP_COMPLETE:
+ params->sequence_hi = rets[0];
+ params->sequence_lo = rets[1];
+ params->bytes_ret_hi = rets[2];
+ params->bytes_ret_lo = rets[3];
+ break;
+ default:
+ ret = -EIO;
+ pr_err_ratelimited("unexpected ibm,platform-dump status %d\n",
+ fwrc);
+ break;
+ }
+
+ params->status = fwrc;
+ return ret;
+}
+
+/*
+ * Platform dump is used with multiple RTAS calls to retrieve the
+ * complete dump for the provided dump ID. Once the complete dump is
+ * retrieved, the hypervisor returns dump complete status (0) for the
+ * last RTAS call and expects the caller issues one more HCALL with
+ * NULL buffer to invalidate the dump so that the hypervisor can remove
+ * the dump.
+ *
+ * After the specific dump is invalidated in the hypervisor, expect the
+ * dump complete status for the new sequence - the user space initiates
+ * new request for the same dump ID.
+ */
+static ssize_t papr_platform_dump_handle_read(struct file *file,
+ char __user *buf, size_t size, loff_t *off)
+{
+ struct ibm_platform_dump_params *params = file->private_data;
+ u64 total_bytes;
+ s32 fwrc;
+
+ /*
+ * Dump already completed with the previous read calls.
+ * In case if the user space issues further reads, returns
+ * -EINVAL.
+ */
+ if (!params->buf_length) {
+ pr_warn_once("Platform dump completed for dump ID %llu\n",
+ (u64) (((u64)params->dump_tag_hi << 32) |
+ params->dump_tag_lo));
+ return -EINVAL;
+ }
+
+ /*
+ * The hypervisor returns status 0 if no more data available to
+ * download. The dump will be invalidated with ioctl (see below).
+ */
+ if (params->status == RTAS_IBM_PLATFORM_DUMP_COMPLETE) {
+ params->buf_length = 0;
+ /*
+ * Returns 0 to the user space so that user
+ * space read stops.
+ */
+ return 0;
+ }
+
+ if (size < SZ_1K) {
+ pr_err_once("Buffer length should be minimum 1024 bytes\n");
+ return -EINVAL;
+ } else if (size > params->buf_length) {
+ /*
+ * Allocate 4K work area. So if the user requests > 4K,
+ * resize the buffer length.
+ */
+ size = params->buf_length;
+ }
+
+ fwrc = rtas_ibm_platform_dump(params,
+ rtas_work_area_phys(params->work_area),
+ size);
+ if (fwrc < 0)
+ return fwrc;
+
+ total_bytes = (u64) (((u64)params->bytes_ret_hi << 32) |
+ params->bytes_ret_lo);
+
+ /*
+ * Kernel or firmware bug, do not continue.
+ */
+ if (WARN(total_bytes > size, "possible write beyond end of work area"))
+ return -EFAULT;
+
+ if (copy_to_user(buf, rtas_work_area_raw_buf(params->work_area),
+ total_bytes))
+ return -EFAULT;
+
+ return total_bytes;
+}
+
+static int papr_platform_dump_handle_release(struct inode *inode,
+ struct file *file)
+{
+ struct ibm_platform_dump_params *params = file->private_data;
+
+ if (params->work_area)
+ rtas_work_area_free(params->work_area);
+
+ mutex_lock(&platform_dump_list_mutex);
+ list_del(¶ms->list);
+ mutex_unlock(&platform_dump_list_mutex);
+
+ kfree(params);
+ file->private_data = NULL;
+ return 0;
+}
+
+/*
+ * This ioctl is used to invalidate the dump assuming the user space
+ * issue this ioctl after obtain the complete dump.
+ * Issue the last RTAS call with NULL buffer to invalidate the dump
+ * which means dump will be freed in the hypervisor.
+ */
+static long papr_platform_dump_invalidate_ioctl(struct file *file,
+ unsigned int ioctl, unsigned long arg)
+{
+ struct ibm_platform_dump_params *params;
+ u64 __user *argp = (void __user *)arg;
+ u64 param_dump_tag, dump_tag;
+
+ if (ioctl != PAPR_PLATFORM_DUMP_IOC_INVALIDATE)
+ return -ENOIOCTLCMD;
+
+ if (get_user(dump_tag, argp))
+ return -EFAULT;
+
+ /*
+ * private_data is freeded during release(), so should not
+ * happen.
+ */
+ if (!file->private_data) {
+ pr_err("No valid FD to invalidate dump for the ID(%llu)\n",
+ dump_tag);
+ return -EINVAL;
+ }
+
+ params = file->private_data;
+ param_dump_tag = (u64) (((u64)params->dump_tag_hi << 32) |
+ params->dump_tag_lo);
+ if (dump_tag != param_dump_tag) {
+ pr_err("Invalid dump ID(%llu) to invalidate dump\n",
+ dump_tag);
+ return -EINVAL;
+ }
+
+ if (params->status != RTAS_IBM_PLATFORM_DUMP_COMPLETE)
+ pr_warn("Platform dump is not complete, but requested "
+ "to invalidate dump for ID(%llu)\n",
+ dump_tag);
+
+ return rtas_ibm_platform_dump(params, 0, 0);
+}
+
+static const struct file_operations papr_platform_dump_handle_ops = {
+ .read = papr_platform_dump_handle_read,
+ .release = papr_platform_dump_handle_release,
+ .unlocked_ioctl = papr_platform_dump_invalidate_ioctl,
+};
+
+/**
+ * papr_platform_dump_create_handle() - Create a fd-based handle for
+ * reading platform dump
+ *
+ * Handler for PAPR_PLATFORM_DUMP_IOC_CREATE_HANDLE ioctl command
+ * Allocates RTAS parameter struct and work area and attached to the
+ * file descriptor for reading by user space with the multiple RTAS
+ * calls until the dump is completed. This memory allocation is freed
+ * when the file is released.
+ *
+ * Multiple dump requests with different IDs are allowed at the same
+ * time, but not with the same dump ID. So if the user space is
+ * already opened file descriptor for the specific dump ID, return
+ * -EALREADY for the next request.
+ *
+ * @dump_tag: Dump ID for the dump requested to retrieve from the
+ * hypervisor
+ *
+ * Return: The installed fd number if successful, -ve errno otherwise.
+ */
+static long papr_platform_dump_create_handle(u64 dump_tag)
+{
+ struct ibm_platform_dump_params *params;
+ u64 param_dump_tag;
+ struct file *file;
+ long err;
+ int fd;
+
+ /*
+ * Return failure if the user space is already opened FD for
+ * the specific dump ID. This check will prevent multiple dump
+ * requests for the same dump ID at the same time. Generally
+ * should not expect this, but in case.
+ */
+ list_for_each_entry(params, &platform_dump_list, list) {
+ param_dump_tag = (u64) (((u64)params->dump_tag_hi << 32) |
+ params->dump_tag_lo);
+ if (dump_tag == param_dump_tag) {
+ pr_err("Platform dump for ID(%llu) is already in progress\n",
+ dump_tag);
+ return -EALREADY;
+ }
+ }
+
+ params = kzalloc(sizeof(struct ibm_platform_dump_params),
+ GFP_KERNEL_ACCOUNT);
+ if (!params)
+ return -ENOMEM;
+
+ params->work_area = rtas_work_area_alloc(SZ_4K);
+ params->buf_length = SZ_4K;
+ params->dump_tag_hi = (u32)(dump_tag >> 32);
+ params->dump_tag_lo = (u32)(dump_tag & 0x00000000ffffffffULL);
+ params->status = RTAS_IBM_PLATFORM_DUMP_START;
+
+ fd = get_unused_fd_flags(O_RDONLY | O_CLOEXEC);
+ if (fd < 0) {
+ err = fd;
+ goto put_fd;
+ }
+
+ file = anon_inode_getfile("[papr-platform-dump]",
+ &papr_platform_dump_handle_ops,
+ (void *)params, O_RDONLY);
+ if (IS_ERR(file)) {
+ err = PTR_ERR(file);
+ goto put_fd;
+ }
+
+ file->f_mode |= FMODE_LSEEK | FMODE_PREAD;
+ fd_install(fd, file);
+
+ list_add(¶ms->list, &platform_dump_list);
+
+ pr_info("%s (%d) initiated platform dump for dump tag %llu\n",
+ current->comm, current->pid, dump_tag);
+ return fd;
+put_fd:
+ rtas_work_area_free(params->work_area);
+ kfree(params);
+ put_unused_fd(fd);
+ return err;
+}
+
+/*
+ * Top-level ioctl handler for /dev/papr-platform-dump.
+ */
+static long papr_platform_dump_dev_ioctl(struct file *filp,
+ unsigned int ioctl,
+ unsigned long arg)
+{
+ u64 __user *argp = (void __user *)arg;
+ u64 dump_tag;
+ long ret;
+
+ if (get_user(dump_tag, argp))
+ return -EFAULT;
+
+ switch (ioctl) {
+ case PAPR_PLATFORM_DUMP_IOC_CREATE_HANDLE:
+ mutex_lock(&platform_dump_list_mutex);
+ ret = papr_platform_dump_create_handle(dump_tag);
+ mutex_unlock(&platform_dump_list_mutex);
+ break;
+ default:
+ ret = -ENOIOCTLCMD;
+ break;
+ }
+ return ret;
+}
+
+static const struct file_operations papr_platform_dump_ops = {
+ .unlocked_ioctl = papr_platform_dump_dev_ioctl,
+};
+
+static struct miscdevice papr_platform_dump_dev = {
+ .minor = MISC_DYNAMIC_MINOR,
+ .name = "papr-platform-dump",
+ .fops = &papr_platform_dump_ops,
+};
+
+static __init int papr_platform_dump_init(void)
+{
+ if (!rtas_function_implemented(RTAS_FN_IBM_PLATFORM_DUMP))
+ return -ENODEV;
+
+ return misc_register(&papr_platform_dump_dev);
+}
+machine_device_initcall(pseries, papr_platform_dump_init);
--
2.43.5
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