On 4/26/21 9:51 PM, Sourabh Jain wrote:
> kexec_file_load uses initial_boot_params in setting up the device-tree
> for the kernel to be loaded. Though initial_boot_params holds info
> about CPUs at the time of boot, it doesn't account for hot added CPUs.
>
> So, kexec'ing with kexec_file_load syscall would leave the kexec'ed
> kernel with inaccurate CPU info. Also, if kdump kernel is loaded with
> kexec_file_load syscall and the system crashes on a hot added CPU,
> capture kernel hangs failing to identify the boot CPU.
>
> Kernel panic - not syncing: sysrq triggered crash
> CPU: 24 PID: 6065 Comm: echo Kdump: loaded Not tainted 5.12.0-rc5upstream #54
> Call Trace:
> [c0000000e590fac0] [c0000000007b2400] dump_stack+0xc4/0x114 (unreliable)
> [c0000000e590fb00] [c000000000145290] panic+0x16c/0x41c
> [c0000000e590fba0] [c0000000008892e0] sysrq_handle_crash+0x30/0x40
> [c0000000e590fc00] [c000000000889cdc] __handle_sysrq+0xcc/0x1f0
> [c0000000e590fca0] [c00000000088a538] write_sysrq_trigger+0xd8/0x178
> [c0000000e590fce0] [c0000000005e9b7c] proc_reg_write+0x10c/0x1b0
> [c0000000e590fd10] [c0000000004f26d0] vfs_write+0xf0/0x330
> [c0000000e590fd60] [c0000000004f2aec] ksys_write+0x7c/0x140
> [c0000000e590fdb0] [c000000000031ee0] system_call_exception+0x150/0x290
> [c0000000e590fe10] [c00000000000ca5c] system_call_common+0xec/0x278
> --- interrupt: c00 at 0x7fff905b9664
> NIP: 00007fff905b9664 LR: 00007fff905320c4 CTR: 0000000000000000
> REGS: c0000000e590fe80 TRAP: 0c00 Not tainted (5.12.0-rc5upstream)
> MSR: 800000000280f033 <SF,VEC,VSX,EE,PR,FP,ME,IR,DR,RI,LE> CR: 28000242
> XER: 00000000
> IRQMASK: 0
> GPR00: 0000000000000004 00007ffff5fedf30 00007fff906a7300 0000000000000001
> GPR04: 000001002a7355b0 0000000000000002 0000000000000001 00007ffff5fef616
> GPR08: 0000000000000001 0000000000000000 0000000000000000 0000000000000000
> GPR12: 0000000000000000 00007fff9073a160 0000000000000000 0000000000000000
> GPR16: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
> GPR20: 0000000000000000 00007fff906a4ee0 0000000000000002 0000000000000001
> GPR24: 00007fff906a0898 0000000000000000 0000000000000002 000001002a7355b0
> GPR28: 0000000000000002 00007fff906a1790 000001002a7355b0 0000000000000002
> NIP [00007fff905b9664] 0x7fff905b9664
> LR [00007fff905320c4] 0x7fff905320c4
> --- interrupt: c00
>
> To avoid this from happening, extract current CPU info from of_root
> device node and use it for setting up the fdt in kexec_file_load case.
>
> Fixes: 6ecd0163d360 ("powerpc/kexec_file: Add appropriate regions for memory reserve map")
>
> Signed-off-by: Sourabh Jain <sourabhjain@xxxxxxxxxxxxx>
> Reviewed-by: Hari Bathini <hbathini@xxxxxxxxxxxxx>
> Cc: <stable@xxxxxxxxxxxxxxx>
> ---
> arch/powerpc/kexec/file_load_64.c | 88 +++++++++++++++++++++++++++++++
> 1 file changed, 88 insertions(+)
>
> ---
> Changelog:
>
> v1 -> v5
> - https://lists.ozlabs.org/pipermail/linuxppc-dev/2021-April/227950.html
>
> v5 -> v6
> - use exiting macro (for_each_property_of_node) to loop through all
> properties of a node.
> - removed devtree_lock while accessing the node properties.
> - function name update, add_node_prop to add_node_props.
> ---
>
> diff --git a/arch/powerpc/kexec/file_load_64.c b/arch/powerpc/kexec/file_load_64.c
> index 02b9e4d0dc40..4f7d4c10f939 100644
> --- a/arch/powerpc/kexec/file_load_64.c
> +++ b/arch/powerpc/kexec/file_load_64.c
> @@ -960,6 +960,89 @@ unsigned int kexec_fdt_totalsize_ppc64(struct kimage *image)
> return fdt_size;
> }
>
> +/**
> + * add_node_props - Reads node properties from device node structure and add
> + * them to fdt.
> + * @fdt: Flattened device tree of the kernel
> + * @node_offset: offset of the node to add a property at
> + * @dn: device node pointer
> + *
> + * Returns 0 on success, negative errno on error.
> + */
> +static int add_node_props(void *fdt, int node_offset, const struct device_node *dn)
> +{
> + int ret = 0;
> + struct property *pp;
> +
> + if (!dn)
> + return -EINVAL;
> +
> + for_each_property_of_node(dn, pp) {
> + ret = fdt_setprop(fdt, node_offset, pp->name, pp->value, pp->length);
> + if (ret < 0) {
> + pr_err("Unable to add %s property: %s\n", pp->name, fdt_strerror(ret));
> + return ret;
> + }
> + }
> + return ret;
> +}
> +
> +/**
> + * update_cpus_node - Update cpus node of flattened device tree using of_root
> + * device node.
> + * @fdt: Flattened device tree of the kernel.
> + *
> + * Returns 0 on success, negative errno on error.
> + */
> +static int update_cpus_node(void *fdt)
> +{
> + struct device_node *cpus_node, *dn;
> + int cpus_offset, cpus_subnode_offset, ret = 0;
> +
> + cpus_offset = fdt_path_offset(fdt, "/cpus");
> + if (cpus_offset < 0 && cpus_offset != -FDT_ERR_NOTFOUND) {
> + pr_err("Malformed device tree: error reading /cpus node: %s\n",
> + fdt_strerror(cpus_offset));
> + return cpus_offset;
> + }
> +
> + if (cpus_offset > 0) {
> + ret = fdt_del_node(fdt, cpus_offset);
> + if (ret < 0) {
> + pr_err("Error deleting /cpus node: %s\n", fdt_strerror(ret));
> + return -EINVAL;
> + }
> + }
> +
> + /* Add cpus node to fdt */
> + cpus_offset = fdt_add_subnode(fdt, fdt_path_offset(fdt, "/"), "cpus");
> + if (cpus_offset < 0) {
> + pr_err("Error creating /cpus node: %s\n", fdt_strerror(cpus_offset));
> + return -EINVAL;
> + }
> +
> + /* Add cpus node properties */
> + cpus_node = of_find_node_by_path("/cpus");
Pretty sure that of_find_node_by_path() returns a device_node with its refcount
incremented.
> + ret = add_node_props(fdt, cpus_offset, cpus_node);
Need a of_node_put(cpus_node) here.
-Tyrel
> + if (ret < 0)
> + return ret;
> +
> + /* Loop through all subnodes of cpus and add them to fdt */
> + for_each_node_by_type(dn, "cpu") {
> + cpus_subnode_offset = fdt_add_subnode(fdt, cpus_offset, dn->full_name);
> + if (cpus_subnode_offset < 0) {
> + pr_err("Unable to add %s subnode: %s\n", dn->full_name,
> + fdt_strerror(cpus_subnode_offset));
> + return cpus_subnode_offset;
> + }
> + ret = add_node_props(fdt, cpus_subnode_offset, dn);
> + if (ret < 0)
> + return ret;
> + }
> + of_node_put(dn);
> + return ret;
> +}
> +
> /**
> * setup_new_fdt_ppc64 - Update the flattend device-tree of the kernel
> * being loaded.
> @@ -1020,6 +1103,11 @@ int setup_new_fdt_ppc64(const struct kimage *image, void *fdt,
> }
> }
>
> + /* Update cpus nodes information to account hotplug CPUs. */
> + ret = update_cpus_node(fdt);
> + if (ret < 0)
> + return ret;
> +
> /* Update memory reserve map */
> ret = get_reserved_memory_ranges(&rmem);
> if (ret)
>
