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@linux.ibm.com Reviewed-by: Hari Bathini hbathini@linux.ibm.com Cc: stable@vger.kernel.org --- arch/powerpc/kexec/file_load_64.c | 98 +++++++++++++++++++++++++++++++ 1 file changed, 98 insertions(+)

--- Changelog:

v1 -> v3 - https://lists.ozlabs.org/pipermail/linuxppc-dev/2021-April/227756.html

v3 -> v4 - Rearranged if-else statement in update_cpus_node function to avoid redundant checks for positive cpus_offset. ---

diff --git a/arch/powerpc/kexec/file_load_64.c b/arch/powerpc/kexec/file_load_64.c index 02b9e4d0dc40..195ef303d530 100644 --- a/arch/powerpc/kexec/file_load_64.c +++ b/arch/powerpc/kexec/file_load_64.c @@ -960,6 +960,99 @@ unsigned int kexec_fdt_totalsize_ppc64(struct kimage *image) return fdt_size; }

+/** + * add_node_prop - Read property 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 + * np: device node pointer + * + * Returns 0 on success, negative errno on error. + */ +static int add_node_prop(void *fdt, int node_offset, const struct device_node *np) +{ + int ret = 0; + struct property *pp; + unsigned long flags; + + if (!np) + return -EINVAL; + + raw_spin_lock_irqsave(&devtree_lock, flags); + for (pp = np->properties; pp; pp = pp->next) { + 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)); + goto out; + } + } +out: + raw_spin_unlock_irqrestore(&devtree_lock, flags); + 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_off, 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; + } else { + 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"); + ret = add_node_prop(fdt, cpus_offset, cpus_node); + 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_off = fdt_add_subnode(fdt, + cpus_offset, + dn->full_name); + if (cpus_subnode_off < 0) { + pr_err("Unable to add %s subnode: %s\n", + dn->full_name, fdt_strerror(cpus_subnode_off)); + return cpus_subnode_off; + } + ret = add_node_prop(fdt, cpus_subnode_off, dn); + if (ret < 0) + return ret; + } + } + return ret; +} + /** * setup_new_fdt_ppc64 - Update the flattend device-tree of the kernel * being loaded. @@ -1020,6 +1113,11 @@ 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)