powerpc64/ftrace: fix module loading without patchable function entries

JIRA: https://issues.redhat.com/browse/RHEL-24555

commit 534f5a8
Author: Anthony Iliopoulos <ailiop@suse.com>
Date:   Wed Feb 5 00:18:21 2025 +0100

    powerpc64/ftrace: fix module loading without patchable function entries

    get_stubs_size assumes that there must always be at least one patchable
    function entry, which is not always the case (modules that export data
    but no code), otherwise it returns -ENOEXEC and thus the section header
    sh_size is set to that value. During module_memory_alloc() the size is
    passed to execmem_alloc() after being page-aligned and thus set to zero
    which will cause it to fail the allocation (and thus module loading) as
    __vmalloc_node_range() checks for zero-sized allocs and returns null:

    [  115.466896] module_64: cast_common: doesn't contain __patchable_function_entries.
    [  115.469189] ------------[ cut here ]------------
    [  115.469496] WARNING: CPU: 0 PID: 274 at mm/vmalloc.c:3778 __vmalloc_node_range_noprof+0x8b4/0x8f0
    ...
    [  115.478574] ---[ end trace 0000000000000000 ]---
    [  115.479545] execmem: unable to allocate memory

    Fix this by removing the check completely, since it is anyway not
    helpful to propagate this as an error upwards.

    Fixes: eec3796 ("powerpc64/ftrace: Move ftrace sequence out of line")
    Signed-off-by: Anthony Iliopoulos <ailiop@suse.com>
    Acked-by: Naveen N Rao (AMD) <naveen@kernel.org>
    Signed-off-by: Madhavan Srinivasan <maddy@linux.ibm.com>
    Link: https://patch.msgid.link/20250204231821.39140-1-ailiop@suse.com

Signed-off-by: Viktor Malik <vmalik@redhat.com>

Author: viktormalik

arch/powerpc/kernel/module_64.c

@@ -258,10 +258,6 @@ static unsigned long get_stubs_size(const Elf64_Ehdr *hdr,
 			break;
 		}
 	}
-	if (i == hdr->e_shnum) {
-		pr_err("%s: doesn't contain __patchable_function_entries.\n", me->name);
-		return -ENOEXEC;
-	}
 #endif
 
 	pr_debug("Looks like a total of %lu stubs, max\n", relocs);