[Devel] [PATCH RHEL9 COMMIT] readykernel: export symbols to be able to livepatch kfree/kvfree replacement

[Konstantin Khorenko]

The commit is pushed to "branch-rh9-5.14.0-427.77.1.vz9.86.x-ovz" and will appear at git at bitbucket.org:openvz/vzkernel.git
after rh9-5.14.0-427.77.1.vz9.86.5
------>
commit 1204de9652226f879b27c733508e19baab74a2ac
Author: Pavel Tikhomirov <ptikhomirov at virtuozzo.com>
Date:   Tue Aug 12 16:01:54 2025 +0800

    readykernel: export symbols to be able to livepatch kfree/kvfree replacement
    
    We can't just use normal readykernel patching for kfree/kvfree, as the
    counterpart with kmalloc/kvmalloc might've allocated non-continious
    memory and that memory should not be freed with kfree even after
    readykernel patch was unloaded.
    
    So the idea is to make the kfree/kvfree change permanent. For that we
    need to export: kallsyms_lookup_name, set_memory_ro, set_memory_rw,
    find_module and copy_to_kernel_nofault. So let's export them to be able
    to do this trick in future.
    
    See prototype implementation here:
    https://bitbucket.org/openvz/kpatch/branch/vz9-fuse_kio_pcs-kvfree-prototype
    85fc534 ("fuse_kio_pcs: Permanently replace kfree with kvfree in pcs_umem_release")
    874c2a8 ("Add kpatch_replace_call helper to manualy replace kernel function calls")
    
    https://virtuozzo.atlassian.net/browse/RK-536
    Signed-off-by: Pavel Tikhomirov <ptikhomirov at virtuozzo.com>
    
    Feature: ReadyKernel
---
 arch/arm/mm/pageattr.c | 2 ++
 kernel/kallsyms.c      | 1 +
 kernel/module.c        | 1 +
 mm/maccess.c           | 1 +
 4 files changed, 5 insertions(+)

diff --git a/arch/arm/mm/pageattr.c b/arch/arm/mm/pageattr.c
index 9790ae3a8c687..ff650f366dec3 100644
--- a/arch/arm/mm/pageattr.c
+++ b/arch/arm/mm/pageattr.c
@@ -66,6 +66,7 @@ int set_memory_ro(unsigned long addr, int numpages)
 					__pgprot(L_PTE_RDONLY),
 					__pgprot(0));
 }
+EXPORT_SYMBOL_GPL(set_memory_ro);
 
 int set_memory_rw(unsigned long addr, int numpages)
 {
@@ -73,6 +74,7 @@ int set_memory_rw(unsigned long addr, int numpages)
 					__pgprot(0),
 					__pgprot(L_PTE_RDONLY));
 }
+EXPORT_SYMBOL_GPL(set_memory_rw);
 
 int set_memory_nx(unsigned long addr, int numpages)
 {
diff --git a/kernel/kallsyms.c b/kernel/kallsyms.c
index c8b43ad04f47f..a0ca1524b3b5d 100644
--- a/kernel/kallsyms.c
+++ b/kernel/kallsyms.c
@@ -188,6 +188,7 @@ unsigned long kallsyms_lookup_name(const char *name)
 	}
 	return module_kallsyms_lookup_name(name);
 }
+EXPORT_SYMBOL_GPL(kallsyms_lookup_name);
 
 /*
  * Iterate over all symbols in vmlinux.  For symbols from modules use
diff --git a/kernel/module.c b/kernel/module.c
index 827fcd008de0a..c4a8eb203df4e 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -581,6 +581,7 @@ struct module *find_module(const char *name)
 {
 	return find_module_all(name, strlen(name), false);
 }
+EXPORT_SYMBOL_GPL(find_module);
 
 #ifdef CONFIG_SMP
 
diff --git a/mm/maccess.c b/mm/maccess.c
index 518a25667323e..ec180d956547f 100644
--- a/mm/maccess.c
+++ b/mm/maccess.c
@@ -76,6 +76,7 @@ long copy_to_kernel_nofault(void *dst, const void *src, size_t size)
 	pagefault_enable();
 	return -EFAULT;
 }
+EXPORT_SYMBOL_GPL(copy_to_kernel_nofault);
 
 long strncpy_from_kernel_nofault(char *dst, const void *unsafe_addr, long count)
 {