Re: [PATCH v10 03/10] powerpc: Always define MODULES_{VADDR,END}

On Wed, Apr 21, 2021 at 3:14 PM Christophe Leroy
[off-list ref] wrote:

Le 21/04/2021 à 04:46, Jordan Niethe a écrit :

quoted

On Fri, Apr 2, 2021 at 12:36 AM Christophe Leroy
[off-list ref] wrote:

quoted

Le 30/03/2021 à 06:51, Jordan Niethe a écrit :

quoted

If MODULES_{VADDR,END} are not defined set them to VMALLOC_START and
VMALLOC_END respectively. This reduces the need for special cases. For
example, powerpc's module_alloc() was previously predicated on
MODULES_VADDR being defined but now is unconditionally defined.

This will be useful reducing conditional code in other places that need
to allocate from the module region (i.e., kprobes).

Signed-off-by: Jordan Niethe <redacted>
---
v10: New to series
---
   arch/powerpc/include/asm/pgtable.h | 5 +++++
   arch/powerpc/kernel/module.c       | 5 +----

You probably also have changes to do in kernel/ptdump.c

In mm/book3s32/mmu.c and mm/kasan/kasan_init_32.c as well allthough that's harmless here.

quoted

   2 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/arch/powerpc/include/asm/pgtable.h b/arch/powerpc/include/asm/pgtable.h
index 4eed82172e33..014c2921f26a 100644
--- a/arch/powerpc/include/asm/pgtable.h
+++ b/arch/powerpc/include/asm/pgtable.h

@@ -167,6 +167,11 @@ struct seq_file;
   void arch_report_meminfo(struct seq_file *m);
   #endif /* CONFIG_PPC64 */

+#ifndef MODULES_VADDR
+#define MODULES_VADDR VMALLOC_START
+#define MODULES_END VMALLOC_END
+#endif
+
   #endif /* __ASSEMBLY__ */

   #endif /* _ASM_POWERPC_PGTABLE_H */

diff --git a/arch/powerpc/kernel/module.c b/arch/powerpc/kernel/module.c
index a211b0253cdb..f1fb58389d58 100644
--- a/arch/powerpc/kernel/module.c
+++ b/arch/powerpc/kernel/module.c

@@ -14,6 +14,7 @@
   #include <asm/firmware.h>
   #include <linux/sort.h>
   #include <asm/setup.h>
+#include <linux/mm.h>

   static LIST_HEAD(module_bug_list);

@@ -87,13 +88,9 @@ int module_finalize(const Elf_Ehdr *hdr,
       return 0;
   }

-#ifdef MODULES_VADDR
   void *module_alloc(unsigned long size)
   {
-     BUILD_BUG_ON(TASK_SIZE > MODULES_VADDR);
-

The above check is needed somewhere, if you remove it from here you have to perform the check
somewhere else.

This also introduces this warning:
fs/proc/kcore.c:626:52: warning: self-comparison always evaluates to
false [-Wtautological-compare]
   626 |  if (MODULES_VADDR != VMALLOC_START && MODULES_END != VMALLOC_END) {
I might leave this patch out of this series and use an #ifdef for now
and make this change separately as a follow up.

x86/32 at least does the same (see
https://elixir.bootlin.com/linux/v5.12-rc8/source/arch/x86/include/asm/pgtable_32_areas.h#L47)

They probably also get the warning, so I think would shouldn't bother.
One day someone will fix fs/proc/kcore.c , that's not a powerpc problem.

Yeah you are right. I'll add the BUILD_BUG_ON() check to
asm/task_size_32.h and keep the patch.

quoted

quoted

quoted

       return __vmalloc_node_range(size, 1, MODULES_VADDR, MODULES_END, GFP_KERNEL,
                                   PAGE_KERNEL_EXEC, VM_FLUSH_RESET_PERMS, NUMA_NO_NODE,
                                   __builtin_return_address(0));
   }
-#endif