[PATCH v3] powerpc/code-patching: Improve verification of patchability

[PATCH v3] powerpc/code-patching: Improve verification of patchability

[Christophe Leroy]

Today, patch_instruction() assumes that it is called exclusively on
valid addresses, and only checks that it is not called on an init
address after init section has been freed.

Improve verification by calling kernel_text_address() instead.

kernel_text_address() already includes a verification of
initmem release.

Cc: Michael Neuling <mikey@neuling.org>
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
---
v3:
- At the same time also remove init_mem_is_free as it was the last user (Was done in patch 3 in v2)
- Drop patch 2 (was merged via mm tree)
---
 arch/powerpc/include/asm/setup.h | 1 -
 arch/powerpc/lib/code-patching.c | 5 ++---
 arch/powerpc/mm/mem.c            | 2 --
 3 files changed, 2 insertions(+), 6 deletions(-)

diff --git a/arch/powerpc/include/asm/setup.h b/arch/powerpc/include/asm/setup.h
index 6c1a7d217d1a..426a2d8d028f 100644
--- a/arch/powerpc/include/asm/setup.h
+++ b/arch/powerpc/include/asm/setup.h
@@ -9,7 +9,6 @@ extern void ppc_printk_progress(char *s, unsigned short hex);
 
 extern unsigned int rtas_data;
 extern unsigned long long memory_limit;
-extern bool init_mem_is_free;
 extern void *zalloc_maybe_bootmem(size_t size, gfp_t mask);
 
 struct device_node;
diff --git a/arch/powerpc/lib/code-patching.c b/arch/powerpc/lib/code-patching.c
index c5ed98823835..5e2fe133639e 100644
--- a/arch/powerpc/lib/code-patching.c
+++ b/arch/powerpc/lib/code-patching.c
@@ -190,10 +190,9 @@ static int do_patch_instruction(u32 *addr, struct ppc_inst instr)
 int patch_instruction(u32 *addr, struct ppc_inst instr)
 {
 	/* Make sure we aren't patching a freed init section */
-	if (init_mem_is_free && init_section_contains(addr, 4)) {
-		pr_debug("Skipping init section patching addr: 0x%px\n", addr);
+	if (!kernel_text_address((unsigned long)addr))
 		return 0;
-	}
+
 	return do_patch_instruction(addr, instr);
 }
 NOKPROBE_SYMBOL(patch_instruction);
diff --git a/arch/powerpc/mm/mem.c b/arch/powerpc/mm/mem.c
index bd5d91a31183..8e301cd8925b 100644
--- a/arch/powerpc/mm/mem.c
+++ b/arch/powerpc/mm/mem.c
@@ -26,7 +26,6 @@
 #include <mm/mmu_decl.h>
 
 unsigned long long memory_limit;
-bool init_mem_is_free;
 
 unsigned long empty_zero_page[PAGE_SIZE / sizeof(unsigned long)] __page_aligned_bss;
 EXPORT_SYMBOL(empty_zero_page);
@@ -312,7 +311,6 @@ void free_initmem(void)
 {
 	ppc_md.progress = ppc_printk_progress;
 	mark_initmem_nx();
-	init_mem_is_free = true;
 	free_initmem_default(POISON_FREE_INITMEM);
 }
 
-- 
2.31.1

Re: [PATCH v3] powerpc/code-patching: Improve verification of patchability

[Michael Ellerman]

On Mon, 15 Nov 2021 11:12:22 +0100, Christophe Leroy wrote:
> Today, patch_instruction() assumes that it is called exclusively on
> valid addresses, and only checks that it is not called on an init
> address after init section has been freed.
> 
> Improve verification by calling kernel_text_address() instead.
> 
> kernel_text_address() already includes a verification of
> initmem release.
> 
> [...]

Applied to powerpc/next.

[1/1] powerpc/code-patching: Improve verification of patchability
      https://git.kernel.org/powerpc/c/8b8a8f0ab3f5519e45c526f826a655817486c5bb

cheers