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

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Message-Id: <bc683d499a411730504b132a924de0ccc2ef1f79.1636971137.git.christophe.leroy@csgroup.eu>
Date:   Mon, 15 Nov 2021 11:12:22 +0100
From:   Christophe Leroy <christophe.leroy@...roup.eu>
To:     Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>
Cc:     Christophe Leroy <christophe.leroy@...roup.eu>,
        linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        Michael Neuling <mikey@...ling.org>
Subject: [PATCH v3] powerpc/code-patching: Improve verification of patchability

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@...ling.org>
Signed-off-by: Christophe Leroy <christophe.leroy@...roup.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