linux-kernel - [PATCH 27/29] x86/mm: Report which part of kernel image is freed

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Date:   Thu, 26 Sep 2019 10:56:00 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     Kees Cook <keescook@...omium.org>,
        Rick Edgecombe <rick.p.edgecombe@...el.com>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Andy Lutomirski <luto@...nel.org>,
        Arnd Bergmann <arnd@...db.de>, linux-arch@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org, linux-alpha@...r.kernel.org,
        linux-ia64@...r.kernel.org, linux-s390@...r.kernel.org,
        linux-c6x-dev@...ux-c6x.org,
        Yoshinori Sato <ysato@...rs.sourceforge.jp>,
        Michal Simek <monstr@...str.eu>, linux-parisc@...r.kernel.org,
        linux-xtensa@...ux-xtensa.org, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH 27/29] x86/mm: Report which part of kernel image is freed

The memory freeing report wasn't very useful for figuring out which
parts of the kernel image were being freed. This adds the details for
clearer reporting.

Before:

[    2.150450] Freeing unused kernel image memory: 1348K
[    2.154574] Write protecting the kernel read-only data: 20480k
[    2.157641] Freeing unused kernel image memory: 2040K
[    2.158827] Freeing unused kernel image memory: 172K

After:

[    2.329678] Freeing unused kernel image (initmem) memory: 1348K
[    2.331953] Write protecting the kernel read-only data: 20480k
[    2.335361] Freeing unused kernel image (text/rodata gap) memory: 2040K
[    2.336927] Freeing unused kernel image (rodata/data gap) memory: 172K

Signed-off-by: Kees Cook <keescook@...omium.org>
---
 arch/x86/include/asm/processor.h | 2 +-
 arch/x86/mm/init.c               | 8 ++++----
 arch/x86/mm/init_64.c            | 6 ++++--
 3 files changed, 9 insertions(+), 7 deletions(-)

diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
index 6e0a3b43d027..790f250d39a8 100644
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -958,7 +958,7 @@ static inline uint32_t hypervisor_cpuid_base(const char *sig, uint32_t leaves)
 
 extern unsigned long arch_align_stack(unsigned long sp);
 void free_init_pages(const char *what, unsigned long begin, unsigned long end);
-extern void free_kernel_image_pages(void *begin, void *end);
+extern void free_kernel_image_pages(const char *what, void *begin, void *end);
 
 void default_idle(void);
 #ifdef	CONFIG_XEN
diff --git a/arch/x86/mm/init.c b/arch/x86/mm/init.c
index fd10d91a6115..e7bb483557c9 100644
--- a/arch/x86/mm/init.c
+++ b/arch/x86/mm/init.c
@@ -829,14 +829,13 @@ void free_init_pages(const char *what, unsigned long begin, unsigned long end)
  * used for the kernel image only.  free_init_pages() will do the
  * right thing for either kind of address.
  */
-void free_kernel_image_pages(void *begin, void *end)
+void free_kernel_image_pages(const char *what, void *begin, void *end)
 {
 	unsigned long begin_ul = (unsigned long)begin;
 	unsigned long end_ul = (unsigned long)end;
 	unsigned long len_pages = (end_ul - begin_ul) >> PAGE_SHIFT;
 
-
-	free_init_pages("unused kernel image", begin_ul, end_ul);
+	free_init_pages(what, begin_ul, end_ul);
 
 	/*
 	 * PTI maps some of the kernel into userspace.  For performance,
@@ -865,7 +864,8 @@ void __ref free_initmem(void)
 
 	mem_encrypt_free_decrypted_mem();
 
-	free_kernel_image_pages(&__init_begin, &__init_end);
+	free_kernel_image_pages("unused kernel image (initmem)",
+				&__init_begin, &__init_end);
 }
 
 #ifdef CONFIG_BLK_DEV_INITRD
diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
index e67ddca8b7a8..dcb9bc961b39 100644
--- a/arch/x86/mm/init_64.c
+++ b/arch/x86/mm/init_64.c
@@ -1334,8 +1334,10 @@ void mark_rodata_ro(void)
 	set_memory_ro(start, (end-start) >> PAGE_SHIFT);
 #endif
 
-	free_kernel_image_pages((void *)text_end, (void *)rodata_start);
-	free_kernel_image_pages((void *)rodata_end, (void *)_sdata);
+	free_kernel_image_pages("unused kernel image (text/rodata gap)",
+				(void *)text_end, (void *)rodata_start);
+	free_kernel_image_pages("unused kernel image (rodata/data gap)",
+				(void *)rodata_end, (void *)_sdata);
 
 	debug_checkwx();
 }
-- 
2.17.1