linux-kernel - [PATCH v3] mips: Print the kernel virtual mem layout on debugging

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Message-Id: <20190507230320.23074-1-fancer.lancer@gmail.com>
Date:   Wed,  8 May 2019 02:03:20 +0300
From:   Serge Semin <fancer.lancer@...il.com>
To:     Ralf Baechle <ralf@...ux-mips.org>,
        Paul Burton <paul.burton@...s.com>,
        James Hogan <jhogan@...nel.org>
Cc:     Serge Semin <Sergey.Semin@...latforms.ru>,
        linux-mips@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH v3] mips: Print the kernel virtual mem layout on debugging

It is useful at least for debugging to have the kernel virtual
memory layout printed at boot time so to have the full information
about the booted kernel. Make the printing optional and available
only when DEBUG_KERNEL config is enabled so not to leak a sensitive
kernel information.

Signed-off-by: Serge Semin <fancer.lancer@...il.com>

---
Changelog v3
- Add MLM_ROUNDUP() and use it to calculate the low memory addresses range.
- Print KB instead of kB for kilobyte quantities.
- Check constants inconsistancies for systems with HIGHMEM only.
---
 arch/mips/mm/init.c | 51 +++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 51 insertions(+)

diff --git a/arch/mips/mm/init.c b/arch/mips/mm/init.c
index bbb196ad5f26..40558b979f96 100644
--- a/arch/mips/mm/init.c
+++ b/arch/mips/mm/init.c
@@ -31,6 +31,7 @@
 #include <linux/gfp.h>
 #include <linux/kcore.h>
 #include <linux/initrd.h>
+#include <linux/sizes.h>
 
 #include <asm/bootinfo.h>
 #include <asm/cachectl.h>
@@ -56,6 +57,55 @@ unsigned long empty_zero_page, zero_page_mask;
 EXPORT_SYMBOL_GPL(empty_zero_page);
 EXPORT_SYMBOL(zero_page_mask);
 
+/*
+ * Print out the kernel virtual memory layout
+ */
+#define MLK(b, t) (void *)b, (void *)t, ((t) - (b)) >> 10
+#define MLM(b, t) (void *)b, (void *)t, ((t) - (b)) >> 20
+#define MLK_ROUNDUP(b, t) (void *)b, (void *)t, DIV_ROUND_UP(((t) - (b)), SZ_1K)
+#define MLM_ROUNDUP(b, t) (void *)b, (void *)t, DIV_ROUND_UP(((t) - (b)), SZ_1M)
+static void __init mem_print_kmap_info(void)
+{
+#ifdef CONFIG_DEBUG_KERNEL
+	pr_notice("Kernel virtual memory layout:\n"
+		  "    lowmem  : 0x%px - 0x%px  (%6td MB)\n"
+		  "      .text : 0x%px - 0x%px  (%6td KB)\n"
+		  "      .data : 0x%px - 0x%px  (%6td KB)\n"
+		  "      .init : 0x%px - 0x%px  (%6td KB)\n"
+		  "      .bss  : 0x%px - 0x%px  (%6td KB)\n"
+		  "    vmalloc : 0x%px - 0x%px  (%6ld MB)\n"
+#ifdef CONFIG_HIGHMEM
+		  "    pkmap   : 0x%px - 0x%px  (%6ld MB)\n"
+#endif
+		  "    fixmap  : 0x%px - 0x%px  (%6ld KB)\n",
+		  MLM_ROUNDUP((void *)PAGE_OFFSET, high_memory),
+		  MLK_ROUNDUP(_text, _etext),
+		  MLK_ROUNDUP(_sdata, _edata),
+		  MLK_ROUNDUP(__init_begin, __init_end),
+		  MLK_ROUNDUP(__bss_start, __bss_stop),
+		  MLM(VMALLOC_START, VMALLOC_END),
+#ifdef CONFIG_HIGHMEM
+		  MLM(PKMAP_BASE, (PKMAP_BASE) + (LAST_PKMAP)*(PAGE_SIZE)),
+#endif
+		  MLK(FIXADDR_START, FIXADDR_TOP));
+
+	/* Check some fundamental inconsistencies. May add something else? */
+#ifdef CONFIG_HIGHMEM
+	BUILD_BUG_ON(VMALLOC_END < PAGE_OFFSET);
+	BUG_ON(VMALLOC_END < (unsigned long)high_memory);
+	BUILD_BUG_ON((PKMAP_BASE) + (LAST_PKMAP)*(PAGE_SIZE) < PAGE_OFFSET);
+	BUG_ON((PKMAP_BASE) + (LAST_PKMAP)*(PAGE_SIZE) <
+		(unsigned long)high_memory);
+	BUILD_BUG_ON(FIXADDR_TOP < PAGE_OFFSET);
+	BUG_ON(FIXADDR_TOP < (unsigned long)high_memory);
+#endif
+#endif /* CONFIG_DEBUG_KERNEL */
+}
+#undef MLK
+#undef MLM
+#undef MLK_ROUNDUP
+#undef MLM_ROUNDUP
+
 /*
  * Not static inline because used by IP27 special magic initialization code
  */
@@ -479,6 +529,7 @@ void __init mem_init(void)
 	setup_zero_pages();	/* Setup zeroed pages.  */
 	mem_init_free_highmem();
 	mem_init_print_info(NULL);
+	mem_print_kmap_info();
 
 #ifdef CONFIG_64BIT
 	if ((unsigned long) &_text > (unsigned long) CKSEG0)
-- 
2.21.0