[POWERPC] DEBUG_PAGEALLOC for 32-bit

Here's an implementation of DEBUG_PAGEALLOC for ppc32. It disables BAT
mapping and is only tested with Hash table based processor though it
shouldn't be too hard to adapt it to others.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
 arch/powerpc/Kconfig.debug       |    9 ++++++
 arch/powerpc/mm/init_32.c        |    4 +++
 arch/powerpc/mm/pgtable_32.c     |   52 +++++++++++++++++++++++++++++++++++++++
 arch/powerpc/mm/ppc_mmu_32.c     |    4 ++-
 include/asm-powerpc/cacheflush.h |    6 ++++
 5 files changed, 74 insertions(+), 1 deletion(-)
Signed-off-by: Paul Mackerras <paulus@samba.org>

diff --git a/arch/powerpc/Kconfig.debug b/arch/powerpc/Kconfig.debug
index 50f48f0..0f8bb86 100644 (file)
--- a/arch/powerpc/Kconfig.debug
+++ b/arch/powerpc/Kconfig.debug
@@ -18,6 +18,15 @@ config DEBUG_STACK_USAGE
 
          This option will slow down process creation somewhat.
 
+config DEBUG_PAGEALLOC
+        bool "Debug page memory allocations"
+        depends on DEBUG_KERNEL && !SOFTWARE_SUSPEND && PPC32
+        help
+          Unmap pages from the kernel linear mapping after free_pages().
+          This results in a large slowdown, but helps to find certain types
+          of memory corruptions.
+
+
 config HCALL_STATS
        bool "Hypervisor call instrumentation"
        depends on PPC_PSERIES && DEBUG_FS

diff --git a/arch/powerpc/mm/init_32.c b/arch/powerpc/mm/init_32.c
index 0e53ca8..5fce6cc 100644 (file)
--- a/arch/powerpc/mm/init_32.c
+++ b/arch/powerpc/mm/init_32.c
@@ -115,6 +115,10 @@ void MMU_setup(void)
        if (strstr(cmd_line, "noltlbs")) {
                __map_without_ltlbs = 1;
        }
+#ifdef CONFIG_DEBUG_PAGEALLOC
+       __map_without_bats = 1;
+       __map_without_ltlbs = 1;
+#endif
 }
 
 /*

diff --git a/arch/powerpc/mm/pgtable_32.c b/arch/powerpc/mm/pgtable_32.c
index f75f2fc..8a2fc16 100644 (file)
--- a/arch/powerpc/mm/pgtable_32.c
+++ b/arch/powerpc/mm/pgtable_32.c
@@ -451,3 +451,55 @@ exit:
        return ret;
 }
 
+#ifdef CONFIG_DEBUG_PAGEALLOC
+
+static int __change_page_attr(struct page *page, pgprot_t prot)
+{
+       pte_t *kpte;
+       pmd_t *kpmd;
+       unsigned long address;
+
+       BUG_ON(PageHighMem(page));
+       address = (unsigned long)page_address(page);
+
+       if (v_mapped_by_bats(address) || v_mapped_by_tlbcam(address))
+               return 0;
+       if (!get_pteptr(&init_mm, address, &kpte, &kpmd))
+               return -EINVAL;
+       set_pte_at(&init_mm, address, kpte, mk_pte(page, prot));
+       wmb();
+       flush_HPTE(0, address, pmd_val(*kpmd));
+       pte_unmap(kpte);
+
+       return 0;
+}
+
+/*
+ * Change the page attributes of an page in the linear mapping.
+ *
+ * THIS CONFLICTS WITH BAT MAPPINGS, DEBUG USE ONLY
+ */
+static int change_page_attr(struct page *page, int numpages, pgprot_t prot)
+{
+       int i, err = 0;
+       unsigned long flags;
+
+       local_irq_save(flags);
+       for (i = 0; i < numpages; i++, page++) {
+               err = __change_page_attr(page, prot);
+               if (err)
+                       break;
+       }
+       local_irq_restore(flags);
+       return err;
+}
+
+
+void kernel_map_pages(struct page *page, int numpages, int enable)
+{
+       if (PageHighMem(page))
+               return;
+
+       change_page_attr(page, numpages, enable ? PAGE_KERNEL : __pgprot(0));
+}
+#endif /* CONFIG_DEBUG_PAGEALLOC */

diff --git a/arch/powerpc/mm/ppc_mmu_32.c b/arch/powerpc/mm/ppc_mmu_32.c
index 7cceb2c..0506667 100644 (file)
--- a/arch/powerpc/mm/ppc_mmu_32.c
+++ b/arch/powerpc/mm/ppc_mmu_32.c
@@ -85,8 +85,10 @@ unsigned long __init mmu_mapin_ram(void)
        unsigned long max_size = (256<<20);
        unsigned long align;
 
-       if (__map_without_bats)
+       if (__map_without_bats) {
+               printk(KERN_DEBUG "RAM mapped without BATs\n");
                return 0;
+       }
 
        /* Set up BAT2 and if necessary BAT3 to cover RAM. */
 

diff --git a/include/asm-powerpc/cacheflush.h b/include/asm-powerpc/cacheflush.h
index 08e93e7..ba667a3 100644 (file)
--- a/include/asm-powerpc/cacheflush.h
+++ b/include/asm-powerpc/cacheflush.h
@@ -64,6 +64,12 @@ extern void flush_dcache_phys_range(unsigned long start, unsigned long stop);
        memcpy(dst, src, len)
 
 
+
+#ifdef CONFIG_DEBUG_PAGEALLOC
+/* internal debugging function */
+void kernel_map_pages(struct page *page, int numpages, int enable);
+#endif
+
 #endif /* __KERNEL__ */
 
 #endif /* _ASM_POWERPC_CACHEFLUSH_H */