[PATCH] x86_64: Unmap NULL during early bootup

We should zap the low mappings, as soon as possible, so that we can catch
kernel bugs more effectively. Previously early boot had NULL mapped
and didn't trap on NULL references.

This patch introduces boot_level4_pgt, which will always have low identity
addresses mapped.  Druing boot, all the processors will use this as their
level4 pgt.  On BP, we will switch to init_level4_pgt as soon as we enter C
code and zap the low mappings as soon as we are done with the usage of
identity low mapped addresses.  On AP's we will zap the low mappings as
soon as we jump to C code.

Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: Ashok Raj <ashok.raj@intel.com>
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

diff --git a/arch/i386/kernel/acpi/boot.c b/arch/i386/kernel/acpi/boot.c
index 82754bb80e20c97e26f3700aa1b14e9f2652f2bc..f36677241ecd528527528cc779ee6fb067de7926 100644 (file)
--- a/arch/i386/kernel/acpi/boot.c
+++ b/arch/i386/kernel/acpi/boot.c
@@ -542,7 +542,7 @@ acpi_scan_rsdp(unsigned long start, unsigned long length)
         * RSDP signature.
         */
        for (offset = 0; offset < length; offset += 16) {
-               if (strncmp((char *)(start + offset), "RSD PTR ", sig_len))
+               if (strncmp((char *)(phys_to_virt(start) + offset), "RSD PTR ", sig_len))
                        continue;
                return (start + offset);
        }

diff --git a/arch/x86_64/kernel/head.S b/arch/x86_64/kernel/head.S
index b92e5f45ed46743ab03fbd7e2dbb4c44da5057ab..15290968e49db562753b720f15b9d564500f5668 100644 (file)
--- a/arch/x86_64/kernel/head.S
+++ b/arch/x86_64/kernel/head.S
@@ -12,6 +12,7 @@
 
 #include <linux/linkage.h>
 #include <linux/threads.h>
+#include <linux/init.h>
 #include <asm/desc.h>
 #include <asm/segment.h>
 #include <asm/page.h>
@@ -70,7 +71,7 @@ startup_32:
        movl    %eax, %cr4
 
        /* Setup early boot stage 4 level pagetables */
-       movl    $(init_level4_pgt - __START_KERNEL_map), %eax
+       movl    $(boot_level4_pgt - __START_KERNEL_map), %eax
        movl    %eax, %cr3
 
        /* Setup EFER (Extended Feature Enable Register) */
@@ -113,7 +114,7 @@ startup_64:
        movq    %rax, %cr4
 
        /* Setup early boot stage 4 level pagetables. */
-       movq    $(init_level4_pgt - __START_KERNEL_map), %rax
+       movq    $(boot_level4_pgt - __START_KERNEL_map), %rax
        movq    %rax, %cr3
 
        /* Check if nx is implemented */
@@ -240,20 +241,10 @@ ljumpvector:
 ENTRY(stext)
 ENTRY(_stext)
 
-       /*
-        * This default setting generates an ident mapping at address 0x100000
-        * and a mapping for the kernel that precisely maps virtual address
-        * 0xffffffff80000000 to physical address 0x000000. (always using
-        * 2Mbyte large pages provided by PAE mode)
-        */
 .org 0x1000
 ENTRY(init_level4_pgt)
-       .quad   0x0000000000002007 + __PHYSICAL_START   /* -> level3_ident_pgt */
-       .fill   255,8,0
-       .quad   0x000000000000a007 + __PHYSICAL_START
-       .fill   254,8,0
-       /* (2^48-(2*1024*1024*1024))/(2^39) = 511 */
-       .quad   0x0000000000003007 + __PHYSICAL_START   /* -> level3_kernel_pgt */
+       /* This gets initialized in x86_64_start_kernel */
+       .fill   512,8,0
 
 .org 0x2000
 ENTRY(level3_ident_pgt)
@@ -350,6 +341,24 @@ ENTRY(wakeup_level4_pgt)
        .quad   0x0000000000003007 + __PHYSICAL_START   /* -> level3_kernel_pgt */
 #endif
 
+#ifndef CONFIG_HOTPLUG_CPU
+       __INITDATA
+#endif
+       /*
+        * This default setting generates an ident mapping at address 0x100000
+        * and a mapping for the kernel that precisely maps virtual address
+        * 0xffffffff80000000 to physical address 0x000000. (always using
+        * 2Mbyte large pages provided by PAE mode)
+        */
+       .align PAGE_SIZE
+ENTRY(boot_level4_pgt)
+       .quad   0x0000000000002007 + __PHYSICAL_START   /* -> level3_ident_pgt */
+       .fill   255,8,0
+       .quad   0x000000000000a007 + __PHYSICAL_START
+       .fill   254,8,0
+       /* (2^48-(2*1024*1024*1024))/(2^39) = 511 */
+       .quad   0x0000000000003007 + __PHYSICAL_START   /* -> level3_kernel_pgt */
+
        .data
 
        .align 16

diff --git a/arch/x86_64/kernel/head64.c b/arch/x86_64/kernel/head64.c
index cf6ab147a2a5dc806cfbd4ead4912cfaca1c8258..e0f12d49db4cd895a20646ee2e7126bf0622c4f2 100644 (file)
--- a/arch/x86_64/kernel/head64.c
+++ b/arch/x86_64/kernel/head64.c
@@ -19,6 +19,7 @@
 #include <asm/bootsetup.h>
 #include <asm/setup.h>
 #include <asm/desc.h>
+#include <asm/pgtable.h>
 
 /* Don't add a printk in there. printk relies on the PDA which is not initialized 
    yet. */
@@ -86,6 +87,13 @@ void __init x86_64_start_kernel(char * real_mode_data)
                set_intr_gate(i, early_idt_handler);
        asm volatile("lidt %0" :: "m" (idt_descr));
        clear_bss();
+
+       /*
+        * switch to init_level4_pgt from boot_level4_pgt
+        */
+       memcpy(init_level4_pgt, boot_level4_pgt, PTRS_PER_PGD*sizeof(pgd_t));
+       asm volatile("movq %0,%%cr3" :: "r" (__pa_symbol(&init_level4_pgt)));
+
        pda_init(0);
        copy_bootdata(real_mode_data);
 #ifdef CONFIG_SMP

diff --git a/arch/x86_64/kernel/mpparse.c b/arch/x86_64/kernel/mpparse.c
index 8f6958e79455e05a2eed59910dc0c04e8b40b1ad..4a581d1cefbd40954a4a49b0d8e328dbf6f7b0f0 100644 (file)
--- a/arch/x86_64/kernel/mpparse.c
+++ b/arch/x86_64/kernel/mpparse.c
@@ -549,7 +549,7 @@ void __init get_smp_config (void)
                 * Read the physical hardware table.  Anything here will
                 * override the defaults.
                 */
-               if (!smp_read_mpc((void *)(unsigned long)mpf->mpf_physptr)) {
+               if (!smp_read_mpc(phys_to_virt(mpf->mpf_physptr))) {
                        smp_found_config = 0;
                        printk(KERN_ERR "BIOS bug, MP table errors detected!...\n");
                        printk(KERN_ERR "... disabling SMP support. (tell your hw vendor)\n");

diff --git a/arch/x86_64/kernel/setup.c b/arch/x86_64/kernel/setup.c
index 99cfa751949ade3822ad89b0baa4864a0b3197a7..f76f3743f5d74df6336ef7a2cb4aa1acd95f95ab 100644 (file)
--- a/arch/x86_64/kernel/setup.c
+++ b/arch/x86_64/kernel/setup.c
@@ -571,6 +571,8 @@ void __init setup_arch(char **cmdline_p)
 
        init_memory_mapping(0, (end_pfn_map << PAGE_SHIFT));
 
+       zap_low_mappings(0);
+
 #ifdef CONFIG_ACPI
        /*
         * Initialize the ACPI boot-time table parser (gets the RSDP and SDT).

diff --git a/arch/x86_64/kernel/setup64.c b/arch/x86_64/kernel/setup64.c
index 79190891fbc56414ad65245f799d13d454002356..06dc354375c3fa684e5d7cbe16e74ec69a4a16f5 100644 (file)
--- a/arch/x86_64/kernel/setup64.c
+++ b/arch/x86_64/kernel/setup64.c
@@ -141,7 +141,6 @@ void pda_init(int cpu)
                        panic("cannot allocate irqstack for cpu %d", cpu); 
        }
 
-       asm volatile("movq %0,%%cr3" :: "r" (__pa_symbol(&init_level4_pgt)));
 
        pda->irqstackptr += IRQSTACKSIZE-64;
 } 
@@ -197,6 +196,7 @@ void __cpuinit cpu_init (void)
        /* CPU 0 is initialised in head64.c */
        if (cpu != 0) {
                pda_init(cpu);
+               zap_low_mappings(cpu);
        } else 
                estacks = boot_exception_stacks; 
 

diff --git a/arch/x86_64/kernel/smpboot.c b/arch/x86_64/kernel/smpboot.c
index 658a81b33f3bf1a1d31087f2e3b3637bd76ddab0..3393fc08823b5362854f2980c44a1b59f727206d 100644 (file)
--- a/arch/x86_64/kernel/smpboot.c
+++ b/arch/x86_64/kernel/smpboot.c
@@ -1063,9 +1063,6 @@ int __cpuinit __cpu_up(unsigned int cpu)
  */
 void __init smp_cpus_done(unsigned int max_cpus)
 {
-#ifndef CONFIG_HOTPLUG_CPU
-       zap_low_mappings();
-#endif
        smp_cleanup_boot();
 
 #ifdef CONFIG_X86_IO_APIC

diff --git a/arch/x86_64/mm/init.c b/arch/x86_64/mm/init.c
index 2b1d6c382396ec17d8d2ac353f6c96b037d138c4..be483a1d7b5420ed865fea3fc5e990cf10d0cd60 100644 (file)
--- a/arch/x86_64/mm/init.c
+++ b/arch/x86_64/mm/init.c
@@ -312,12 +312,19 @@ void __init init_memory_mapping(unsigned long start, unsigned long end)
 
 extern struct x8664_pda cpu_pda[NR_CPUS];
 
-/* Assumes all CPUs still execute in init_mm */
-void zap_low_mappings(void)
+void __cpuinit zap_low_mappings(int cpu)
 {
-       pgd_t *pgd = pgd_offset_k(0UL);
-       pgd_clear(pgd);
-       flush_tlb_all();
+       if (cpu == 0) {
+               pgd_t *pgd = pgd_offset_k(0UL);
+               pgd_clear(pgd);
+       } else {
+               /*
+                * For AP's, zap the low identity mappings by changing the cr3
+                * to init_level4_pgt and doing local flush tlb all
+                */
+               asm volatile("movq %0,%%cr3" :: "r" (__pa_symbol(&init_level4_pgt)));
+       }
+       __flush_tlb_all();
 }
 
 /* Compute zone sizes for the DMA and DMA32 zones in a node. */
@@ -474,14 +481,13 @@ void __init mem_init(void)
                datasize >> 10,
                initsize >> 10);
 
+#ifdef CONFIG_SMP
        /*
-        * Subtle. SMP is doing its boot stuff late (because it has to
-        * fork idle threads) - but it also needs low mappings for the
-        * protected-mode entry to work. We zap these entries only after
-        * the WP-bit has been tested.
+        * Sync boot_level4_pgt mappings with the init_level4_pgt
+        * except for the low identity mappings which are already zapped
+        * in init_level4_pgt. This sync-up is essential for AP's bringup
         */
-#ifndef CONFIG_SMP
-       zap_low_mappings();
+       memcpy(boot_level4_pgt+1, init_level4_pgt+1, (PTRS_PER_PGD-1)*sizeof(pgd_t));
 #endif
 }
 

diff --git a/include/asm-x86_64/pgtable.h b/include/asm-x86_64/pgtable.h
index 7a07196a72022f56ebef52ace38ec35d88be7c9e..a204efb553dc2b7a02334280b6d47a1e533f356c 100644 (file)
--- a/include/asm-x86_64/pgtable.h
+++ b/include/asm-x86_64/pgtable.h
@@ -16,6 +16,7 @@ extern pud_t level3_physmem_pgt[512];
 extern pud_t level3_ident_pgt[512];
 extern pmd_t level2_kernel_pgt[512];
 extern pgd_t init_level4_pgt[];
+extern pgd_t boot_level4_pgt[];
 extern unsigned long __supported_pte_mask;
 
 #define swapper_pg_dir init_level4_pgt

diff --git a/include/asm-x86_64/proto.h b/include/asm-x86_64/proto.h
index c251152a0658958c3b0a39fd2503741ab003376d..34501086afef57a81ab0369dcea9e0e1bad2c76f 100644 (file)
--- a/include/asm-x86_64/proto.h
+++ b/include/asm-x86_64/proto.h
@@ -11,6 +11,8 @@ struct pt_regs;
 extern void start_kernel(void);
 extern void pda_init(int); 
 
+extern void zap_low_mappings(int cpu);
+
 extern void early_idt_handler(void);
 
 extern void mcheck_init(struct cpuinfo_x86 *c);

diff --git a/include/asm-x86_64/smp.h b/include/asm-x86_64/smp.h
index c57ce40713426d6ef69b657adccb8d3e274745bb..592161e979e5396ce508472c42850dd82e5262e4 100644 (file)
--- a/include/asm-x86_64/smp.h
+++ b/include/asm-x86_64/smp.h
@@ -47,7 +47,6 @@ extern void lock_ipi_call_lock(void);
 extern void unlock_ipi_call_lock(void);
 extern int smp_num_siblings;
 extern void smp_send_reschedule(int cpu);
-extern void zap_low_mappings(void);
 void smp_stop_cpu(void);
 extern int smp_call_function_single(int cpuid, void (*func) (void *info),
                                void *info, int retry, int wait);