From f6c2e3330d3fdd5474bc3756da46fca889a30e33 Mon Sep 17 00:00:00 2001 From: "Siddha, Suresh B" Date: Sat, 5 Nov 2005 17:25:53 +0100 Subject: [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 Signed-off-by: Ashok Raj Signed-off-by: Andi Kleen Signed-off-by: Linus Torvalds --- arch/x86_64/kernel/head64.c | 8 ++++++++ 1 file changed, 8 insertions(+) (limited to 'arch/x86_64/kernel/head64.c') diff --git a/arch/x86_64/kernel/head64.c b/arch/x86_64/kernel/head64.c index cf6ab147a2a5..e0f12d49db4c 100644 --- a/arch/x86_64/kernel/head64.c +++ b/arch/x86_64/kernel/head64.c @@ -19,6 +19,7 @@ #include #include #include +#include /* 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 -- cgit v1.2.3