Subject: [PATCH 1/3] boot: fortify early_idt_handlers definition From: Fernando Luis Vazquez Cao <fernando@xxxxxxxxxxxxx> The current definition is too brittle which makes it easy to screw things up when modifying the code. Add some comments while at it. Signed-off-by: Fernando Luis Vazquez Cao <fernando@xxxxxxxxxxxxx> --- diff -urNp linux-3.3-rc6-orig/arch/x86/include/asm/segment.h linux-3.3-rc6/arch/x86/include/asm/segment.h --- linux-3.3-rc6-orig/arch/x86/include/asm/segment.h 2012-01-05 08:55:44.000000000 +0900 +++ linux-3.3-rc6/arch/x86/include/asm/segment.h 2012-03-09 17:50:40.965438325 +0900 @@ -210,8 +210,10 @@ #define TLS_SIZE (GDT_ENTRY_TLS_ENTRIES * 8) #ifdef __KERNEL__ +#define EARLY_IDT_HANDLER_SIZE 16 #ifndef __ASSEMBLY__ -extern const char early_idt_handlers[NUM_EXCEPTION_VECTORS][10]; +extern const char + early_idt_handlers[NUM_EXCEPTION_VECTORS][EARLY_IDT_HANDLER_SIZE]; #endif #endif diff -urNp linux-3.3-rc6-orig/arch/x86/kernel/head_64.S linux-3.3-rc6/arch/x86/kernel/head_64.S --- linux-3.3-rc6-orig/arch/x86/kernel/head_64.S 2012-03-09 17:48:04.563492864 +0900 +++ linux-3.3-rc6/arch/x86/kernel/head_64.S 2012-03-09 18:06:13.329009305 +0900 @@ -272,11 +272,20 @@ bad_address: .section ".init.text","ax" #ifdef CONFIG_EARLY_PRINTK .globl early_idt_handlers + .align EARLY_IDT_HANDLER_SIZE early_idt_handlers: i = 0 .rept NUM_EXCEPTION_VECTORS movl $i, %esi jmp early_idt_handler + /* + * early_idt_handlers is treated as a + * [NUM_EXCEPTION_VECTORS][EARLY_IDT_HANDLER_SIZE] array from C code + * so we have to make sure that each handler fits in its + * EARLY_IDT_HANDLER_SIZE bytes long slot. Handlers shorter than that + * will be taken care of by the align directive below. + */ + .align EARLY_IDT_HANDLER_SIZE i = i + 1 .endr #endif
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