From: "Eric W. Biederman" For one kernel to report a crash another kernel has created we need to have 2 kernels loaded simultaneously in memory. To accomplish this the two kernels need to built to run at different physical addresses. This patch adds the CONFIG_PHYSICAL_START option to the x86_64 kernel so we can do just that. You need to know what you are doing and the ramifications are before changing this value, and most users won't care so I have made it depend on CONFIG_EMBEDDED bzImage kernels will work and run at a different address when compiled with this option but they will still load at 1MB. If you need a kernel loaded at a different address as well you need to boot a vmlinux. Signed-off-by: Eric Biederman Signed-off-by: Andrew Morton --- 25-akpm/arch/x86_64/Kconfig | 11 +++++++++++ 25-akpm/arch/x86_64/boot/compressed/head.S | 7 ++++--- 25-akpm/arch/x86_64/boot/compressed/misc.c | 7 ++++--- 25-akpm/arch/x86_64/kernel/head.S | 18 +++++++++--------- 25-akpm/include/asm-x86_64/page.h | 6 ++++-- 5 files changed, 32 insertions(+), 17 deletions(-) diff -puN arch/x86_64/boot/compressed/head.S~x86_64-config-kernel-start arch/x86_64/boot/compressed/head.S --- 25/arch/x86_64/boot/compressed/head.S~x86_64-config-kernel-start 2005-01-23 14:47:15.075905280 -0800 +++ 25-akpm/arch/x86_64/boot/compressed/head.S 2005-01-23 14:47:15.084903912 -0800 @@ -28,6 +28,7 @@ #include #include +#include .code32 .globl startup_32 @@ -77,7 +78,7 @@ startup_32: jnz 3f addl $8,%esp xorl %ebx,%ebx - ljmp $(__KERNEL_CS), $0x100000 + ljmp $(__KERNEL_CS), $__PHYSICAL_START /* * We come here, if we were loaded high. @@ -103,7 +104,7 @@ startup_32: popl %ecx # lcount popl %edx # high_buffer_start popl %eax # hcount - movl $0x100000,%edi + movl $__PHYSICAL_START,%edi cli # make sure we don't get interrupted ljmp $(__KERNEL_CS), $0x1000 # and jump to the move routine @@ -128,7 +129,7 @@ move_routine_start: movsl movl %ebx,%esi # Restore setup pointer xorl %ebx,%ebx - ljmp $(__KERNEL_CS), $0x100000 + ljmp $(__KERNEL_CS), $__PHYSICAL_START move_routine_end: diff -puN arch/x86_64/boot/compressed/misc.c~x86_64-config-kernel-start arch/x86_64/boot/compressed/misc.c --- 25/arch/x86_64/boot/compressed/misc.c~x86_64-config-kernel-start 2005-01-23 14:47:15.076905128 -0800 +++ 25-akpm/arch/x86_64/boot/compressed/misc.c 2005-01-23 14:47:15.084903912 -0800 @@ -11,6 +11,7 @@ #include "miscsetup.h" #include +#include /* * gzip declarations @@ -284,7 +285,7 @@ void setup_normal_output_buffer(void) #else if ((ALT_MEM_K > EXT_MEM_K ? ALT_MEM_K : EXT_MEM_K) < 1024) error("Less than 2MB of memory"); #endif - output_data = (char *)0x100000; /* Points to 1M */ + output_data = (char *)__PHYSICAL_START; /* Normally Points to 1M */ free_mem_end_ptr = (long)real_mode; } @@ -307,8 +308,8 @@ void setup_output_buffer_if_we_run_high( low_buffer_size = low_buffer_end - LOW_BUFFER_START; high_loaded = 1; free_mem_end_ptr = (long)high_buffer_start; - if ( (0x100000 + low_buffer_size) > ((ulg)high_buffer_start)) { - high_buffer_start = (uch *)(0x100000 + low_buffer_size); + if ( (__PHYSICAL_START + low_buffer_size) > ((ulg)high_buffer_start)) { + high_buffer_start = (uch *)(__PHYSICAL_START + low_buffer_size); mv->hcount = 0; /* say: we need not to move high_buffer */ } else mv->hcount = -1; diff -puN arch/x86_64/Kconfig~x86_64-config-kernel-start arch/x86_64/Kconfig --- 25/arch/x86_64/Kconfig~x86_64-config-kernel-start 2005-01-23 14:47:15.078904824 -0800 +++ 25-akpm/arch/x86_64/Kconfig 2005-01-23 14:47:15.085903760 -0800 @@ -350,6 +350,17 @@ config X86_MCE_INTEL help Additional support for intel specific MCE features such as the thermal monitor. + +config PHYSICAL_START + hex "Physical address where the kernel is loaded" if EMBEDDED + default "0x100000" + help + This gives the physical address where the kernel is loaded. + Primarily used in the case of kexec on panic where the + fail safe kernel needs to run at a different address than + the panic-ed kernel. + + Don't change this unless you know what you are doing. endmenu # diff -puN arch/x86_64/kernel/head.S~x86_64-config-kernel-start arch/x86_64/kernel/head.S --- 25/arch/x86_64/kernel/head.S~x86_64-config-kernel-start 2005-01-23 14:47:15.079904672 -0800 +++ 25-akpm/arch/x86_64/kernel/head.S 2005-01-23 14:47:15.086903608 -0800 @@ -235,23 +235,23 @@ ENTRY(_stext) */ .org 0x1000 ENTRY(init_level4_pgt) - .quad 0x0000000000102007 /* -> level3_ident_pgt */ + .quad 0x0000000000002007 + __PHYSICAL_START /* -> level3_ident_pgt */ .fill 255,8,0 - .quad 0x000000000010a007 + .quad 0x000000000000a007 + __PHYSICAL_START .fill 254,8,0 /* (2^48-(2*1024*1024*1024))/(2^39) = 511 */ - .quad 0x0000000000103007 /* -> level3_kernel_pgt */ + .quad 0x0000000000003007 + __PHYSICAL_START /* -> level3_kernel_pgt */ .org 0x2000 ENTRY(level3_ident_pgt) - .quad 0x0000000000104007 + .quad 0x0000000000004007 + __PHYSICAL_START .fill 511,8,0 .org 0x3000 ENTRY(level3_kernel_pgt) .fill 510,8,0 /* (2^48-(2*1024*1024*1024)-((2^39)*511))/(2^30) = 510 */ - .quad 0x0000000000105007 /* -> level2_kernel_pgt */ + .quad 0x0000000000005007 + __PHYSICAL_START /* -> level2_kernel_pgt */ .fill 1,8,0 .org 0x4000 @@ -324,17 +324,17 @@ ENTRY(empty_bad_pmd_table) .org 0xa000 ENTRY(level3_physmem_pgt) - .quad 0x0000000000105007 /* -> level2_kernel_pgt (so that __va works even before pagetable_init) */ + .quad 0x0000000000005007 + __PHYSICAL_START /* -> level2_kernel_pgt (so that __va works even before pagetable_init) */ .org 0xb000 #ifdef CONFIG_ACPI_SLEEP ENTRY(wakeup_level4_pgt) - .quad 0x0000000000102007 /* -> level3_ident_pgt */ + .quad 0x0000000000002007 + __PHYSICAL_START /* -> level3_ident_pgt */ .fill 255,8,0 - .quad 0x000000000010a007 + .quad 0x000000000000a007 + __PHYSICAL_START .fill 254,8,0 /* (2^48-(2*1024*1024*1024))/(2^39) = 511 */ - .quad 0x0000000000103007 /* -> level3_kernel_pgt */ + .quad 0x0000000000003007 + __PHYSICAL_START /* -> level3_kernel_pgt */ #endif .data diff -puN include/asm-x86_64/page.h~x86_64-config-kernel-start include/asm-x86_64/page.h --- 25/include/asm-x86_64/page.h~x86_64-config-kernel-start 2005-01-23 14:47:15.080904520 -0800 +++ 25-akpm/include/asm-x86_64/page.h 2005-01-23 14:47:15.086903608 -0800 @@ -67,12 +67,14 @@ extern unsigned long vm_stack_flags, vm_ extern unsigned long vm_data_default_flags, vm_data_default_flags32; extern unsigned long vm_force_exec32; -#define __START_KERNEL 0xffffffff80100000UL +#define __PHYSICAL_START ((unsigned long)CONFIG_PHYSICAL_START) +#define __START_KERNEL (__START_KERNEL_map + __PHYSICAL_START) #define __START_KERNEL_map 0xffffffff80000000UL #define __PAGE_OFFSET 0xffff810000000000UL #else -#define __START_KERNEL 0xffffffff80100000 +#define __PHYSICAL_START CONFIG_PHYSICAL_START +#define __START_KERNEL (__START_KERNEL_map + __PHYSICAL_START) #define __START_KERNEL_map 0xffffffff80000000 #define __PAGE_OFFSET 0xffff810000000000 #endif /* !__ASSEMBLY__ */ _