The boot code becomes a little complicated, and hits some bugs, e.g.
Commit 3a63f70bf4c3a ("x86/boot: Early parse RSDP and save it in
boot_params") broke kexec boot on EFI systems.There is few hint when bug happens. Catching the exception and printing message can give a immediate help, instead of adding more debug_putstr() to narraw down the problem. At present, page fault exception handler is added. And the printed out message looks like: early boot page fault: ENTRY(startup_64) is at: 000000047f67d200 nip: 000000047fdeedd3 fault address: fffffffeef6fde30 Signed-off-by: Pingfan Liu <[email protected]> Cc: Thomas Gleixner <[email protected]> Cc: Ingo Molnar <[email protected]> Cc: Borislav Petkov <[email protected]> Cc: "H. Peter Anvin" <[email protected]> Cc: "Kirill A. Shutemov" <[email protected]> Cc: Cao jin <[email protected]> Cc: Wei Huang <[email protected]> Cc: Chao Fan <[email protected]> Cc: Nicolai Stange <[email protected]> Cc: Dou Liyang <[email protected]> Cc: [email protected] --- arch/x86/boot/compressed/head_64.S | 11 +++++++ arch/x86/boot/compressed/misc.c | 61 ++++++++++++++++++++++++++++++++++++++ 2 files changed, 72 insertions(+) diff --git a/arch/x86/boot/compressed/head_64.S b/arch/x86/boot/compressed/head_64.S index e4a25f9..f589aa2 100644 --- a/arch/x86/boot/compressed/head_64.S +++ b/arch/x86/boot/compressed/head_64.S @@ -527,6 +527,10 @@ relocated: shrq $3, %rcx rep stosq + pushq %rsi /* Save the real mode argument */ + leaq startup_64(%rip), %rdi + call setup_early_boot_idt + popq %rsi /* * Do the extraction, and jump to the new kernel.. */ @@ -659,6 +663,13 @@ no_longmode: #include "../../kernel/verify_cpu.S" + .code64 +.align 8 +ENTRY(boot_page_fault) + mov 8(%rsp), %rdi + call do_boot_page_fault + iretq + .data gdt64: .word gdt_end - gdt diff --git a/arch/x86/boot/compressed/misc.c b/arch/x86/boot/compressed/misc.c index 475a3c6..8aaa582 100644 --- a/arch/x86/boot/compressed/misc.c +++ b/arch/x86/boot/compressed/misc.c @@ -76,6 +76,11 @@ static int lines, cols; #ifdef CONFIG_KERNEL_LZ4 #include "../../../../lib/decompress_unlz4.c" #endif + +#include "../../include/asm/desc.h" +#include "../../include/asm/idt.h" +#include "../../include/asm/traps.h" + /* * NOTE: When adding a new decompressor, please update the analysis in * ../header.S. @@ -429,3 +434,59 @@ void fortify_panic(const char *name) { error("detected buffer overflow"); } + +static unsigned long rt_startup_64; + +void do_boot_page_fault(unsigned long retaddr) +{ + struct desc_ptr idt = { .address = 0, .size = 0 }; + unsigned long fault_address = read_cr2(); + + debug_putstr("early boot page fault:\n"); + debug_putstr("ENTRY(startup_64) is at: "); + debug_puthex(rt_startup_64); + debug_putstr("\n"); + debug_putstr("nip: "); + debug_puthex(retaddr); + debug_putstr("\n"); + debug_putstr("fault address: "); + debug_puthex(fault_address); + debug_putstr("\n"); + + load_idt(&idt); +} + +asmlinkage void boot_page_fault(void); + +static struct idt_data boot_idts[] = { + INTG(X86_TRAP_PF, 0), +}; + +static gate_desc early_boot_idt_table[IDT_ENTRIES] __page_aligned_bss; + +static struct desc_ptr early_boot_idt_descr __ro_after_init = { + .size = (IDT_ENTRIES * 2 * sizeof(unsigned long)) - 1, +}; + +static void +idt_setup_from_table(gate_desc *idt, const struct idt_data *t, int size) +{ + gate_desc desc; + + for (; size > 0; t++, size--) { + idt_init_desc(&desc, t); + write_idt_entry(idt, t->vector, &desc); + } +} + +void setup_early_boot_idt(unsigned long rip) +{ + rt_startup_64 = rip; + /* fill it with runtime address */ + boot_idts[0].addr = boot_page_fault; + early_boot_idt_descr.address = (unsigned long)early_boot_idt_table; + + idt_setup_from_table(early_boot_idt_table, boot_idts, + ARRAY_SIZE(boot_idts)); + load_idt(&early_boot_idt_descr); +} -- 2.7.4
