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 <kernelf...@gmail.com>
Cc: Thomas Gleixner <t...@linutronix.de>
Cc: Ingo Molnar <mi...@redhat.com>
Cc: Borislav Petkov <b...@alien8.de>
Cc: "H. Peter Anvin" <h...@zytor.com>
Cc: "Kirill A. Shutemov" <kirill.shute...@linux.intel.com>
Cc: Cao jin <caoj.f...@cn.fujitsu.com>
Cc: Wei Huang <w...@redhat.com>
Cc: Chao Fan <fanc.f...@cn.fujitsu.com>
Cc: Nicolai Stange <nsta...@suse.de>
Cc: Dou Liyang <douly.f...@cn.fujitsu.com>
Cc: linux-kernel@vger.kernel.org
---
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
