3 files changed, 113 insertions, 0 deletions

diff --git a/arch/x86_64/Kconfig b/arch/x86_64/Kconfig
index 4f3e925962c3..dd2d116b9ab8 100644
--- a/arch/x86_64/Kconfig
+++ b/arch/x86_64/Kconfig
@@ -427,6 +427,13 @@ config KEXEC
           support.  As of this writing the exact hardware interface is
           strongly in flux, so no good recommendation can be made.
 
+config CRASH_DUMP
+        bool "kernel crash dumps (EXPERIMENTAL)"
+        depends on EMBEDDED
+        depends on EXPERIMENTAL
+        help
+                Generate crash dump after being started by kexec.
+
 config SECCOMP
         bool "Enable seccomp to safely compute untrusted bytecode"
         depends on PROC_FS
diff --git a/arch/x86_64/kernel/crash.c b/arch/x86_64/kernel/crash.c
index abc601f36b6e..4e6c3b729e39 100644
--- a/arch/x86_64/kernel/crash.c
+++ b/arch/x86_64/kernel/crash.c
@@ -11,9 +11,12 @@
 #include <linux/types.h>
 #include <linux/kernel.h>
 #include <linux/smp.h>
+#include <linux/irq.h>
 #include <linux/reboot.h>
 #include <linux/kexec.h>
 #include <linux/delay.h>
+#include <linux/elf.h>
+#include <linux/elfcore.h>
 
 #include <asm/processor.h>
 #include <asm/hardirq.h>
@@ -24,6 +27,71 @@
 /* This keeps a track of which one is crashing cpu. */
 static int crashing_cpu;
 
+static u32 *append_elf_note(u32 *buf, char *name, unsigned type,
+                                                void *data, size_t data_len)
+{
+        struct elf_note note;
+
+        note.n_namesz = strlen(name) + 1;
+        note.n_descsz = data_len;
+        note.n_type   = type;
+        memcpy(buf, &note, sizeof(note));
+        buf += (sizeof(note) +3)/4;
+        memcpy(buf, name, note.n_namesz);
+        buf += (note.n_namesz + 3)/4;
+        memcpy(buf, data, note.n_descsz);
+        buf += (note.n_descsz + 3)/4;
+
+        return buf;
+}
+
+static void final_note(u32 *buf)
+{
+        struct elf_note note;
+
+        note.n_namesz = 0;
+        note.n_descsz = 0;
+        note.n_type   = 0;
+        memcpy(buf, &note, sizeof(note));
+}
+
+static void crash_save_this_cpu(struct pt_regs *regs, int cpu)
+{
+        struct elf_prstatus prstatus;
+        u32 *buf;
+
+        if ((cpu < 0) || (cpu >= NR_CPUS))
+                return;
+
+        /* Using ELF notes here is opportunistic.
+         * I need a well defined structure format
+         * for the data I pass, and I need tags
+         * on the data to indicate what information I have
+         * squirrelled away.  ELF notes happen to provide
+         * all of that that no need to invent something new.
+         */
+
+        buf = (u32*)per_cpu_ptr(crash_notes, cpu);
+
+        if (!buf)
+                return;
+
+        memset(&prstatus, 0, sizeof(prstatus));
+        prstatus.pr_pid = current->pid;
+        elf_core_copy_regs(&prstatus.pr_reg, regs);
+        buf = append_elf_note(buf, "CORE", NT_PRSTATUS, &prstatus,
+                                        sizeof(prstatus));
+        final_note(buf);
+}
+
+static void crash_save_self(struct pt_regs *regs)
+{
+        int cpu;
+
+        cpu = smp_processor_id();
+        crash_save_this_cpu(regs, cpu);
+}
+
 #ifdef CONFIG_SMP
 static atomic_t waiting_for_crash_ipi;
 
@@ -38,6 +106,7 @@ static int crash_nmi_callback(struct pt_regs *regs, int cpu)
                 return 1;
         local_irq_disable();
 
+        crash_save_this_cpu(regs, cpu);
         disable_local_APIC();
         atomic_dec(&waiting_for_crash_ipi);
         /* Assume hlt works */
@@ -113,4 +182,5 @@ void machine_crash_shutdown(struct pt_regs *regs)
         disable_IO_APIC();
 #endif
 
+        crash_save_self(regs);
 }
diff --git a/include/asm-x86_64/kexec.h b/include/asm-x86_64/kexec.h
index cea78543a574..ae28cd44bcd3 100644
--- a/include/asm-x86_64/kexec.h
+++ b/include/asm-x86_64/kexec.h
@@ -3,6 +3,7 @@
 
 #include <asm/page.h>
 #include <asm/proto.h>
+#include <asm/ptrace.h>
 
 /*
  * KEXEC_SOURCE_MEMORY_LIMIT maximum page get_free_page can return.
@@ -27,4 +28,39 @@
 
 #define MAX_NOTE_BYTES 1024
 
+/*
+ * Saving the registers of the cpu on which panic occured in
+ * crash_kexec to save a valid sp. The registers of other cpus
+ * will be saved in machine_crash_shutdown while shooting down them.
+ */
+
+static inline void crash_setup_regs(struct pt_regs *newregs,
+                                                struct pt_regs *oldregs)
+{
+        if (oldregs)
+                memcpy(newregs, oldregs, sizeof(*newregs));
+        else {
+                __asm__ __volatile__("movq %%rbx,%0" : "=m"(newregs->rbx));
+                __asm__ __volatile__("movq %%rcx,%0" : "=m"(newregs->rcx));
+                __asm__ __volatile__("movq %%rdx,%0" : "=m"(newregs->rdx));
+                __asm__ __volatile__("movq %%rsi,%0" : "=m"(newregs->rsi));
+                __asm__ __volatile__("movq %%rdi,%0" : "=m"(newregs->rdi));
+                __asm__ __volatile__("movq %%rbp,%0" : "=m"(newregs->rbp));
+                __asm__ __volatile__("movq %%rax,%0" : "=m"(newregs->rax));
+                __asm__ __volatile__("movq %%rsp,%0" : "=m"(newregs->rsp));
+                __asm__ __volatile__("movq %%r8,%0" : "=m"(newregs->r8));
+                __asm__ __volatile__("movq %%r9,%0" : "=m"(newregs->r9));
+                __asm__ __volatile__("movq %%r10,%0" : "=m"(newregs->r10));
+                __asm__ __volatile__("movq %%r11,%0" : "=m"(newregs->r11));
+                __asm__ __volatile__("movq %%r12,%0" : "=m"(newregs->r12));
+                __asm__ __volatile__("movq %%r13,%0" : "=m"(newregs->r13));
+                __asm__ __volatile__("movq %%r14,%0" : "=m"(newregs->r14));
+                __asm__ __volatile__("movq %%r15,%0" : "=m"(newregs->r15));
+                __asm__ __volatile__("movl %%ss, %%eax;" :"=a"(newregs->ss));
+                __asm__ __volatile__("movl %%cs, %%eax;" :"=a"(newregs->cs));
+                __asm__ __volatile__("pushfq; popq %0" :"=m"(newregs->eflags));
+
+                newregs->rip = (unsigned long)current_text_addr();
+        }
+}
 #endif /* _X86_64_KEXEC_H */