commit da49e2010b3cb88b4755d69d38fe90af6ba218b2

Author: Dave Anderson <anderson@redhat.com>

Date:   Fri Jun 1 10:58:00 2018 -0400

    Update for the recognition of the new x86_64 CPU_ENTRY_AREA virtual

    address range introduced in Linux 4.15.  The memory range exists

    above the vmemmap range and below the mapped kernel static text/data

    region, and where all of the x86_64 exception stacks have been moved.

    Without the patch, reads from the new memory region fail because the

    address range is not recognized as a legitimate virtual address.

    Most notable is the failure of "bt" on tasks whose backtraces

    originate from any of the exception stacks, which fail with the two

    error messages "bt: seek error: kernel virtual address: <address>

    type: stack contents" followed by "bt: read of stack at <address>

    failed".

    (anderson@redhat.com)

diff --git a/defs.h b/defs.h

index 931be07..6e6f6be 100644

--- a/defs.h

+++ b/defs.h

@@ -3391,6 +3391,9 @@ struct arm64_stackframe {

 #define VSYSCALL_START             0xffffffffff600000

 #define VSYSCALL_END               0xffffffffff601000

+#define CPU_ENTRY_AREA_START       0xfffffe0000000000

+#define CPU_ENTRY_AREA_END         0xfffffe7fffffffff

+

 #define PTOV(X)               ((unsigned long)(X)+(machdep->kvbase))

 #define VTOP(X)               x86_64_VTOP((ulong)(X))

 #define IS_VMALLOC_ADDR(X)    x86_64_IS_VMALLOC_ADDR((ulong)(X))

@@ -5829,6 +5832,8 @@ struct machine_specific {

 	ulong kpti_entry_stack;

 	ulong kpti_entry_stack_size;

 	ulong ptrs_per_pgd;

+	ulong cpu_entry_area_start;

+	ulong cpu_entry_area_end;

 };

 #define KSYMS_START    (0x1)

diff --git a/x86_64.c b/x86_64.c

index 1d5e155..54b6539 100644

--- a/x86_64.c

+++ b/x86_64.c

@@ -407,6 +407,11 @@ x86_64_init(int when)

 				machdep->machspec->modules_end = MODULES_END_2_6_31;

 			}

 		}

+		if (STRUCT_EXISTS("cpu_entry_area")) {

+			machdep->machspec->cpu_entry_area_start = CPU_ENTRY_AREA_START;	

+			machdep->machspec->cpu_entry_area_end = CPU_ENTRY_AREA_END;	

+		}

+

                 STRUCT_SIZE_INIT(cpuinfo_x86, "cpuinfo_x86");

 		/* 

 		 * Before 2.6.25 the structure was called gate_struct

@@ -879,20 +884,21 @@ x86_64_dump_machdep_table(ulong arg)

 	/* pml4 and upml is legacy for extension modules */

 	if (ms->pml4) {

-		fprintf(fp, "			  pml4: %lx\n", (ulong)ms->pml4);

-		fprintf(fp, "		last_pml4_read: %lx\n", (ulong)ms->last_pml4_read);

+		fprintf(fp, "                     pml4: %lx\n", (ulong)ms->pml4);

+		fprintf(fp, "           last_pml4_read: %lx\n", (ulong)ms->last_pml4_read);

 	} else {

-		fprintf(fp, "		      pml4: (unused)\n");

-		fprintf(fp, "	    last_pml4_read: (unused)\n");

+		fprintf(fp, "                     pml4: (unused)\n");

+		fprintf(fp, "           last_pml4_read: (unused)\n");

 	}

 	if (ms->upml) {

-		fprintf(fp, "		      upml: %lx\n", (ulong)ms->upml);

-		fprintf(fp, "	    last_upml_read: %lx\n", (ulong)ms->last_upml_read);

+		fprintf(fp, "                     upml: %lx\n", (ulong)ms->upml);

+		fprintf(fp, "           last_upml_read: %lx\n", (ulong)ms->last_upml_read);

 	} else {

-		fprintf(fp, "		      upml: (unused)\n");

-		fprintf(fp, "	    last_upml_read: (unused)\n");

+		fprintf(fp, "                 GART_end: %lx\n", ms->GART_end);

+		fprintf(fp, "                     upml: (unused)\n");

+		fprintf(fp, "           last_upml_read: (unused)\n");

 	}

 	if (ms->p4d) {

@@ -1016,10 +1022,14 @@ x86_64_dump_machdep_table(ulong arg)

 			fprintf(fp, "\n   ");

 		fprintf(fp, "%016lx ", ms->stkinfo.ibase[c]);

 	}

-	fprintf(fp, "\n                 kpti_entry_stack_size: %ld", ms->kpti_entry_stack_size);

-	fprintf(fp, "\n                      kpti_entry_stack: ");

+	fprintf(fp, "\n    kpti_entry_stack_size: ");

+	if (ms->kpti_entry_stack_size)

+		fprintf(fp, "%ld", ms->kpti_entry_stack_size);

+	else

+		fprintf(fp, "(unused)");

+	fprintf(fp, "\n         kpti_entry_stack: ");

 	if (machdep->flags & KPTI) {

-		fprintf(fp, "%lx\n   ", ms->kpti_entry_stack);

+		fprintf(fp, "(percpu: %lx):\n   ", ms->kpti_entry_stack);

 		for (c = 0; c < cpus; c++) {

 			if (c && !(c%4))

 				fprintf(fp, "\n   ");

@@ -1028,6 +1038,16 @@ x86_64_dump_machdep_table(ulong arg)

 		fprintf(fp, "\n");

 	} else

 		fprintf(fp, "(unused)\n");

+	fprintf(fp, "     cpu_entry_area_start: ");

+	if (ms->cpu_entry_area_start)

+		fprintf(fp, "%016lx\n", (ulong)ms->cpu_entry_area_start);

+	else

+		fprintf(fp, "(unused)\n");

+	fprintf(fp, "       cpu_entry_area_end: ");

+	if (ms->cpu_entry_area_end)

+		fprintf(fp, "%016lx\n", (ulong)ms->cpu_entry_area_end);

+	else

+		fprintf(fp, "(unused)\n");

 }

 /*

@@ -1586,7 +1606,10 @@ x86_64_IS_VMALLOC_ADDR(ulong vaddr)

                 ((machdep->flags & VMEMMAP) && 

 		 (vaddr >= VMEMMAP_VADDR && vaddr <= VMEMMAP_END)) ||

                 (vaddr >= MODULES_VADDR && vaddr <= MODULES_END) ||

-		(vaddr >= VSYSCALL_START && vaddr < VSYSCALL_END));

+		(vaddr >= VSYSCALL_START && vaddr < VSYSCALL_END) ||

+		(machdep->machspec->cpu_entry_area_start && 

+		 vaddr >= machdep->machspec->cpu_entry_area_start &&

+		 vaddr <= machdep->machspec->cpu_entry_area_end));

 }

 static int