x86_64: Fix ktext mapping if it starts above 0xffffffffa0000000

When all of kernel text is relocated beyond the pre-kASLR highest virtual
address, the scan for region end is not even attempted.

If the kernel text start address is found above LINUX_KTEXT_END_NOKASLR,
unconditionally scan for the region end up to LINUX_KTEXT_END.

The corresponding test case is derived from a real-world dump.

Signed-off-by: Petr Tesarik <[email protected]>

Author: ptesarik

src/addrxlat/x86_64.c

@@ -541,9 +541,10 @@ linux_ktext_extents(struct os_init_data *ctl,
 
 	linearoff = ctl->sys->meth[ADDRXLAT_SYS_METH_KTEXT].param.linear.off;
 	*high = *low;
-	status = highest_linear(&step, high, LINUX_KTEXT_END_NOKASLR,
-				linearoff);
-	if (status == ADDRXLAT_OK && *high == LINUX_KTEXT_END_NOKASLR) {
+	if (*high <= LINUX_KTEXT_END_NOKASLR)
+		status = highest_linear(&step, high, LINUX_KTEXT_END_NOKASLR,
+					linearoff);
+	if (status == ADDRXLAT_OK && *high >= LINUX_KTEXT_END_NOKASLR) {
 		++*high;
 		status = highest_linear(&step, high, LINUX_KTEXT_END,
 					linearoff);

tests/Makefile.am

@@ -297,6 +297,7 @@ test_scripts = \
 	xlat-linux-x86_64-ktext-40M \
 	xlat-linux-x86_64-ktext-512M \
 	xlat-linux-x86_64-ktext-520M \
+	xlat-linux-x86_64-ktext-54M-kaslr \
 	xlat-linux-x86_64-old \
 	xlat-linux-x86_64-old-nover \
 	xlat-linux-x86_64-2.6.11 \
@@ -479,6 +480,9 @@ dist_check_DATA = \
 	xlat-linux-x86_64-ktext-520M.data \
 	xlat-linux-x86_64-ktext-520M.expect \
 	xlat-linux-x86_64-ktext-520M.sym \
+	xlat-linux-x86_64-ktext-54M-kaslr.data \
+	xlat-linux-x86_64-ktext-54M-kaslr.expect \
+	xlat-linux-x86_64-ktext-54M-kaslr.sym \
 	xlat-linux-x86_64-old.expect \
 	xlat-linux-x86_64-old-nover.data \
 	xlat-linux-x86_64-old-nover.expect \

tests/xlat-linux-x86_64-ktext-54M-kaslr

@@ -0,0 +1,14 @@
+#! /bin/bash
+
+#
+# Check Linux X86_64 translation with a 54M kASLR ktext mapping starting
+# above the fixed (non-kASLR) virtual address region.
+#
+
+opts=(
+    arch=x86_64
+    ostype=linux
+    phys_base=0x23c00000
+)
+
+. "$srcdir"/xlat-os-common

tests/xlat-linux-x86_64-ktext-54M-kaslr.data

@@ -0,0 +1,9 @@
+# kernel text
+@0x4c610ff8
+000000004c615067
+@0x4c615ff0
+000000004c616063
+@0x4c616000
+0000000000000000*313
+000000004ae001e1*27+200000
+0000000000000000*172

tests/xlat-linux-x86_64-ktext-54M-kaslr.expect

@@ -0,0 +1,40 @@
+@rootpgt: PGT
+  target_as=MACHPHYSADDR
+  root=KVADDR:0xffffffffa8a10000
+  pte_mask=0x0
+  pte_format=x86_64
+  fields=12,9,9,9,9
+
+@ktext: LINEAR
+  target_as=KPHYSADDR
+  off=0xa3c00000
+
+@machphys_kphys: LINEAR
+  target_as=KPHYSADDR
+  off=0x0
+
+@kphys_machphys: LINEAR
+  target_as=MACHPHYSADDR
+  off=0x0
+
+KV -> HW:
+0-7fffffffffff: @rootpgt
+800000000000-ffff7fffffffffff: NONE
+ffff800000000000-ffffffffffffffff: @rootpgt
+
+KV -> PHYS:
+0-7fffffffffff: @rootpgt
+800000000000-ffff7fffffffffff: NONE
+ffff800000000000-ffffffffa71fffff: @rootpgt
+ffffffffa7200000-ffffffffaa7fffff: @ktext
+ffffffffaa800000-ffffffffffffffff: @rootpgt
+
+KPHYS -> DIRECT:
+
+MACHPHYS -> KPHYS:
+0-fffffffffffff: @machphys_kphys
+10000000000000-ffffffffffffffff: NONE
+
+KPHYS -> MACHPHYS:
+0-fffffffffffff: @kphys_machphys
+10000000000000-ffffffffffffffff: NONE

tests/xlat-linux-x86_64-ktext-54M-kaslr.sym

@@ -0,0 +1,4 @@
+@VALUE(init_top_pgt)
+ffffffffa8a10000
+@VALUE(_stext)
+ffffffffa7200000