# HG changeset patch
# User Jan Beulich <jbeulich@xxxxxxxxxx>
# Date 1311407355 -3600
# Node ID 537918f518eec3d8e2e2dad403fce40303321523
# Parent 42edf1481c5704c8ce1eb171a713b5411df0551a
add privileged (dom0) kernel feature indication
With our switching away from supporting 32-bit Dom0 operation, users
complained that attempts (perhaps due to lack of knowledge of that
change) to boot the no longer privileged kernel in Dom0 resulted in
apparently silent failure. To make the mismatch explicit and visible,
add dom0 feature flag that the kernel can set to indicate operation as
dom0 is supported.
Due to the way elf_xen_parse_features() worked up to now (getting
fixed here), adding features indications to the old, string based ELF
note would make the respective kernel unusable on older hypervisors.
For that reason, a new ELF Note is being introduced that allows
specifying supported features as a bit array instead (with features
unknown to the hypervisor simply ignored, as now also done by
elf_xen_parse_features(), whereas here unknown kernel-required
features still keep the kernel [and hence VM] from booting).
Introduce and use elf_note_numeric_array() to be forward
compatible (or else an old hypervisor wouldn't be able to parse kernel
specified features occupying more than 64 bits - thanks, Ian!).
Signed-off-by: Jan Beulich <jbeulich@xxxxxxxxxx>
---
diff -r 42edf1481c57 -r 537918f518ee tools/libxc/xc_dom_elfloader.c
--- a/tools/libxc/xc_dom_elfloader.c Fri Jul 22 08:55:19 2011 +0100
+++ b/tools/libxc/xc_dom_elfloader.c Sat Jul 23 08:49:15 2011 +0100
@@ -286,6 +286,13 @@
if ( (rc = elf_xen_parse(elf, &dom->parms)) != 0 )
return rc;
+ if ( elf_xen_feature_get(XENFEAT_dom0, dom->parms.f_required) )
+ {
+ xc_dom_panic(dom->xch, XC_INVALID_KERNEL, "%s: Kernel does not"
+ " support unprivileged (DomU) operation", __FUNCTION__);
+ return -EINVAL;
+ }
+
/* find kernel segment */
dom->kernel_seg.vstart = dom->parms.virt_kstart;
dom->kernel_seg.vend = dom->parms.virt_kend;
diff -r 42edf1481c57 -r 537918f518ee xen/arch/ia64/xen/domain.c
--- a/xen/arch/ia64/xen/domain.c Fri Jul 22 08:55:19 2011 +0100
+++ b/xen/arch/ia64/xen/domain.c Sat Jul 23 08:49:15 2011 +0100
@@ -2164,6 +2164,13 @@
return -1;
}
+ if (parms.elf_notes[XEN_ELFNOTE_FEATURES].type != XEN_ENT_NONE &&
+ !test_bit(XENFEAT_dom0, parms.f_supported))
+ {
+ printk("Kernel does not support Dom0 operation\n");
+ return -1;
+ }
+
p_start = parms.virt_base;
pkern_start = parms.virt_kstart;
pkern_end = parms.virt_kend;
diff -r 42edf1481c57 -r 537918f518ee xen/arch/x86/domain_build.c
--- a/xen/arch/x86/domain_build.c Fri Jul 22 08:55:19 2011 +0100
+++ b/xen/arch/x86/domain_build.c Sat Jul 23 08:49:15 2011 +0100
@@ -415,6 +415,13 @@
return -EINVAL;
}
+ if ( parms.elf_notes[XEN_ELFNOTE_FEATURES].type != XEN_ENT_NONE &&
+ !test_bit(XENFEAT_dom0, parms.f_supported) )
+ {
+ printk("Kernel does not support Dom0 operation\n");
+ return -EINVAL;
+ }
+
#if defined(__x86_64__)
if ( compat32 )
{
diff -r 42edf1481c57 -r 537918f518ee xen/common/kernel.c
--- a/xen/common/kernel.c Fri Jul 22 08:55:19 2011 +0100
+++ b/xen/common/kernel.c Sat Jul 23 08:49:15 2011 +0100
@@ -287,6 +287,8 @@
(1U << XENFEAT_auto_translated_physmap);
if ( supervisor_mode_kernel )
fi.submap |= 1U << XENFEAT_supervisor_mode_kernel;
+ if ( current->domain == dom0 )
+ fi.submap |= 1U << XENFEAT_dom0;
#ifdef CONFIG_X86
if ( !is_hvm_vcpu(current) )
fi.submap |= (1U << XENFEAT_mmu_pt_update_preserve_ad) |
diff -r 42edf1481c57 -r 537918f518ee xen/common/libelf/libelf-dominfo.c
--- a/xen/common/libelf/libelf-dominfo.c Fri Jul 22 08:55:19 2011 +0100
+++ b/xen/common/libelf/libelf-dominfo.c Sat Jul 23 08:49:15 2011 +0100
@@ -26,7 +26,8 @@
[XENFEAT_writable_descriptor_tables] = "writable_descriptor_tables",
[XENFEAT_auto_translated_physmap] = "auto_translated_physmap",
[XENFEAT_supervisor_mode_kernel] = "supervisor_mode_kernel",
- [XENFEAT_pae_pgdir_above_4gb] = "pae_pgdir_above_4gb"
+ [XENFEAT_pae_pgdir_above_4gb] = "pae_pgdir_above_4gb",
+ [XENFEAT_dom0] = "dom0"
};
static const int elf_xen_features =
sizeof(elf_xen_feature_names) / sizeof(elf_xen_feature_names[0]);
@@ -83,7 +84,7 @@
}
}
}
- if ( i == elf_xen_features )
+ if ( i == elf_xen_features && required && feature[0] == '!' )
return -1;
}
@@ -114,6 +115,7 @@
[XEN_ELFNOTE_LOADER] = { "LOADER", 1},
[XEN_ELFNOTE_PAE_MODE] = { "PAE_MODE", 1},
[XEN_ELFNOTE_FEATURES] = { "FEATURES", 1},
+ [XEN_ELFNOTE_SUPPORTED_FEATURES] = { "SUPPORTED_FEATURES", 0},
[XEN_ELFNOTE_BSD_SYMTAB] = { "BSD_SYMTAB", 1},
[XEN_ELFNOTE_SUSPEND_CANCEL] = { "SUSPEND_CANCEL", 0 },
[XEN_ELFNOTE_MOD_START_PFN] = { "MOD_START_PFN", 0 },
@@ -122,6 +124,7 @@
const char *str = NULL;
uint64_t val = 0;
+ unsigned int i;
int type = elf_uval(elf, note, type);
if ( (type >= sizeof(note_desc) / sizeof(note_desc[0])) ||
@@ -200,6 +203,12 @@
return -1;
break;
+ case XEN_ELFNOTE_SUPPORTED_FEATURES:
+ for ( i = 0; i < XENFEAT_NR_SUBMAPS; ++i )
+ parms->f_supported[i] |= elf_note_numeric_array(
+ elf, note, sizeof(*parms->f_supported), i);
+ break;
+
}
return 0;
}
diff -r 42edf1481c57 -r 537918f518ee xen/common/libelf/libelf-tools.c
--- a/xen/common/libelf/libelf-tools.c Fri Jul 22 08:55:19 2011 +0100
+++ b/xen/common/libelf/libelf-tools.c Sat Jul 23 08:49:15 2011 +0100
@@ -227,6 +227,27 @@
return 0;
}
}
+
+uint64_t elf_note_numeric_array(struct elf_binary *elf, const elf_note *note,
+ unsigned int unitsz, unsigned int idx)
+{
+ const void *desc = elf_note_desc(elf, note);
+ int descsz = elf_uval(elf, note, descsz);
+
+ if ( descsz % unitsz || idx >= descsz / unitsz )
+ return 0;
+ switch (unitsz)
+ {
+ case 1:
+ case 2:
+ case 4:
+ case 8:
+ return elf_access_unsigned(elf, desc, idx * unitsz, unitsz);
+ default:
+ return 0;
+ }
+}
+
const elf_note *elf_note_next(struct elf_binary *elf, const elf_note * note)
{
int namesz = (elf_uval(elf, note, namesz) + 3) & ~3;
diff -r 42edf1481c57 -r 537918f518ee xen/include/public/elfnote.h
--- a/xen/include/public/elfnote.h Fri Jul 22 08:55:19 2011 +0100
+++ b/xen/include/public/elfnote.h Sat Jul 23 08:49:15 2011 +0100
@@ -179,9 +179,22 @@
#define XEN_ELFNOTE_MOD_START_PFN 16
/*
+ * The features supported by this kernel (numeric).
+ *
+ * Other than XEN_ELFNOTE_FEATURES on pre-4.2 Xen, this note allows a
+ * kernel to specify support for features that older hypervisors don't
+ * know about. The set of features 4.2 and newer hypervisors will
+ * consider supported by the kernel is the combination of the sets
+ * specified through this and the string note.
+ *
+ * LEGACY: FEATURES
+ */
+#define XEN_ELFNOTE_SUPPORTED_FEATURES 17
+
+/*
* The number of the highest elfnote defined.
*/
-#define XEN_ELFNOTE_MAX XEN_ELFNOTE_MOD_START_PFN
+#define XEN_ELFNOTE_MAX XEN_ELFNOTE_SUPPORTED_FEATURES
/*
* System information exported through crash notes.
diff -r 42edf1481c57 -r 537918f518ee xen/include/public/features.h
--- a/xen/include/public/features.h Fri Jul 22 08:55:19 2011 +0100
+++ b/xen/include/public/features.h Sat Jul 23 08:49:15 2011 +0100
@@ -75,7 +75,10 @@
#define XENFEAT_hvm_safe_pvclock 9
/* x86: pirq can be used by HVM guests */
-#define XENFEAT_hvm_pirqs 10
+#define XENFEAT_hvm_pirqs 10
+
+/* operation as Dom0 is supported */
+#define XENFEAT_dom0 11
#define XENFEAT_NR_SUBMAPS 1
diff -r 42edf1481c57 -r 537918f518ee xen/include/xen/libelf.h
--- a/xen/include/xen/libelf.h Fri Jul 22 08:55:19 2011 +0100
+++ b/xen/include/xen/libelf.h Sat Jul 23 08:49:15 2011 +0100
@@ -179,6 +179,8 @@
const char *elf_note_name(struct elf_binary *elf, const elf_note * note);
const void *elf_note_desc(struct elf_binary *elf, const elf_note * note);
uint64_t elf_note_numeric(struct elf_binary *elf, const elf_note * note);
+uint64_t elf_note_numeric_array(struct elf_binary *, const elf_note *,
+ unsigned int unitsz, unsigned int idx);
const elf_note *elf_note_next(struct elf_binary *elf, const elf_note * note);
int elf_is_elfbinary(const void *image);
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