xen: branch for v6.13-rc1

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Merge tag 'for-linus-6.13-rc1-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip

Pull xen updates from Juergen Gross:

 - a series for booting as a PVH guest, doing some cleanups after the
   previous work to make PVH boot code position independent

 - a fix of the xenbus driver avoiding a leak in an error case

* tag 'for-linus-6.13-rc1-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip:
  xen: Fix the issue of resource not being properly released in xenbus_dev_probe()
  x86/pvh: Avoid absolute symbol references in .head.text
  x86/xen: Avoid relocatable quantities in Xen ELF notes
  x86/pvh: Omit needless clearing of phys_base
  x86/pvh: Use correct size value in GDT descriptor
  x86/pvh: Call C code via the kernel virtual mapping

arch/x86/kernel/vmlinux.lds.S

@@ -531,3 +531,22 @@ INIT_PER_CPU(irq_stack_backing_store);
 #endif
 
 #endif /* CONFIG_X86_64 */
+
+/*
+ * The symbols below are referenced using relative relocations in the
+ * respective ELF notes. This produces build time constants that the
+ * linker will never mark as relocatable. (Using just ABSOLUTE() is not
+ * sufficient for that).
+ */
+#ifdef CONFIG_XEN
+#ifdef CONFIG_XEN_PV
+xen_elfnote_entry_value =
+	ABSOLUTE(xen_elfnote_entry) + ABSOLUTE(startup_xen);
+#endif
+xen_elfnote_hypercall_page_value =
+	ABSOLUTE(xen_elfnote_hypercall_page) + ABSOLUTE(hypercall_page);
+#endif
+#ifdef CONFIG_PVH
+xen_elfnote_phys32_entry_value =
+	ABSOLUTE(xen_elfnote_phys32_entry) + ABSOLUTE(pvh_start_xen - LOAD_OFFSET);
+#endif

arch/x86/platform/pvh/head.S

@@ -6,7 +6,9 @@
 
 	.code32
 	.text
+#ifdef CONFIG_X86_32
 #define _pa(x)          ((x) - __START_KERNEL_map)
+#endif
 #define rva(x)          ((x) - pvh_start_xen)
 
 #include <linux/elfnote.h>
@@ -52,7 +54,7 @@
 #define PVH_CS_SEL		(PVH_GDT_ENTRY_CS * 8)
 #define PVH_DS_SEL		(PVH_GDT_ENTRY_DS * 8)
 
-SYM_CODE_START_LOCAL(pvh_start_xen)
+SYM_CODE_START(pvh_start_xen)
 	UNWIND_HINT_END_OF_STACK
 	cld
 
@@ -72,8 +74,7 @@ SYM_CODE_START_LOCAL(pvh_start_xen)
 	movl $0, %esp
 
 	leal rva(gdt)(%ebp), %eax
-	leal rva(gdt_start)(%ebp), %ecx
+	addl %eax, 2(%eax)
-	movl %ecx, 2(%eax)
 	lgdt (%eax)
 
 	mov $PVH_DS_SEL,%eax
@@ -103,10 +104,23 @@ SYM_CODE_START_LOCAL(pvh_start_xen)
 	btsl $_EFER_LME, %eax
 	wrmsr
 
+	/*
+	 * Reuse the non-relocatable symbol emitted for the ELF note to
+	 * subtract the build time physical address of pvh_start_xen() from
+	 * its actual runtime address, without relying on absolute 32-bit ELF
+	 * relocations, as these are not supported by the linker when running
+	 * in -pie mode, and should be avoided in .head.text in general.
+	 */
 	mov %ebp, %ebx
-	subl $_pa(pvh_start_xen), %ebx /* offset */
+	subl rva(xen_elfnote_phys32_entry)(%ebp), %ebx
 	jz .Lpagetable_done
 
+	/*
+	 * Store the resulting load offset in phys_base.  __pa() needs
+	 * phys_base set to calculate the hypercall page in xen_pvh_init().
+	 */
+	movl %ebx, rva(phys_base)(%ebp)
+
 	/* Fixup page-tables for relocation. */
 	leal rva(pvh_init_top_pgt)(%ebp), %edi
 	movl $PTRS_PER_PGD, %ecx
@@ -165,20 +179,12 @@ SYM_CODE_START_LOCAL(pvh_start_xen)
 	xor %edx, %edx
 	wrmsr
 
-	/*
+	/* Call xen_prepare_pvh() via the kernel virtual mapping */
-	 * Calculate load offset and store in phys_base.  __pa() needs
+	leaq xen_prepare_pvh(%rip), %rax
-	 * phys_base set to calculate the hypercall page in xen_pvh_init().
+	subq phys_base(%rip), %rax
-	 */
+	addq $__START_KERNEL_map, %rax
-	movq %rbp, %rbx
+	ANNOTATE_RETPOLINE_SAFE
-	subq $_pa(pvh_start_xen), %rbx
+	call *%rax
-	movq %rbx, phys_base(%rip)
-	call xen_prepare_pvh
-	/*
-	 * Clear phys_base.  __startup_64 will *add* to its value,
-	 * so reset to 0.
-	 */
-	xor  %rbx, %rbx
-	movq %rbx, phys_base(%rip)
 
 	/* startup_64 expects boot_params in %rsi. */
 	lea pvh_bootparams(%rip), %rsi
@@ -217,8 +223,8 @@ SYM_CODE_END(pvh_start_xen)
 	.section ".init.data","aw"
 	.balign 8
 SYM_DATA_START_LOCAL(gdt)
-	.word gdt_end - gdt_start
+	.word gdt_end - gdt_start - 1
-	.long _pa(gdt_start) /* x86-64 will overwrite if relocated. */
+	.long gdt_start - gdt
 	.word 0
 SYM_DATA_END(gdt)
 SYM_DATA_START_LOCAL(gdt_start)
@@ -300,5 +306,5 @@ SYM_DATA_END(pvh_level2_kernel_pgt)
 		     .long KERNEL_IMAGE_SIZE - 1)
 #endif
 
-	ELFNOTE(Xen, XEN_ELFNOTE_PHYS32_ENTRY,
+	ELFNOTE(Xen, XEN_ELFNOTE_PHYS32_ENTRY, .global xen_elfnote_phys32_entry;
-	             _ASM_PTR (pvh_start_xen - __START_KERNEL_map))
+		xen_elfnote_phys32_entry: _ASM_PTR xen_elfnote_phys32_entry_value - .)

arch/x86/tools/relocs.c

@@ -56,6 +56,7 @@ static const char * const	sym_regex_kernel[S_NSYMTYPES] = {
 	[S_ABS] =
 	"^(xen_irq_disable_direct_reloc$|"
 	"xen_save_fl_direct_reloc$|"
+	"xen_elfnote_.+_offset$|"
 	"VDSO|"
 	"__kcfi_typeid_|"
 	"__crc_)",

arch/x86/xen/xen-head.S

@@ -94,7 +94,8 @@ SYM_CODE_END(xen_cpu_bringup_again)
 	ELFNOTE(Xen, XEN_ELFNOTE_VIRT_BASE,      _ASM_PTR __START_KERNEL_map)
 	/* Map the p2m table to a 512GB-aligned user address. */
 	ELFNOTE(Xen, XEN_ELFNOTE_INIT_P2M,       .quad (PUD_SIZE * PTRS_PER_PUD))
-	ELFNOTE(Xen, XEN_ELFNOTE_ENTRY,          _ASM_PTR startup_xen)
+	ELFNOTE(Xen, XEN_ELFNOTE_ENTRY,          .globl xen_elfnote_entry;
+		xen_elfnote_entry: _ASM_PTR xen_elfnote_entry_value - .)
 	ELFNOTE(Xen, XEN_ELFNOTE_FEATURES,       .ascii "!writable_page_tables")
 	ELFNOTE(Xen, XEN_ELFNOTE_PAE_MODE,       .asciz "yes")
 	ELFNOTE(Xen, XEN_ELFNOTE_L1_MFN_VALID,
@@ -115,7 +116,8 @@ SYM_CODE_END(xen_cpu_bringup_again)
 #else
 # define FEATURES_DOM0 0
 #endif
-	ELFNOTE(Xen, XEN_ELFNOTE_HYPERCALL_PAGE, _ASM_PTR hypercall_page)
+	ELFNOTE(Xen, XEN_ELFNOTE_HYPERCALL_PAGE, .globl xen_elfnote_hypercall_page;
+		xen_elfnote_hypercall_page: _ASM_PTR xen_elfnote_hypercall_page_value - .)
 	ELFNOTE(Xen, XEN_ELFNOTE_SUPPORTED_FEATURES,
 		.long FEATURES_PV | FEATURES_PVH | FEATURES_DOM0)
 	ELFNOTE(Xen, XEN_ELFNOTE_LOADER,         .asciz "generic")

drivers/xen/xenbus/xenbus_probe.c

@@ -313,7 +313,7 @@ int xenbus_dev_probe(struct device *_dev)
 	if (err) {
 		dev_warn(&dev->dev, "watch_otherend on %s failed.\n",
 		       dev->nodename);
-		return err;
+		goto fail_remove;
 	}
 
 	dev->spurious_threshold = 1;
@@ -322,6 +322,12 @@ int xenbus_dev_probe(struct device *_dev)
 			 dev->nodename);
 
 	return 0;
+fail_remove:
+	if (drv->remove) {
+		down(&dev->reclaim_sem);
+		drv->remove(dev);
+		up(&dev->reclaim_sem);
+	}
 fail_put:
 	module_put(drv->driver.owner);
 fail: