x86/kexec: Annotate embedded data with ELF metadata

Scanning for embedded endbranch instructions involves parsing the .text
disassembly.  Data in the kexec trampoline has no ELF metadata, so objdump
treats it as instructions and tries to disassemble.  Convert:

  ffff82d040396108 <compatibility_mode_far>:
  ffff82d040396108:       00 00                   add    %al,(%rax)
  ffff82d04039610a:       00 00                   add    %al,(%rax)
  ffff82d04039610c:       10 00                   adc    %al,(%rax)

  ffff82d04039610e <compat_mode_gdt_desc>:
  ffff82d04039610e:       17                      (bad)
          ...

  ffff82d040396118 <compat_mode_gdt>:
          ...
  ffff82d040396120:       ff                      (bad)
  ffff82d040396121:       ff 00                   incl   (%rax)
  ffff82d040396123:       00 00                   add    %al,(%rax)
  ffff82d040396125:       93                      xchg   %eax,%ebx
  ffff82d040396126:       cf                      iret
  ffff82d040396127:       00 ff                   add    %bh,%bh
  ffff82d040396129:       ff 00                   incl   (%rax)
  ffff82d04039612b:       00 00                   add    %al,(%rax)
  ffff82d04039612d:       9b                      fwait
  ffff82d04039612e:       cf                      iret
          ...

  ffff82d040396130 <compat_mode_idt>:
          ...

  ffff82d0403961b6 <kexec_reloc_size>:
  ffff82d0403961b6:       b6 01                   mov    $0x1,%dh
          ...

to:

  ffff82d040396108 <compatibility_mode_far>:
  ffff82d040396108:       00 00 00 00 10 00                               ......

  ffff82d04039610e <compat_mode_gdt_desc>:
  ffff82d04039610e:       17 00 00 00 00 00 00 00 00 00                   ..........

  ffff82d040396118 <compat_mode_gdt>:
          ...
  ffff82d040396120:       ff ff 00 00 00 93 cf 00 ff ff 00 00 00 9b cf 00 ................

  ffff82d040396130 <compat_mode_idt>:
  ffff82d040396130:       00 00 00 00 00 00                               ......

  ffff82d040396136 <reloc_stack>:
          ...

Most data just gains type and size metadata.

The reloc_stack label is the wrong end of the data block to have a size, so
move it to the lowest address and introduce .Lreloc_stack_base as a
replacement.  Also, fix the fact that it is misaligned by 2 bytes.

While kexec_reloc_size could gain metadata, it's use in the linker
assertion (while correct) is deeply confusing to follow.  Drop it entirely,
using a linker symbol instead to denote the end of the trampoline.

No functional change.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>

diff --git a/xen/arch/x86/include/asm/machine_kexec.h b/xen/arch/x86/include/asm/machine_kexec.h
index ba0d469d077b3e915669399938ec6482ac66c123..d4880818c1d9c91506b37d1fcfd1210ec406f275 100644 (file)
--- a/xen/arch/x86/include/asm/machine_kexec.h
+++ b/xen/arch/x86/include/asm/machine_kexec.h
@@ -9,7 +9,7 @@ extern void kexec_reloc(unsigned long reloc_code, unsigned long reloc_pt,
                         unsigned long ind_maddr, unsigned long entry_maddr,
                         unsigned long flags);
 
-extern unsigned int kexec_reloc_size;
+extern const char kexec_reloc_end[];
 
 #endif
 

diff --git a/xen/arch/x86/machine_kexec.c b/xen/arch/x86/machine_kexec.c
index 08ec9fd43b1de0c75d89e13a5f5add1730552e2d..751a9efcaf6a7f183eaa36182af85cd72ba86ec8 100644 (file)
--- a/xen/arch/x86/machine_kexec.c
+++ b/xen/arch/x86/machine_kexec.c
@@ -117,7 +117,7 @@ int machine_kexec_load(struct kexec_image *image)
     }
 
     code_page = __map_domain_page(image->control_code_page);
-    memcpy(code_page, kexec_reloc, kexec_reloc_size);
+    memcpy(code_page, kexec_reloc, kexec_reloc_end - (char *)kexec_reloc);
     unmap_domain_page(code_page);
 
     /*

diff --git a/xen/arch/x86/x86_64/kexec_reloc.S b/xen/arch/x86/x86_64/kexec_reloc.S
index d488d127cfb9a91de24d37909a4db132cdb42adb..89316bc3a7ac078d0581188d08b5f381afce6b38 100644 (file)
--- a/xen/arch/x86/x86_64/kexec_reloc.S
+++ b/xen/arch/x86/x86_64/kexec_reloc.S
@@ -34,7 +34,7 @@ ENTRY(kexec_reloc)
         movq    %rcx, %rbp
 
         /* Setup stack. */
-        leaq    (reloc_stack - kexec_reloc)(%rdi), %rsp
+        leaq    (.Lreloc_stack_base - kexec_reloc)(%rdi), %rsp
 
         /* Load reloc page table. */
         movq    %rsi, %cr3
@@ -175,10 +175,16 @@ compatibility_mode_far:
         .long 0x00000000             /* set in call_32_bit above */
         .word 0x0010
 
+        .type compatibility_mode_far, @object
+        .size compatibility_mode_far, . - compatibility_mode_far
+
 compat_mode_gdt_desc:
         .word .Lcompat_mode_gdt_end - compat_mode_gdt -1
         .quad 0x0000000000000000     /* set in call_32_bit above */
 
+        .type compat_mode_gdt_desc, @object
+        .size compat_mode_gdt_desc, . - compat_mode_gdt_desc
+
         .align 8
 compat_mode_gdt:
         .quad 0x0000000000000000     /* null                              */
@@ -186,16 +192,23 @@ compat_mode_gdt:
         .quad 0x00cf9b000000ffff     /* 0x0010 ring 0 code, compatibility */
 .Lcompat_mode_gdt_end:
 
+        .type compat_mode_gdt, @object
+        .size compat_mode_gdt, . - compat_mode_gdt
+
 compat_mode_idt:
         .word 0                      /* limit */
         .long 0                      /* base */
 
+        .type compat_mode_idt, @object
+        .size compat_mode_idt, . - compat_mode_idt
+
         /*
          * 16 words of stack are more than enough.
          */
-        .fill 16,8,0
+        .align 8
 reloc_stack:
+        .fill 16,8,0
+.Lreloc_stack_base:
 
-        .globl kexec_reloc_size
-kexec_reloc_size:
-        .long . - kexec_reloc
+        .type reloc_stack, @object
+        .size reloc_stack, . - reloc_stack

diff --git a/xen/arch/x86/xen.lds.S b/xen/arch/x86/xen.lds.S
index 82ad8feb6e991a9e66924763d7012820c379ebbd..7ffecd4630704e71034610729b0edfecd09ed436 100644 (file)
--- a/xen/arch/x86/xen.lds.S
+++ b/xen/arch/x86/xen.lds.S
@@ -84,6 +84,7 @@ SECTIONS
        _etextentry = .;
 
        *(.text.kexec)          /* Page aligned in the object file. */
+       kexec_reloc_end = .;
 
        *(.text.cold)
        *(.text.unlikely)
@@ -428,7 +429,7 @@ ASSERT(__2M_rwdata_end <= XEN_VIRT_END - XEN_VIRT_START + __XEN_VIRT_START -
        "Xen image overlaps stubs area")
 
 #ifdef CONFIG_KEXEC
-ASSERT(kexec_reloc_size - kexec_reloc <= PAGE_SIZE, "kexec_reloc is too large")
+ASSERT(kexec_reloc_end - kexec_reloc <= PAGE_SIZE, "kexec_reloc is too large")
 #endif
 
 /* The Multiboot setup paths relies on this to simplify superpage PTE creation. */