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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [PATCH v2.1 6.5/70] 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.
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@xxxxxxxxxx>
---
CC: Jan Beulich <JBeulich@xxxxxxxx>
CC: Roger Pau Monné <roger.pau@xxxxxxxxxx>
CC: Wei Liu <wl@xxxxxxx>
The remainder of the 32bit code has mode-invariant lengths, so disassembles
safely as 64bit. The only differences come from 32/64bit implicit register
sizes.
v2.1:
* New
---
xen/arch/x86/include/asm/machine_kexec.h | 2 +-
xen/arch/x86/machine_kexec.c | 2 +-
xen/arch/x86/x86_64/kexec_reloc.S | 22 +++++++++++++++++-----
xen/arch/x86/xen.lds.S | 3 ++-
4 files changed, 21 insertions(+), 8 deletions(-)
diff --git a/xen/arch/x86/include/asm/machine_kexec.h
b/xen/arch/x86/include/asm/machine_kexec.h
index ba0d469d077b..d4880818c1d9 100644
--- 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 08ec9fd43b1d..751a9efcaf6a 100644
--- 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 d488d127cfb9..05bf8810cee6 100644
--- 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 +192,22 @@ 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
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 c399178ac123..13fc7ee008c1 100644
--- a/xen/arch/x86/xen.lds.S
+++ b/xen/arch/x86/xen.lds.S
@@ -87,6 +87,7 @@ SECTIONS
*(.text.unlikely)
*(.fixup)
*(.text.kexec)
+ kexec_reloc_end = .;
*(.gnu.warning)
_etext = .; /* End of text section */
} PHDR(text) = 0x9090
@@ -433,7 +434,7 @@ 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. */
--
2.11.0
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