x86/power: Move restore_registers() to top of the file

Because restore_registers() is page-aligned, the assembler inexplicably
adds an unreachable jump from after the end of the previous function to
the beginning of restore_registers().

That confuses objtool, understandably.  It also creates significant text
fragmentation.  As a result, most of the object file is wasted text
(nops).

Move restore_registers() to the beginning of the file to both prevent
the text fragmentation and avoid the dead jump instruction.

$ size /tmp/hibernate_asm_64.before.o /tmp/hibernate_asm_64.after.o
   text	   data	    bss	    dec	    hex	filename
   4415	      0	      0	   4415	   113f	/tmp/hibernate_asm_64.before.o
    524	      0	      0	    524	    20c	/tmp/hibernate_asm_64.after.o

Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Cc: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Link: https://lore.kernel.org/r/8c7f634201d26453d73fe55032cbbdc05d004387.1611263462.git.jpoimboe@redhat.com

diff --git a/arch/x86/power/hibernate_asm_64.S b/arch/x86/power/hibernate_asm_64.S
index 715509d..91c4602 100644 (file)
--- a/arch/x86/power/hibernate_asm_64.S
+++ b/arch/x86/power/hibernate_asm_64.S
@@ -23,6 +23,52 @@
 #include <asm/frame.h>
 #include <asm/nospec-branch.h>
 
+        /* code below belongs to the image kernel */
+       .align PAGE_SIZE
+SYM_FUNC_START(restore_registers)
+       /* go back to the original page tables */
+       movq    %r9, %cr3
+
+       /* Flush TLB, including "global" things (vmalloc) */
+       movq    mmu_cr4_features(%rip), %rax
+       movq    %rax, %rdx
+       andq    $~(X86_CR4_PGE), %rdx
+       movq    %rdx, %cr4;  # turn off PGE
+       movq    %cr3, %rcx;  # flush TLB
+       movq    %rcx, %cr3
+       movq    %rax, %cr4;  # turn PGE back on
+
+       /* We don't restore %rax, it must be 0 anyway */
+       movq    $saved_context, %rax
+       movq    pt_regs_sp(%rax), %rsp
+       movq    pt_regs_bp(%rax), %rbp
+       movq    pt_regs_si(%rax), %rsi
+       movq    pt_regs_di(%rax), %rdi
+       movq    pt_regs_bx(%rax), %rbx
+       movq    pt_regs_cx(%rax), %rcx
+       movq    pt_regs_dx(%rax), %rdx
+       movq    pt_regs_r8(%rax), %r8
+       movq    pt_regs_r9(%rax), %r9
+       movq    pt_regs_r10(%rax), %r10
+       movq    pt_regs_r11(%rax), %r11
+       movq    pt_regs_r12(%rax), %r12
+       movq    pt_regs_r13(%rax), %r13
+       movq    pt_regs_r14(%rax), %r14
+       movq    pt_regs_r15(%rax), %r15
+       pushq   pt_regs_flags(%rax)
+       popfq
+
+       /* Saved in save_processor_state. */
+       lgdt    saved_context_gdt_desc(%rax)
+
+       xorl    %eax, %eax
+
+       /* tell the hibernation core that we've just restored the memory */
+       movq    %rax, in_suspend(%rip)
+
+       ret
+SYM_FUNC_END(restore_registers)
+
 SYM_FUNC_START(swsusp_arch_suspend)
        movq    $saved_context, %rax
        movq    %rsp, pt_regs_sp(%rax)
@@ -102,49 +148,3 @@ SYM_CODE_START(core_restore_code)
        ANNOTATE_RETPOLINE_SAFE
        jmpq    *%r8
 SYM_CODE_END(core_restore_code)
-
-        /* code below belongs to the image kernel */
-       .align PAGE_SIZE
-SYM_FUNC_START(restore_registers)
-       /* go back to the original page tables */
-       movq    %r9, %cr3
-
-       /* Flush TLB, including "global" things (vmalloc) */
-       movq    mmu_cr4_features(%rip), %rax
-       movq    %rax, %rdx
-       andq    $~(X86_CR4_PGE), %rdx
-       movq    %rdx, %cr4;  # turn off PGE
-       movq    %cr3, %rcx;  # flush TLB
-       movq    %rcx, %cr3
-       movq    %rax, %cr4;  # turn PGE back on
-
-       /* We don't restore %rax, it must be 0 anyway */
-       movq    $saved_context, %rax
-       movq    pt_regs_sp(%rax), %rsp
-       movq    pt_regs_bp(%rax), %rbp
-       movq    pt_regs_si(%rax), %rsi
-       movq    pt_regs_di(%rax), %rdi
-       movq    pt_regs_bx(%rax), %rbx
-       movq    pt_regs_cx(%rax), %rcx
-       movq    pt_regs_dx(%rax), %rdx
-       movq    pt_regs_r8(%rax), %r8
-       movq    pt_regs_r9(%rax), %r9
-       movq    pt_regs_r10(%rax), %r10
-       movq    pt_regs_r11(%rax), %r11
-       movq    pt_regs_r12(%rax), %r12
-       movq    pt_regs_r13(%rax), %r13
-       movq    pt_regs_r14(%rax), %r14
-       movq    pt_regs_r15(%rax), %r15
-       pushq   pt_regs_flags(%rax)
-       popfq
-
-       /* Saved in save_processor_state. */
-       lgdt    saved_context_gdt_desc(%rax)
-
-       xorl    %eax, %eax
-
-       /* tell the hibernation core that we've just restored the memory */
-       movq    %rax, in_suspend(%rip)
-
-       ret
-SYM_FUNC_END(restore_registers)