x86/asm/entry/32: Use smaller PUSH instructions instead of MOV, to build 'pt_regs' on stack

This mimics the recent similar 64-bit change.
Saves ~110 bytes of code.

Patch was run-tested on 32 and 64 bits, Intel and AMD CPU.
I also looked at the diff of entry_64.o disassembly, to have
a different view of the changes.

Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Alexei Starovoitov <ast@plumgrid.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Will Drewry <wad@chromium.org>
Link: http://lkml.kernel.org/r/1427821211-25099-2-git-send-email-dvlasenk@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 46 insertions, 36 deletions

diff --git a/arch/x86/ia32/ia32entry.S b/arch/x86/ia32/ia32entry.S
index dec8c1de9c9e..8d01cce7b6b8 100644
--- a/arch/x86/ia32/ia32entry.S
+++ b/arch/x86/ia32/ia32entry.S
@@ -126,26 +126,27 @@ ENTRY(ia32_sysenter_target)
         movl    %ebp, %ebp
         movl    %eax, %eax
 
-        /* Construct iret frame (ss,rsp,rflags,cs,rip) */
-        pushq_cfi $__USER32_DS
-        /*CFI_REL_OFFSET ss,0*/
-        pushq_cfi %rbp
-        CFI_REL_OFFSET rsp,0
-        pushfq_cfi
-        /*CFI_REL_OFFSET rflags,0*/
-        movl    ASM_THREAD_INFO(TI_sysenter_return, %rsp, 3*8), %r10d
+        movl    ASM_THREAD_INFO(TI_sysenter_return, %rsp, 0), %r10d
         CFI_REGISTER rip,r10
-        pushq_cfi $__USER32_CS
-        /*CFI_REL_OFFSET cs,0*/
-        /* Store thread_info->sysenter_return in rip stack slot */
-        pushq_cfi %r10
-        CFI_REL_OFFSET rip,0
-        /* Store orig_ax */
-        pushq_cfi %rax
-        /* Construct the rest of "struct pt_regs" */
+
+        /* Construct struct pt_regs on stack */
+        pushq_cfi       $__USER32_DS            /* pt_regs->ss */
+        pushq_cfi       %rbp                    /* pt_regs->sp */
+        CFI_REL_OFFSET  rsp,0
+        pushfq_cfi                              /* pt_regs->flags */
+        pushq_cfi       $__USER32_CS            /* pt_regs->cs */
+        pushq_cfi       %r10 /* pt_regs->ip = thread_info->sysenter_return */
+        CFI_REL_OFFSET  rip,0
+        pushq_cfi_reg   rax                     /* pt_regs->orig_ax */
+        pushq_cfi_reg   rdi                     /* pt_regs->di */
+        pushq_cfi_reg   rsi                     /* pt_regs->si */
+        pushq_cfi_reg   rdx                     /* pt_regs->dx */
+        pushq_cfi_reg   rcx                     /* pt_regs->cx */
+        pushq_cfi_reg   rax                     /* pt_regs->ax */
         cld
-        ALLOC_PT_GPREGS_ON_STACK
-        SAVE_C_REGS_EXCEPT_R891011
+        sub     $(10*8),%rsp /* pt_regs->r8-11,bp,bx,r12-15 not saved */
+        CFI_ADJUST_CFA_OFFSET 10*8
+
         /*
          * no need to do an access_ok check here because rbp has been
          * 32bit zero extended
@@ -334,20 +335,24 @@ ENTRY(ia32_cstar_target)
         /* Zero-extending 32-bit regs, do not remove */
         movl    %eax,%eax
 
-        ALLOC_PT_GPREGS_ON_STACK 6*8 /* 6*8: space for orig_ax and iret frame */
-        SAVE_C_REGS_EXCEPT_RCX_R891011
-        movq    %rax,ORIG_RAX(%rsp)
-        movq    %rcx,RIP(%rsp)
-        CFI_REL_OFFSET rip,RIP
-        movq    %rbp,RCX(%rsp) /* this lies slightly to ptrace */
+        /* Construct struct pt_regs on stack */
+        pushq_cfi       $__USER32_DS            /* pt_regs->ss */
+        pushq_cfi       %r8                     /* pt_regs->sp */
+        CFI_REL_OFFSET rsp,0
+        pushq_cfi       %r11                    /* pt_regs->flags */
+        pushq_cfi       $__USER32_CS            /* pt_regs->cs */
+        pushq_cfi       %rcx                    /* pt_regs->ip */
+        CFI_REL_OFFSET rip,0
+        pushq_cfi_reg   rax                     /* pt_regs->orig_ax */
+        pushq_cfi_reg   rdi                     /* pt_regs->di */
+        pushq_cfi_reg   rsi                     /* pt_regs->si */
+        pushq_cfi_reg   rdx                     /* pt_regs->dx */
+        pushq_cfi_reg   rbp                     /* pt_regs->cx */
         movl    %ebp,%ecx
-        movq    $__USER32_CS,CS(%rsp)
-        movq    $__USER32_DS,SS(%rsp)
-        movq    %r11,EFLAGS(%rsp)
-        /*CFI_REL_OFFSET rflags,EFLAGS*/
-        movq    %r8,RSP(%rsp)
-        CFI_REL_OFFSET rsp,RSP
-        /* iret stack frame is complete now */
+        pushq_cfi_reg   rax                     /* pt_regs->ax */
+        sub     $(10*8),%rsp /* pt_regs->r8-11,bp,bx,r12-15 not saved */
+        CFI_ADJUST_CFA_OFFSET 10*8
+
         /*
          * no need to do an access_ok check here because r8 has been
          * 32bit zero extended
@@ -478,12 +483,17 @@ ENTRY(ia32_syscall)
         /* Zero-extending 32-bit regs, do not remove */
         movl    %eax,%eax
 
-        pushq_cfi %rax          /* store orig_ax */
+        /* Construct struct pt_regs on stack (iret frame is already on stack) */
+        pushq_cfi_reg   rax                     /* pt_regs->orig_ax */
+        pushq_cfi_reg   rdi                     /* pt_regs->di */
+        pushq_cfi_reg   rsi                     /* pt_regs->si */
+        pushq_cfi_reg   rdx                     /* pt_regs->dx */
+        pushq_cfi_reg   rcx                     /* pt_regs->cx */
+        pushq_cfi_reg   rax                     /* pt_regs->ax */
         cld
-        /* note the registers are not zero extended to the sf.
-           this could be a problem. */
-        ALLOC_PT_GPREGS_ON_STACK
-        SAVE_C_REGS_EXCEPT_R891011
+        sub     $(10*8),%rsp /* pt_regs->r8-11,bp,bx,r12-15 not saved */
+        CFI_ADJUST_CFA_OFFSET 10*8
+
         orl $TS_COMPAT, ASM_THREAD_INFO(TI_status, %rsp, SIZEOF_PTREGS)
         testl $_TIF_WORK_SYSCALL_ENTRY, ASM_THREAD_INFO(TI_flags, %rsp, SIZEOF_PTREGS)
         jnz ia32_tracesys