arch/x86/entry/calling.h

   1 #include <linux/jump_label.h>
   2
   3 /*
   4
   5  x86 function call convention, 64-bit:
   6  -------------------------------------
   7   arguments           |  callee-saved      | extra caller-saved | return
   8  [callee-clobbered]   |                    | [callee-clobbered] |
   9  ---------------------------------------------------------------------------
  10  rdi rsi rdx rcx r8-9 | rbx rbp [*] r12-15 | r10-11             | rax, rdx [**]
  11
  12  ( rsp is obviously invariant across normal function calls. (gcc can 'merge'
  13    functions when it sees tail-call optimization possibilities) rflags is
  14    clobbered. Leftover arguments are passed over the stack frame.)
  15
  16  [*]  In the frame-pointers case rbp is fixed to the stack frame.
  17
  18  [**] for struct return values wider than 64 bits the return convention is a
  19       bit more complex: up to 128 bits width we return small structures
  20       straight in rax, rdx. For structures larger than that (3 words or
  21       larger) the caller puts a pointer to an on-stack return struct
  22       [allocated in the caller's stack frame] into the first argument - i.e.
  23       into rdi. All other arguments shift up by one in this case.
  24       Fortunately this case is rare in the kernel.
  25
  26 For 32-bit we have the following conventions - kernel is built with
  27 -mregparm=3 and -freg-struct-return:
  28
  29  x86 function calling convention, 32-bit:
  30  ----------------------------------------
  31   arguments         | callee-saved        | extra caller-saved | return
  32  [callee-clobbered] |                     | [callee-clobbered] |
  33  -------------------------------------------------------------------------
  34  eax edx ecx        | ebx edi esi ebp [*] | <none>             | eax, edx [**]
  35
  36  ( here too esp is obviously invariant across normal function calls. eflags
  37    is clobbered. Leftover arguments are passed over the stack frame. )
  38
  39  [*]  In the frame-pointers case ebp is fixed to the stack frame.
  40
  41  [**] We build with -freg-struct-return, which on 32-bit means similar
  42       semantics as on 64-bit: edx can be used for a second return value
  43       (i.e. covering integer and structure sizes up to 64 bits) - after that
  44       it gets more complex and more expensive: 3-word or larger struct returns
  45       get done in the caller's frame and the pointer to the return struct goes
  46       into regparm0, i.e. eax - the other arguments shift up and the
  47       function's register parameters degenerate to regparm=2 in essence.
  48
  49 */
  50
  51 #ifdef CONFIG_X86_64
  52
  53 /*
  54  * 64-bit system call stack frame layout defines and helpers,
  55  * for assembly code:
  56  */
  57
  58 /* The layout forms the "struct pt_regs" on the stack: */
  59 /*
  60  * C ABI says these regs are callee-preserved. They aren't saved on kernel entry
  61  * unless syscall needs a complete, fully filled "struct pt_regs".
  62  */
  63 #define R15             0*8
  64 #define R14             1*8
  65 #define R13             2*8
  66 #define R12             3*8
  67 #define RBP             4*8
  68 #define RBX             5*8
  69 /* These regs are callee-clobbered. Always saved on kernel entry. */
  70 #define R11             6*8
  71 #define R10             7*8
  72 #define R9              8*8
  73 #define R8              9*8
  74 #define RAX             10*8
  75 #define RCX             11*8
  76 #define RDX             12*8
  77 #define RSI             13*8
  78 #define RDI             14*8
  79 /*
  80  * On syscall entry, this is syscall#. On CPU exception, this is error code.
  81  * On hw interrupt, it's IRQ number:
  82  */
  83 #define ORIG_RAX        15*8
  84 /* Return frame for iretq */
  85 #define RIP             16*8
  86 #define CS              17*8
  87 #define EFLAGS          18*8
  88 #define RSP             19*8
  89 #define SS              20*8
  90
  91 #define SIZEOF_PTREGS   21*8
  92
  93         .macro ALLOC_PT_GPREGS_ON_STACK
  94         addq    $-(15*8), %rsp
  95         .endm
  96
  97         .macro SAVE_C_REGS_HELPER offset=0 rax=1 rcx=1 r8910=1 r11=1
  98         .if \r11
  99         movq %r11, 6*8+\offset(%rsp)
 100         .endif
 101         .if \r8910
 102         movq %r10, 7*8+\offset(%rsp)
 103         movq %r9,  8*8+\offset(%rsp)
 104         movq %r8,  9*8+\offset(%rsp)
 105         .endif
 106         .if \rax
 107         movq %rax, 10*8+\offset(%rsp)
 108         .endif
 109         .if \rcx
 110         movq %rcx, 11*8+\offset(%rsp)
 111         .endif
 112         movq %rdx, 12*8+\offset(%rsp)
 113         movq %rsi, 13*8+\offset(%rsp)
 114         movq %rdi, 14*8+\offset(%rsp)
 115         .endm
 116         .macro SAVE_C_REGS offset=0
 117         SAVE_C_REGS_HELPER \offset, 1, 1, 1, 1
 118         .endm
 119         .macro SAVE_C_REGS_EXCEPT_RAX_RCX offset=0
 120         SAVE_C_REGS_HELPER \offset, 0, 0, 1, 1
 121         .endm
 122         .macro SAVE_C_REGS_EXCEPT_R891011
 123         SAVE_C_REGS_HELPER 0, 1, 1, 0, 0
 124         .endm
 125         .macro SAVE_C_REGS_EXCEPT_RCX_R891011
 126         SAVE_C_REGS_HELPER 0, 1, 0, 0, 0
 127         .endm
 128         .macro SAVE_C_REGS_EXCEPT_RAX_RCX_R11
 129         SAVE_C_REGS_HELPER 0, 0, 0, 1, 0
 130         .endm
 131
 132         .macro SAVE_EXTRA_REGS offset=0
 133         movq %r15, 0*8+\offset(%rsp)
 134         movq %r14, 1*8+\offset(%rsp)
 135         movq %r13, 2*8+\offset(%rsp)
 136         movq %r12, 3*8+\offset(%rsp)
 137         movq %rbp, 4*8+\offset(%rsp)
 138         movq %rbx, 5*8+\offset(%rsp)
 139         .endm
 140
 141         .macro RESTORE_EXTRA_REGS offset=0
 142         movq 0*8+\offset(%rsp), %r15
 143         movq 1*8+\offset(%rsp), %r14
 144         movq 2*8+\offset(%rsp), %r13
 145         movq 3*8+\offset(%rsp), %r12
 146         movq 4*8+\offset(%rsp), %rbp
 147         movq 5*8+\offset(%rsp), %rbx
 148         .endm
 149
 150         .macro RESTORE_C_REGS_HELPER rstor_rax=1, rstor_rcx=1, rstor_r11=1, rstor_r8910=1, rstor_rdx=1
 151         .if \rstor_r11
 152         movq 6*8(%rsp), %r11
 153         .endif
 154         .if \rstor_r8910
 155         movq 7*8(%rsp), %r10
 156         movq 8*8(%rsp), %r9
 157         movq 9*8(%rsp), %r8
 158         .endif
 159         .if \rstor_rax
 160         movq 10*8(%rsp), %rax
 161         .endif
 162         .if \rstor_rcx
 163         movq 11*8(%rsp), %rcx
 164         .endif
 165         .if \rstor_rdx
 166         movq 12*8(%rsp), %rdx
 167         .endif
 168         movq 13*8(%rsp), %rsi
 169         movq 14*8(%rsp), %rdi
 170         .endm
 171         .macro RESTORE_C_REGS
 172         RESTORE_C_REGS_HELPER 1,1,1,1,1
 173         .endm
 174         .macro RESTORE_C_REGS_EXCEPT_RAX
 175         RESTORE_C_REGS_HELPER 0,1,1,1,1
 176         .endm
 177         .macro RESTORE_C_REGS_EXCEPT_RCX
 178         RESTORE_C_REGS_HELPER 1,0,1,1,1
 179         .endm
 180         .macro RESTORE_C_REGS_EXCEPT_R11
 181         RESTORE_C_REGS_HELPER 1,1,0,1,1
 182         .endm
 183         .macro RESTORE_C_REGS_EXCEPT_RCX_R11
 184         RESTORE_C_REGS_HELPER 1,0,0,1,1
 185         .endm
 186
 187         .macro REMOVE_PT_GPREGS_FROM_STACK addskip=0
 188         subq $-(15*8+\addskip), %rsp
 189         .endm
 190
 191         .macro icebp
 192         .byte 0xf1
 193         .endm
 194
 195 /*
 196  * This is a sneaky trick to help the unwinder find pt_regs on the stack.  The
 197  * frame pointer is replaced with an encoded pointer to pt_regs.  The encoding
 198  * is just setting the LSB, which makes it an invalid stack address and is also
 199  * a signal to the unwinder that it's a pt_regs pointer in disguise.
 200  *
 201  * NOTE: This macro must be used *after* SAVE_EXTRA_REGS because it corrupts
 202  * the original rbp.
 203  */
 204 .macro ENCODE_FRAME_POINTER ptregs_offset=0
 205 #ifdef CONFIG_FRAME_POINTER
 206         .if \ptregs_offset
 207                 leaq \ptregs_offset(%rsp), %rbp
 208         .else
 209                 mov %rsp, %rbp
 210         .endif
 211         orq     $0x1, %rbp
 212 #endif
 213 .endm
 214
 215 #endif /* CONFIG_X86_64 */
 216
 217 /*
 218  * This does 'call enter_from_user_mode' unless we can avoid it based on
 219  * kernel config or using the static jump infrastructure.
 220  */
 221 .macro CALL_enter_from_user_mode
 222 #ifdef CONFIG_CONTEXT_TRACKING
 223 #ifdef HAVE_JUMP_LABEL
 224         STATIC_JUMP_IF_FALSE .Lafter_call_\@, context_tracking_enabled, def=0
 225 #endif
 226         call enter_from_user_mode
 227 .Lafter_call_\@:
 228 #endif
 229 .endm