1 #include <linux/jump_label.h>
2 #include <asm/cpufeatures.h>
6 x86 function call convention, 64-bit:
7 -------------------------------------
8 arguments | callee-saved | extra caller-saved | return
9 [callee-clobbered] | | [callee-clobbered] |
10 ---------------------------------------------------------------------------
11 rdi rsi rdx rcx r8-9 | rbx rbp [*] r12-15 | r10-11 | rax, rdx [**]
13 ( rsp is obviously invariant across normal function calls. (gcc can 'merge'
14 functions when it sees tail-call optimization possibilities) rflags is
15 clobbered. Leftover arguments are passed over the stack frame.)
17 [*] In the frame-pointers case rbp is fixed to the stack frame.
19 [**] for struct return values wider than 64 bits the return convention is a
20 bit more complex: up to 128 bits width we return small structures
21 straight in rax, rdx. For structures larger than that (3 words or
22 larger) the caller puts a pointer to an on-stack return struct
23 [allocated in the caller's stack frame] into the first argument - i.e.
24 into rdi. All other arguments shift up by one in this case.
25 Fortunately this case is rare in the kernel.
27 For 32-bit we have the following conventions - kernel is built with
28 -mregparm=3 and -freg-struct-return:
30 x86 function calling convention, 32-bit:
31 ----------------------------------------
32 arguments | callee-saved | extra caller-saved | return
33 [callee-clobbered] | | [callee-clobbered] |
34 -------------------------------------------------------------------------
35 eax edx ecx | ebx edi esi ebp [*] | <none> | eax, edx [**]
37 ( here too esp is obviously invariant across normal function calls. eflags
38 is clobbered. Leftover arguments are passed over the stack frame. )
40 [*] In the frame-pointers case ebp is fixed to the stack frame.
42 [**] We build with -freg-struct-return, which on 32-bit means similar
43 semantics as on 64-bit: edx can be used for a second return value
44 (i.e. covering integer and structure sizes up to 64 bits) - after that
45 it gets more complex and more expensive: 3-word or larger struct returns
46 get done in the caller's frame and the pointer to the return struct goes
47 into regparm0, i.e. eax - the other arguments shift up and the
48 function's register parameters degenerate to regparm=2 in essence.
55 * 64-bit system call stack frame layout defines and helpers,
59 /* The layout forms the "struct pt_regs" on the stack: */
61 * C ABI says these regs are callee-preserved. They aren't saved on kernel entry
62 * unless syscall needs a complete, fully filled "struct pt_regs".
70 /* These regs are callee-clobbered. Always saved on kernel entry. */
81 * On syscall entry, this is syscall#. On CPU exception, this is error code.
82 * On hw interrupt, it's IRQ number:
85 /* Return frame for iretq */
92 #define SIZEOF_PTREGS 21*8
94 .macro ALLOC_PT_GPREGS_ON_STACK addskip=0
95 addq $-(15*8+\addskip), %rsp
98 .macro SAVE_C_REGS_HELPER offset=0 rax=1 rcx=1 r8910=1 r11=1
100 movq %r11, 6*8+\offset(%rsp)
103 movq %r10, 7*8+\offset(%rsp)
104 movq %r9, 8*8+\offset(%rsp)
105 movq %r8, 9*8+\offset(%rsp)
108 movq %rax, 10*8+\offset(%rsp)
111 movq %rcx, 11*8+\offset(%rsp)
113 movq %rdx, 12*8+\offset(%rsp)
114 movq %rsi, 13*8+\offset(%rsp)
115 movq %rdi, 14*8+\offset(%rsp)
117 .macro SAVE_C_REGS offset=0
118 SAVE_C_REGS_HELPER \offset, 1, 1, 1, 1
120 .macro SAVE_C_REGS_EXCEPT_RAX_RCX offset=0
121 SAVE_C_REGS_HELPER \offset, 0, 0, 1, 1
123 .macro SAVE_C_REGS_EXCEPT_R891011
124 SAVE_C_REGS_HELPER 0, 1, 1, 0, 0
126 .macro SAVE_C_REGS_EXCEPT_RCX_R891011
127 SAVE_C_REGS_HELPER 0, 1, 0, 0, 0
129 .macro SAVE_C_REGS_EXCEPT_RAX_RCX_R11
130 SAVE_C_REGS_HELPER 0, 0, 0, 1, 0
133 .macro SAVE_EXTRA_REGS offset=0
134 movq %r15, 0*8+\offset(%rsp)
135 movq %r14, 1*8+\offset(%rsp)
136 movq %r13, 2*8+\offset(%rsp)
137 movq %r12, 3*8+\offset(%rsp)
138 movq %rbp, 4*8+\offset(%rsp)
139 movq %rbx, 5*8+\offset(%rsp)
142 .macro RESTORE_EXTRA_REGS offset=0
143 movq 0*8+\offset(%rsp), %r15
144 movq 1*8+\offset(%rsp), %r14
145 movq 2*8+\offset(%rsp), %r13
146 movq 3*8+\offset(%rsp), %r12
147 movq 4*8+\offset(%rsp), %rbp
148 movq 5*8+\offset(%rsp), %rbx
151 .macro ZERO_EXTRA_REGS
160 .macro RESTORE_C_REGS_HELPER rstor_rax=1, rstor_rcx=1, rstor_r11=1, rstor_r8910=1, rstor_rdx=1
170 movq 10*8(%rsp), %rax
173 movq 11*8(%rsp), %rcx
176 movq 12*8(%rsp), %rdx
178 movq 13*8(%rsp), %rsi
179 movq 14*8(%rsp), %rdi
181 .macro RESTORE_C_REGS
182 RESTORE_C_REGS_HELPER 1,1,1,1,1
184 .macro RESTORE_C_REGS_EXCEPT_RAX
185 RESTORE_C_REGS_HELPER 0,1,1,1,1
187 .macro RESTORE_C_REGS_EXCEPT_RCX
188 RESTORE_C_REGS_HELPER 1,0,1,1,1
190 .macro RESTORE_C_REGS_EXCEPT_R11
191 RESTORE_C_REGS_HELPER 1,1,0,1,1
193 .macro RESTORE_C_REGS_EXCEPT_RCX_R11
194 RESTORE_C_REGS_HELPER 1,0,0,1,1
197 .macro REMOVE_PT_GPREGS_FROM_STACK addskip=0
198 subq $-(15*8+\addskip), %rsp
206 * Mitigate Spectre v1 for conditional swapgs code paths.
208 * FENCE_SWAPGS_USER_ENTRY is used in the user entry swapgs code path, to
209 * prevent a speculative swapgs when coming from kernel space.
211 * FENCE_SWAPGS_KERNEL_ENTRY is used in the kernel entry non-swapgs code path,
212 * to prevent the swapgs from getting speculatively skipped when coming from
215 .macro FENCE_SWAPGS_USER_ENTRY
216 ALTERNATIVE "", "lfence", X86_FEATURE_FENCE_SWAPGS_USER
218 .macro FENCE_SWAPGS_KERNEL_ENTRY
219 ALTERNATIVE "", "lfence", X86_FEATURE_FENCE_SWAPGS_KERNEL
222 #endif /* CONFIG_X86_64 */
225 * This does 'call enter_from_user_mode' unless we can avoid it based on
226 * kernel config or using the static jump infrastructure.
228 .macro CALL_enter_from_user_mode
229 #ifdef CONFIG_CONTEXT_TRACKING
230 #ifdef HAVE_JUMP_LABEL
231 STATIC_JUMP_IF_FALSE .Lafter_call_\@, context_tracking_enabled, def=0
233 call enter_from_user_mode