1 #ifndef ASMSAFE_H
2 #define ASMSAFE_H
3 /*
4 macros to safely call C functions from most inline ASM
5 these should replace the use of __attribute__((naked)) functions for C code,
6 because C code is not actually legal in naked functions and can break in obscure ways.
7 see http://chdk.wikia.com/wiki/CHDK_Coding_Guidelines#Naked_functions
8 usage
9 asm volatile (
10 ...
11 ASM_SAFE("BL my_func\n")
12 ...
13 )
14
15 you can set up arguments for the function inside the ASM_SAFE without worrying about preserving values
16 e.g
17 ASM_SAFE(
18 "MOV R0,#1\n"
19 "BL my_func\n"
20 )
21 */
22
23 // push all regs except SP and PC
24 // push CSPR via R0
25 // restore value for R0 from stack
26 #define ASM_SAFE_ENTER \
27 "STMFD SP!, {R0-R12,LR}\n" \
28 "MRS R0, CPSR\n" \
29 "STR R0,[SP,#-4]!\n" \
30 "LDR R0,[SP,#4]\n"
31
32 // pop CSPR via R0
33 // pop all regs except SP and PC
34 #define ASM_SAFE_LEAVE \
35 "LDR R0,[SP],#4\n" \
36 "MSR CPSR_cxsf,R0\n" \
37 "LDMFD SP!, {R0-R12,LR}\n"
38
39 #define ASM_SAFE(asmcode) \
40 ASM_SAFE_ENTER \
41 asmcode \
42 ASM_SAFE_LEAVE
43
44 #endif // ASMSAFE_H