Brendan Shanks : loader: Add comments to 'start' in macOS preloader.
Module: wine Branch: master Commit: 4ec770a139774255d199c5844d8630b32455c8d9 URL: https://gitlab.winehq.org/wine/wine/-/commit/4ec770a139774255d199c5844d8630b... Author: Brendan Shanks <bshanks(a)codeweavers.com> Date: Mon Nov 28 15:50:54 2022 -0800 loader: Add comments to 'start' in macOS preloader. --- loader/preloader_mac.c | 129 ++++++++++++++++++++++++++++++++++--------------- 1 file changed, 91 insertions(+), 38 deletions(-) diff --git a/loader/preloader_mac.c b/loader/preloader_mac.c index 01a41f08d8c..7b7e589d684 100644 --- a/loader/preloader_mac.c +++ b/loader/preloader_mac.c @@ -101,6 +101,47 @@ void *__stack_chk_guard = 0; void __stack_chk_fail_local(void) { return; } void __stack_chk_fail(void) { return; } +/* + * When 'start' is called, stack frame looks like: + * + * : + * | STRING AREA | + * +-------------+ + * | 0 | + * +-------------+ + * | exec_path | extra "apple" parameters start after NULL terminating env array + * +-------------+ + * | 0 | + * +-------------+ + * | env[n] | + * +-------------+ + * : + * : + * +-------------+ + * | env[0] | + * +-------------+ + * | 0 | + * +-------------+ + * | arg[argc-1] | + * +-------------+ + * : + * : + * +-------------+ + * | arg[0] | + * +-------------+ + * | argc | argc is always 4 bytes long, even in 64-bit architectures + * +-------------+ <- sp + * + * Where arg[i] and env[i] point into the STRING AREA + * + * See also: + * macOS C runtime 'start': + * <https://github.com/apple-oss-distributions/Csu/blob/Csu-88/start.s> + * + * macOS dyld '__dyld_start' (pre-dyld4): + * <https://github.com/apple-oss-distributions/dyld/blob/dyld-852.2/src/dyldStartup.s> + */ + #ifdef __i386__ static const size_t page_size = 0x1000; @@ -132,13 +173,14 @@ static const size_t page_mask = 0xfff; __ASM_GLOBAL_FUNC( start, __ASM_CFI("\t.cfi_undefined %eip\n") /* The first 16 bytes are used as a function signature on i386 */ - "\t.byte 0x6a,0x00\n" /* pushl $0 */ - "\t.byte 0x89,0xe5\n" /* movl %esp,%ebp */ - "\t.byte 0x83,0xe4,0xf0\n" /* andl $-16,%esp */ - "\t.byte 0x83,0xec,0x10\n" /* subl $16,%esp */ - "\t.byte 0x8b,0x5d,0x04\n" /* movl 4(%ebp),%ebx */ - "\t.byte 0x89,0x5c,0x24,0x00\n" /* movl %ebx,0(%esp) */ - + "\t.byte 0x6a,0x00\n" /* pushl $0: push a zero for debugger end of frames marker */ + "\t.byte 0x89,0xe5\n" /* movl %esp,%ebp: pointer to base of kernel frame */ + "\t.byte 0x83,0xe4,0xf0\n" /* andl $-16,%esp: force SSE alignment */ + "\t.byte 0x83,0xec,0x10\n" /* subl $16,%esp: room for new argc, argv, & envp, SSE aligned */ + "\t.byte 0x8b,0x5d,0x04\n" /* movl 4(%ebp),%ebx: pickup argc in %ebx */ + "\t.byte 0x89,0x5c,0x24,0x00\n" /* movl %ebx,0(%esp): argc to reserved stack word */ + + /* call wld_start(stack, &is_unix_thread) */ "\tleal 4(%ebp),%eax\n" "\tmovl %eax,0(%esp)\n" /* stack */ "\tleal 8(%esp),%eax\n" @@ -146,16 +188,21 @@ __ASM_GLOBAL_FUNC( start, "\tmovl $0,(%eax)\n" "\tcall _wld_start\n" + /* argc/argv need to be fixed to remove argv[0]. + * With LC_MAIN, pointers to argv/env/apple are passed so this is easy. + * With LC_UNIXTHREAD, argv[1] to the end of apple[] need to be moved. + */ "\tmovl 4(%ebp),%edi\n" - "\tdecl %edi\n" /* argc */ - "\tleal 12(%ebp),%esi\n" /* argv */ - "\tleal 4(%esi,%edi,4),%edx\n" /* env */ - "\tmovl %edx,%ecx\n" /* apple data */ + "\tdecl %edi\n" /* %edi = argc (decremented) */ + "\tleal 12(%ebp),%esi\n" /* %esi = &argv[1] */ + "\tleal 4(%esi,%edi,4),%edx\n" /* %edx = env */ + "\tmovl %edx,%ecx\n" "1:\tmovl (%ecx),%ebx\n" "\tadd $4,%ecx\n" - "\torl %ebx,%ebx\n" - "\tjnz 1b\n" + "\torl %ebx,%ebx\n" /* look for the NULL ending the env[] array */ + "\tjnz 1b\n" /* %ecx = apple data */ + /* jmp based on is_unix_thread */ "\tcmpl $0,8(%esp)\n" "\tjne 2f\n" @@ -164,16 +211,16 @@ __ASM_GLOBAL_FUNC( start, "\tmovl %esi,4(%esp)\n" /* argv */ "\tmovl %edx,8(%esp)\n" /* env */ "\tmovl %ecx,12(%esp)\n" /* apple data */ - "\tcall *%eax\n" - "\tmovl %eax,(%esp)\n" - "\tcall _wld_exit\n" + "\tcall *%eax\n" /* call main(argc,argv,env,apple) */ + "\tmovl %eax,(%esp)\n" /* pass result from main() to exit() */ + "\tcall _wld_exit\n" /* need to use call to keep stack aligned */ "\thlt\n" /* LC_UNIXTHREAD */ "2:\tmovl (%ecx),%ebx\n" "\tadd $4,%ecx\n" - "\torl %ebx,%ebx\n" - "\tjnz 2b\n" + "\torl %ebx,%ebx\n" /* look for the NULL ending the apple[] array */ + "\tjnz 2b\n" /* %ecx = end of apple[] */ "\tsubl %ebp,%ecx\n" "\tsubl $8,%ecx\n" @@ -186,8 +233,8 @@ __ASM_GLOBAL_FUNC( start, "\tcld\n" "\trep; movsd\n" /* argv, ... */ - "\tmovl $0,%ebp\n" - "\tjmpl *%eax\n" ) + "\tmovl $0,%ebp\n" /* restore ebp back to zero */ + "\tjmpl *%eax\n" ) /* jump to the entry point */ #elif defined(__x86_64__) @@ -221,41 +268,47 @@ static const size_t page_mask = 0xfff; __ASM_GLOBAL_FUNC( start, __ASM_CFI("\t.cfi_undefined %rip\n") - "\tpushq $0\n" - "\tmovq %rsp,%rbp\n" - "\tandq $-16,%rsp\n" - "\tsubq $16,%rsp\n" + "\tpushq $0\n" /* push a zero for debugger end of frames marker */ + "\tmovq %rsp,%rbp\n" /* pointer to base of kernel frame */ + "\tandq $-16,%rsp\n" /* force SSE alignment */ + "\tsubq $16,%rsp\n" /* room for local variables */ + /* call wld_start(stack, &is_unix_thread) */ "\tleaq 8(%rbp),%rdi\n" /* stack */ "\tmovq %rsp,%rsi\n" /* &is_unix_thread */ "\tmovq $0,(%rsi)\n" "\tcall _wld_start\n" + /* argc/argv need to be fixed to remove argv[0]. + * With LC_MAIN, pointers to argv/env/apple are passed so this is easy. + * With LC_UNIXTHREAD, argv[1] to the end of apple[] need to be moved. + */ "\tmovq 8(%rbp),%rdi\n" - "\tdec %rdi\n" /* argc */ - "\tleaq 24(%rbp),%rsi\n" /* argv */ - "\tleaq 8(%rsi,%rdi,8),%rdx\n" /* env */ - "\tmovq %rdx,%rcx\n" /* apple data */ + "\tdec %rdi\n" /* %rdi = argc (decremented) */ + "\tleaq 24(%rbp),%rsi\n" /* %rsi = &argv[1] */ + "\tleaq 8(%rsi,%rdi,8),%rdx\n" /* %rdx = env */ + "\tmovq %rdx,%rcx\n" "1:\tmovq (%rcx),%r8\n" "\taddq $8,%rcx\n" - "\torq %r8,%r8\n" - "\tjnz 1b\n" + "\torq %r8,%r8\n" /* look for the NULL ending the env[] array */ + "\tjnz 1b\n" /* %rcx = apple data */ + /* jmp based on is_unix_thread */ "\tcmpl $0,0(%rsp)\n" "\tjne 2f\n" /* LC_MAIN */ - "\taddq $16,%rsp\n" - "\tcall *%rax\n" - "\tmovq %rax,%rdi\n" - "\tcall _wld_exit\n" + "\taddq $16,%rsp\n" /* remove local variables */ + "\tcall *%rax\n" /* call main(argc,argv,env,apple) */ + "\tmovq %rax,%rdi\n" /* pass result from main() to exit() */ + "\tcall _wld_exit\n" /* need to use call to keep stack aligned */ "\thlt\n" /* LC_UNIXTHREAD */ "2:\tmovq (%rcx),%r8\n" "\taddq $8,%rcx\n" - "\torq %r8,%r8\n" - "\tjnz 2b\n" + "\torq %r8,%r8\n" /* look for the NULL ending the apple[] array */ + "\tjnz 2b\n" /* %rcx = end of apple[] */ "\tsubq %rbp,%rcx\n" "\tsubq $16,%rcx\n" @@ -268,8 +321,8 @@ __ASM_GLOBAL_FUNC( start, "\tcld\n" "\trep; movsq\n" /* argv, ... */ - "\tmovq $0,%rbp\n" - "\tjmpq *%rax\n" ) + "\tmovq $0,%rbp\n" /* restore ebp back to zero */ + "\tjmpq *%rax\n" ) /* jump to the entry point */ #else #error preloader not implemented for this CPU
participants (1)
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Alexandre Julliard