*: generalize "const trick"
While at it, change all "__asm__" to "asm" Co-authored-by: canyie <31466456+canyie@users.noreply.github.com> Signed-off-by: YU Jincheng <shana@zju.edu.cn> Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
This commit is contained in:
YU Jincheng
Denys Vlasenko
parent
17e6fb06b3
commit
1f925038ab
@ -435,7 +435,7 @@ struct test_statics {
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};
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/* See test_ptr_hack.c */
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extern struct test_statics *const test_ptr_to_statics;
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extern struct test_statics *BB_GLOBAL_CONST test_ptr_to_statics;
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#define S (*test_ptr_to_statics)
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#define args (S.args )
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@ -446,8 +446,7 @@ extern struct test_statics *const test_ptr_to_statics;
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#define leaving (S.leaving )
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#define INIT_S() do { \
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(*(struct test_statics**)not_const_pp(&test_ptr_to_statics)) = xzalloc(sizeof(S)); \
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barrier(); \
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ASSIGN_CONST_PTR(test_ptr_to_statics, xzalloc(sizeof(S))); \
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} while (0)
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#define DEINIT_S() do { \
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free(group_array); \
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@ -365,13 +365,27 @@ struct BUG_off_t_size_is_misdetected {
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#endif
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#endif
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/* We use a trick to have more optimized code (fewer pointer reloads
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* and reduced binary size by a few kilobytes) like:
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* ash.c: extern struct globals *const ash_ptr_to_globals;
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* ash_ptr_hack.c: struct globals *ash_ptr_to_globals;
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* This way, compiler in ash.c knows the pointer can not change.
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*
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* However, this may break on weird arches or toolchains. In this case,
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* set "-DBB_GLOBAL_CONST=''" in CONFIG_EXTRA_CFLAGS to disable
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* this optimization.
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*/
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#ifndef BB_GLOBAL_CONST
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# define BB_GLOBAL_CONST const
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#endif
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#if defined(errno)
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/* If errno is a define, assume it's "define errno (*__errno_location())"
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* and we will cache it's result in this variable */
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extern int *const bb_errno;
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#undef errno
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#define errno (*bb_errno)
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#define bb_cached_errno_ptr 1
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extern int *BB_GLOBAL_CONST bb_errno;
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# undef errno
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# define errno (*bb_errno)
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# define bb_cached_errno_ptr 1
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#endif
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#if !(ULONG_MAX > 0xffffffff)
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@ -2270,6 +2284,8 @@ struct globals;
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* If you want to assign a value, use SET_PTR_TO_GLOBALS(x) */
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extern struct globals *const ptr_to_globals;
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#define barrier() asm volatile ("":::"memory")
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#if defined(__clang_major__) && __clang_major__ >= 9
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/* Clang/llvm drops assignment to "constant" storage. Silently.
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* Needs serious convincing to not eliminate the store.
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@ -2277,7 +2293,7 @@ extern struct globals *const ptr_to_globals;
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static ALWAYS_INLINE void* not_const_pp(const void *p)
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{
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void *pp;
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__asm__ __volatile__(
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asm volatile (
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"# forget that p points to const"
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: /*outputs*/ "=r" (pp)
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: /*inputs*/ "0" (p)
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@ -2288,13 +2304,13 @@ static ALWAYS_INLINE void* not_const_pp(const void *p)
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static ALWAYS_INLINE void* not_const_pp(const void *p) { return (void*)p; }
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#endif
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/* At least gcc 3.4.6 on mipsel system needs optimization barrier */
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#define barrier() __asm__ __volatile__("":::"memory")
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#define SET_PTR_TO_GLOBALS(x) do { \
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(*(struct globals**)not_const_pp(&ptr_to_globals)) = (void*)(x); \
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#define ASSIGN_CONST_PTR(p, v) do { \
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*(void**)not_const_pp(&p) = (void*)(v); \
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/* At least gcc 3.4.6 on mipsel needs optimization barrier */ \
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barrier(); \
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} while (0)
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#define SET_PTR_TO_GLOBALS(x) ASSIGN_CONST_PTR(ptr_to_globals, x)
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#define FREE_PTR_TO_GLOBALS() do { \
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if (ENABLE_FEATURE_CLEAN_UP) { \
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free(ptr_to_globals); \
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@ -247,8 +247,7 @@ void lbb_prepare(const char *applet
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IF_FEATURE_INDIVIDUAL(, char **argv))
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{
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#ifdef bb_cached_errno_ptr
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(*(int **)not_const_pp(&bb_errno)) = get_perrno();
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barrier();
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ASSIGN_CONST_PTR(bb_errno, get_perrno());
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#endif
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applet_name = applet;
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@ -192,7 +192,7 @@ struct lineedit_statics {
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};
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/* See lineedit_ptr_hack.c */
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extern struct lineedit_statics *const lineedit_ptr_to_statics;
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extern struct lineedit_statics *BB_GLOBAL_CONST lineedit_ptr_to_statics;
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#define S (*lineedit_ptr_to_statics)
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#define state (S.state )
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@ -214,8 +214,7 @@ extern struct lineedit_statics *const lineedit_ptr_to_statics;
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#define delbuf (S.delbuf )
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#define INIT_S() do { \
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(*(struct lineedit_statics**)not_const_pp(&lineedit_ptr_to_statics)) = xzalloc(sizeof(S)); \
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barrier(); \
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ASSIGN_CONST_PTR(lineedit_ptr_to_statics, xzalloc(sizeof(S))); \
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} while (0)
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static void deinit_S(void)
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@ -505,7 +505,7 @@ static void cpuid(unsigned int *eax, unsigned int *ebx, unsigned int *ecx,
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unsigned int *edx)
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{
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/* EAX value specifies what information to return */
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__asm__(
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asm (
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" pushl %%ebx\n" /* Save EBX */
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" cpuid\n"
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" movl %%ebx, %1\n" /* Save content of EBX */
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23
shell/ash.c
23
shell/ash.c
@ -303,20 +303,6 @@ typedef long arith_t;
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# error "Do not even bother, ash will not run on NOMMU machine"
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#endif
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/* We use a trick to have more optimized code (fewer pointer reloads):
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* ash.c: extern struct globals *const ash_ptr_to_globals;
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* ash_ptr_hack.c: struct globals *ash_ptr_to_globals;
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* This way, compiler in ash.c knows the pointer can not change.
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*
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* However, this may break on weird arches or toolchains. In this case,
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* set "-DBB_GLOBAL_CONST=''" in CONFIG_EXTRA_CFLAGS to disable
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* this optimization.
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*/
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#ifndef BB_GLOBAL_CONST
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# define BB_GLOBAL_CONST const
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#endif
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/* ============ Hash table sizes. Configurable. */
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#define VTABSIZE 39
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@ -518,8 +504,7 @@ extern struct globals_misc *BB_GLOBAL_CONST ash_ptr_to_globals_misc;
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#define random_gen (G_misc.random_gen )
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#define backgndpid (G_misc.backgndpid )
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#define INIT_G_misc() do { \
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(*(struct globals_misc**)not_const_pp(&ash_ptr_to_globals_misc)) = xzalloc(sizeof(G_misc)); \
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barrier(); \
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ASSIGN_CONST_PTR(ash_ptr_to_globals_misc, xzalloc(sizeof(G_misc))); \
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savestatus = -1; \
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curdir = nullstr; \
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physdir = nullstr; \
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@ -1597,8 +1582,7 @@ extern struct globals_memstack *BB_GLOBAL_CONST ash_ptr_to_globals_memstack;
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#define g_stacknleft (G_memstack.g_stacknleft)
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#define stackbase (G_memstack.stackbase )
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#define INIT_G_memstack() do { \
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(*(struct globals_memstack**)not_const_pp(&ash_ptr_to_globals_memstack)) = xzalloc(sizeof(G_memstack)); \
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barrier(); \
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ASSIGN_CONST_PTR(ash_ptr_to_globals_memstack, xzalloc(sizeof(G_memstack))); \
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g_stackp = &stackbase; \
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g_stacknxt = stackbase.space; \
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g_stacknleft = MINSIZE; \
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@ -2229,8 +2213,7 @@ extern struct globals_var *BB_GLOBAL_CONST ash_ptr_to_globals_var;
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#endif
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#define INIT_G_var() do { \
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unsigned i; \
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(*(struct globals_var**)not_const_pp(&ash_ptr_to_globals_var)) = xzalloc(sizeof(G_var)); \
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barrier(); \
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ASSIGN_CONST_PTR(ash_ptr_to_globals_var, xzalloc(sizeof(G_var))); \
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for (i = 0; i < ARRAY_SIZE(varinit_data); i++) { \
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varinit[i].flags = varinit_data[i].flags; \
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varinit[i].var_text = varinit_data[i].var_text; \
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