!80 [Backport] generalize "const trick"

From: @cf-zhao 
Reviewed-by: @duguhaotian, @jackey_1024 
Signed-off-by: @duguhaotian

backport-generalize-const-trick.patch

@@ -0,0 +1,212 @@
+commit 1f925038ab9c6bd8f6b3cd40ed7aab0ef10d898e
+Author: YU Jincheng <shana@zju.edu.cn>
+Date:   Wed Sep 29 17:37:26 2021 +0800
+
+    *: 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>
+
+diff --git a/coreutils/test.c b/coreutils/test.c
+index 7c65743..fc95672 100644
+--- a/coreutils/test.c
++++ b/coreutils/test.c
+@@ -435,7 +435,7 @@ struct test_statics {
+ };
+ 
+ /* See test_ptr_hack.c */
+-extern struct test_statics *const test_ptr_to_statics;
++extern struct test_statics *BB_GLOBAL_CONST test_ptr_to_statics;
+ 
+ #define S (*test_ptr_to_statics)
+ #define args            (S.args         )
+@@ -446,8 +446,7 @@ extern struct test_statics *const test_ptr_to_statics;
+ #define leaving         (S.leaving      )
+ 
+ #define INIT_S() do { \
+-	(*(struct test_statics**)not_const_pp(&test_ptr_to_statics)) = xzalloc(sizeof(S)); \
+-	barrier(); \
++	ASSIGN_CONST_PTR(test_ptr_to_statics, xzalloc(sizeof(S))); \
+ } while (0)
+ #define DEINIT_S() do { \
+ 	free(group_array); \
+diff --git a/include/libbb.h b/include/libbb.h
+index dfcaa05..02cc008 100644
+--- a/include/libbb.h
++++ b/include/libbb.h
+@@ -365,13 +365,27 @@ struct BUG_off_t_size_is_misdetected {
+ #endif
+ #endif
+ 
++/* We use a trick to have more optimized code (fewer pointer reloads
++ * and reduced binary size by a few kilobytes) like:
++ *  ash.c:   extern struct globals *const ash_ptr_to_globals;
++ *  ash_ptr_hack.c: struct globals *ash_ptr_to_globals;
++ * This way, compiler in ash.c knows the pointer can not change.
++ *
++ * However, this may break on weird arches or toolchains. In this case,
++ * set "-DBB_GLOBAL_CONST=''" in CONFIG_EXTRA_CFLAGS to disable
++ * this optimization.
++ */
++#ifndef BB_GLOBAL_CONST
++# define BB_GLOBAL_CONST const
++#endif
++
+ #if defined(errno)
+ /* If errno is a define, assume it's "define errno (*__errno_location())"
+  * and we will cache it's result in this variable */
+-extern int *const bb_errno;
+-#undef errno
+-#define errno (*bb_errno)
+-#define bb_cached_errno_ptr 1
++extern int *BB_GLOBAL_CONST bb_errno;
++# undef errno
++# define errno (*bb_errno)
++# define bb_cached_errno_ptr 1
+ #endif
+ 
+ #if !(ULONG_MAX > 0xffffffff)
+@@ -2270,6 +2284,8 @@ struct globals;
+  * If you want to assign a value, use SET_PTR_TO_GLOBALS(x) */
+ extern struct globals *const ptr_to_globals;
+ 
++#define barrier() asm volatile ("":::"memory")
++
+ #if defined(__clang_major__) && __clang_major__ >= 9
+ /* Clang/llvm drops assignment to "constant" storage. Silently.
+  * Needs serious convincing to not eliminate the store.
+@@ -2277,7 +2293,7 @@ extern struct globals *const ptr_to_globals;
+ static ALWAYS_INLINE void* not_const_pp(const void *p)
+ {
+ 	void *pp;
+-	__asm__ __volatile__(
++	asm volatile (
+ 		"# forget that p points to const"
+ 		: /*outputs*/ "=r" (pp)
+ 		: /*inputs*/ "0" (p)
+@@ -2288,13 +2304,13 @@ static ALWAYS_INLINE void* not_const_pp(const void *p)
+ static ALWAYS_INLINE void* not_const_pp(const void *p) { return (void*)p; }
+ #endif
+ 
+-/* At least gcc 3.4.6 on mipsel system needs optimization barrier */
+-#define barrier() __asm__ __volatile__("":::"memory")
+-#define SET_PTR_TO_GLOBALS(x) do { \
+-	(*(struct globals**)not_const_pp(&ptr_to_globals)) = (void*)(x); \
++#define ASSIGN_CONST_PTR(p, v) do { \
++	*(void**)not_const_pp(&p) = (void*)(v); \
++	/* At least gcc 3.4.6 on mipsel needs optimization barrier */ \
+ 	barrier(); \
+ } while (0)
+ 
++#define SET_PTR_TO_GLOBALS(x) ASSIGN_CONST_PTR(ptr_to_globals, x)
+ #define FREE_PTR_TO_GLOBALS() do { \
+ 	if (ENABLE_FEATURE_CLEAN_UP) { \
+ 		free(ptr_to_globals); \
+diff --git a/libbb/appletlib.c b/libbb/appletlib.c
+index 5c5d7eb..bf26c99 100644
+--- a/libbb/appletlib.c
++++ b/libbb/appletlib.c
+@@ -247,8 +247,7 @@ void lbb_prepare(const char *applet
+ 		IF_FEATURE_INDIVIDUAL(, char **argv))
+ {
+ #ifdef bb_cached_errno_ptr
+-	(*(int **)not_const_pp(&bb_errno)) = get_perrno();
+-	barrier();
++	ASSIGN_CONST_PTR(bb_errno, get_perrno());
+ #endif
+ 	applet_name = applet;
+ 
+diff --git a/libbb/lineedit.c b/libbb/lineedit.c
+index a7a3ee1..3c87abc 100644
+--- a/libbb/lineedit.c
++++ b/libbb/lineedit.c
+@@ -192,7 +192,7 @@ struct lineedit_statics {
+ };
+ 
+ /* See lineedit_ptr_hack.c */
+-extern struct lineedit_statics *const lineedit_ptr_to_statics;
++extern struct lineedit_statics *BB_GLOBAL_CONST lineedit_ptr_to_statics;
+ 
+ #define S (*lineedit_ptr_to_statics)
+ #define state            (S.state           )
+@@ -214,8 +214,7 @@ extern struct lineedit_statics *const lineedit_ptr_to_statics;
+ #define delbuf           (S.delbuf          )
+ 
+ #define INIT_S() do { \
+-	(*(struct lineedit_statics**)not_const_pp(&lineedit_ptr_to_statics)) = xzalloc(sizeof(S)); \
+-	barrier(); \
++	ASSIGN_CONST_PTR(lineedit_ptr_to_statics, xzalloc(sizeof(S))); \
+ } while (0)
+ 
+ static void deinit_S(void)
+diff --git a/procps/powertop.c b/procps/powertop.c
+index fc6018b..24c2b32 100644
+--- a/procps/powertop.c
++++ b/procps/powertop.c
+@@ -505,7 +505,7 @@ static void cpuid(unsigned int *eax, unsigned int *ebx, unsigned int *ecx,
+ 				unsigned int *edx)
+ {
+ 	/* EAX value specifies what information to return */
+-	__asm__(
++	asm (
+ 		"	pushl %%ebx\n"     /* Save EBX */
+ 		"	cpuid\n"
+ 		"	movl %%ebx, %1\n"  /* Save content of EBX */
+diff --git a/shell/ash.c b/shell/ash.c
+index 4bf0615..7b85981 100644
+--- a/shell/ash.c
++++ b/shell/ash.c
+@@ -303,20 +303,6 @@ typedef long arith_t;
+ # error "Do not even bother, ash will not run on NOMMU machine"
+ #endif
+ 
+-/* We use a trick to have more optimized code (fewer pointer reloads):
+- *  ash.c:   extern struct globals *const ash_ptr_to_globals;
+- *  ash_ptr_hack.c: struct globals *ash_ptr_to_globals;
+- * This way, compiler in ash.c knows the pointer can not change.
+- *
+- * However, this may break on weird arches or toolchains. In this case,
+- * set "-DBB_GLOBAL_CONST=''" in CONFIG_EXTRA_CFLAGS to disable
+- * this optimization.
+- */
+-#ifndef BB_GLOBAL_CONST
+-# define BB_GLOBAL_CONST const
+-#endif
+-
+-
+ /* ============ Hash table sizes. Configurable. */
+ 
+ #define VTABSIZE 39
+@@ -518,8 +504,7 @@ extern struct globals_misc *BB_GLOBAL_CONST ash_ptr_to_globals_misc;
+ #define random_gen  (G_misc.random_gen )
+ #define backgndpid  (G_misc.backgndpid )
+ #define INIT_G_misc() do { \
+-	(*(struct globals_misc**)not_const_pp(&ash_ptr_to_globals_misc)) = xzalloc(sizeof(G_misc)); \
+-	barrier(); \
++	ASSIGN_CONST_PTR(ash_ptr_to_globals_misc, xzalloc(sizeof(G_misc))); \
+ 	savestatus = -1; \
+ 	curdir = nullstr; \
+ 	physdir = nullstr; \
+@@ -1597,8 +1582,7 @@ extern struct globals_memstack *BB_GLOBAL_CONST ash_ptr_to_globals_memstack;
+ #define g_stacknleft (G_memstack.g_stacknleft)
+ #define stackbase    (G_memstack.stackbase   )
+ #define INIT_G_memstack() do { \
+-	(*(struct globals_memstack**)not_const_pp(&ash_ptr_to_globals_memstack)) = xzalloc(sizeof(G_memstack)); \
+-	barrier(); \
++	ASSIGN_CONST_PTR(ash_ptr_to_globals_memstack, xzalloc(sizeof(G_memstack))); \
+ 	g_stackp = &stackbase; \
+ 	g_stacknxt = stackbase.space; \
+ 	g_stacknleft = MINSIZE; \
+@@ -2229,8 +2213,7 @@ extern struct globals_var *BB_GLOBAL_CONST ash_ptr_to_globals_var;
+ #endif
+ #define INIT_G_var() do { \
+ 	unsigned i; \
+-	(*(struct globals_var**)not_const_pp(&ash_ptr_to_globals_var)) = xzalloc(sizeof(G_var)); \
+-	barrier(); \
++	ASSIGN_CONST_PTR(ash_ptr_to_globals_var, xzalloc(sizeof(G_var))); \
+ 	for (i = 0; i < ARRAY_SIZE(varinit_data); i++) { \
+ 		varinit[i].flags    = varinit_data[i].flags; \
+ 		varinit[i].var_text = varinit_data[i].var_text; \

busybox.spec

@@ -4,7 +4,7 @@
 %endif
 
 %if "%{!?RELEASE:1}"
-%define RELEASE 18
+%define RELEASE 19
 %endif
 Epoch: 1
 
@@ -23,6 +23,7 @@ Source3: busybox-dynamic.config
 Patch6000: backport-CVE-2022-28391.patch
 Patch6001: backport-CVE-2022-30065.patch
 Patch6002: backport-fix-use-after-free-in-bc-module.patch
+Patch6003: backport-generalize-const-trick.patch
 
 BuildRoot:      %_topdir/BUILDROOT
 #Dependency
@@ -98,6 +99,9 @@ install -m 644 docs/busybox.dynamic.1 $RPM_BUILD_ROOT/%{_mandir}/man1/busybox.1
 %{_mandir}/man1/busybox.petitboot.1.gz
 
 %changelog
+* Fri Dec 16 2022 cf_zhao <zhaochuanfeng@huawei.com> - 1:1.34.1-19
+- Backport generalize "const trick" which commited in 1f925038ab9c6bd8f6b3cd40ed7aab0ef10d898e
+
 * Fri Oct 28 2022 jikui <jikui2@huawei.com> - 1:1.34.1-18
 - fix use after free in bc module