From 610c4c385b38280c7bde7a48d95ec019cbfe1ab4 Mon Sep 17 00:00:00 2001 From: Ron Yorston Date: Wed, 30 Mar 2016 00:42:05 +0200 Subject: [PATCH] applet_tables: save space by removing applet name offsets The array applet_nameofs consumes two bytes per applet. It encodes nofork/noexec flags suid flags the offset of the applet name in the applet_name string Change the applet_table build tool to store the flags in two separate arrays (applet_flags and applet_suid). Replace applet_nameofs[] with a smaller version that only stores a limited number of offsets. This requires changes to the macros APPLET_IS_NOFORK, APPLET_IS_NOEXEC and APPLET_SUID. According to Valgrind the original find_applet_by_name required 353 cycles per call, averaged over all names. Adjusting the number of known offsets allows space to be traded off against execution time: KNOWN_OFFSETS cycles bytes (wrt KNOWN_OFFSETS = 0) 0 9057 - 2 4604 32 4 2407 75 8 1342 98 16 908 130 32 884 194 This patch uses KNOWN_OFFSETS = 8. v2: Remove some dead code from the applet_table tool; Treat the applet in the middle of the table as a special case. v3: Use the middle applet to adjust the start of the linear search as well as the last applet found. v4: Use an augmented linear search in find_applet_by_name. Drop the special treatment of the middle name from get_applet_name: most of the advantage now derives from the last stored value. v5: Don't store index in applet_nameofs, it can be calculated. v6: Tweaks by Denys function old new delta find_applet_by_name 25 125 +100 applet_suid - 92 +92 run_applet_no_and_exit 452 460 +8 run_applet_and_exit 695 697 +2 applet_name_compare 31 - -31 applet_nameofs 734 14 -720 ------------------------------------------------------------------------------ (add/remove: 1/1 grow/shrink: 3/1 up/down: 202/-751) Total: -549 bytes text data bss dec hex filename 925464 906 17160 943530 e65aa busybox_old 924915 906 17160 942981 e6385 busybox_unstripped Signed-off-by: Ron Yorston Signed-off-by: Denys Vlasenko --- applets/applet_tables.c | 78 +++++++++++++++++++++++++++--------- include/busybox.h | 15 +++---- libbb/appletlib.c | 82 +++++++++++++++++++++++++------------- libbb/vfork_daemon_rexec.c | 3 +- 4 files changed, 120 insertions(+), 58 deletions(-) diff --git a/applets/applet_tables.c b/applets/applet_tables.c index 92bf1e447..48544f08d 100644 --- a/applets/applet_tables.c +++ b/applets/applet_tables.c @@ -41,8 +41,6 @@ struct bb_applet { enum { NUM_APPLETS = ARRAY_SIZE(applets) }; -static int offset[NUM_APPLETS]; - static int cmp_name(const void *a, const void *b) { const struct bb_applet *aa = a; @@ -60,22 +58,37 @@ static int str_isalnum_(const char *s) return 1; } +// Before linear search, narrow it down by looking at N "equidistant" names: +// KNOWN_APPNAME_OFFSETS cycles code_size +// 0 9057 +// 2 4604 +32 +// 4 2407 +75 +// 8 1342 +98 +// 16 908 +130 +// 32 884 +194 +// With 8, applet_nameofs[] table has 7 elements. +#define KNOWN_APPNAME_OFFSETS 8 + int main(int argc, char **argv) { - int i; - int ofs; + int i, j; + int ofs, offset[KNOWN_APPNAME_OFFSETS], index[KNOWN_APPNAME_OFFSETS]; // unsigned MAX_APPLET_NAME_LEN = 1; qsort(applets, NUM_APPLETS, sizeof(applets[0]), cmp_name); + for (i = 0; i < KNOWN_APPNAME_OFFSETS; i++) + index[i] = i * NUM_APPLETS / KNOWN_APPNAME_OFFSETS; + ofs = 0; for (i = 0; i < NUM_APPLETS; i++) { - offset[i] = ofs; + for (j = 0; j < KNOWN_APPNAME_OFFSETS; j++) + if (i == index[j]) + offset[j] = ofs; ofs += strlen(applets[i].name) + 1; } - /* We reuse 4 high-order bits of offset array for other purposes, - * so if they are indeed needed, refuse to proceed */ - if (ofs > 0xfff) + /* If the list of names is too long refuse to proceed */ + if (ofs > 0xffff) return 1; if (!argv[1]) return 1; @@ -94,7 +107,17 @@ int main(int argc, char **argv) printf("#define SINGLE_APPLET_STR \"%s\"\n", applets[0].name); printf("#define SINGLE_APPLET_MAIN %s_main\n", applets[0].main); } - printf("\n"); + + if (KNOWN_APPNAME_OFFSETS > 0 && NUM_APPLETS > 2*KNOWN_APPNAME_OFFSETS) { + printf("#define KNOWN_APPNAME_OFFSETS %u\n\n", KNOWN_APPNAME_OFFSETS); + printf("const uint16_t applet_nameofs[] ALIGN2 = {\n"); + for (i = 1; i < KNOWN_APPNAME_OFFSETS; i++) + printf("%d,\n", offset[i]); + printf("};\n\n"); + } + else { + printf("#define KNOWN_APPNAME_OFFSETS 0\n\n"); + } //printf("#ifndef SKIP_definitions\n"); printf("const char applet_names[] ALIGN1 = \"\"\n"); @@ -119,20 +142,39 @@ int main(int argc, char **argv) printf("};\n"); printf("#endif\n\n"); - printf("const uint16_t applet_nameofs[] ALIGN2 = {\n"); - for (i = 0; i < NUM_APPLETS; i++) { - printf("0x%04x,\n", - offset[i] #if ENABLE_FEATURE_PREFER_APPLETS - + (applets[i].nofork << 12) - + (applets[i].noexec << 13) + printf("const uint8_t applet_flags[] ALIGN1 = {\n"); + i = 0; + while (i < NUM_APPLETS) { + int v = applets[i].nofork + (applets[i].noexec << 1); + if (++i < NUM_APPLETS) + v |= (applets[i].nofork + (applets[i].noexec << 1)) << 2; + if (++i < NUM_APPLETS) + v |= (applets[i].nofork + (applets[i].noexec << 1)) << 4; + if (++i < NUM_APPLETS) + v |= (applets[i].nofork + (applets[i].noexec << 1)) << 6; + printf("0x%02x,\n", v); + i++; + } + printf("};\n\n"); #endif + #if ENABLE_FEATURE_SUID - + (applets[i].need_suid << 14) /* 2 bits */ -#endif - ); + printf("const uint8_t applet_suid[] ALIGN1 = {\n"); + i = 0; + while (i < NUM_APPLETS) { + int v = applets[i].need_suid; /* 2 bits */ + if (++i < NUM_APPLETS) + v |= applets[i].need_suid << 2; + if (++i < NUM_APPLETS) + v |= applets[i].need_suid << 4; + if (++i < NUM_APPLETS) + v |= applets[i].need_suid << 6; + printf("0x%02x,\n", v); + i++; } printf("};\n\n"); +#endif #if ENABLE_FEATURE_INSTALLER printf("const uint8_t applet_install_loc[] ALIGN1 = {\n"); diff --git a/include/busybox.h b/include/busybox.h index b1e31e5ee..737627bd0 100644 --- a/include/busybox.h +++ b/include/busybox.h @@ -15,25 +15,20 @@ PUSH_AND_SET_FUNCTION_VISIBILITY_TO_HIDDEN /* Keep in sync with applets/applet_tables.c! */ extern const char applet_names[] ALIGN1; extern int (*const applet_main[])(int argc, char **argv); -extern const uint16_t applet_nameofs[]; +extern const uint8_t applet_flags[] ALIGN1; +extern const uint8_t applet_suid[] ALIGN1; extern const uint8_t applet_install_loc[] ALIGN1; -#if ENABLE_FEATURE_SUID || ENABLE_FEATURE_PREFER_APPLETS -# define APPLET_NAME(i) (applet_names + (applet_nameofs[i] & 0x0fff)) -#else -# define APPLET_NAME(i) (applet_names + applet_nameofs[i]) -#endif - #if ENABLE_FEATURE_PREFER_APPLETS -# define APPLET_IS_NOFORK(i) (applet_nameofs[i] & (1 << 12)) -# define APPLET_IS_NOEXEC(i) (applet_nameofs[i] & (1 << 13)) +# define APPLET_IS_NOFORK(i) (applet_flags[(i)/4] & (1 << (2 * ((i)%4)))) +# define APPLET_IS_NOEXEC(i) (applet_flags[(i)/4] & (1 << ((2 * ((i)%4))+1))) #else # define APPLET_IS_NOFORK(i) 0 # define APPLET_IS_NOEXEC(i) 0 #endif #if ENABLE_FEATURE_SUID -# define APPLET_SUID(i) ((applet_nameofs[i] >> 14) & 0x3) +# define APPLET_SUID(i) ((applet_suid[(i)/4] >> (2 * ((i)%4)) & 3)) #endif #if ENABLE_FEATURE_INSTALLER diff --git a/libbb/appletlib.c b/libbb/appletlib.c index 95e589e74..aeaf238f1 100644 --- a/libbb/appletlib.c +++ b/libbb/appletlib.c @@ -139,36 +139,56 @@ void FAST_FUNC bb_show_usage(void) xfunc_die(); } -#if NUM_APPLETS > 8 -static int applet_name_compare(const void *name, const void *idx) -{ - int i = (int)(ptrdiff_t)idx - 1; - return strcmp(name, APPLET_NAME(i)); -} -#endif int FAST_FUNC find_applet_by_name(const char *name) { -#if NUM_APPLETS > 8 - /* Do a binary search to find the applet entry given the name. */ + unsigned i, max; + int j; const char *p; - p = bsearch(name, (void*)(ptrdiff_t)1, ARRAY_SIZE(applet_main), 1, applet_name_compare); - /* - * if (!p) return -1; - * ^^^^^^^^^^^^^^^^^^ the code below will do this if p == NULL :) - */ - return (int)(ptrdiff_t)p - 1; + + p = applet_names; + i = 0; +#if KNOWN_APPNAME_OFFSETS <= 0 + max = NUM_APPLETS; #else - /* A version which does not pull in bsearch */ - int i = 0; - const char *p = applet_names; - while (i < NUM_APPLETS) { - if (strcmp(name, p) == 0) - return i; - p += strlen(p) + 1; + max = NUM_APPLETS * KNOWN_APPNAME_OFFSETS; + for (j = ARRAY_SIZE(applet_nameofs)-1; j >= 0; j--) { + const char *pp = applet_names + applet_nameofs[j]; + if (strcmp(name, pp) >= 0) { + //bb_error_msg("name:'%s' >= pp:'%s'", name, pp); + p = pp; + i = max - NUM_APPLETS; + break; + } + max -= NUM_APPLETS; + } + max /= (unsigned)KNOWN_APPNAME_OFFSETS; + i /= (unsigned)KNOWN_APPNAME_OFFSETS; + //bb_error_msg("name:'%s' starting from:'%s' i:%u max:%u", name, p, i, max); +#endif + + /* Open-coding without strcmp/strlen calls for speed */ + while (i < max) { + char ch; + j = 0; + /* Do we see "name\0" in applet_names[p] position? */ + while ((ch = *p) == name[j]) { + if (ch == '\0') { + //bb_error_msg("found:'%s' i:%u", name, i); + return i; /* yes */ + } + p++; + j++; + } + /* No. + * p => 1st non-matching char in applet_names[], + * skip to and including NUL. + */ + while (ch != '\0') + ch = *++p; + p++; i++; } return -1; -#endif } @@ -583,6 +603,7 @@ static void install_links(const char *busybox, int use_symbolic_links, * busybox.h::bb_install_loc_t, or else... */ int (*lf)(const char *, const char *); char *fpc; + const char *appname = applet_names; unsigned i; int rc; @@ -593,7 +614,7 @@ static void install_links(const char *busybox, int use_symbolic_links, for (i = 0; i < ARRAY_SIZE(applet_main); i++) { fpc = concat_path_file( custom_install_dir ? custom_install_dir : install_dir[APPLET_INSTALL_LOC(i)], - APPLET_NAME(i)); + appname); // debug: bb_error_msg("%slinking %s to busybox", // use_symbolic_links ? "sym" : "", fpc); rc = lf(busybox, fpc); @@ -601,6 +622,8 @@ static void install_links(const char *busybox, int use_symbolic_links, bb_simple_perror_msg(fpc); } free(fpc); + while (*appname++ != '\0') + continue; } } # else @@ -754,7 +777,7 @@ void FAST_FUNC run_applet_no_and_exit(int applet_no, char **argv) /* Reinit some shared global data */ xfunc_error_retval = EXIT_FAILURE; - applet_name = APPLET_NAME(applet_no); + applet_name = bb_get_last_path_component_nostrip(argv[0]); /* Special case. POSIX says "test --help" * should be no different from e.g. "test --foo". @@ -785,11 +808,14 @@ void FAST_FUNC run_applet_no_and_exit(int applet_no, char **argv) void FAST_FUNC run_applet_and_exit(const char *name, char **argv) { - int applet = find_applet_by_name(name); - if (applet >= 0) - run_applet_no_and_exit(applet, argv); + int applet; + if (is_prefixed_with(name, "busybox")) exit(busybox_main(argv)); + /* find_applet_by_name() search is more expensive, so goes second */ + applet = find_applet_by_name(name); + if (applet >= 0) + run_applet_no_and_exit(applet, argv); } #endif /* !defined(SINGLE_APPLET_MAIN) */ diff --git a/libbb/vfork_daemon_rexec.c b/libbb/vfork_daemon_rexec.c index d6ca7b263..1adb5b3c4 100644 --- a/libbb/vfork_daemon_rexec.c +++ b/libbb/vfork_daemon_rexec.c @@ -116,8 +116,6 @@ int FAST_FUNC run_nofork_applet(int applet_no, char **argv) save_nofork_data(&old); - applet_name = APPLET_NAME(applet_no); - xfunc_error_retval = EXIT_FAILURE; /* In case getopt() or getopt32() was already called: @@ -157,6 +155,7 @@ int FAST_FUNC run_nofork_applet(int applet_no, char **argv) * need argv untouched because they free argv[i]! */ char *tmp_argv[argc+1]; memcpy(tmp_argv, argv, (argc+1) * sizeof(tmp_argv[0])); + applet_name = tmp_argv[0]; /* Finally we can call NOFORK applet's main() */ rc = applet_main[applet_no](argc, tmp_argv); } else { -- 2.25.1