dff2bd733
Denys Vlasenko
2019-05-24
Subject
libarchive: treat one "FIXME: avoid seek"
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archival/libarchive/open_transformer.c +27 -17include/bb_archive.h +6 -0include/libbb.h +1 -0libbb/read_printf.c +7 -5
archival/libarchive/open_transformer.c+27 -17
| @@ -159,47 +159,44 @@ void FAST_FUNC fork_transformer(int fd, const char *transform_prog) | |
| */ | |
| static transformer_state_t *setup_transformer_on_fd(int fd, int fail_if_not_compressed) | |
| { | |
| - | union { |
| - | uint8_t b[4]; |
| - | uint16_t b16[2]; |
| - | uint32_t b32[1]; |
| - | } magic; |
| transformer_state_t *xstate; | |
| xstate = xzalloc(sizeof(*xstate)); | |
| xstate->src_fd = fd; | |
| - | xstate->signature_skipped = 2; |
| /* .gz and .bz2 both have 2-byte signature, and their | |
| * unpack_XXX_stream wants this header skipped. */ | |
| - | xread(fd, magic.b16, sizeof(magic.b16[0])); |
| + | xstate->signature_skipped = 2; |
| + | xread(fd, xstate->magic.b16, 2); |
| if (ENABLE_FEATURE_SEAMLESS_GZ | |
| - | && magic.b16[0] == GZIP_MAGIC |
| + | && xstate->magic.b16[0] == GZIP_MAGIC |
| ) { | |
| xstate->xformer = unpack_gz_stream; | |
| USE_FOR_NOMMU(xstate->xformer_prog = "gunzip";) | |
| goto found_magic; | |
| } | |
| if (ENABLE_FEATURE_SEAMLESS_Z | |
| - | && magic.b16[0] == COMPRESS_MAGIC |
| + | && xstate->magic.b16[0] == COMPRESS_MAGIC |
| ) { | |
| xstate->xformer = unpack_Z_stream; | |
| USE_FOR_NOMMU(xstate->xformer_prog = "uncompress";) | |
| goto found_magic; | |
| } | |
| if (ENABLE_FEATURE_SEAMLESS_BZ2 | |
| - | && magic.b16[0] == BZIP2_MAGIC |
| + | && xstate->magic.b16[0] == BZIP2_MAGIC |
| ) { | |
| xstate->xformer = unpack_bz2_stream; | |
| USE_FOR_NOMMU(xstate->xformer_prog = "bunzip2";) | |
| goto found_magic; | |
| } | |
| if (ENABLE_FEATURE_SEAMLESS_XZ | |
| - | && magic.b16[0] == XZ_MAGIC1 |
| + | && xstate->magic.b16[0] == XZ_MAGIC1 |
| ) { | |
| + | uint32_t v32; |
| xstate->signature_skipped = 6; | |
| - | xread(fd, magic.b32, sizeof(magic.b32[0])); |
| - | if (magic.b32[0] == XZ_MAGIC2) { |
| + | xread(fd, &xstate->magic.b16[1], 4); |
| + | move_from_unaligned32(v32, &xstate->magic.b16[1]); |
| + | if (v32 == XZ_MAGIC2) { |
| xstate->xformer = unpack_xz_stream; | |
| USE_FOR_NOMMU(xstate->xformer_prog = "unxz";) | |
| goto found_magic; | |
| @@ -344,11 +341,24 @@ void* FAST_FUNC xmalloc_open_zipped_read_close(const char *fname, size_t *maxsz_ | |
| *maxsz_p = xstate->mem_output_size; | |
| } | |
| } else { | |
| - | /* File is not compressed */ |
| - | //FIXME: avoid seek |
| - | xlseek(xstate->src_fd, - xstate->signature_skipped, SEEK_CUR); |
| + | /* File is not compressed. |
| + | * We already read first few bytes, account for that. |
| + | * Exmaple where it happens: |
| + | * "modinfo MODULE.ko" (not compressed) |
| + | * open("MODULE.ko", O_RDONLY|O_LARGEFILE) = 4 |
| + | * read(4, "\177E", 2) = 2 |
| + | * fstat64(4, ...) |
| + | * mmap(...) |
| + | * read(4, "LF\2\1\1\0\0\0\0"... |
| + | * ...and we avoided seeking on the fd! :) |
| + | */ |
| xstate->signature_skipped = 0; | |
| - | image = xmalloc_read(xstate->src_fd, maxsz_p); |
| + | image = xmalloc_read_with_initial_buf( |
| + | xstate->src_fd, |
| + | maxsz_p, |
| + | xmemdup(&xstate->magic, xstate->signature_skipped), |
| + | xstate->signature_skipped |
| + | ); |
| } | |
| if (!image) | |
include/bb_archive.h+6 -0
| @@ -235,6 +235,12 @@ typedef struct transformer_state_t { | |
| off_t bytes_in; /* used in unzip code only: needs to know packed size */ | |
| uint32_t crc32; | |
| time_t mtime; /* gunzip code may set this on exit */ | |
| + | |
| + | union { /* if we read magic, it's saved here */ |
| + | uint8_t b[8]; |
| + | uint16_t b16[4]; |
| + | uint32_t b32[2]; |
| + | } magic; |
| } transformer_state_t; | |
| void init_transformer_state(transformer_state_t *xstate) FAST_FUNC; | |
include/libbb.h+1 -0
| @@ -881,6 +881,7 @@ extern ssize_t open_read_close(const char *filename, void *buf, size_t maxsz) FA | |
| extern char *xmalloc_reads(int fd, size_t *maxsz_p) FAST_FUNC; | |
| /* Reads block up to *maxsz_p (default: INT_MAX - 4095) */ | |
| extern void *xmalloc_read(int fd, size_t *maxsz_p) FAST_FUNC RETURNS_MALLOC; | |
| + | extern void *xmalloc_read_with_initial_buf(int fd, size_t *maxsz_p, char *buf, size_t total) FAST_FUNC; |
| /* Returns NULL if file can't be opened (default max size: INT_MAX - 4095) */ | |
| extern void *xmalloc_open_read_close(const char *filename, size_t *maxsz_p) FAST_FUNC RETURNS_MALLOC; | |
| /* Never returns NULL */ | |
libbb/read_printf.c+7 -5
| @@ -102,10 +102,9 @@ char* FAST_FUNC xmalloc_reads(int fd, size_t *maxsz_p) | |
| // Read (potentially big) files in one go. File size is estimated | |
| // by stat. Extra '\0' byte is appended. | |
| - | void* FAST_FUNC xmalloc_read(int fd, size_t *maxsz_p) |
| + | void* FAST_FUNC xmalloc_read_with_initial_buf(int fd, size_t *maxsz_p, char *buf, size_t total) |
| { | |
| - | char *buf; |
| - | size_t size, rd_size, total; |
| + | size_t size, rd_size; |
| size_t to_read; | |
| struct stat st; | |
| @@ -118,8 +117,6 @@ void* FAST_FUNC xmalloc_read(int fd, size_t *maxsz_p) | |
| /* In order to make such files readable, we add small const */ | |
| size = (st.st_size | 0x3ff) + 1; | |
| - | total = 0; |
| - | buf = NULL; |
| while (1) { | |
| if (to_read < size) | |
| size = to_read; | |
| @@ -148,6 +145,11 @@ void* FAST_FUNC xmalloc_read(int fd, size_t *maxsz_p) | |
| return buf; | |
| } | |
| + | void* FAST_FUNC xmalloc_read(int fd, size_t *maxsz_p) |
| + | { |
| + | return xmalloc_read_with_initial_buf(fd, maxsz_p, NULL, 0); |
| + | } |
| + | |
| #ifdef USING_LSEEK_TO_GET_SIZE | |
| /* Alternatively, file size can be obtained by lseek to the end. | |
| * The code is slightly bigger. Retained in case fstat approach | |