diff options
Diffstat (limited to 'src')
| -rw-r--r-- | src/shred.c | 88 |
1 files changed, 49 insertions, 39 deletions
diff --git a/src/shred.c b/src/shred.c index 78e160980..9de751a85 100644 --- a/src/shred.c +++ b/src/shred.c @@ -108,11 +108,18 @@ #include "randint.h" #include "randread.h" -#define DEFAULT_PASSES 25 /* Default */ +/* Default number of times to overwrite. */ +enum { DEFAULT_PASSES = 25 }; /* How many seconds to wait before checking whether to output another verbose output line. */ -#define VERBOSE_UPDATE 5 +enum { VERBOSE_UPDATE = 5 }; + +/* Sector size and corresponding mask, for recovering after write failures. + The size must be a power of 2. */ +enum { SECTOR_SIZE = 512 }; +enum { SECTOR_MASK = SECTOR_SIZE - 1 }; +verify (0 < SECTOR_SIZE && (SECTOR_SIZE & SECTOR_MASK) == 0); struct Options { @@ -251,13 +258,13 @@ fillpattern (int type, unsigned char *r, size_t size) r[1] = (bits >> 8) & 255; r[2] = bits & 255; for (i = 3; i < size / 2; i *= 2) - memcpy ((char *) r + i, (char *) r, i); + memcpy (r + i, r, i); if (i < size) - memcpy ((char *) r + i, (char *) r, size - i); + memcpy (r + i, r, size - i); - /* Invert the first bit of every 512-byte sector. */ + /* Invert the first bit of every sector. */ if (type & 0x1000) - for (i = 0; i < size; i += 512) + for (i = 0; i < size; i += SECTOR_SIZE) r[i] ^= 0x80; } @@ -358,7 +365,18 @@ dopass (int fd, char const *qname, off_t *sizep, int type, size_t lim; /* Amount of data to try writing */ size_t soff; /* Offset into buffer for next write */ ssize_t ssize; /* Return value from write */ - uint32_t r[3 * 1024]; /* Fill pattern. */ + + /* Fill pattern buffer. Aligning it to a 32-bit boundary speeds up randread + in some cases. */ + typedef uint32_t fill_pattern_buffer[3 * 1024]; + union + { + fill_pattern_buffer buffer; + char c[sizeof (fill_pattern_buffer)]; + unsigned char u[sizeof (fill_pattern_buffer)]; + } r; + + off_t sizeof_r = sizeof r; char pass_string[PASS_NAME_SIZE]; /* Name of current pass */ bool write_error = false; bool first_write = true; @@ -367,7 +385,7 @@ dopass (int fd, char const *qname, off_t *sizep, int type, char previous_offset_buf[LONGEST_HUMAN_READABLE + 1]; char const *previous_human_offset IF_LINT (= 0); - if (lseek (fd, (off_t) 0, SEEK_SET) == -1) + if (lseek (fd, 0, SEEK_SET) == -1) { error (0, errno, _("%s: cannot rewind"), qname); return -1; @@ -376,13 +394,9 @@ dopass (int fd, char const *qname, off_t *sizep, int type, /* Constant fill patterns need only be set up once. */ if (type >= 0) { - lim = sizeof r; - if ((off_t) lim > size && size != -1) - { - lim = (size_t) size; - } - fillpattern (type, (unsigned char *) r, lim); - passname ((unsigned char *) r, pass_string); + lim = (0 <= size && size < sizeof_r ? size : sizeof r); + fillpattern (type, r.u, lim); + passname (r.u, pass_string); } else { @@ -402,11 +416,11 @@ dopass (int fd, char const *qname, off_t *sizep, int type, { /* How much to write this time? */ lim = sizeof r; - if ((off_t) lim > size - offset && size != -1) + if (0 <= size && size - offset < sizeof_r) { if (size < offset) break; - lim = (size_t) (size - offset); + lim = size - offset; if (!lim) break; } @@ -415,11 +429,10 @@ dopass (int fd, char const *qname, off_t *sizep, int type, /* Loop to retry partial writes. */ for (soff = 0; soff < lim; soff += ssize, first_write = false) { - ssize = write (fd, (char *) r + soff, lim - soff); + ssize = write (fd, r.c + soff, lim - soff); if (ssize <= 0) { - if ((ssize == 0 || errno == ENOSPC) - && size == -1) + if (size < 0 && (ssize == 0 || errno == ENOSPC)) { /* Ah, we have found the end of the file */ *sizep = size = offset + soff; @@ -444,22 +457,20 @@ dopass (int fd, char const *qname, off_t *sizep, int type, continue; } error (0, errnum, _("%s: error writing at offset %s"), - qname, umaxtostr ((uintmax_t) offset + soff, buf)); - /* - * I sometimes use shred on bad media, before throwing it - * out. Thus, I don't want it to give up on bad blocks. - * This code assumes 512-byte blocks and tries to skip - * over them. It works because lim is always a multiple - * of 512, except at the end. - */ - if (errnum == EIO && soff % 512 == 0 && lim >= soff + 512 - && size != -1) + qname, umaxtostr (offset + soff, buf)); + + /* 'shred' is often used on bad media, before throwing it + out. Thus, it shouldn't give up on bad blocks. This + code works because lim is always a multiple of + SECTOR_SIZE, except at the end. */ + verify (sizeof r % SECTOR_SIZE == 0); + if (errnum == EIO && 0 <= size && (soff | SECTOR_MASK) < lim) { - if (lseek (fd, (off_t) (offset + soff + 512), SEEK_SET) - != -1) + size_t soff1 = (soff | SECTOR_MASK) + 1; + if (lseek (fd, offset + soff1, SEEK_SET) != -1) { /* Arrange to skip this block. */ - ssize = 512; + ssize = soff1 - soff; write_error = true; continue; } @@ -496,7 +507,7 @@ dopass (int fd, char const *qname, off_t *sizep, int type, if (offset == size || !STREQ (previous_human_offset, human_offset)) { - if (size == -1) + if (size < 0) error (0, 0, _("%s: pass %lu/%lu (%s)...%s"), qname, k, n, pass_string, human_offset); else @@ -797,7 +808,7 @@ do_wipefd (int fd, char const *qname, struct randint_source *s, } else { - size = lseek (fd, (off_t) 0, SEEK_END); + size = lseek (fd, 0, SEEK_END); if (size <= 0) { /* We are unable to determine the length, up front. @@ -855,7 +866,7 @@ do_wipefd (int fd, char const *qname, struct randint_source *s, /* Okay, now deallocate the data. The effect of ftruncate on non-regular files is unspecified, so don't worry about any errors reported for them. */ - if (flags->remove_file && ftruncate (fd, (off_t) 0) != 0 + if (flags->remove_file && ftruncate (fd, 0) != 0 && S_ISREG (st.st_mode)) { error (0, errno, _("%s: error truncating"), qname); @@ -1115,13 +1126,12 @@ main (int argc, char **argv) { uintmax_t tmp; if (xstrtoumax (optarg, NULL, 10, &tmp, NULL) != LONGINT_OK - || (uint32_t) tmp != tmp - || ((size_t) (tmp * sizeof (int)) / sizeof (int) != tmp)) + || MIN (UINT32_MAX, SIZE_MAX / sizeof (int)) < tmp) { error (EXIT_FAILURE, 0, _("%s: invalid number of passes"), quotearg_colon (optarg)); } - flags.n_iterations = (size_t) tmp; + flags.n_iterations = tmp; } break; |