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Update.
* elf/dl-load.c (_dl_map_object_from_fd): Determine whether there are holes between the segments. Only call mprotect to set proection to PROT_NONE if there are some. * elf/dl-load.c (struct filebuf): Actually use FILEBUF_SIZE. Update comment.
This commit is contained in:
Ulrich Drepper
parent
4f6f0a8fcf
commit
6fffb9a2c1
@ -1,5 +1,12 @@
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2003-03-03 Ulrich Drepper <drepper@redhat.com>
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* elf/dl-load.c (_dl_map_object_from_fd): Determine whether there
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are holes between the segments. Only call mprotect to set
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proection to PROT_NONE if there are some.
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* elf/dl-load.c (struct filebuf): Actually use FILEBUF_SIZE.
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Update comment.
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* include/sched.h (__clone2): Use ... instead of adding all the
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new parameters.
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@ -98,15 +98,17 @@ ELF_PREFERRED_ADDRESS_DATA;
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/* Type for the buffer we put the ELF header and hopefully the program
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header. This buffer does not really have to be too large. In most
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cases the program header follows the ELF header directly. If this
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is not the case all bets are off and we can make the header arbitrarily
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large and still won't get it read. This means the only question is
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how large are the ELF and program header combined. The ELF header
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in 64-bit files is 56 bytes long. Each program header entry is again
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56 bytes long. I.e., even with a file which has 17 program header
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entries we only have to read 1kB. And 17 program header entries is
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plenty, normal files have < 10. If this heuristic should really fail
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for some file the code in `_dl_map_object_from_fd' knows how to
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recover. */
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is not the case all bets are off and we can make the header
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arbitrarily large and still won't get it read. This means the only
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question is how large are the ELF and program header combined. The
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ELF header 32-bit files is 52 bytes long and in 64-bit files is 64
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bytes long. Each program header entry is again 32 and 56 bytes
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long respectively. I.e., even with a file which has 7 program
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header entries we only have to read 512B. Add to this a bit of
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margin for program notes and reading 512B and 640B for 32-bit and
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64-bit files respecitvely is enough. If this heuristic should
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really fail for some file the code in `_dl_map_object_from_fd'
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knows how to recover. */
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struct filebuf
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{
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ssize_t len;
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@ -115,7 +117,7 @@ struct filebuf
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#else
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# define FILEBUF_SIZE 640
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#endif
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char buf[512] __attribute__ ((aligned (__alignof (ElfW(Ehdr)))));
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char buf[FILEBUF_SIZE] __attribute__ ((aligned (__alignof (ElfW(Ehdr)))));
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};
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/* This is the decomposed LD_LIBRARY_PATH search path. */
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@ -883,6 +885,7 @@ _dl_map_object_from_fd (const char *name, int fd, struct filebuf *fbp,
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int prot;
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} loadcmds[l->l_phnum], *c;
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size_t nloadcmds = 0;
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bool has_holes = false;
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/* The struct is initialized to zero so this is not necessary:
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l->l_ld = 0;
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@ -928,6 +931,11 @@ _dl_map_object_from_fd (const char *name, int fd, struct filebuf *fbp,
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c->allocend = ph->p_vaddr + ph->p_memsz;
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c->mapoff = ph->p_offset & ~(ph->p_align - 1);
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/* Determine whether there is a gap between the last segment
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and this one. */
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if (nloadcmds > 1 && c[-1].mapend != c->mapstart)
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has_holes = true;
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/* Optimize a common case. */
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#if (PF_R | PF_W | PF_X) == 7 && (PROT_READ | PROT_WRITE | PROT_EXEC) == 7
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c->prot = (PF_TO_PROT
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@ -1057,14 +1065,15 @@ cannot allocate TLS data structures for initial thread");
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l->l_map_end = l->l_map_start + maplength;
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l->l_addr = l->l_map_start - c->mapstart;
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/* Change protection on the excess portion to disallow all access;
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the portions we do not remap later will be inaccessible as if
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unallocated. Then jump into the normal segment-mapping loop to
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handle the portion of the segment past the end of the file
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mapping. */
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__mprotect ((caddr_t) (l->l_addr + c->mapend),
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loadcmds[nloadcmds - 1].allocend - c->mapend,
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PROT_NONE);
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if (has_holes)
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/* Change protection on the excess portion to disallow all access;
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the portions we do not remap later will be inaccessible as if
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unallocated. Then jump into the normal segment-mapping loop to
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handle the portion of the segment past the end of the file
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mapping. */
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__mprotect ((caddr_t) (l->l_addr + c->mapend),
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loadcmds[nloadcmds - 1].allocend - c->mapend,
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PROT_NONE);
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goto postmap;
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}
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@ -1124,23 +1133,18 @@ cannot allocate TLS data structures for initial thread");
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if (zeropage > zero)
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{
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/* Zero the final part of the last page of the segment. */
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if ((c->prot & PROT_WRITE) == 0)
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if (__builtin_expect ((c->prot & PROT_WRITE) == 0, 0))
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{
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/* Dag nab it. */
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if (__builtin_expect (__mprotect ((caddr_t)
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(zero
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& ~(GL(dl_pagesize)
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- 1)),
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GL(dl_pagesize),
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c->prot|PROT_WRITE) < 0,
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0))
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if (__mprotect ((caddr_t) (zero & ~(GL(dl_pagesize) - 1)),
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GL(dl_pagesize), c->prot|PROT_WRITE) < 0)
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{
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errstring = N_("cannot change memory protections");
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goto call_lose_errno;
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}
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}
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memset ((void *) zero, '\0', zeropage - zero);
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if ((c->prot & PROT_WRITE) == 0)
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if (__builtin_expect ((c->prot & PROT_WRITE) == 0, 0))
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__mprotect ((caddr_t) (zero & ~(GL(dl_pagesize) - 1)),
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GL(dl_pagesize), c->prot);
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}
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