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libexec: mmap support, prealloc variants

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In libexec, split the memory allocation method into cleared and
non-cleared. Cleared gives zeroed memory, non-cleared gives 'junk'
memory (that will be overwritten anyway, and so needn't be cleared)
that is faster to get.

Also introduce the 'memmap' method that can be used, if available,
to map code and data from executables into a process using the
third-party mmap() mode.

Change-Id: I26694fd3c21deb8b97e01ed675dfc14719b0672b
This commit is contained in:
Ben Gras
2013-04-24 10:18:16 +00:00
parent 6fa5ce74ce
commit 0cfff08e56
8 changed files with 129 additions and 32 deletions
Download Patch File Download Diff File Expand all files Collapse all files
lib/libexec/exec_elf.c
+98 -24
View File
@@ -150,7 +150,8 @@ int libexec_load_elf(struct exec_info *execi)
assert(execi->copymem);
assert(execi->clearmem);
assert(execi->allocmem_prealloc);
assert(execi->allocmem_prealloc_cleared);
assert(execi->allocmem_prealloc_junk);
assert(execi->allocmem_ondemand);
for (i = 0; i < hdr->e_phnum; i++) {
@@ -167,51 +168,124 @@ int libexec_load_elf(struct exec_info *execi)
for (i = 0; i < hdr->e_phnum; i++) {
vir_bytes seg_membytes, page_offset, p_vaddr, vaddr;
vir_bytes chunk, vfileend, vmemend;
off_t foffset, fbytes;
Elf_Phdr *ph = &phdr[i];
int try_mmap = 1;
u16_t clearend = 0;
int pagechunk;
int mmap_prot = PROT_READ;
if(!(ph->p_flags & PF_R)) {
printf("libexec: warning: unreadable segment\n");
}
if(ph->p_flags & PF_W) {
mmap_prot |= PROT_WRITE;
#if ELF_DEBUG
printf("libexec: adding PROT_WRITE\n");
#endif
} else {
#if ELF_DEBUG
printf("libexec: not adding PROT_WRITE\n");
#endif
}
if (ph->p_type != PT_LOAD || ph->p_memsz == 0) continue;
if((ph->p_vaddr % PAGE_SIZE) != (ph->p_offset % PAGE_SIZE)) {
printf("libexec: unaligned ELF program?\n");
try_mmap = 0;
}
if(!execi->memmap) {
try_mmap = 0;
}
foffset = ph->p_offset;
fbytes = ph->p_filesz;
vaddr = p_vaddr = ph->p_vaddr + execi->load_offset;
seg_membytes = ph->p_memsz;
page_offset = vaddr % PAGE_SIZE;
vaddr -= page_offset;
foffset -= page_offset;
seg_membytes += page_offset;
fbytes += page_offset;
vfileend = p_vaddr + ph->p_filesz;
/* if there's usable memory after the file end, we have
* to tell VM to clear the memory part of the page when it's
* mapped in
*/
if((pagechunk = (vfileend % PAGE_SIZE))
&& ph->p_filesz < ph->p_memsz) {
clearend = PAGE_SIZE - pagechunk;
}
seg_membytes = roundup(seg_membytes, PAGE_SIZE);
fbytes = roundup(fbytes, PAGE_SIZE);
if(first || startv > vaddr) startv = vaddr;
first = 0;
/* make us some memory */
if(execi->allocmem_prealloc(execi, vaddr, seg_membytes) != OK) {
if(execi->clearproc) execi->clearproc(execi);
return ENOMEM;
}
if(try_mmap && execi->memmap(execi, vaddr, fbytes, foffset, clearend, mmap_prot) == OK) {
#if ELF_DEBUG
printf("mmapped 0x%lx-0x%lx\n", vaddr, vaddr+seg_membytes);
printf("libexec: mmap 0x%lx-0x%lx done, clearend 0x%x\n",
vaddr, vaddr+fbytes, clearend);
#endif
/* Copy executable section into it */
if(execi->copymem(execi, ph->p_offset, p_vaddr, ph->p_filesz) != OK) {
if(execi->clearproc) execi->clearproc(execi);
return ENOMEM;
}
if(seg_membytes > fbytes) {
int rem_mem = seg_membytes - fbytes;;
vir_bytes remstart = vaddr + fbytes;
if(execi->allocmem_ondemand(execi,
remstart, rem_mem) != OK) {
printf("libexec: mmap extra mem failed\n");
return ENOMEM;
}
#if ELF_DEBUG
else printf("libexec: allocated 0x%lx-0x%lx\n",
remstart, remstart+rem_mem);
#endif
}
} else {
if(try_mmap) printf("libexec: mmap failed\n");
/* make us some memory */
if(execi->allocmem_prealloc_junk(execi, vaddr, seg_membytes) != OK) {
if(execi->clearproc) execi->clearproc(execi);
return ENOMEM;
}
#if ELF_DEBUG
printf("copied 0x%lx-0x%lx\n", p_vaddr, p_vaddr+ph->p_filesz);
printf("mmapped 0x%lx-0x%lx\n", vaddr, vaddr+seg_membytes);
#endif
/* Clear remaining bits */
vfileend = p_vaddr + ph->p_filesz;
vmemend = vaddr + seg_membytes;
if((chunk = p_vaddr - vaddr) > 0) {
/* Copy executable section into it */
if(execi->copymem(execi, ph->p_offset, p_vaddr, ph->p_filesz) != OK) {
if(execi->clearproc) execi->clearproc(execi);
return ENOMEM;
}
#if ELF_DEBUG
printf("start clearing 0x%lx-0x%lx\n", vaddr, vaddr+chunk);
printf("copied 0x%lx-0x%lx\n", p_vaddr, p_vaddr+ph->p_filesz);
#endif
execi->clearmem(execi, vaddr, chunk);
}
if((chunk = vmemend - vfileend) > 0) {
/* Clear remaining bits */
vmemend = vaddr + seg_membytes;
if((chunk = p_vaddr - vaddr) > 0) {
#if ELF_DEBUG
printf("end clearing 0x%lx-0x%lx\n", vfileend, vaddr+chunk);
printf("start clearing 0x%lx-0x%lx\n", vaddr, vaddr+chunk);
#endif
execi->clearmem(execi, vfileend, chunk);
execi->clearmem(execi, vaddr, chunk);
}
if((chunk = vmemend - vfileend) > 0) {
#if ELF_DEBUG
printf("end clearing 0x%lx-0x%lx\n", vfileend, vaddr+chunk);
#endif
execi->clearmem(execi, vfileend, chunk);
}
}
}