elflink: Force extra_copy to begin immediately after filesz
With the PLT properly in the BSS, we can miss copying some PLT symbols.
Since it's difficult to find exactly which symbols we need to copy, just
begin copying immediately after filesz. We were only skipping a few bytes
anyway and this shrinks the code.
Signed-off-by: Steve Fox <[EMAIL PROTECTED]>
---
diff --git a/elflink.c b/elflink.c
index 36679fc..174d7ca 100644
--- a/elflink.c
+++ b/elflink.c
@@ -151,7 +151,7 @@ static char share_path[PATH_MAX+1];
#define MAX_HTLB_SEGS 2
struct seg_info {
- void *vaddr, *extra_vaddr;
+ void *vaddr;
unsigned long filesz, memsz, extrasz;
int prot;
int fd;
@@ -436,12 +436,12 @@ static void get_extracopy(struct seg_info *seg, Elf_Phdr
*phdr, int phnum)
Elf_Sym *sym; /* a symbol */
char *strtab = NULL; /* string table for dynamic symbols */
int ret, numsyms, found_sym = 0;
- void *start, *end, *start_orig, *end_orig;
+ void *start, *end, *end_orig;
void *sym_start, *sym_end;
extern void __libhuge_filesz __attribute__((weak));
end_orig = seg->vaddr + seg->memsz;
- start_orig = seg->vaddr + seg->filesz;
+ start = seg->vaddr + seg->filesz;
if (seg->filesz == seg->memsz)
return;
if (!minimal_copy)
@@ -465,11 +465,10 @@ static void get_extracopy(struct seg_info *seg, Elf_Phdr
*phdr, int phnum)
* We must ensure any returns done hereafter have sane start and end
* values, as the criss-cross apple sauce algorithm is beginning
*/
- start = end_orig;
- end = start_orig;
+ end = start;
for (sym = symtab; sym < symtab + numsyms; sym++) {
- if (!keep_symbol(sym, start_orig, end_orig))
+ if (!keep_symbol(sym, start, end_orig))
continue;
/* TODO - add filtering so that we only look at symbols from
glibc
(@@GLIBC_*) */
@@ -478,8 +477,6 @@ static void get_extracopy(struct seg_info *seg, Elf_Phdr
*phdr, int phnum)
found_sym = 1;
sym_start = (void *)sym->st_value;
sym_end = (void *)(sym->st_value + sym->st_size);
- if (sym_start < start)
- start = sym_start;
if (sym_end > end)
end = sym_end;
}
@@ -487,8 +484,6 @@ static void get_extracopy(struct seg_info *seg, Elf_Phdr
*phdr, int phnum)
if (&__libhuge_filesz > end) {
/* be careful if the algorithm didn't find any symbols
* to copy */
- if (start == end_orig)
- start = start_orig;
end = &__libhuge_filesz;
found_sym = 1;
DEBUG("Found __libhuge_filesz at %p\n", &__libhuge_filesz);
@@ -498,21 +493,17 @@ static void get_extracopy(struct seg_info *seg, Elf_Phdr
*phdr, int phnum)
check_bss(end, end_orig);
if (found_sym) {
- /* Return the copy window */
- seg->extra_vaddr = start;
seg->extrasz = end - start;
}
/*
- * else no need to copy anything, so leave seg->extra_vaddr as
- * NULL
+ * else no need to copy anything, so leave seg->extrasz as zero
*/
return;
bail:
DEBUG("Unable to perform minimal copy\n");
bail2:
- seg->extra_vaddr = start_orig;
- seg->extrasz = end_orig - start_orig;
+ seg->extrasz = end_orig - start;
}
static void parse_elf_relinked(Elf_Ehdr *ehdr)
@@ -715,17 +706,14 @@ static int prepare_segment(struct seg_info *seg)
{
int hpage_size = gethugepagesize();
void *p;
- unsigned long gap;
unsigned long size;
/*
* Calculate the BSS size that we must copy in order to minimize
* the size of the shared mapping.
*/
- if (seg->extra_vaddr) {
- size = ALIGN((unsigned long)seg->extra_vaddr +
- seg->extrasz - (unsigned long)seg->vaddr,
- hpage_size);
+ if (seg->extrasz > 0) {
+ size = ALIGN(seg->filesz + seg->extrasz, hpage_size);
} else {
size = ALIGN(seg->filesz, hpage_size);
}
@@ -751,11 +739,10 @@ static int prepare_segment(struct seg_info *seg)
memcpy(p, seg->vaddr, seg->filesz);
DEBUG_CONT("done\n");
- if (seg->extra_vaddr) {
+ if (seg->extrasz > 0) {
DEBUG("Copying extra %#0lx bytes from %p...",
- seg->extrasz, seg->extra_vaddr);
- gap = seg->extra_vaddr - (seg->vaddr + seg->filesz);
- memcpy((p + seg->filesz + gap), seg->extra_vaddr,
+ seg->extrasz, seg->vaddr + seg->filesz);
+ memcpy((p + seg->filesz), seg->vaddr + seg->filesz,
seg->extrasz);
DEBUG_CONT("done\n");
}
--
Steve Fox
IBM Linux Technology Center
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