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| author |   Alexey Dobriyan <adobriyan@gmail.com> | 2020-01-30 22:16:50 -0800 |
|---|---|---|
| committer |   Linus Torvalds <torvalds@linux-foundation.org> | 2020-01-31 10:30:41 -0800 |
| commit | 1f83d80677a24ae737fe0ab4008e7c72b8a33b35 (patch) | |
| tree | 7a6ada15ce4f36e1b79ea262461bb06f9f02f880 /fs | |
| parent | lib/find_bit.c: uninline helper _find_next_bit() (diff) | |
| download | linux-dev-1f83d80677a24ae737fe0ab4008e7c72b8a33b35.tar.xz linux-dev-1f83d80677a24ae737fe0ab4008e7c72b8a33b35.zip | |
fs/binfmt_elf.c: smaller code generation around auxv vector fill
Filling auxv vector as array with index (auxv[i++] = ...) generates
terrible code. "saved_auxv" should be reworked because it is the worst
member of mm_struct by size/usefullness ratio but do it later.
Meanwhile help gcc a little with *auxv++ idiom.
Space savings on x86_64:
add/remove: 0/0 grow/shrink: 0/1 up/down: 0/-127 (-127)
Function old new delta
load_elf_binary 5470 5343 -127
Link: http://lkml.kernel.org/r/20191208172301.GD19716@avx2
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'fs')
| -rw-r--r-- | fs/binfmt_elf.c | 15 |
1 files changed, 8 insertions, 7 deletions
diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c index ecd8d2698515..7bb0deb5bf3b 100644 --- a/fs/binfmt_elf.c +++ b/fs/binfmt_elf.c @@ -176,7 +176,7 @@ create_elf_tables(struct linux_binprm *bprm, struct elfhdr *exec, unsigned char k_rand_bytes[16]; int items; elf_addr_t *elf_info; - int ei_index = 0; + int ei_index; const struct cred *cred = current_cred(); struct vm_area_struct *vma; @@ -230,8 +230,8 @@ create_elf_tables(struct linux_binprm *bprm, struct elfhdr *exec, /* update AT_VECTOR_SIZE_BASE if the number of NEW_AUX_ENT() changes */ #define NEW_AUX_ENT(id, val) \ do { \ - elf_info[ei_index++] = id; \ - elf_info[ei_index++] = val; \ + *elf_info++ = id; \ + *elf_info++ = val; \ } while (0) #ifdef ARCH_DLINFO @@ -275,12 +275,13 @@ create_elf_tables(struct linux_binprm *bprm, struct elfhdr *exec, } #undef NEW_AUX_ENT /* AT_NULL is zero; clear the rest too */ - memset(&elf_info[ei_index], 0, - sizeof current->mm->saved_auxv - ei_index * sizeof elf_info[0]); + memset(elf_info, 0, (char *)current->mm->saved_auxv + + sizeof(current->mm->saved_auxv) - (char *)elf_info); /* And advance past the AT_NULL entry. */ - ei_index += 2; + elf_info += 2; + ei_index = elf_info - (elf_addr_t *)current->mm->saved_auxv; sp = STACK_ADD(p, ei_index); items = (argc + 1) + (envc + 1) + 1; @@ -338,7 +339,7 @@ create_elf_tables(struct linux_binprm *bprm, struct elfhdr *exec, current->mm->env_end = p; /* Put the elf_info on the stack in the right place. */ - if (copy_to_user(sp, elf_info, ei_index * sizeof(elf_addr_t))) + if (copy_to_user(sp, current->mm->saved_auxv, ei_index * sizeof(elf_addr_t))) return -EFAULT; return 0; } |