The patch titled
Subject: fs/binfmt_elf.c: smaller code generation around auxv vector fill
has been added to the -mm tree. Its filename is
elf-smaller-code-generation-around-auxv-vector-fill.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/elf-smaller-code-generation-around-auxv-vector-fill.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/elf-smaller-code-generation-around-auxv-vector-fill.patch
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*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next and is updated
there every 3-4 working days
------------------------------------------------------
From: Alexey Dobriyan <adobriyan@xxxxxxxxx>
Subject: 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@xxxxxxxxx>
Reviewed-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/binfmt_elf.c | 15 ++++++++-------
1 file changed, 8 insertions(+), 7 deletions(-)
--- a/fs/binfmt_elf.c~elf-smaller-code-generation-around-auxv-vector-fill
+++ a/fs/binfmt_elf.c
@@ -176,7 +176,7 @@ create_elf_tables(struct linux_binprm *b
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 *b
/* 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 *b
}
#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 *b
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;
}
_
Patches currently in -mm which might be from adobriyan@xxxxxxxxx are
ramfs-support-o_tmpfile.patch
elf-smaller-code-generation-around-auxv-vector-fill.patch
