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save 3 bytes by not clearing [AT_NULL].a_un.a_ptr

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committer: jreiser <jreiser> 1034698533 +0000
This commit is contained in:
John Reiser
2002-10-15 16:15:33 +00:00
parent c069efaa1b
commit d96646b0e0
1 changed files with 4 additions and 5 deletions
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src/stub/fold_elf86.asm
+4 -5
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@@ -117,11 +117,10 @@ EXTERN upx_main
sub eax,eax ; 0, also AT_NULL sub eax,eax ; 0, also AT_NULL
db 0x3c ; "cmpb al, byte ..." like "jmp 1+L60" but 1 byte shorter db 0x3c ; "cmpb al, byte ..." like "jmp 1+L60" but 1 byte shorter
L60: L60:
scasd ; a_un scasd ; a_un.a_val etc.
scasd ; a_val scasd ; a_type
jne L60 ; not AT_NULL jne L60 ; not AT_NULL
mov edx,[edi] ; &hatch ; edi now points at [AT_NULL]a_un.a_ptr which contains result of make_hatch()
stosd ; clear a_un.a_ptr for AT_NULL
; _dl_start and company (ld-linux.so.2) once assumed that it had virgin stack, ; _dl_start and company (ld-linux.so.2) once assumed that it had virgin stack,
; and did not initialize all its stack local variables to zero. ; and did not initialize all its stack local variables to zero.
@@ -156,7 +155,7 @@ L60:
mov ch, PAGE_SIZE>>8 ; 0x1000 mov ch, PAGE_SIZE>>8 ; 0x1000
add ecx, [p_memsz + szElf32_Ehdr + ebx] ; length to unmap add ecx, [p_memsz + szElf32_Ehdr + ebx] ; length to unmap
mov bh, 0 ; from 0x401000 to 0x400000 mov bh, 0 ; from 0x401000 to 0x400000
jmp edx ; unmap ourselves via escape hatch, then goto entry jmp [edi] ; unmap ourselves via escape hatch, then goto entry
; called twice: ; called twice:
; 1st with esi==edi, ecx=0, edx= bitmap of slots needed: just update edx. ; 1st with esi==edi, ecx=0, edx= bitmap of slots needed: just update edx.