Dnia piątek, 7 października 2005 18:16, linux-os (Dick Johnson) napisał:
> On Fri, 7 Oct 2005, [UTF-8] Pawe? Sikora wrote:
> > Dnia pitek, 7 padziernika 2005 17:33, Horst von Brand napisa:
> >> Pawe Sikora <[email protected]> wrote:
> >>> Dnia pitek, 7 padziernika 2005 15:46, Horst von Brand napisa:
> >>
> >> [...]
> >>
> >>>> binutils-2.16.91.0.2-4 doesn't. It looks like you are using broken
> >>>> tools.
> >>>
> >>> I didn't say that is (or not) a binutils bug.
> >>> I'm only saying that kernel is killng a valid micro application.
> >>
> >> If binutils generates an invalid executable, it is not a valid
> >> application.
> >
> > ehh, please look again at my first post :)
> > binutils-2.16 generates VALID app with .text/.interp and *without* .bss.
> > kernel always calls padzero() for the .bss section inside
> > load_elf_binary(). finally it kills a valid app. did i miss something?
> >
>
> The executable created by this:
>
> $ cat <<EOF >xxx.S
> .section .rodata
> hello: .string "Hello World!\n"
> STRLEN = .-hello
> WRITE=4
> EXIT=1
>
> .section .text
> .global _start
> .type _start,@function
> _start:
> movl $WRITE, %eax
> movl $1, %ebx
> movl $hello, %ecx
> movl $STRLEN, %edx
> int $0x80
> movl $EXIT, %eax
> movl $0, %ebx
> int $0x80
> .end
> EOF
>
> $ as -o xxx.o xxx.S
> $ ld -o xxx xxx.o
> $ ./xxx
> Hello World!
> $
>
> ... does not have a .bss section. It also runs fine. The linker
> creates a 0 length .bss section starting at label "_end". There
> is no way to prevent it from happening so the kernel's zeroing
> the zero-length section is perfectly valid. Maybe you have
> executed `strip` and stripped out that section? If so, you
> no longer have a valid executable and the kernel should kill
> it.
What????????????
Do you suggest that stripped executables are invalid?
$ cat xxx.S
.section .text
.global _start
.type _start,@function
_start:
movl $1, %eax
movl $0, %ebx
int $0x80
.end
$ as xxx.S -o xxx.o; ld xxx.o -o xxx -s; objdump -x xxx
xxx: file format elf32-i386
xxx
architecture: i386, flags 0x00000102:
EXEC_P, D_PAGED
start address 0x08048094
Program Header:
LOAD off 0x00000000 vaddr 0x08048000 paddr 0x08048000 align 2**12
filesz 0x000000a0 memsz 0x000000a0 flags r-x
PAX_FLAGS off 0x00000000 vaddr 0x00000000 paddr 0x00000000 align 2**2
filesz 0x00000000 memsz 0x00000000 flags --- 2800
Sections:
Idx Name Size VMA LMA File off Algn
0 .text 0000000c 08048094 08048094 00000094 2**2
CONTENTS, ALLOC, LOAD, READONLY, CODE
We have a pure executable, no .data/.rodata/.bss/etc.
On 2.6.14rc3-git6 this executable doesn't work:
$ strace ./xxx
execve("./xxx", ["./xxx"], [/* 24 vars */]) = -1 EFAULT (Bad address)
--- SIGSEGV (Segmentation fault) @ 0 (0) ---
+++ killed by SIGSEGV +++
With hacked kernel it works pretty fine:
$ strace ./xxx
execve("./xxx", ["./xxx"], [/* 24 vars */]) = 0
_exit(0)
--
The only thing necessary for the triumph of evil
is for good men to do nothing.
- Edmund Burke
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