Thank you! I've known to how to create a *compat* PIC library, firstly using
`-fvisibility=hidden' in compile command line to hidden all symbols, then
using `objcopy -R' to remove .got section totally! However, assemble result is
just like this
call__i686.get_pc_thunk.bx
addl
yunfeng zhang writes:
> Sorry! I've made a mistake! But using LD_PRELOAD to force to reposition a
> variable/function from a module is violating software engineer. And the more
> important is, as the result, all user *all* pay the bill for this even they
> make sure they don't need the feature, s
On Nov 27, 2009, yunfeng zhang wrote:
> The rsult is also same, you go too far.
If the g in the main program didn't preempt the definition in the
library, then something is amiss in your system.
> Here data in 0x1000 and its follower have an *exact* map to foo.so in
> disk, you need review my c
Sorry! I've made a mistake! But using LD_PRELOAD to force to reposition a
variable/function from a module is violating software engineer. And the more
important is, as the result, all user *all* pay the bill for this even they
make sure they don't need the feature, such as, glibc itself.
On 11/26/2009 02:04 PM, yunfeng zhang wrote:
The result is the same
#include
extern int g __attribute__((visibility("hidden")));
int g;
int foo(int a, int b)
{
g = a + b;
printf("%x, %x",&g, foo);
return g;
}
load and call `foo' in the library, an outputting (with v
Yunfeng Zhang, please try this example.
elf.tar.gz
Description: GNU Zip compressed data
yunfeng zhang wrote:
> a.out
> f.map
> is it 5 + 3 = 4 + 4?
If you refuse to look at the source code that gcc generates, you will never
know what the difference is.
I cannot make that decision for you.
cheers,
DaveK
You can run a.out several times
24>>a5e0<<, 249>>41c<<
11>>15e0<<, 110>>41c<<
c7>>85e0<<, c77>>41c<<
8c>>35e0<<, 8c2>>41c<<
...
Now open f.map
g = 0x15e0, foo = 0x41c
is it 5 + 3 = 4 + 4?
2009/11/27 Dave Korn :
> yunfeng zhang wrote:
>
>> have an *exact* map to foo.so in disk
>
> This is wher
yunfeng zhang wrote:
> have an *exact* map to foo.so in disk
This is where your misunderstanding arises. Just as 5+3 can add up to the
same result as 4+4, so you cannot ignore that the final mapped addresses you
are seeing add up to the same result via different routes. Compile your
sources u
The rsult is also same, you go too far.
Code I want to show a fact in Linux, when a process load a library into memory,
such as 0x1000
foo.so 0x1000
ELF header
.text section
.data section
.bss section
...
Here data in 0x1000 and its follower have an *exact* map to foo.so in disk, you
need r
On Nov 26, 2009, yunfeng zhang wrote:
> The result is the same
But the code isn't. See how, with hidden, we use the fixed offset.
Now remove the hidden attribute, define g also in the main program, and
see what it prints.
--
Alexandre Oliva, freedom fighterhttp://FSFLA.org/~lxoliva/
You
The result is the same
#include
extern int g __attribute__((visibility("hidden")));
int g;
int foo(int a, int b)
{
g = a + b;
printf("%x, %x", &g, foo);
return g;
}
load and call `foo' in the library, an outputting (with vdso) is
cc15bc, cc03fc
and open f.map
0x1
On 11/25/2009 06:24 PM, yunfeng zhang wrote:
It seems that original limitation isn't clear or sufficient
For a sample:
// f.c
int g;
void foo(void)
{
g = 1;
}
compile with `gcc -shared -fPIC -Wl,-soname,f.so,-Map,f.map -o f.so f.c'...
With -fPIC, the variable G may be overridden by a
It seems that original limitation isn't clear or sufficient
For a sample:
// f.c
int g;
void foo(void)
{
g = 1;
}
compile with `gcc -shared -fPIC -Wl,-soname,f.so,-Map,f.map -o f.so f.c',
according to f.map, offsetof(g - foo) in library is 0x1550 - 0x3cc = 0x1184,
however let's load the
On 11/23/2009 05:58 PM, yunfeng zhang wrote:
next:
pop %ebx //<< A.
...
movl new_offset(%ebx), %eax //<< B. load global variable foo to eax.
...
.global foo //<< C.
OK!, to ld, offsetof(C - A) is const...
Your premise is wrong right there. C-A is *not* a constant.
yunfeng zhang wrote:
> The idea I got is about removing .got section in ELF format totally.
>
> Before we go, let's see the limitation on the idea
> 1) It must be deployed on aligned segment model, such as Linux, which cs.start
> = ds.start.
> 2) Currently, I only know how to do on x86 ELF.
>
> H
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