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Date: Tue, 24 May 2022 07:54:43 +0200
From: Kuba Kazimierczak <kuba@...imierczak.name>
To: musl@...ts.openwall.com
Subject: Linking musl with -shared -static - is this supported?
Hi, I'm on Alpine Linux, musl version 1.2.2. I'm attempting to create a
statically-linked shared object using "-shared -static" and use it in a
driver program as follows:
/tmp # cat lib.c
#include <stdlib.h>
unsigned int add(unsigned int a, unsigned int b)
{
free(malloc(1));
return (a+b);
}
/tmp # cat main.c
#include <stdio.h>
extern unsigned int add(unsigned int a, unsigned int b);
int main(void)
{
printf("%d\n", add(1,2));
return 0;
}
/tmp # clang-14 -g -c -fPIC lib.c
/tmp # clang-14 -shared -static -o liblib.so lib.o
/tmp # clang-14 -g -L. main.c -o main -llib
/tmp # LD_LIBRARY_PATH=$PWD ./main
Segmentation fault
The segfault happens in musl's malloc implementation internals:
#0 0x00007f9c882adc7a in get_random_secret () at
src/malloc/mallocng/glue.h:45
#1 __malloc_alloc_meta () at src/malloc/mallocng/malloc.c:50
#2 0x00007f9c882ae11b in alloc_group (req=1, sc=0) at
src/malloc/mallocng/malloc.c:179
#3 alloc_slot (sc=sc@...ry=0, req=req@...ry=1) at
src/malloc/mallocng/malloc.c:291
#4 0x00007f9c882ae646 in __libc_malloc_impl (n=1) at
src/malloc/mallocng/malloc.c:369
#5 0x00007f9c882ad208 in add (a=1, b=2) at lib.c:5
#6 0x000055909082f22e in main () at main.c:7
I see get_random_secret is trying to use struct __libc.argv, which is
probably not initialized in this case.
Is this use case supported at all?
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