| Message ID | 20230820181900.3786107-1-vt@altlinux.org |
|---|---|
| State | New |
| Headers | show |
| Series | [RFC] tools/nolibc: x86_64: Make it compile with -pie | expand |
Hi Vitaly, On 2023-08-20 21:19:00+0300, Vitaly Chikunov wrote: > Use RIP-relative addressing when setting `environ` and `_auxv` in > startup code. > > Some toolchains have `-pie` enabled by default. On them or when -pie is > specified manually gcc produces error like this: > > ld: /tmp/cci0uPcR.o: relocation R_X86_64_32S against symbol `environ' can not be used when making a PIE object; recompile with -fPIE > ld: failed to set dynamic section sizes: bad value > > This is because asm() startup code accesses there pointers with absolute > addressing. > > This may inspire others to fix the problem for other architectures too. > > Signed-off-by: Vitaly Chikunov <vt@altlinux.org> > --- > tools/include/nolibc/arch-x86_64.h | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/tools/include/nolibc/arch-x86_64.h b/tools/include/nolibc/arch-x86_64.h > index 6fc4d8392742..a6be44b333ce 100644 > --- a/tools/include/nolibc/arch-x86_64.h > +++ b/tools/include/nolibc/arch-x86_64.h > @@ -199,14 +199,14 @@ void __attribute__((weak,noreturn,optimize("omit-frame-pointer"))) __no_stack_pr > "pop %rdi\n" /* argc (first arg, %rdi) */ > "mov %rsp, %rsi\n" /* argv[] (second arg, %rsi) */ > "lea 8(%rsi,%rdi,8),%rdx\n" /* then a NULL then envp (third arg, %rdx) */ > - "mov %rdx, environ\n" /* save environ */ > + "mov %rdx, environ(%rip)\n" /* save environ */ > "xor %ebp, %ebp\n" /* zero the stack frame */ > "mov %rdx, %rax\n" /* search for auxv (follows NULL after last env) */ > "0:\n" > "add $8, %rax\n" /* search for auxv using rax, it follows the */ > "cmp -8(%rax), %rbp\n" /* ... NULL after last env (rbp is zero here) */ > "jnz 0b\n" > - "mov %rax, _auxv\n" /* save it into _auxv */ > + "mov %rax, _auxv(%rip)\n" /* save it into _auxv */ > "and $-16, %rsp\n" /* x86 ABI : esp must be 16-byte aligned before call */ > "call main\n" /* main() returns the status code, we'll exit with it. */ > "mov %eax, %edi\n" /* retrieve exit code (32 bit) */ > -- > 2.33.8 > nolibc recently switched to startup code that is mostly implemented in C instead of assembly. See the current linux-next tree. That should make this change unnecessary I guess. Thomas
Thomas, On Sun, Aug 20, 2023 at 09:13:51PM +0200, Thomas Weißschuh wrote: > On 2023-08-20 21:19:00+0300, Vitaly Chikunov wrote: > > Use RIP-relative addressing when setting `environ` and `_auxv` in > > startup code. > > > > Some toolchains have `-pie` enabled by default. On them or when -pie is > > specified manually gcc produces error like this: > > > > ld: /tmp/cci0uPcR.o: relocation R_X86_64_32S against symbol `environ' can not be used when making a PIE object; recompile with -fPIE > > ld: failed to set dynamic section sizes: bad value > > > > This is because asm() startup code accesses there pointers with absolute > > addressing. > > > > This may inspire others to fix the problem for other architectures too. > > > > Signed-off-by: Vitaly Chikunov <vt@altlinux.org> > > --- > > tools/include/nolibc/arch-x86_64.h | 4 ++-- > > 1 file changed, 2 insertions(+), 2 deletions(-) > > > > diff --git a/tools/include/nolibc/arch-x86_64.h b/tools/include/nolibc/arch-x86_64.h > > index 6fc4d8392742..a6be44b333ce 100644 > > --- a/tools/include/nolibc/arch-x86_64.h > > +++ b/tools/include/nolibc/arch-x86_64.h > > @@ -199,14 +199,14 @@ void __attribute__((weak,noreturn,optimize("omit-frame-pointer"))) __no_stack_pr > > "pop %rdi\n" /* argc (first arg, %rdi) */ > > "mov %rsp, %rsi\n" /* argv[] (second arg, %rsi) */ > > "lea 8(%rsi,%rdi,8),%rdx\n" /* then a NULL then envp (third arg, %rdx) */ > > - "mov %rdx, environ\n" /* save environ */ > > + "mov %rdx, environ(%rip)\n" /* save environ */ > > "xor %ebp, %ebp\n" /* zero the stack frame */ > > "mov %rdx, %rax\n" /* search for auxv (follows NULL after last env) */ > > "0:\n" > > "add $8, %rax\n" /* search for auxv using rax, it follows the */ > > "cmp -8(%rax), %rbp\n" /* ... NULL after last env (rbp is zero here) */ > > "jnz 0b\n" > > - "mov %rax, _auxv\n" /* save it into _auxv */ > > + "mov %rax, _auxv(%rip)\n" /* save it into _auxv */ > > "and $-16, %rsp\n" /* x86 ABI : esp must be 16-byte aligned before call */ > > "call main\n" /* main() returns the status code, we'll exit with it. */ > > "mov %eax, %edi\n" /* retrieve exit code (32 bit) */ > > -- > > 2.33.8 > > > > nolibc recently switched to startup code that is mostly implemented in C > instead of assembly. > See the current linux-next tree. > > That should make this change unnecessary I guess. Yes seems so! Zhangjin Wu done a fine job. Thanks, > > > Thomas
diff --git a/tools/include/nolibc/arch-x86_64.h b/tools/include/nolibc/arch-x86_64.h index 6fc4d8392742..a6be44b333ce 100644 --- a/tools/include/nolibc/arch-x86_64.h +++ b/tools/include/nolibc/arch-x86_64.h @@ -199,14 +199,14 @@ void __attribute__((weak,noreturn,optimize("omit-frame-pointer"))) __no_stack_pr "pop %rdi\n" /* argc (first arg, %rdi) */ "mov %rsp, %rsi\n" /* argv[] (second arg, %rsi) */ "lea 8(%rsi,%rdi,8),%rdx\n" /* then a NULL then envp (third arg, %rdx) */ - "mov %rdx, environ\n" /* save environ */ + "mov %rdx, environ(%rip)\n" /* save environ */ "xor %ebp, %ebp\n" /* zero the stack frame */ "mov %rdx, %rax\n" /* search for auxv (follows NULL after last env) */ "0:\n" "add $8, %rax\n" /* search for auxv using rax, it follows the */ "cmp -8(%rax), %rbp\n" /* ... NULL after last env (rbp is zero here) */ "jnz 0b\n" - "mov %rax, _auxv\n" /* save it into _auxv */ + "mov %rax, _auxv(%rip)\n" /* save it into _auxv */ "and $-16, %rsp\n" /* x86 ABI : esp must be 16-byte aligned before call */ "call main\n" /* main() returns the status code, we'll exit with it. */ "mov %eax, %edi\n" /* retrieve exit code (32 bit) */
Use RIP-relative addressing when setting `environ` and `_auxv` in startup code. Some toolchains have `-pie` enabled by default. On them or when -pie is specified manually gcc produces error like this: ld: /tmp/cci0uPcR.o: relocation R_X86_64_32S against symbol `environ' can not be used when making a PIE object; recompile with -fPIE ld: failed to set dynamic section sizes: bad value This is because asm() startup code accesses there pointers with absolute addressing. This may inspire others to fix the problem for other architectures too. Signed-off-by: Vitaly Chikunov <vt@altlinux.org> --- tools/include/nolibc/arch-x86_64.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)