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authorlinted <linted@users.noreply.github.com>2022-07-23 16:25:41 -0400
committerWaldemar Brodkorb <wbx@openadk.org>2022-07-26 09:56:03 +0200
commit2c58afdb3ae6f900583cf7264cba6ab8a797e3e2 (patch)
treeabb641e31fcab71a4e78905fd0124ca8b9a25eae /libc/sysdeps/linux/x86_64
parent01961b12bc71d6eb4d9bda3632d73bb6764b8e85 (diff)
Added support for creation of Static Position-Independent Executables (PIE) on i386, x86_64, and arm.
This patch adds the generation of rcrt1.o which is used by gcc when compiling with the --static-pie flag. rcrt1.o differs from crt1.o and Scrt1.o in that it the executable has a dynamic section but no relocations have been performed prior to _start being called. crt1.o assumes there to be no dynamic relocations, and Scrt1.o has all relocations performed prior to execution by lsdo. The new reloc_static_pie function handles parsing the dynamic section, and performing the relocations in a architecture agnostic method. It also sets _dl_load_base which is used when initalizing TLS to ensure loading from the proper location. This allows for easier porting of static-pie support to additional architectures as only modifications to crt1.S to find the load address are required. Signed-off-by: linted <linted@users.noreply.github.com>
Diffstat (limited to 'libc/sysdeps/linux/x86_64')
-rw-r--r--libc/sysdeps/linux/x86_64/crt1.S16
1 files changed, 15 insertions, 1 deletions
diff --git a/libc/sysdeps/linux/x86_64/crt1.S b/libc/sysdeps/linux/x86_64/crt1.S
index 87777dd5d..701cbf2f6 100644
--- a/libc/sysdeps/linux/x86_64/crt1.S
+++ b/libc/sysdeps/linux/x86_64/crt1.S
@@ -80,6 +80,20 @@ _start:
the outermost frame obviously. */
xorl %ebp, %ebp
+#ifdef L_rcrt1
+ pushq %rdi /* save rdi (but should be 0...) */
+ pushq %rdx /* store rdx (rtld_fini) */
+ xorq %rcx, %rcx /* ensure rcx is 0 */
+ addq _start@GOTPCREL(%rip), %rcx /* get offset of _start from beginning of file */
+ movq _start@GOTPCREL(%rip), %rax /* get run time address of _start */
+ subq %rcx, %rax /* calculate run time load offset */
+ movq %rax, %rdi /* load offset -> param 1 */
+ call reloc_static_pie /* relocate dynamic addrs */
+ xorq %rax, %rax /* cleanup */
+ popq %rdx
+ popq %rdi
+#endif
+
/* Extract the arguments as encoded on the stack and set up
the arguments for __libc_start_main (int (*main) (int, char **, char **),
int argc, char *argv,
@@ -107,7 +121,7 @@ _start:
which grow downwards). */
pushq %rsp
-#if defined(L_Scrt1)
+#if defined(L_Scrt1) || defined(L_rcrt1)
/* Give address for main() */
movq main@GOTPCREL(%rip), %rdi