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Add a workaround to correctly align the stack before calling into C code.

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When enough time has passed for users to update their userland the kernel
fix will be applied. This will change the ABI to have x0 point to the args
and sp be correctly aligned.

It is expected this compatibility code can be removed when the kernel and
qemu usermode emulation have both been updated for the new ABI.

This fixes clang failures, and most likely other crashes.

Obtained from:	ABT Systems Ltd
Sponsored by:	The FreeBSD Foundation
This commit is contained in:
Andrew Turner 2015-06-22 19:43:08 +00:00
parent 7090067b2a
commit 65706c12b2
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=284707
2 changed files with 14 additions and 6 deletions
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10
lib/csu/aarch64/crt1.c
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@ -58,9 +58,13 @@ __asm(" .text \n"
" .align 0 \n"
" .globl _start \n"
" _start: \n"
" mov x3, x2 \n" /* cleanup */
" ldr x0, [sp] \n" /* Load argc */
" add x1, sp, #8 \n" /* load argv */
/* TODO: Remove this when the kernel correctly aligns the stack */
" cbnz x0, 1f \n" /* Are we using a new kernel? */
" mov x0, sp \n" /* No, load the args from sp */
" and sp, x0, #~0xf \n" /* And align the stack */
"1: mov x3, x2 \n" /* cleanup */
" add x1, x0, #8 \n" /* load argv */
" ldr x0, [x0] \n" /* load argc */
" add x2, x1, x0, lsl #3 \n" /* env is after argv */
" add x2, x2, #8 \n" /* argv is null terminated */
" b __start ");

10
libexec/rtld-elf/aarch64/rtld_start.S
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@ -34,10 +34,14 @@ ENTRY(.rtld_start)
mov x19, x0 /* Put ps_strings in a callee-saved register */
mov x20, sp /* And the stack pointer */
sub x8, x20, #16 /* Make room for obj_main & exit proc */
mov sp, x8 /* Update the stack pointer */
/* Handle the old style stack */
/* TODO: Remove this when the kernel correctly aligns the stack */
cbnz x0, 1f
mov x0, sp /* sp points to the args */
and sp, x0, #~0xf /* Align the stack as needed */
1: sub sp, sp, #16 /* Make room for obj_main & exit proc */
mov x0, x20 /* Pass the stack we were given to _rtld */
mov x1, sp /* exit_proc */
add x2, x1, #8 /* obj_main */
bl _rtld /* Call the loader */