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tools/nolibc: mips: add support for PIC

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MIPS requires some extra instructions to set up the $gp register for the
with a pointer to the global data area.

This isn't needed for non-PIC builds, but this patch enables the code
unconditionally to prevent bitrot.

Also enable PIC in one of the test configurations for ongoing
validation.

Link: https://lore.kernel.org/r/20231108-nolibc-pic-v2-1-4fb0d6284757@weissschuh.net
Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
This commit is contained in:
Thomas Weißschuh 2023-11-08 19:14:43 +01:00
parent 8bcf9a4855
commit 544102458a
2 changed files with 7 additions and 2 deletions
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7
tools/include/nolibc/arch-mips.h
View file

@ -184,8 +184,13 @@ void __attribute__((weak, noreturn, optimize("Os", "omit-frame-pointer"))) __no_
__asm__ volatile (
".set push\n"
".set noreorder\n"
".option pic0\n"
"bal 1f\n" /* prime $ra for .cpload */
"nop\n"
"1:\n"
".cpload $ra\n"
"move $a0, $sp\n" /* save stack pointer to $a0, as arg1 of _start_c */
"addiu $sp, $sp, -4\n" /* space for .cprestore to store $gp */
".cprestore 0\n"
"li $t0, -8\n"
"and $sp, $sp, $t0\n" /* $sp must be 8-byte aligned */
"addiu $sp, $sp, -16\n" /* the callee expects to save a0..a3 there */

2
tools/testing/selftests/nolibc/Makefile
View file

@ -147,7 +147,7 @@ CFLAGS_ppc = -m32 -mbig-endian -mno-vsx $(call cc-option,-mmultiple)
CFLAGS_ppc64 = -m64 -mbig-endian -mno-vsx $(call cc-option,-mmultiple)
CFLAGS_ppc64le = -m64 -mlittle-endian -mno-vsx $(call cc-option,-mabi=elfv2)
CFLAGS_s390 = -m64
CFLAGS_mips32le = -EL -mabi=32
CFLAGS_mips32le = -EL -mabi=32 -fPIC
CFLAGS_mips32be = -EB -mabi=32
CFLAGS_STACKPROTECTOR ?= $(call cc-option,-mstack-protector-guard=global $(call cc-option,-fstack-protector-all))
CFLAGS ?= -Os -fno-ident -fno-asynchronous-unwind-tables -std=c89 -W -Wall -Wextra \