tools/nolibc: mips: load current function to $t9

The MIPS calling convention requires the address of the current function
to be available in $t9.
This was not done so far.

For GCC this seems to have worked, but when compiled with clang the
executable segfault instantly.
Properly load the address of _start_c() into $t9 before calling it.

Acked-by: Willy Tarreau <w@1wt.eu>
Link: https://lore.kernel.org/r/20240807-nolibc-llvm-v2-2-c20f2f5fc7c2@weissschuh.net
Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>

diff --git a/tools/include/nolibc/arch-mips.h b/tools/include/nolibc/arch-mips.h
index 62cc50ef32882168996f20fd7e203aa78966c717..a2ee77ed2fbb2853ce8d5e8fda055c2b1fafc41e 100644 (file)
--- a/tools/include/nolibc/arch-mips.h
+++ b/tools/include/nolibc/arch-mips.h
@@ -194,7 +194,9 @@ void __attribute__((weak, noreturn, optimize("Os", "omit-frame-pointer"))) __no_
                "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        */
-               "jal   _start_c\n"       /* transfer to c runtime                          */
+               "lui $t9, %hi(_start_c)\n" /* ABI requires current function address in $t9 */
+               "ori $t9, %lo(_start_c)\n"
+               "jalr $t9\n"             /* transfer to c runtime                          */
                " nop\n"                 /* delayed slot                                   */
                ".set pop\n"
        );