From 756c8af8589265e99e454fe3adcda1d0bc5e1963 Mon Sep 17 00:00:00 2001 From: Rich Felker Date: Thu, 4 Feb 2016 23:01:03 +0000 Subject: [PATCH] in mips cancellable syscall asm, don't assume gp register is valid the old __cp_cancel code path loaded the address of __cancel from the GOT using the $gp register, which happened to be set to point to the correct GOT by the calling C function, but there is no ABI requirement that this happen. instead, go the roundabout way and compute the address of __cancel via pc-relative and gp-relative addressing starting with a fake return address generated by a bal instruction, which is the same trick crt1 uses to bootstrap. --- src/thread/mips/syscall_cp.s | 15 +++++++++++++-- 1 file changed, 13 insertions(+), 2 deletions(-) diff --git a/src/thread/mips/syscall_cp.s b/src/thread/mips/syscall_cp.s index 8f76d40e..b01a5704 100644 --- a/src/thread/mips/syscall_cp.s +++ b/src/thread/mips/syscall_cp.s @@ -9,6 +9,9 @@ .global __cp_cancel .hidden __cp_cancel .type __cp_cancel,@function +.global __cp_cancel_data +.hidden __cp_cancel_data +.type __cp_cancel_data,@function .hidden __cancel .global __syscall_cp_asm .hidden __syscall_cp_asm @@ -40,7 +43,15 @@ __cp_end: nop __cp_cancel: + move $2, $ra + bal 1f addu $sp, $sp, 32 - lw $25, %call16(__cancel)($gp) +__cp_cancel_data: + .gpword __cp_cancel_data + .gpword __cancel +1: lw $3, ($ra) + subu $3, $ra, $3 + lw $25, 4($ra) + addu $25, $25, $3 jr $25 - nop + move $ra, $2