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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.
This commit is contained in:
Rich Felker 2016-02-04 23:01:03 +00:00
parent aecda35373
commit 756c8af858
1 changed files with 13 additions and 2 deletions
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15
src/thread/mips/syscall_cp.s
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@ -9,6 +9,9 @@
.global __cp_cancel .global __cp_cancel
.hidden __cp_cancel .hidden __cp_cancel
.type __cp_cancel,@function .type __cp_cancel,@function
.global __cp_cancel_data
.hidden __cp_cancel_data
.type __cp_cancel_data,@function
.hidden __cancel .hidden __cancel
.global __syscall_cp_asm .global __syscall_cp_asm
.hidden __syscall_cp_asm .hidden __syscall_cp_asm
@ -40,7 +43,15 @@ __cp_end:
nop nop
__cp_cancel: __cp_cancel:
move $2, $ra
bal 1f
addu $sp, $sp, 32 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 jr $25
nop move $ra, $2