yuzu/unicorn
1
0
Fork 0
mirror of https://github.com/yuzu-emu/unicorn.git synced 2025-03-23 06:25:12 +00:00
Code Issues Packages Projects Releases Wiki Activity

target-mips: fix hflags modified in delay / forbidden slot

Browse source 
All instructions which may change hflags terminate tb. However, this doesn't
work if such an instruction is placed in delay or forbidden slot.
gen_branch() clears MIPS_HFLAG_BMASK in ctx->hflags and then generates code
to overwrite hflags with ctx->hflags, consequently we loose any execution-time
hflags modifications. For example, in the following scenario hflag related to
Status.CU1 will not be updated:
/* Set Status.CU1 in delay slot */
mfc0 $24, $12, 0
lui $25, 0x2000
or $25, $25, $24
b check_Status_CU1
mtc0 $25, $12, 0

With this change we clear MIPS_HFLAG_BMASK in execution-time hflags if
instruction in delay or forbidden slot wants to terminate tb for some reason
(i.e. ctx->bstate != BS_NONE).

Also, die early and loudly if "unknown branch" is encountered as this should
never happen.

Backports commit a5f533909e746ca6e534b232fb42c9c6fd81b468 from qemu
This commit is contained in:
Leon Alrae 2018-02-12 16:23:41 -05:00 committed by Lioncash
parent cdc72c7db1
commit 6cd0c5d775
No known key found for this signature in database
GPG key ID: 4E3C3CC1031BA9C7
1 changed files with 16 additions and 4 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

20
qemu/target-mips/translate.c
View file

@ -10614,15 +10614,27 @@ static void gen_rdhwr(DisasContext *ctx, int rt, int rd)
tcg_temp_free(tcg_ctx, t0);
}
static inline void clear_branch_hflags(DisasContext *ctx)
{
TCGContext *tcg_ctx = ctx->uc->tcg_ctx;
ctx->hflags &= ~MIPS_HFLAG_BMASK;
if (ctx->bstate == BS_NONE) {
save_cpu_state(ctx, 0);
} else {
/* it is not safe to save ctx->hflags as hflags may be changed
in execution time by the instruction in delay / forbidden slot. */
tcg_gen_andi_i32(tcg_ctx, tcg_ctx->hflags, tcg_ctx->hflags, ~MIPS_HFLAG_BMASK);
}
}
static void gen_branch(DisasContext *ctx, int insn_bytes)
{
TCGContext *tcg_ctx = ctx->uc->tcg_ctx;
if (ctx->hflags & MIPS_HFLAG_BMASK) {
int proc_hflags = ctx->hflags & MIPS_HFLAG_BMASK;
/* Branches completion */
ctx->hflags &= ~MIPS_HFLAG_BMASK;
clear_branch_hflags(ctx);
ctx->bstate = BS_BRANCH;
save_cpu_state(ctx, 0);
/* FIXME: Need to clear can_do_io. */
switch (proc_hflags & MIPS_HFLAG_BMASK_BASE) {
case MIPS_HFLAG_FBNSLOT:
@ -10680,8 +10692,8 @@ static void gen_branch(DisasContext *ctx, int insn_bytes)
tcg_gen_exit_tb(tcg_ctx, 0);
break;
default:
MIPS_DEBUG("unknown branch");
break;
fprintf(stderr, "unknown branch 0x%x\n", proc_hflags);
abort();
}
}
}