On 11/5/26 20:22, James Hilliard wrote:
Linux/MIPS enables software fixups for user-mode unaligned scalar
accesses by default through MIPS_FIXADE/TIF_FIXADE. QEMU linux-user did
not model that ABI, so MIPS guests took fatal AdEL/AdES exceptions unless
translation was forced to use unaligned host accesses.
Key MIPS translation blocks on the linux-user unaligned policy, implement
sysmips(MIPS_FIXADE) to toggle that policy, and raise SIGBUS/BUS_ADRALN
when fixups are disabled.
Reviewed-by: Richard Henderson <[email protected]>
Signed-off-by: James Hilliard <[email protected]>
---
Changes v5 -> v6:
- Rename the TB flag from TB_FLAG_UNALIGN to TB_FLAG_MIPS_FIXADE
to match the MIPS_FIXADE ABI policy.
Changes v2 -> v3:
- Split MIPS_FLUSH_CACHE and MIPS_ATOMIC_SET into preparatory sysmips
patches. (suggested by Richard Henderson)
---
linux-user/mips/cpu_loop.c | 5 +++++
linux-user/mips/target_syscall.h | 1 +
linux-user/mips64/target_syscall.h | 1 +
linux-user/syscall.c | 8 ++++++++
target/mips/cpu.c | 8 ++++++--
target/mips/cpu.h | 4 ++++
target/mips/tcg/translate.c | 6 +++++-
7 files changed, 30 insertions(+), 3 deletions(-)
diff --git a/target/mips/cpu.c b/target/mips/cpu.c
index f803d47763..6e827c72de 100644
--- a/target/mips/cpu.c
+++ b/target/mips/cpu.c
@@ -565,11 +565,15 @@ static int mips_cpu_mmu_index(CPUState *cs, bool ifunc)
static TCGTBCPUState mips_get_tb_cpu_state(CPUState *cs)
{
CPUMIPSState *env = cpu_env(cs);
+ uint32_t flags = env->hflags & MIPS_HFLAG_TB_MASK;
+
+#ifdef CONFIG_USER_ONLY
+ flags |= TB_FLAG_MIPS_FIXADE * !cs->prctl_unalign_sigbus;
I'm not a big fan of this optimized style where you need to think
twice about what is being done. The following uses 3 lines but is
a no-brainer:
if (!cs->prctl_unalign_sigbus) {
flags |= TB_FLAG_MIPS_FIXADE
}
+#endif
return (TCGTBCPUState){
.pc = env->active_tc.PC,
- .flags = env->hflags & (MIPS_HFLAG_TMASK | MIPS_HFLAG_BMASK |
- MIPS_HFLAG_HWRENA_ULR),
+ .flags = flags,
};
}
