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target-mips: Fix exceptions while UX=0

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Commit 01f728857941 ("target-mips: Status.UX/SX/KX enable 32-bit address
wrapping") added a new hflag MIPS_HFLAG_AWRAP, which indicates that
64-bit addressing is disallowed in the current mode, so hflag users
don't need to worry about the complexities of working that out, for
example checking both MIPS_HFLAG_KSU and MIPS_HFLAG_UX.

However when exceptions are taken outside of exception level,
mips_cpu_do_interrupt() manipulates the env->hflags directly rather than
using compute_hflags() to update them, and this code wasn't updated
accordingly. As a result, when UX is cleared, MIPS_HFLAG_AWRAP is set,
but it doesn't get cleared on entry back into kernel mode due to an
exception. Kernel mode then cannot access the 64-bit segments resulting
in a nested exception loop. The same applies to errors and debug
exceptions.

Fix by updating mips_cpu_do_interrupt() to clear the MIPS_HFLAG_WRAP
flag when necessary, according to compute_hflags().

Backports commit 7871abb94c2f4adc39f2487f6edf5e69ba872a65 from qemu
This commit is contained in:
James Hogan 2018-02-17 18:57:41 -05:00 committed by Lioncash
parent 386e398c56
commit 8689c6efef
No known key found for this signature in database
GPG Key ID: 4E3C3CC1031BA9C7
1 changed files with 12 additions and 0 deletions
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12
qemu/target-mips/helper.c
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@ -511,6 +511,10 @@ void mips_cpu_do_interrupt(CPUState *cs)
enter_debug_mode:
if (env->insn_flags & ISA_MIPS3) {
env->hflags |= MIPS_HFLAG_64;
if (!(env->insn_flags & ISA_MIPS64R6) ||
env->CP0_Status & (1 << CP0St_KX)) {
env->hflags &= ~MIPS_HFLAG_AWRAP;
}
}
env->hflags |= MIPS_HFLAG_DM | MIPS_HFLAG_CP0;
env->hflags &= ~(MIPS_HFLAG_KSU);
@ -535,6 +539,10 @@ void mips_cpu_do_interrupt(CPUState *cs)
env->CP0_Status |= (1 << CP0St_ERL) | (1 << CP0St_BEV);
if (env->insn_flags & ISA_MIPS3) {
env->hflags |= MIPS_HFLAG_64;
if (!(env->insn_flags & ISA_MIPS64R6) ||
env->CP0_Status & (1 << CP0St_KX)) {
env->hflags &= ~MIPS_HFLAG_AWRAP;
}
}
env->hflags |= MIPS_HFLAG_CP0;
env->hflags &= ~(MIPS_HFLAG_KSU);
@ -712,6 +720,10 @@ void mips_cpu_do_interrupt(CPUState *cs)
env->CP0_Status |= (1 << CP0St_EXL);
if (env->insn_flags & ISA_MIPS3) {
env->hflags |= MIPS_HFLAG_64;
if (!(env->insn_flags & ISA_MIPS64R6) ||
env->CP0_Status & (1 << CP0St_KX)) {
env->hflags &= ~MIPS_HFLAG_AWRAP;
}
}
env->hflags |= MIPS_HFLAG_CP0;
env->hflags &= ~(MIPS_HFLAG_KSU);