Messages in this thread | | | Subject | Re: [PATCH v2 2/2] ARM: Make the dumped instructions are consistent with the disassembled ones | From | "Leizhen (ThunderTown)" <> | Date | Mon, 10 Oct 2022 18:46:12 +0800 |
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On 2022/10/10 18:10, Ard Biesheuvel wrote: > On Mon, 10 Oct 2022 at 11:56, Zhen Lei <thunder.leizhen@huawei.com> wrote: >> >> In ARM, the mapping of instruction memory is always little-endian, except >> some BE-32 supported ARM architectures. Such as ARMv7-R, its instruction >> endianness may be BE-32. Of course, its data endianness will also be BE-32 >> mode. Due to two negatives make a positive, the instruction stored in the >> register after reading is in little-endian format. But for the case of >> BE-8, the instruction endianness is LE, the instruction stored in the >> register after reading is in big-endian format, which is inconsistent >> with the disassembled one. >> >> For example: >> The content of disassembly: >> c0429ee8: e3500000 cmp r0, #0 >> c0429eec: 159f2044 ldrne r2, [pc, #68] >> c0429ef0: 108f2002 addne r2, pc, r2 >> c0429ef4: 1882000a stmne r2, {r1, r3} >> c0429ef8: e7f000f0 udf #0 >> >> The output of undefined instruction exception: >> Internal error: Oops - undefined instruction: 0 [#1] SMP ARM >> ... ... >> Code: 000050e3 44209f15 02208f10 0a008218 (f000f0e7) >> >> This inconveniences the checking of instructions. What's worse is that, >> for somebody who don't know about this, might think the instructions are >> all broken. >> >> So, when CONFIG_CPU_ENDIAN_BE8=y, let's convert the instructions to >> little-endian format before they are printed. The conversion result is >> as follows: >> Code: e3500000 159f2044 108f2002 1882000a (e7f000f0) >> >> Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com> >> --- >> arch/arm/kernel/traps.c | 7 +++++++ >> 1 file changed, 7 insertions(+) >> >> diff --git a/arch/arm/kernel/traps.c b/arch/arm/kernel/traps.c >> index 34aa80c09c508c1..50b00c9091f079d 100644 >> --- a/arch/arm/kernel/traps.c >> +++ b/arch/arm/kernel/traps.c >> @@ -193,6 +193,13 @@ static void dump_instr(const char *lvl, struct pt_regs *regs) >> bad = get_user(val, &((u32 __user *)addr)[i]); >> } >> >> + if (IS_ENABLED(CONFIG_CPU_ENDIAN_BE8)) { >> + if (thumb) >> + val = (__force unsigned int)cpu_to_le16(val); > > Better use swab16() here instead of the ugly __force cast, given that > the swab is going to occur unconditionally here.
Good idea.
> > >> + else >> + val = (__force unsigned int)cpu_to_le32(val); > > and swab32() here
OK
> > >> + } >> + >> if (!bad) >> p += sprintf(p, i == 0 ? "(%0*x) " : "%0*x ", >> width, val); >> -- >> 2.25.1 >> >> >> _______________________________________________ >> linux-arm-kernel mailing list >> linux-arm-kernel@lists.infradead.org >> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel > . >
-- Regards, Zhen Lei
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