Subject: [PATCH 3/4] arm64: traps: Pretty-print pstate in register dumps

From: [email-masked] (Will Deacon)
Date: Fri, 20 Oct 2017 16:58:37 +0100

On Thu, Oct 19, 2017 at 05:17:55PM +0100, Mark Rutland wrote:
> On Thu, Oct 19, 2017 at 04:55:33PM +0100, Will Deacon wrote:
> > We can decode the PSTATE easily enough, so pretty-print it in register
> > dumps.
> > 
> > Signed-off-by: Will Deacon <[email-masked]>
> > ---
> >  arch/arm64/kernel/process.c | 20 +++++++++++++++++++-
> >  1 file changed, 19 insertions(+), 1 deletion(-)
> > 
> > diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c
> > index c20896b8fb2d..be3cf9cd7dec 100644
> > --- a/arch/arm64/kernel/process.c
> > +++ b/arch/arm64/kernel/process.c
> > @@ -170,6 +170,23 @@ void machine_restart(char *cmd)
> >  	while (1);
> >  }
> >  
> > +static void print_pstate(struct pt_regs *regs)
> > +{
> > +	u64 pstate = regs->pstate;
> > +	printk("pstate: %08llx (%c%c%c%c %c%c%c%c %cPAN %cUAO)\n",
> > +		pstate,
> > +		pstate & PSR_N_BIT ? 'N' : 'n',
> > +		pstate & PSR_Z_BIT ? 'Z' : 'z',
> > +		pstate & PSR_C_BIT ? 'C' : 'c',
> > +		pstate & PSR_V_BIT ? 'V' : 'v',
> > +		pstate & PSR_D_BIT ? 'D' : 'd',
> > +		pstate & PSR_A_BIT ? 'A' : 'a',
> > +		pstate & PSR_I_BIT ? 'I' : 'i',
> > +		pstate & PSR_F_BIT ? 'F' : 'f',
> > +		pstate & PSR_PAN_BIT ? '+' : '-',
> > +		pstate & PSR_UAO_BIT ? '+' : '-');
> > +}
> 
> Given we use __show_regs for user state, I think we need to check
> compat_user_mode() regs, and adjust the decoding accordingly.
> 
> e.g. AArch32 has an E bit where the D in DAIF is.

Yes, you're right. There's lots of exciting bits in the AArch32 pstate
too. I ended up with the diff below.

Will

--->8

+static void print_pstate(struct pt_regs *regs)
+{
+	u64 pstate = regs->pstate;
+
+	if (compat_user_mode(regs))
+		printk("pstate: %08llx (%c%c%c%c %c %s %s-endian %c%c%c)\n",
+			pstate,
+			pstate & COMPAT_PSR_N_BIT ? 'N' : 'n',
+			pstate & COMPAT_PSR_Z_BIT ? 'Z' : 'z',
+			pstate & COMPAT_PSR_C_BIT ? 'C' : 'c',
+			pstate & COMPAT_PSR_V_BIT ? 'V' : 'v',
+			pstate & COMPAT_PSR_Q_BIT ? 'Q' : 'q',
+			pstate & COMPAT_PSR_T_BIT ? "T32" : "A32",
+			pstate & COMPAT_PSR_E_BIT ? "big" : "little",
+			pstate & COMPAT_PSR_A_BIT ? 'A' : 'a',
+			pstate & COMPAT_PSR_I_BIT ? 'I' : 'i',
+			pstate & COMPAT_PSR_F_BIT ? 'F' : 'f');
+	else
+		printk("pstate: %08llx (%c%c%c%c %c%c%c%c %cPAN %cUAO)\n",
+			pstate,
+			pstate & PSR_N_BIT ? 'N' : 'n',
+			pstate & PSR_Z_BIT ? 'Z' : 'z',
+			pstate & PSR_C_BIT ? 'C' : 'c',
+			pstate & PSR_V_BIT ? 'V' : 'v',
+			pstate & PSR_D_BIT ? 'D' : 'd',
+			pstate & PSR_A_BIT ? 'A' : 'a',
+			pstate & PSR_I_BIT ? 'I' : 'i',
+			pstate & PSR_F_BIT ? 'F' : 'f',
+			pstate & PSR_PAN_BIT ? '+' : '-',
+			pstate & PSR_UAO_BIT ? '+' : '-');
+}