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[198.145.64.163]) by smtp.gmail.com with ESMTPSA id u11sm3814980pjn.2.2020.02.26.13.42.02 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 26 Feb 2020 13:42:02 -0800 (PST) Date: Wed, 26 Feb 2020 13:42:01 -0800 From: Kees Cook To: Mark Brown Cc: Catalin Marinas , Will Deacon , Alexander Viro , Paul Elliott , Peter Zijlstra , Yu-cheng Yu , Amit Kachhap , Vincenzo Frascino , Marc Zyngier , Eugene Syromiatnikov , Szabolcs Nagy , "H . J . Lu " , Andrew Jones , Arnd Bergmann , Jann Horn , Richard Henderson , Kristina =?utf-8?Q?Mart=C5=A1enko?= , Thomas Gleixner , Florian Weimer , Sudakshina Das , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, linux-fsdevel@vger.kernel.org, Dave Martin Subject: Re: [PATCH v7 06/11] arm64: BTI: Decode BYTPE bits when printing PSTATE Message-ID: <202002261341.D2BB57A@keescook> References: <20200226155714.43937-1-broonie@kernel.org> <20200226155714.43937-7-broonie@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200226155714.43937-7-broonie@kernel.org> Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Wed, Feb 26, 2020 at 03:57:09PM +0000, Mark Brown wrote: > From: Dave Martin > > The current code to print PSTATE symbolically when generating > backtraces etc., does not include the BYTPE field used by Branch > Target Identification. > > So, decode BYTPE and print it too. > > In the interests of human-readability, print the classes of BTI > matched. The symbolic notation, BYTPE (PSTATE[11:10]) and > permitted classes of subsequent instruction are: > > -- (BTYPE=0b00): any insn > jc (BTYPE=0b01): BTI jc, BTI j, BTI c, PACIxSP > -c (BYTPE=0b10): BTI jc, BTI c, PACIxSP > j- (BTYPE=0b11): BTI jc, BTI j > > Signed-off-by: Dave Martin Reviewed-by: Kees Cook -Kees > Signed-off-by: Mark Brown > --- > arch/arm64/kernel/process.c | 17 +++++++++++++++-- > 1 file changed, 15 insertions(+), 2 deletions(-) > > diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c > index b8e3faa8d406..24af13d7bde6 100644 > --- a/arch/arm64/kernel/process.c > +++ b/arch/arm64/kernel/process.c > @@ -211,6 +211,15 @@ void machine_restart(char *cmd) > while (1); > } > > +#define bstr(suffix, str) [PSR_BTYPE_ ## suffix >> PSR_BTYPE_SHIFT] = str > +static const char *const btypes[] = { > + bstr(NONE, "--"), > + bstr( JC, "jc"), > + bstr( C, "-c"), > + bstr( J , "j-") > +}; > +#undef bstr > + > static void print_pstate(struct pt_regs *regs) > { > u64 pstate = regs->pstate; > @@ -229,7 +238,10 @@ static void print_pstate(struct pt_regs *regs) > pstate & PSR_AA32_I_BIT ? 'I' : 'i', > pstate & PSR_AA32_F_BIT ? 'F' : 'f'); > } else { > - printk("pstate: %08llx (%c%c%c%c %c%c%c%c %cPAN %cUAO)\n", > + const char *btype_str = btypes[(pstate & PSR_BTYPE_MASK) >> > + PSR_BTYPE_SHIFT]; > + > + printk("pstate: %08llx (%c%c%c%c %c%c%c%c %cPAN %cUAO BTYPE=%s)\n", > pstate, > pstate & PSR_N_BIT ? 'N' : 'n', > pstate & PSR_Z_BIT ? 'Z' : 'z', > @@ -240,7 +252,8 @@ static void print_pstate(struct pt_regs *regs) > pstate & PSR_I_BIT ? 'I' : 'i', > pstate & PSR_F_BIT ? 'F' : 'f', > pstate & PSR_PAN_BIT ? '+' : '-', > - pstate & PSR_UAO_BIT ? '+' : '-'); > + pstate & PSR_UAO_BIT ? '+' : '-', > + btype_str); > } > } > > -- > 2.20.1 > -- Kees Cook