arm64: BTI: Decode BYTPE bits when printing PSTATE

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: Mark Brown <broonie@kernel.org>
Signed-off-by: Dave Martin <Dave.Martin@arm.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c
index b8e3faa8d4061c971e2f23d705a85e0f6dd554ca..24af13d7bde66706f29ec5825ea44440adb0c31d 100644 (file)
--- 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);
        }
 }