[v7,06/11] arm64: BTI: Decode BYTPE bits when printing PSTATE
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Message ID 20200226155714.43937-7-broonie@kernel.org
State New
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Series
  • [v7,01/11] ELF: UAPI and Kconfig additions for ELF program properties
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Commit Message

Mark Brown Feb. 26, 2020, 3:57 p.m. UTC
From: Dave Martin <Dave.Martin@arm.com>

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 <Dave.Martin@arm.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
---
 arch/arm64/kernel/process.c | 17 +++++++++++++++--
 1 file changed, 15 insertions(+), 2 deletions(-)

Comments

Kees Cook Feb. 26, 2020, 9:42 p.m. UTC | #1
On Wed, Feb 26, 2020 at 03:57:09PM +0000, Mark Brown wrote:
> From: Dave Martin <Dave.Martin@arm.com>
> 
> 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 <Dave.Martin@arm.com>

Reviewed-by: Kees Cook <keescook@chromium.org>

-Kees

> Signed-off-by: Mark Brown <broonie@kernel.org>
> ---
>  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
>

Patch
diff mbox series

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);
 	}
 }