[v2,11/14] target/arm: Implement gdbstub pauth extension

The extension is primarily defined by the Linux kernel NT_ARM_PAC_MASK
ptrace register set.

The original gdb feature consists of two masks, data and code, which are
used to mask out the authentication code within a pointer.  Following
discussion with Luis Machado, add two more masks in order to support
pointers within the high half of the address space (i.e. TTBR1 vs TTBR0).

Cc: Luis Machado <luis.machado@arm.com>
Cc: Thiago Jung Bauermann <thiago.bauermann@linaro.org>
Resolves: https://gitlab.com/qemu-project/qemu/-/issues/1105
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
 configs/targets/aarch64-linux-user.mak    |  2 +-
 configs/targets/aarch64-softmmu.mak       |  2 +-
 configs/targets/aarch64_be-linux-user.mak |  2 +-
 target/arm/internals.h                    |  2 ++
 target/arm/gdbstub.c                      |  5 ++++
 target/arm/gdbstub64.c                    | 34 +++++++++++++++++++++++
 gdb-xml/aarch64-pauth.xml                 | 15 ++++++++++
 7 files changed, 59 insertions(+), 3 deletions(-)
 create mode 100644 gdb-xml/aarch64-pauth.xml

Hi,

On 2/21/23 02:19, Richard Henderson wrote:
> The extension is primarily defined by the Linux kernel NT_ARM_PAC_MASK
> ptrace register set.
>
> The original gdb feature consists of two masks, data and code, which are
> used to mask out the authentication code within a pointer.  Following
> discussion with Luis Machado, add two more masks in order to support
> pointers within the high half of the address space (i.e. TTBR1 vs TTBR0).
>
> Cc: Luis Machado <luis.machado@arm.com>
> Cc: Thiago Jung Bauermann <thiago.bauermann@linaro.org>
> Resolves: https://gitlab.com/qemu-project/qemu/-/issues/1105
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
> ---
>   configs/targets/aarch64-linux-user.mak    |  2 +-
>   configs/targets/aarch64-softmmu.mak       |  2 +-
>   configs/targets/aarch64_be-linux-user.mak |  2 +-
>   target/arm/internals.h                    |  2 ++
>   target/arm/gdbstub.c                      |  5 ++++
>   target/arm/gdbstub64.c                    | 34 +++++++++++++++++++++++
>   gdb-xml/aarch64-pauth.xml                 | 15 ++++++++++
>   7 files changed, 59 insertions(+), 3 deletions(-)
>   create mode 100644 gdb-xml/aarch64-pauth.xml
>
> diff --git a/configs/targets/aarch64-linux-user.mak b/configs/targets/aarch64-linux-user.mak
> index db552f1839..ba8bc5fe3f 100644
> --- a/configs/targets/aarch64-linux-user.mak
> +++ b/configs/targets/aarch64-linux-user.mak
> @@ -1,6 +1,6 @@
>   TARGET_ARCH=aarch64
>   TARGET_BASE_ARCH=arm
> -TARGET_XML_FILES= gdb-xml/aarch64-core.xml gdb-xml/aarch64-fpu.xml
> +TARGET_XML_FILES= gdb-xml/aarch64-core.xml gdb-xml/aarch64-fpu.xml gdb-xml/aarch64-pauth.xml
>   TARGET_HAS_BFLT=y
>   CONFIG_SEMIHOSTING=y
>   CONFIG_ARM_COMPATIBLE_SEMIHOSTING=y
> diff --git a/configs/targets/aarch64-softmmu.mak b/configs/targets/aarch64-softmmu.mak
> index d489e6da83..b4338e9568 100644
> --- a/configs/targets/aarch64-softmmu.mak
> +++ b/configs/targets/aarch64-softmmu.mak
> @@ -1,5 +1,5 @@
>   TARGET_ARCH=aarch64
>   TARGET_BASE_ARCH=arm
>   TARGET_SUPPORTS_MTTCG=y
> -TARGET_XML_FILES= gdb-xml/aarch64-core.xml gdb-xml/aarch64-fpu.xml gdb-xml/arm-core.xml gdb-xml/arm-vfp.xml gdb-xml/arm-vfp3.xml gdb-xml/arm-vfp-sysregs.xml gdb-xml/arm-neon.xml gdb-xml/arm-m-profile.xml gdb-xml/arm-m-profile-mve.xml
> +TARGET_XML_FILES= gdb-xml/aarch64-core.xml gdb-xml/aarch64-fpu.xml gdb-xml/arm-core.xml gdb-xml/arm-vfp.xml gdb-xml/arm-vfp3.xml gdb-xml/arm-vfp-sysregs.xml gdb-xml/arm-neon.xml gdb-xml/arm-m-profile.xml gdb-xml/arm-m-profile-mve.xml gdb-xml/aarch64-pauth.xml
>   TARGET_NEED_FDT=y
> diff --git a/configs/targets/aarch64_be-linux-user.mak b/configs/targets/aarch64_be-linux-user.mak
> index dc78044fb1..acb5620cdb 100644
> --- a/configs/targets/aarch64_be-linux-user.mak
> +++ b/configs/targets/aarch64_be-linux-user.mak
> @@ -1,7 +1,7 @@
>   TARGET_ARCH=aarch64
>   TARGET_BASE_ARCH=arm
>   TARGET_BIG_ENDIAN=y
> -TARGET_XML_FILES= gdb-xml/aarch64-core.xml gdb-xml/aarch64-fpu.xml
> +TARGET_XML_FILES= gdb-xml/aarch64-core.xml gdb-xml/aarch64-fpu.xml gdb-xml/aarch64-pauth.xml
>   TARGET_HAS_BFLT=y
>   CONFIG_SEMIHOSTING=y
>   CONFIG_ARM_COMPATIBLE_SEMIHOSTING=y
> diff --git a/target/arm/internals.h b/target/arm/internals.h
> index 370655061e..fb88b16579 100644
> --- a/target/arm/internals.h
> +++ b/target/arm/internals.h
> @@ -1331,6 +1331,8 @@ int aarch64_gdb_get_sve_reg(CPUARMState *env, GByteArray *buf, int reg);
>   int aarch64_gdb_set_sve_reg(CPUARMState *env, uint8_t *buf, int reg);
>   int aarch64_gdb_get_fpu_reg(CPUARMState *env, GByteArray *buf, int reg);
>   int aarch64_gdb_set_fpu_reg(CPUARMState *env, uint8_t *buf, int reg);
> +int aarch64_gdb_get_pauth_reg(CPUARMState *env, GByteArray *buf, int reg);
> +int aarch64_gdb_set_pauth_reg(CPUARMState *env, uint8_t *buf, int reg);
>   void arm_cpu_sve_finalize(ARMCPU *cpu, Error **errp);
>   void arm_cpu_sme_finalize(ARMCPU *cpu, Error **errp);
>   void arm_cpu_pauth_finalize(ARMCPU *cpu, Error **errp);
> diff --git a/target/arm/gdbstub.c b/target/arm/gdbstub.c
> index bf8aff7824..062c8d447a 100644
> --- a/target/arm/gdbstub.c
> +++ b/target/arm/gdbstub.c
> @@ -355,6 +355,11 @@ void arm_cpu_register_gdb_regs_for_features(ARMCPU *cpu)
>                                        aarch64_gdb_set_fpu_reg,
>                                        34, "aarch64-fpu.xml", 0);
>           }
> +        if (isar_feature_aa64_pauth(&cpu->isar)) {
> +            gdb_register_coprocessor(cs, aarch64_gdb_get_pauth_reg,
> +                                     aarch64_gdb_set_pauth_reg,
> +                                     4, "aarch64-pauth.xml", 0);
> +        }
>   #endif
>       } else {
>           if (arm_feature(env, ARM_FEATURE_NEON)) {
> diff --git a/target/arm/gdbstub64.c b/target/arm/gdbstub64.c
> index 3d9e9e97c8..3bee892fb7 100644
> --- a/target/arm/gdbstub64.c
> +++ b/target/arm/gdbstub64.c
> @@ -210,6 +210,40 @@ int aarch64_gdb_set_sve_reg(CPUARMState *env, uint8_t *buf, int reg)
>       return 0;
>   }
>
> +int aarch64_gdb_get_pauth_reg(CPUARMState *env, GByteArray *buf, int reg)
> +{
> +    switch (reg) {
> +    case 0: /* pauth_dmask */
> +    case 1: /* pauth_cmask */
> +    case 2: /* pauth_dmask_high */
> +    case 3: /* pauth_cmask_high */
> +        /*
> +         * Note that older versions of this feature only contained
> +         * pauth_{d,c}mask, for use with Linux user processes, and
> +         * thus exclusively in the low half of the address space.
> +         *
> +         * To support system mode, and to debug kernels, two new regs
> +         * were added to cover the high half of the address space.
> +         * For the purpose of pauth_ptr_mask, we can use any well-formed
> +         * address within the address space half -- here, 0 and -1.
> +         */
> +        {
> +            bool is_data = !(reg & 1);
> +            bool is_high = reg & 2;
> +            uint64_t mask = pauth_ptr_mask(env, -is_high, is_data);
> +            return gdb_get_reg64(buf, mask);
> +        }
> +    default:
> +        return 0;
> +    }
> +}
> +
> +int aarch64_gdb_set_pauth_reg(CPUARMState *env, uint8_t *buf, int reg)
> +{
> +    /* All pseudo registers are read-only. */
> +    return 0;
> +}
> +
>   static void output_vector_union_type(GString *s, int reg_width,
>                                        const char *name)
>   {
> diff --git a/gdb-xml/aarch64-pauth.xml b/gdb-xml/aarch64-pauth.xml
> new file mode 100644
> index 0000000000..24af5f903c
> --- /dev/null
> +++ b/gdb-xml/aarch64-pauth.xml
> @@ -0,0 +1,15 @@
> +<?xml version="1.0"?>
> +<!-- Copyright (C) 2018-2022 Free Software Foundation, Inc.
> +
> +     Copying and distribution of this file, with or without modification,
> +     are permitted in any medium without royalty provided the copyright
> +     notice and this notice are preserved.  -->
> +
> +<!DOCTYPE feature SYSTEM "gdb-target.dtd">
> +<feature name="org.gnu.gdb.aarch64.pauth">
> +  <reg name="pauth_dmask" bitsize="64"/>
> +  <reg name="pauth_cmask" bitsize="64"/>
> +  <reg name="pauth_dmask_high" bitsize="64"/>
> +  <reg name="pauth_cmask_high" bitsize="64"/>
> +</feature>
> +

FTR, I've pushed the gdb-side changes: https://sourceware.org/git/?p=binutils-gdb.git;a=commit;h=6d0020873deb2f2c4e0965dc2ebf227bc1db3140
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On Tue, 21 Feb 2023 at 02:21, Richard Henderson
<richard.henderson@linaro.org> wrote:
>
> The extension is primarily defined by the Linux kernel NT_ARM_PAC_MASK
> ptrace register set.
>
> The original gdb feature consists of two masks, data and code, which are
> used to mask out the authentication code within a pointer.  Following
> discussion with Luis Machado, add two more masks in order to support
> pointers within the high half of the address space (i.e. TTBR1 vs TTBR0).
>
> Cc: Luis Machado <luis.machado@arm.com>
> Cc: Thiago Jung Bauermann <thiago.bauermann@linaro.org>
> Resolves: https://gitlab.com/qemu-project/qemu/-/issues/1105
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>

thanks
-- PMM