[PATCH v5 10/25] AArch64: Add MTE register set support for GDB and gdbserver

Luis Machado via Gdb-patches
2021-01-27T20:21:42Z

Updates on v4:

- Use get_ptrace_pid in a couple spots.

--

AArch64 MTE support in the Linux kernel exposes a new register
through ptrace. This patch adds the required code to support it.

include/ChangeLog:

YYYY-MM-DD Luis Machado <luis.machado@linaro.org>

* elf/common.h (NT_ARM_TAGGED_ADDR_CTRL): Define.

gdb/ChangeLog:

YYYY-MM-DD Luis Machado <luis.machado@linaro.org>

* aarch64-linux-nat.c (fetch_mteregs_from_thread): New function.
(store_mteregs_to_thread): New function.
(aarch64_linux_nat_target::fetch_registers): Update to call
fetch_mteregs_from_thread.
(aarch64_linux_nat_target::store_registers): Update to call
store_mteregs_to_thread.
* aarch64-tdep.c (aarch64_mte_register_names): New struct.
(aarch64_cannot_store_register): Handle MTE registers.
(aarch64_gdbarch_init): Initialize and setup MTE registers.
* aarch64-tdep.h (gdbarch_tdep) <mte_reg_base>: New field.
<has_mte>: New method.
* arch/aarch64-linux.h (AARCH64_LINUX_SIZEOF_MTE): Define.

gdbserver/ChangeLog:

YYYY-MM-DD Luis Machado <luis.machado@linaro.org>

* linux-aarch64-low.cc (aarch64_fill_mteregset): New function.
(aarch64_store_mteregset): New function.
(aarch64_regsets): Add MTE register set entry.
(aarch64_sve_regsets): Add MTE register set entry.
---
gdb/aarch64-linux-nat.c | 68 ++++++++++++++++++++++++++++++++++
gdb/aarch64-tdep.c | 24 ++++++++++++
gdb/aarch64-tdep.h | 9 +++++
gdb/arch/aarch64-mte-linux.h | 3 ++
gdbserver/linux-aarch64-low.cc | 29 +++++++++++++++
include/elf/common.h | 3 ++
6 files changed, 136 insertions(+)

diff --git a/gdb/aarch64-linux-nat.c b/gdb/aarch64-linux-nat.c
index c56880e33d..fe3ba44c55 100644
--- a/gdb/aarch64-linux-nat.c
+++ b/gdb/aarch64-linux-nat.c
@@ -461,6 +461,58 @@ fetch_pauth_masks_from_thread (struct regcache *regcache)
&pauth_regset[1]);
}

+/* Fill GDB's register array with the MTE register values from
+ the current thread. */
+
+static void
+fetch_mteregs_from_thread (struct regcache *regcache)
+{
+ struct gdbarch_tdep *tdep = gdbarch_tdep (regcache->arch ());
+ int regno = tdep->mte_reg_base;
+
+ gdb_assert (regno != -1);
+
+ uint64_t tag_ctl = 0;
+ struct iovec iovec;
+
+ iovec.iov_base = &tag_ctl;
+ iovec.iov_len = sizeof (tag_ctl);
+
+ int tid = get_ptrace_pid (regcache->ptid ());
+ if (ptrace (PTRACE_GETREGSET, tid, NT_ARM_TAGGED_ADDR_CTRL, &iovec) != 0)
+ perror_with_name (_("unable to fetch MTE registers."));
+
+ regcache->raw_supply (regno, &tag_ctl);
+}
+
+/* Store to the current thread the valid MTE register set in the GDB's
+ register array. */
+
+static void
+store_mteregs_to_thread (struct regcache *regcache)
+{
+ struct gdbarch_tdep *tdep = gdbarch_tdep (regcache->arch ());
+ int regno = tdep->mte_reg_base;
+
+ gdb_assert (regno != -1);
+
+ uint64_t tag_ctl = 0;
+
+ if (REG_VALID != regcache->get_register_status (regno))
+ return;
+
+ regcache->raw_collect (regno, (char *) &tag_ctl);
+
+ struct iovec iovec;
+
+ iovec.iov_base = &tag_ctl;
+ iovec.iov_len = sizeof (tag_ctl);
+
+ int tid = get_ptrace_pid (regcache->ptid ());
+ if (ptrace (PTRACE_SETREGSET, tid, NT_ARM_TAGGED_ADDR_CTRL, &iovec) != 0)
+ perror_with_name (_("unable to store MTE registers."));
+}
+
/* Implement the "fetch_registers" target_ops method. */

void
@@ -479,6 +531,9 @@ aarch64_linux_nat_target::fetch_registers (struct regcache *regcache,

if (tdep->has_pauth ())
fetch_pauth_masks_from_thread (regcache);
+
+ if (tdep->has_mte ())
+ fetch_mteregs_from_thread (regcache);
}
else if (regno < AARCH64_V0_REGNUM)
fetch_gregs_from_thread (regcache);
@@ -493,6 +548,11 @@ aarch64_linux_nat_target::fetch_registers (struct regcache *regcache,
|| regno == AARCH64_PAUTH_CMASK_REGNUM (tdep->pauth_reg_base))
fetch_pauth_masks_from_thread (regcache);
}
+
+ /* Fetch individual MTE registers. */
+ if (tdep->has_mte ()
+ && (regno == tdep->mte_reg_base))
+ fetch_mteregs_from_thread (regcache);
}

/* Implement the "store_registers" target_ops method. */
@@ -510,6 +570,9 @@ aarch64_linux_nat_target::store_registers (struct regcache *regcache,
store_sveregs_to_thread (regcache);
else
store_fpregs_to_thread (regcache);
+
+ if (tdep->has_mte ())
+ store_mteregs_to_thread (regcache);
}
else if (regno < AARCH64_V0_REGNUM)
store_gregs_to_thread (regcache);
@@ -517,6 +580,11 @@ aarch64_linux_nat_target::store_registers (struct regcache *regcache,
store_sveregs_to_thread (regcache);
else
store_fpregs_to_thread (regcache);
+
+ /* Store MTE registers. */
+ if (tdep->has_mte ()
+ && (regno == tdep->mte_reg_base))
+ store_mteregs_to_thread (regcache);
}

/* Fill register REGNO (if it is a general-purpose register) in
diff --git a/gdb/aarch64-tdep.c b/gdb/aarch64-tdep.c
index 685c50b84d..44833eb94d 100644
--- a/gdb/aarch64-tdep.c
+++ b/gdb/aarch64-tdep.c
@@ -172,6 +172,12 @@ static const char *const aarch64_pauth_register_names[] =
"pauth_cmask"
};

+static const char *const aarch64_mte_register_names[] =
+{
+ /* Tag Control Register. */
+ "tag_ctl"
+};
+
/* AArch64 prologue cache structure. */
struct aarch64_prologue_cache
{
@@ -3346,6 +3352,7 @@ aarch64_gdbarch_init (struct gdbarch_info info, struct gdbarch_list *arches)
bool valid_p = true;
int i, num_regs = 0, num_pseudo_regs = 0;
int first_pauth_regnum = -1, pauth_ra_state_offset = -1;
+ int first_mte_regnum = -1;

/* Use the vector length passed via the target info. Here -1 is used for no
SVE, and 0 is unset. If unset then use the vector length from the existing
@@ -3383,6 +3390,8 @@ aarch64_gdbarch_init (struct gdbarch_info info, struct gdbarch_list *arches)
feature_fpu = tdesc_find_feature (tdesc, "org.gnu.gdb.aarch64.fpu");
feature_sve = tdesc_find_feature (tdesc, "org.gnu.gdb.aarch64.sve");
feature_pauth = tdesc_find_feature (tdesc, "org.gnu.gdb.aarch64.pauth");
+ const struct tdesc_feature *feature_mte
+ = tdesc_find_feature (tdesc, "org.gnu.gdb.aarch64.mte");

if (feature_core == nullptr)
return nullptr;
@@ -3453,6 +3462,20 @@ aarch64_gdbarch_init (struct gdbarch_info info, struct gdbarch_list *arches)
num_pseudo_regs += 1; /* Count RA_STATE pseudo register. */
}

+ /* Add the MTE registers. */
+ if (feature_mte != NULL)
+ {
+ first_mte_regnum = num_regs;
+ /* Validate the descriptor provides the mandatory MTE registers and
+ allocate their numbers. */
+ for (i = 0; i < ARRAY_SIZE (aarch64_mte_register_names); i++)
+ valid_p &= tdesc_numbered_register (feature_mte, tdesc_data.get (),
+ first_mte_regnum + i,
+ aarch64_mte_register_names[i]);
+
+ num_regs += i;
+ }
+
if (!valid_p)
return nullptr;

@@ -3470,6 +3493,7 @@ aarch64_gdbarch_init (struct gdbarch_info info, struct gdbarch_list *arches)
tdep->pauth_reg_base = first_pauth_regnum;
tdep->pauth_ra_state_regnum = (feature_pauth == NULL) ? -1
: pauth_ra_state_offset + num_regs;
+ tdep->mte_reg_base = first_mte_regnum;

set_gdbarch_push_dummy_call (gdbarch, aarch64_push_dummy_call);
set_gdbarch_frame_align (gdbarch, aarch64_frame_align);
diff --git a/gdb/aarch64-tdep.h b/gdb/aarch64-tdep.h
index f6d24292f8..7bf612b012 100644
--- a/gdb/aarch64-tdep.h
+++ b/gdb/aarch64-tdep.h
@@ -100,6 +100,15 @@ struct gdbarch_tdep
{
return pauth_reg_base != -1;
}
+
+ /* First MTE register. This is -1 if no MTE registers are available. */
+ int mte_reg_base;
+
+ /* Returns true if the target supports MTE. */
+ bool has_mte () const
+ {
+ return mte_reg_base != -1;
+ }
};

const target_desc *aarch64_read_description (uint64_t vq, bool pauth_p,
diff --git a/gdb/arch/aarch64-mte-linux.h b/gdb/arch/aarch64-mte-linux.h
index c6a91c2db4..4124e80543 100644
--- a/gdb/arch/aarch64-mte-linux.h
+++ b/gdb/arch/aarch64-mte-linux.h
@@ -25,4 +25,7 @@
#define HWCAP2_MTE (1 << 18)
#endif

+/* The MTE regset consists of a single 64-bit register. */
+#define AARCH64_LINUX_SIZEOF_MTE 8
+
#endif /* ARCH_AARCH64_LINUX_H */
diff --git a/gdbserver/linux-aarch64-low.cc b/gdbserver/linux-aarch64-low.cc
index 14493c1fbe..a066d963a5 100644
--- a/gdbserver/linux-aarch64-low.cc
+++ b/gdbserver/linux-aarch64-low.cc
@@ -261,6 +261,29 @@ aarch64_store_pauthregset (struct regcache *regcache, const void *buf)
&pauth_regset[1]);
}

+/* Fill BUF with the MTE registers from the regcache. */
+
+static void
+aarch64_fill_mteregset (struct regcache *regcache, void *buf)
+{
+ uint64_t *mte_regset = (uint64_t *) buf;
+ int mte_base = find_regno (regcache->tdesc, "tag_ctl");
+
+ collect_register (regcache, mte_base, mte_regset);
+}
+
+/* Store the MTE registers to regcache. */
+
+static void
+aarch64_store_mteregset (struct regcache *regcache, const void *buf)
+{
+ uint64_t *mte_regset = (uint64_t *) buf;
+ int mte_base = find_regno (regcache->tdesc, "tag_ctl");
+
+ /* Tag Control register */
+ supply_register (regcache, mte_base, mte_regset);
+}
+
bool
aarch64_target::low_supports_breakpoints ()
{
@@ -706,6 +729,9 @@ static struct regset_info aarch64_regsets[] =
{ PTRACE_GETREGSET, PTRACE_SETREGSET, NT_ARM_PAC_MASK,
AARCH64_PAUTH_REGS_SIZE, OPTIONAL_REGS,
NULL, aarch64_store_pauthregset },
+ { PTRACE_GETREGSET, PTRACE_SETREGSET, NT_ARM_TAGGED_ADDR_CTRL,
+ AARCH64_LINUX_SIZEOF_MTE, OPTIONAL_REGS, aarch64_fill_mteregset,
+ aarch64_store_mteregset },
NULL_REGSET
};

@@ -735,6 +761,9 @@ static struct regset_info aarch64_sve_regsets[] =
{ PTRACE_GETREGSET, PTRACE_SETREGSET, NT_ARM_PAC_MASK,
AARCH64_PAUTH_REGS_SIZE, OPTIONAL_REGS,
NULL, aarch64_store_pauthregset },
+ { PTRACE_GETREGSET, PTRACE_SETREGSET, NT_ARM_TAGGED_ADDR_CTRL,
+ AARCH64_LINUX_SIZEOF_MTE, OPTIONAL_REGS, aarch64_fill_mteregset,
+ aarch64_store_mteregset },
NULL_REGSET
};

diff --git a/include/elf/common.h b/include/elf/common.h
index e7d55ae078..da911b8e18 100644
--- a/include/elf/common.h
+++ b/include/elf/common.h
@@ -672,6 +672,9 @@
/* note name must be "LINUX". */
#define NT_ARM_PAC_MASK 0x406 /* AArch pointer authentication code masks */
/* note name must be "LINUX". */
+#define NT_ARM_TAGGED_ADDR_CTRL 0x409 /* AArch64 tagged address control
+ (prctl()) */
+ /* note name must be "LINUX". */
#define NT_ARC_V2 0x600 /* ARC HS accumulator/extra registers. */
/* note name must be "LINUX". */
#define NT_SIGINFO 0x53494749 /* Fields of siginfo_t. */
--
2.25.1