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[PATCH 7/9] aarch64: Add thread state types

From: Sergey Bugaev
Subject: [PATCH 7/9] aarch64: Add thread state types
Date: Mon, 15 Apr 2024 12:01:47 +0300

* TPIDR_EL0, the TLS pointer, is included in the generic state directly.
* TPIDR2_EL0, part of the SME extension, is not included in the generic
  state.  If we add SME support, it will be a part of something like
* CPSR is not a real register in AArch64 (unlike in AArch32), but a
  collection of individually accessible bits and pieces from PSTATE.
  Due to how the kernel accesses user mode's PSTATE (via SPSR), it's
  convenient to represent PSTATE as a pseudo-register in the same
  format as SPSR.  This is also what QEMU and XNU do.
* There is no hardware-enforced 'natural' order to place the registers
  in, since no registers get pushed onto the stack on exception entry.
  Saving and restoring registers from an instance of struct
  aarch64_thread_state is implemented entirely in software, and the
  format is essentially arbitrary.
* aarch64_float_state includes registers of a 128-bit type; this may
  create issues for compilers other than GCC.
* fp_reserved is not a register, but a placeholder.  If and when Arm
  adds another floating-point meta-register, this will be changed to
  represent it, and that would not be considered a compatibility break,
  so don't access fp_reserved by name, or its value, from userland.
  Instead, memset the whole structure to 0 if starting from scratch, or
  memcpy an existing structure.

More thread state types could be added in the future, such as
aarch64_debug_state, aarch64_virt_state (for hardware-accelerated
virtualization), potentially ones for PAC, SVE/SME, etc.
 aarch64/Makefrag.am                          |  1 +
 aarch64/include/mach/aarch64/thread_status.h | 43 ++++++++++++++++++++
 2 files changed, 44 insertions(+)
 create mode 100644 aarch64/include/mach/aarch64/thread_status.h

diff --git a/aarch64/Makefrag.am b/aarch64/Makefrag.am
index 13c9439a..dd1837d4 100644
--- a/aarch64/Makefrag.am
+++ b/aarch64/Makefrag.am
@@ -36,6 +36,7 @@ include_mach_aarch64_HEADERS = \
        aarch64/include/mach/aarch64/mach_aarch64_types.h \
        aarch64/include/mach/aarch64/machine_types.defs \
        aarch64/include/mach/aarch64/syscall_sw.h \
+       aarch64/include/mach/aarch64/thread_status.h \
        aarch64/include/mach/aarch64/vm_param.h \
diff --git a/aarch64/include/mach/aarch64/thread_status.h 
new file mode 100644
index 00000000..c0c7773e
--- /dev/null
+++ b/aarch64/include/mach/aarch64/thread_status.h
@@ -0,0 +1,43 @@
+ * Copyright (c) 2023-2024 Free Software Foundation.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+#ifndef        _MACH_AARCH64_THREAD_STATUS_H_
+#define AARCH64_THREAD_STATE   1
+#define AARCH64_FLOAT_STATE    2
+struct aarch64_thread_state {
+       uint64_t x[31];
+       uint64_t sp;
+       uint64_t pc;
+       uint64_t tpidr_el0;
+       uint64_t cpsr;                  /* in SPSR format */
+#define AARCH64_THREAD_STATE_COUNT     (sizeof(struct aarch64_thread_state) / 
sizeof(unsigned int))
+struct aarch64_float_state {
+       __int128 v[32];
+       uint64_t fpsr;
+       uint64_t fpcr;
+       uint64_t fpmr;
+       uint64_t fp_reserved;           /* for when ARM adds another FP 
register */
+#define AARCH64_FLOAT_STATE_COUNT      (sizeof(struct aarch64_float_state) / 
sizeof(unsigned int))
+#endif /* _MACH_AARHC64_THREAD_STATUS_H_ */

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