tashaboot: arm64 bootloader

A small arm64 bootloader. No board code, no device tree porting, the
architecture manual is the whole story: exception vectors in the
fixed 16 slot layout (Table D1-7), ESR_ELx decoded by exception class
(D1-2172), EL entry and eret chains per the programmers model
(D1-2146), cache maintenance by set/way over the CLIDR_EL1 levels,
semihosting for console and file io per DUI 0203, and the A64 boot
protocol from Documentation/arch/arm64/booting.rst.

The loader boots a stock mainline Image end to end on the qemu virt
machine. Boot receipt with 7.3-rc3 (42MB Image):

  tashaboot 0.1
  loaded 43450368 bytes at 40200000, entry 40200000
  jumping
  [    0.000000] Booting Linux on physical CPU 0x0000000000 [0x411fd070]
  [    0.000000] Linux version 7.3.0-rc3
  [    0.000000] Machine model: linux,dummy-virt
  [    0.000000] earlycon: pl11 MMIO32:0x0000000009000000
  ...
  ---[ end Kernel panic - not syncing: VFS: Unable to mount root fs ]---

The panic is the expected end state, no root filesystem is handed
over yet.

The boot chain, state per stage, start to payload:

+-----------+-----+--------------+----------------------------------+
| stage     | EL  | state        | work                             |
+-----------+-----+--------------+----------------------------------+
| firmware  | any | MMU maybe on | x0 = dtb, jump in               |
+-----------+-----+--------------+----------------------------------+
| tashaboot | 3-2 |              | SCR_EL3.NS = 1, eret to EL2     |
+-----------+-----+--------------+----------------------------------+
|           | 2   | virt scrub   | HCR/CNTHCTL/CPTR/HSTR, CNTFRQ,  |
|           |     |              | VBAR_EL2, MMU off, tlbi alle2   |
+-----------+-----+--------------+----------------------------------+
|           | 2   |              | load Image over semihosting,    |
|           |     |              | validate header, place per      |
|           |     |              | booting.rst                     |
+-----------+-----+--------------+----------------------------------+
|           | 2   | caches clean | flush dcache, inval icache,     |
|           |     |              | args ride x20/x21, regs last    |
+-----------+-----+--------------+----------------------------------+
| payload   | 2   | fresh start  | x0 = dtb, x1-x3 = 0, DAIF       |
|           |     |              | masked, br to image entry       |
+-----------+-----+--------------+----------------------------------+

Two handoff bugs the kernel caught, both AAPCS clobbers in the final
jump. Cache maintenance was called after the register setup, x0-x18
are caller saved, so tb_flush_dcache_all() wiped the dtb pointer and
the kernel spun in setup_machine_fdt() with an invalid device tree
blob. The flush helpers also clobbered x1 (u-boot's void call
convention left mov x1, x0 in cache.S) which handed the kernel a wild
x0. The arguments ride in x20/x21 across the cache calls now, callee
saved, and the register setup is the last thing before the branch.

What is missing on purpose: no SMP bringup (secondary cores park),
no PSCI, no initrd or root filesystem handoff, single serial
console. Those come next.

Signed-off-by: Bradley Morgan <brads@mainlining.org>

1 files changed, 133 insertions, 0 deletions

diff --git a/include/compiler.h b/include/compiler.h
new file mode 100644
index 0000000..e659047
--- /dev/null
+++ b/include/compiler.h
@@ -0,0 +1,133 @@
+/*
+ * Copyright (c) 2008 Travis Geiselbrecht
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining
+ * a copy of this software and associated documentation files
+ * (the "Software"), to deal in the Software without restriction,
+ * including without limitation the rights to use, copy, modify, merge,
+ * publish, distribute, sublicense, and/or sell copies of the Software,
+ * and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be
+ * included in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
+ * IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
+ * CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
+ * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
+ * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+#ifndef __COMPILER_H
+#define __COMPILER_H
+
+#ifndef __ASSEMBLY__
+
+#if __GNUC__
+#define likely(x)       __builtin_expect(!!(x), 1)
+#define unlikely(x)     __builtin_expect(!!(x), 0)
+#define __USED __attribute__((__used__))
+#define __UNUSED __attribute__((__unused__))
+#define __PACKED __attribute__((packed))
+#define __ALIGNED(x) __attribute__((aligned(x)))
+#define __PRINTFLIKE(__fmt,__varargs) __attribute__((__format__ (__printf__, __fmt, __varargs)))
+#define __SCANFLIKE(__fmt,__varargs) __attribute__((__format__ (__scanf__, __fmt, __varargs)))
+#define __SECTION(x) __attribute((section(x)))
+#define __PURE __attribute((pure))
+#define __CONST __attribute((const))
+#define __NO_RETURN __attribute__((noreturn)) 
+#define __MALLOC __attribute__((malloc))
+#define __WEAK __attribute__((weak))
+#define __GNU_INLINE __attribute__((gnu_inline))
+#define __GET_CALLER(x) __builtin_return_address(0)
+#define __GET_FRAME(x) __builtin_frame_address(0)
+
+#define INCBIN(symname, sizename, filename, section)					\
+	__asm__ (".section " section "; .align 4; .globl "#symname);		\
+	__asm__ (""#symname ":\n.incbin \"" filename "\"");					\
+	__asm__ (".section " section "; .align 1;");						\
+	__asm__ (""#symname "_end:");										\
+	__asm__ (".section " section "; .align 4; .globl "#sizename);		\
+	__asm__ (""#sizename ": .long "#symname "_end - "#symname " - 1");	\
+	extern unsigned char symname[];										\
+	extern unsigned int sizename
+
+#define INCFILE(symname, sizename, filename) INCBIN(symname, sizename, filename, ".rodata")
+
+/* look for gcc 3.0 and above */
+#if (__GNUC__ > 3) || (__GNUC__ == 3 && __GNUC_MINOR__ >= 0)
+#define __ALWAYS_INLINE __attribute__((always_inline))
+#else
+#define __ALWAYS_INLINE
+#endif
+
+/* look for gcc 3.1 and above */
+#if !defined(__DEPRECATED) // seems to be built in in some versions of the compiler
+#if (__GNUC__ > 3) || (__GNUC__ == 3 && __GNUC_MINOR__ >= 1)
+#define __DEPRECATED __attribute((deprecated))
+#else
+#define __DEPRECATED
+#endif
+#endif
+
+/* look for gcc 3.3 and above */
+#if (__GNUC__ > 3) || (__GNUC__ == 3 && __GNUC_MINOR__ >= 3)
+/* the may_alias attribute was introduced in gcc 3.3; before that, there
+ * was no way to specify aliasiang rules on a type-by-type basis */
+#define __MAY_ALIAS __attribute__((may_alias)) 
+
+/* nonnull was added in gcc 3.3 as well */
+#define __NONNULL(x) __attribute((nonnull x))
+#else
+#define __MAY_ALIAS
+#define __NONNULL(x)
+#endif
+
+/* look for gcc 3.4 and above */
+#if (__GNUC__ > 3) || (__GNUC__ == 3 && __GNUC_MINOR__ >= 4)
+#define __WARN_UNUSED_RESULT __attribute((warn_unused_result))
+#else
+#define __WARN_UNUSED_RESULT
+#endif
+
+#if (__GNUC__ > 4) || (__GNUC__ == 4 && __GNUC_MINOR__ >= 1)
+#define __EXTERNALLY_VISIBLE __attribute__((externally_visible))
+#else
+#define __EXTERNALLY_VISIBLE
+#endif
+
+#else
+
+#define likely(x)       (x)
+#define unlikely(x)     (x)
+#define __USED
+#define __UNUSED 
+#define __PACKED 
+#define __ALIGNED(x)
+#define __PRINTFLIKE(__fmt,__varargs)
+#define __SCANFLIKE(__fmt,__varargs)
+#define __SECTION(x)
+#define __PURE
+#define __CONST
+#define __NONNULL(x)
+#define __DEPRECATED
+#define __WARN_UNUSED_RESULT
+#define __ALWAYS_INLINE
+#define __MAY_ALIAS
+#define __NO_RETURN
+#endif
+
+#endif
+
+/* TODO: add type check */
+#define countof(a) (sizeof(a) / sizeof((a)[0]))
+
+#define IS_ENABLED(define)		_IS_ENABLED(define)
+#define _comma_if_enabled_1		,
+#define _IS_ENABLED(value)		__IS_ENABLED(_comma_if_enabled_##value)
+#define __IS_ENABLED(comma)		___IS_ENABLED(comma 1, 0)
+#define ___IS_ENABLED(_, enabled, ...)	enabled
+
+#endif