#endif /* !__ASSEMBLY__ */
/*
- * gdb is expecting the following registers layout.
+ * gdb remote procotol (well most versions of it) expects the following
+ * register layout.
*
* General purpose regs:
* r0-r30: 64 bit
* sp,pc : 64 bit
- * pstate : 64 bit
- * Total: 34
+ * pstate : 32 bit
+ * Total: 33 + 1
* FPU regs:
* f0-f31: 128 bit
- * Total: 32
- * Extra regs
* fpsr & fpcr: 32 bit
- * Total: 2
+ * Total: 32 + 2
*
+ * To expand a little on the "most versions of it"... when the gdb remote
+ * protocol for AArch64 was developed it depended on a statement in the
+ * Architecture Reference Manual that claimed "SPSR_ELx is a 32-bit register".
+ * and, as a result, allocated only 32-bits for the PSTATE in the remote
+ * protocol. In fact this statement is still present in ARM DDI 0487A.i.
+ *
+ * Unfortunately "is a 32-bit register" has a very special meaning for
+ * system registers. It means that "the upper bits, bits[63:32], are
+ * RES0.". RES0 is heavily used in the ARM architecture documents as a
+ * way to leave space for future architecture changes. So to translate a
+ * little for people who don't spend their spare time reading ARM architecture
+ * manuals, what "is a 32-bit register" actually means in this context is
+ * "is a 64-bit register but one with no meaning allocated to any of the
+ * upper 32-bits... *yet*".
+ *
+ * Perhaps then we should not be surprised that this has led to some
+ * confusion. Specifically a patch, influenced by the above translation,
+ * that extended PSTATE to 64-bit was accepted into gdb-7.7 but the patch
+ * was reverted in gdb-7.8.1 and all later releases, when this was
+ * discovered to be an undocumented protocol change.
+ *
+ * So... it is *not* wrong for us to only allocate 32-bits to PSTATE
+ * here even though the kernel itself allocates 64-bits for the same
+ * state. That is because this bit of code tells the kernel how the gdb
+ * remote protocol (well most versions of it) describes the register state.
+ *
+ * Note that if you are using one of the versions of gdb that supports
+ * the gdb-7.7 version of the protocol you cannot use kgdb directly
+ * without providing a custom register description (gdb can load new
+ * protocol descriptions at runtime).
*/
-#define _GP_REGS 34
+#define _GP_REGS 33
#define _FP_REGS 32
-#define _EXTRA_REGS 2
+#define _EXTRA_REGS 3
/*
* general purpose registers size in bytes.
* pstate is only 4 bytes. subtract 4 bytes
{
unsigned int tmp;
arch_spinlock_t lockval;
+ u32 owner;
+
+ /*
+ * Ensure prior spin_lock operations to other locks have completed
+ * on this CPU before we test whether "lock" is locked.
+ */
+ smp_mb();
+ owner = READ_ONCE(lock->owner) << 16;
asm volatile(
" sevl\n"
"1: wfe\n"
"2: ldaxr %w0, %2\n"
+ /* Is the lock free? */
" eor %w1, %w0, %w0, ror #16\n"
-" cbnz %w1, 1b\n"
+" cbz %w1, 3f\n"
+ /* Lock taken -- has there been a subsequent unlock->lock transition? */
+" eor %w1, %w3, %w0, lsl #16\n"
+" cbz %w1, 1b\n"
+ /*
+ * The owner has been updated, so there was an unlock->lock
+ * transition that we missed. That means we can rely on the
+ * store-release of the unlock operation paired with the
+ * load-acquire of the lock operation to publish any of our
+ * previous stores to the new lock owner and therefore don't
+ * need to bother with the writeback below.
+ */
+" b 4f\n"
+"3:\n"
+ /*
+ * Serialise against any concurrent lockers by writing back the
+ * unlocked lock value
+ */
ARM64_LSE_ATOMIC_INSN(
/* LL/SC */
" stxr %w1, %w0, %2\n"
-" cbnz %w1, 2b\n", /* Serialise against any concurrent lockers */
- /* LSE atomics */
" nop\n"
-" nop\n")
+" nop\n",
+ /* LSE atomics */
+" mov %w1, %w0\n"
+" cas %w0, %w0, %2\n"
+" eor %w1, %w1, %w0\n")
+ /* Somebody else wrote to the lock, GOTO 10 and reload the value */
+" cbnz %w1, 2b\n"
+"4:"
: "=&r" (lockval), "=&r" (tmp), "+Q" (*lock)
- :
+ : "r" (owner)
: "memory");
}
static inline int arch_spin_is_locked(arch_spinlock_t *lock)
{
+ smp_mb(); /* See arch_spin_unlock_wait */
return !arch_spin_value_unlocked(READ_ONCE(*lock));
}
{ "x30", 8, offsetof(struct pt_regs, regs[30])},
{ "sp", 8, offsetof(struct pt_regs, sp)},
{ "pc", 8, offsetof(struct pt_regs, pc)},
- { "pstate", 8, offsetof(struct pt_regs, pstate)},
+ /*
+ * struct pt_regs thinks PSTATE is 64-bits wide but gdb remote
+ * protocol disagrees. Therefore we must extract only the lower
+ * 32-bits. Look for the big comment in asm/kgdb.h for more
+ * detail.
+ */
+ { "pstate", 4, offsetof(struct pt_regs, pstate)
+#ifdef CONFIG_CPU_BIG_ENDIAN
+ + 4
+#endif
+ },
{ "v0", 16, -1 },
{ "v1", 16, -1 },
{ "v2", 16, -1 },
memset((char *)gdb_regs, 0, NUMREGBYTES);
thread_regs = task_pt_regs(task);
memcpy((void *)gdb_regs, (void *)thread_regs->regs, GP_REG_BYTES);
+ /* Special case for PSTATE (check comments in asm/kgdb.h for details) */
+ dbg_get_reg(33, gdb_regs + GP_REG_BYTES, thread_regs);
}
void kgdb_arch_set_pc(struct pt_regs *regs, unsigned long pc)
/*
* We need to switch to kernel mode so that we can use __get_user
- * to safely read from kernel space. Note that we now dump the
- * code first, just in case the backtrace kills us.
+ * to safely read from kernel space.
*/
fs = get_fs();
set_fs(KERNEL_DS);
print_ip_sym(where);
}
-static void dump_instr(const char *lvl, struct pt_regs *regs)
+static void __dump_instr(const char *lvl, struct pt_regs *regs)
{
unsigned long addr = instruction_pointer(regs);
- mm_segment_t fs;
char str[sizeof("00000000 ") * 5 + 2 + 1], *p = str;
int i;
- /*
- * We need to switch to kernel mode so that we can use __get_user
- * to safely read from kernel space. Note that we now dump the
- * code first, just in case the backtrace kills us.
- */
- fs = get_fs();
- set_fs(KERNEL_DS);
-
for (i = -4; i < 1; i++) {
unsigned int val, bad;
}
}
printk("%sCode: %s\n", lvl, str);
+}
- set_fs(fs);
+static void dump_instr(const char *lvl, struct pt_regs *regs)
+{
+ if (!user_mode(regs)) {
+ mm_segment_t fs = get_fs();
+ set_fs(KERNEL_DS);
+ __dump_instr(lvl, regs);
+ set_fs(fs);
+ } else {
+ __dump_instr(lvl, regs);
+ }
}
static void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk)
return 1;
}
-static struct fault_info {
+static const struct fault_info {
int (*fn)(unsigned long addr, unsigned int esr, struct pt_regs *regs);
int sig;
int code;
if (!ret)
ret = init_fn(pmu);
} else {
- ret = probe_current_pmu(pmu, probe_table);
cpumask_setall(&pmu->supported_cpus);
+ ret = probe_current_pmu(pmu, probe_table);
}
if (ret) {
projects / cascardo / linux.git / commitdiff