Rework dbregs, to switch the registers during context switches, and not on
each user->kernel transition via userret. Reloads of DR6/DR7 are expensive
on both native and xen.

branches: 1.12.12; 1.12.14;
Introduce PT_GETDBREGS and PT_SETDBREGS in ptrace(2) on i386 and amd64

This interface is modeled after FreeBSD API with the usage.

This replaced previous watchpoint API. The previous one was introduced
recently in NetBSD-current and remove its spurs without any
backward-compatibility.

Design choices for Debug Register accessors:
- exec() (TRAP_EXEC event) must remove debug registers from LWP
- debug registers are only per-LWP, not per-process globally
- debug registers must not be inherited after (v)forking a process
- debug registers must not be inherited after forking a thread
- a debugger is responsible to set global watchpoints/breakpoints with the
debug registers, to achieve this PTRACE_LWP_CREATE/PTRACE_LWP_EXIT event
monitoring function is designed to be used
- debug register traps must generate SIGTRAP with si_code TRAP_DBREG
- debugger is responsible to retrieve debug register state to distinguish
the exact debug register trap (DR6 is Status Register on x86)
- kernel must not remove debug register traps after triggering a trap event
a debugger is responsible to detach this trap with appropriate PT_SETDBREGS
call (DR7 is Control Register on x86)
- debug registers must not be exposed in mcontext
- userland must not be allowed to set a trap on the kernel

Implementation notes on i386 and amd64:
- the initial state of debug register is retrieved on boot and this value is
stored in a local copy (initdbregs), this value is used to initialize dbreg
context after PT_GETDBREGS
- struct dbregs is stored in pcb as a pointer and by default not initialized
- reserved registers (DR4-DR5, DR9-DR15) are ignored

Further ideas:
- restrict this interface with securelevel

Tested on real hardware i386 (Intel Pentium IV) and amd64 (Intel i7).

This commit enables 390 debug register ATF tests in kernel/arch/x86.
All tests are passing.

This commit does not cover netbsd32 compat code. Currently other interface
PT_GET_SIGINFO/PT_SET_SIGINFO is required in netbsd32 compat code in order to
validate reliably PT_GETDBREGS/PT_SETDBREGS.

This implementation does not cover FreeBSD specific defines in their
<x86/reg.h>: DBREG_DR7_LOCAL_ENABLE, DBREG_DR7_GLOBAL_ENABLE, DBREG_DR7_LEN_1
etc. These values tend to be reinvented by each tracer on its own. GNU
Debugger (GDB) works with NetBSD debug registers after adding this patch:

--- gdb/amd64bsd-nat.c.orig 2016-02-10 03:19:39.000000000 +0000
+++ gdb/amd64bsd-nat.c
@@ -167,6 +167,10 @@ amd64bsd_target (void)

#ifdef HAVE_PT_GETDBREGS

+#ifndef DBREG_DRX
+#define DBREG_DRX(d,x) ((d)->dr[(x)])
+#endif
+
static unsigned long
amd64bsd_dr_get (ptid_t ptid, int regnum)
{


Another reason to stop introducing unpopular defines covering machine
specific register macros is that these value varies across generations of
the same CPU family.

GDB demo:
(gdb) c
Continuing.

Watchpoint 2: traceme

Old value = 0
New value = 16
main (argc=1, argv=0x7f7fff79fe30) at test.c:8
8 printf("traceme=%d\n", traceme);

(Currently the GDB interface is not reliable due to NetBSD support bugs)

Sponsored by <The NetBSD Foundation>

Allow to mix single-step with hardware assisted watchpoints on amd64

This case needs new handling in trap recognition.

Sponsored by <The NetBSD Foundation>

branches: 1.10.2;
Add support for hardware assisted watchpoints/breakpoints API in ptrace(2)

Add new ptrace(2) calls:
- PT_COUNT_WATCHPOINTS - count the number of available hardware watchpoints
- PT_READ_WATCHPOINT - read struct ptrace_watchpoint from the kernel state
- PT_WRITE_WATCHPOINT - write new struct ptrace_watchpoint state, this
includes enabling and disabling watchpoints

The ptrace_watchpoint structure contains MI and MD parts:

typedef struct ptrace_watchpoint {
int pw_index; /* HW Watchpoint ID (count from 0) */
lwpid_t pw_lwpid; /* LWP described */
struct mdpw pw_md; /* MD fields */
} ptrace_watchpoint_t;

For example amd64 defines MD as follows:
struct mdpw {
void *md_address;
int md_condition;
int md_length;
};

These calls are protected with the __HAVE_PTRACE_WATCHPOINTS guard.

Tested on amd64, initial support added for i386 and XEN.

Sponsored by <The NetBSD Foundation>

branches: 1.9.44; 1.9.64; 1.9.68;
Remove clause 3 and 4 from TNF licenses

branches: 1.8.44; 1.8.46; 1.8.48;
Merge newlock2 to head.

branches: 1.7.8;
The comment says this is the same as the i386 counterpart, so catch
up on de-__P and ANSIficiation that i386 has.

branches: 1.6.2; 1.6.4; 1.6.6;
Change "inline" back to "__inline" in .h files -- C99 is still too
new, and some apps compile things in C89 mode. C89 keywords stay.

As per core@.

branches: 1.5.2; 1.5.4; 1.5.6;
Remove leading __ from __(const|inline|signed|volatile) -- it is obsolete.

merge ktrace-lwp.

branches: 1.3.16;
Reduce code duplication by adding mi_userret() in sys/userret.h
containing signal posting, kernel-exit handling and sa_upcall processing.

XXX the pc532, sparc, sparc64 and vax ports should have their
XXX userret() code rearranged to use this.

Move UCB-licensed code from 4-clause to 3-clause licence.

Patches provided by Joel Baker in PR 22364, verified by myself.

branches: 1.1.2;
Rename the x86_64 port to amd64, as this is the actual name used for
the processor family now. x86_64 is kept as the MACHINE_ARCH value,
since it's already widely used (by e.g. the toolchain, etc), and
by other operating systems.