Initial fix of upstream merge.

Author: Geoffrey Challen

CHANGES

@@ -12,6 +12,96 @@ various other people, all of whom are (hopefully) listed below.
 ------------------------------------------------------------
 
 
+OS/161 2.0.3 released 20160124
+------------------------------
+
+20170124 dholland in base
+   - Remove obsolete, redundant, or not useful test programs:
+	guzzle (same as hog)
+	kitchen (equivalent to multiexec -n 4 sink)
+	sink (same as conman)
+	sty (equivalent to multiexec -n 6 hog)
+	quinthuge (offers little over triplehuge, can be done with multiexec)
+	quintmat, quintsort (ditto)
+
+20170118 dholland in base
+   - Make -g -Og the flags when "debug" is enabled in a kernel config
+     (which it is in the non-OPT ones) and add an additional kernel
+     config verb "debugonly" to get just -g in case that becomes
+     necessary. This should significantly improve the output code
+     quality from gcc without compromising debugging. (However, gcc
+     being gcc, it also sometimes leads to additional spurious
+     warnings that don't occur with either -g or -O2.)
+
+20170118 dholland in base
+   - Add a MI mainbus_debugger() function that goes through the right
+     MD paths to trigger the debugger hook in the ltrace device. Also
+     add a menu function "debug" to trigger it.
+
+20170118 dholland in base
+   - Add some bits to forktest to try to catch the case where the fork
+     child returns from the next system call instead of from fork.
+     (Which is a moderately common bug, caused by races copying the
+     trapframe information in the kernel.)
+
+20170117 dholland in base
+   - Add a menu command "deadlock" to intentionally deadlock.
+
+20170117 dholland in base, from Sam Fishman
+   - Fix parallelvm -w so that if one of the forks fails the whole
+     thing doesn't wedge.
+
+20170117 dholland in base, reported by Sam Fishman
+   - Don't do semfs I/O from NULL, or from/to insufficiently sized
+     buffers. Like the 20150615 change, except covering the rest of
+     the tests that use the semaphores that were doing it wrong:
+     multiexec, parallelvm, and schedpong.
+
+20170117 dholland in base, from Sam Fishman
+   - Add assembler directives to exception-mips1.S that tell gdb how
+     to read trap frames correctly. Garbage-collect old stuff left
+     over from making it work with a (much) older version of gdb a
+     long time back. This also usually makes it possible to trace back
+     through a syscall into a userlevel process; include a gdb script
+     with tools for making this useful.
+
+20170117 dholland in base
+   - Merge the deadlock detector into base. It was a success last year.
+   - Mention in the comments that the hangman hooks in locks need to
+     be called atomically.
+
+20170117 dholland in base, reported by Jeffrey Cai, patch from Sam Fishman
+   - Fix off-by-one in tac that makes it skip the first line of files.
+
+20170117 dholland in base, from Sam Fishman
+   - Make badcall's "pipe with unaligned pointer" test clean up after
+     itself if the operation succeeds. Otherwise it leaks fds and that
+     can intefere with other tests.
+
+20170116 dholland in base, reported by Sam Fishman
+   - Don't allow opening an entirely empty pathname to succeed, and
+     don't allow success for this case in badcall either.
+
+20170116 dholland in base, from Sasha Fedorova
+   - Fix write buffer size in filetest.
+
+20160325 dholland in base
+   - Fix macro parenthesis bug in ROUNDUP().
+
+20160304 dholland in base, from Sam Fishman
+   - Make runtest.py handle spacing in the command strings it's given.
+
+20160216 dholland in base
+   - Fix spacing problems in ls -l output for large files.
+
+20160203 dholland in base
+   - Expand comments attached to cpustacks[]/cputhreads[], prompted by
+     James Mickens.
+
+20160125 dholland in base, from Nikhil Benesch.
+   - Fix stupid argument handling bug in test.py.
+
+
 OS/161 2.0.2 released 20160112
 ------------------------------
 
@@ -53,6 +143,14 @@ OS/161 2.0.2 released 20160112
      anyway. If they aren't actually constant because of bugs, reading
      a stale or even garbage value is not going to hurt more.
 
+20160107 dholland in deadlock-detector
+   - Add a deadlock detector. For now this will be supplied to
+     instructors as a supplementary patch, because it intrudes into
+     the synchronization primitives and affects what students do
+     there. We are planning to try it on our students this coming
+     semester; if that works out well, I'll probably merge it into
+     base.
+
 20160107 dholland in base
    - In testbin/multiexec, if fork fails partway through, continue
      with the forks we got. Otherwise the subprocesses we started hang

kern/arch/mips/include/trapframe.h

@@ -69,8 +69,6 @@ struct trapframe {
 	uint32_t tf_s7;
 	uint32_t tf_t8;
 	uint32_t tf_t9;
-	uint32_t tf_k0;		/* dummy (see exception-mips1.S comments) */
-	uint32_t tf_k1;		/* dummy */
 	uint32_t tf_gp;
 	uint32_t tf_sp;
 	uint32_t tf_s8;

kern/arch/mips/locore/exception-mips1.S

@@ -101,6 +101,8 @@ mips_general_end:
    .text
    .type common_exception,@function
    .ent common_exception
+   .cfi_startproc
+   .cfi_signal_frame
 common_exception:
    mfc0 k0, c0_status		/* Get status register */
    andi k0, k0, CST_KUp		/* Check the we-were-in-user-mode bit */
@@ -130,11 +132,12 @@ common_exception:
     */
 
    /*
-    * Allocate stack space for 37 words to hold the trap frame,
+    * Allocate stack space for 35 words to hold the trap frame,
     * plus four more words for a minimal argument block, plus
     * one more for proper (64-bit) stack alignment.
     */
-   addi sp, sp, -168
+   addi sp, sp, -160
+   .cfi_def_cfa sp, 0
 
    /*
     * Save general registers.
@@ -143,70 +146,89 @@ common_exception:
     *
     * The order here must match mips/include/trapframe.h.
     *
-    * gdb disassembles this code to try to figure out what registers
-    * are where, and it isn't very bright. So in order to make gdb be
-    * able to trace the stack back through here, we play some silly
-    * games.
+    * gdb uses the .cfi_offset assembler directives inserted below to
+    * to figure out where each register is stored. Since we've marked
+    * this function as a "signal handler" with the .cfi_signal_frame
+    * directive, gdb won't complain about the fact that the stack
+    * is noncontiguous (if we're coming from userland).
     *
-    * In particular:
-    *    (1) We store the return address register into the epc slot,
-    *        which makes gdb think it's the return address slot. Then
-    *        we store the real epc value over that.
-    *    (2) We store the current sp into the sp slot, which makes gdb
-    *        think it's the stack pointer slot. Then we store the real
-    *        value.
-    *    (3) gdb also assumes that saved registers in a function are
-    *        saved in order. This is why we put epc where it is, and
-    *        handle the real value of ra afterwards.
-    *    (4) Because gdb will think we're saving k0 and k1, we need to
-    *        leave slots for them in the trap frame, even though the
-    *        stuff we save there is useless.
+    * We also play a trick with the return address: we mark the ra
+    * register as stored to the stack normally and then mark the
+    * return address for *this* function as being in the k1 register
+    * using the .cfi_return_column directive. gdb is then able to
+    * recognize that the ra we've stored here is the return address
+    * for the function that was executing when this exception was
+    * taken.
     *
-    * This logic has not been tested against a recent gdb and has
-    * probably bitrotted. Someone(TM) should figure out what gdb
-    * currently expects -- or maybe even patch gdb to understand a
-    * better form of this that doesn't waste so many cycles.
+    * All of the cfi (call frame information) material is compiled
+    * into the .eh_frame section of the compiled kernel.
     */
-   sw ra, 160(sp)	/* dummy for gdb */
-   sw s8, 156(sp)	/* save s8 */
-   sw sp, 152(sp)	/* dummy for gdb */
-   sw gp, 148(sp)	/* save gp */
-   sw k1, 144(sp)	/* dummy for gdb */
-   sw k0, 140(sp)	/* dummy for gdb */
-
-   sw k1, 152(sp)	/* real saved sp */
+   sw s8, 148(sp)	/* save s8 */
+   .cfi_offset s8, 148
+   sw k1, 144(sp)	/* real saved sp */
+   .cfi_offset sp, 144
+   sw gp, 140(sp)	/* save gp */
    nop			/* delay slot for store */
+   .cfi_offset gp, 140
 
+   .cfi_return_column k1
    mfc0 k1, c0_epc	/* Copr.0 reg 13 == PC for exception */
-   sw k1, 160(sp)	/* real saved PC */
+   sw k1, 152(sp)	/* real saved PC */
+   .cfi_offset k1, 152
 
    sw t9, 136(sp)
+   .cfi_offset t9, 136
    sw t8, 132(sp)
+   .cfi_offset t8, 132
    sw s7, 128(sp)
+   .cfi_offset s7, 128
    sw s6, 124(sp)
+   .cfi_offset s6, 124
    sw s5, 120(sp)
+   .cfi_offset s5, 120
    sw s4, 116(sp)
+   .cfi_offset s4, 116
    sw s3, 112(sp)
+   .cfi_offset s3, 112
    sw s2, 108(sp)
+   .cfi_offset s2, 108
    sw s1, 104(sp)
+   .cfi_offset s1, 104
    sw s0, 100(sp)
+   .cfi_offset s0, 100
    sw t7, 96(sp)
+   .cfi_offset t7, 96
    sw t6, 92(sp)
+   .cfi_offset t6, 92
    sw t5, 88(sp)
+   .cfi_offset t5, 88
    sw t4, 84(sp)
+   .cfi_offset t4, 84
    sw t3, 80(sp)
+   .cfi_offset t3, 80
    sw t2, 76(sp)
+   .cfi_offset t2, 76
    sw t1, 72(sp)
+   .cfi_offset t1, 72
    sw t0, 68(sp)
+   .cfi_offset t0, 68
    sw a3, 64(sp)
+   .cfi_offset a3, 64
    sw a2, 60(sp)
+   .cfi_offset a2, 60
    sw a1, 56(sp)
+   .cfi_offset a1, 56
    sw a0, 52(sp)
+   .cfi_offset a0, 52
    sw v1, 48(sp)
+   .cfi_offset v1, 48
    sw v0, 44(sp)
+   .cfi_offset v0, 44
    sw AT, 40(sp)
+   .cfi_offset AT, 40
 
    sw ra, 36(sp)
+   .cfi_offset ra, 36
 
    /*
     * Save special registers.
@@ -227,11 +249,6 @@ common_exception:
    mfc0 t4, c0_cause
    sw   t4, 24(sp)               /* Copr.0 reg 13 == exception cause */
 
-   /*
-    * Pretend to save $0 for gdb's benefit.
-    */
-   sw $0, 12(sp)
-
    /*
     * Load the curthread register if coming from user mode.
     */
@@ -260,9 +277,6 @@ common_exception:
    jal mips_trap		/* call it */
    nop				/* delay slot */
 
-   /* Something must be here or gdb doesn't find the stack frame. */
-   nop
-
    /*
     * Now restore stuff and return from the exception.
     * Interrupts should be off.
@@ -309,20 +323,17 @@ exception_return:
    lw s7, 128(sp)
    lw t8, 132(sp)
    lw t9, 136(sp)
+   lw gp, 140(sp)		/* restore gp */
+   /*     144(sp)		   stack pointer - below */
+   lw s8, 148(sp)		/* restore s8 */
+   lw k1, 152(sp)		/* fetch exception return PC into k1 */
 
-   /*     140(sp)		   "saved" k0 was dummy garbage anyway */
-   /*     144(sp)		   "saved" k1 was dummy garbage anyway */
-
-   lw gp, 148(sp)		/* restore gp */
-   /*     152(sp)		   stack pointer - below */
-   lw s8, 156(sp)		/* restore s8 */
-   lw k0, 160(sp)		/* fetch exception return PC into k0 */
-
-   lw sp, 152(sp)		/* fetch saved sp (must be last) */
+   lw sp, 144(sp)		/* fetch saved sp (must be last) */
 
    /* done */
-   jr k0			/* jump back */
+   jr k1			/* jump back */
    rfe				/* in delay slot */
+   .cfi_endproc
    .end common_exception
 
 /*

kern/arch/mips/locore/trap.c

@@ -130,8 +130,8 @@ mips_trap(struct trapframe *tf)
 	bool iskern;
 	int spl;
 
-	/* The trap frame is supposed to be 37 registers long. */
-	KASSERT(sizeof(struct trapframe)==(37*4));
+	/* The trap frame is supposed to be 35 registers long. */
+	KASSERT(sizeof(struct trapframe)==(35*4));
 
 	/*
 	 * Extract the exception code info from the register fields.

kern/arch/mips/thread/cpu.c

@@ -54,6 +54,14 @@
  *
  * These arrays are also used to start up new CPUs, for roughly the
  * same reasons.
+ *
+ * The values in the current cpu's slots in these arrays are updated
+ * with the current thread's information in trap.c before heading to
+ * userlevel, as well as being initialized in cpu_machdep_init below.
+ * This means that (unless something really horrible happens) on entry
+ * to the kernel, and when a new CPU starts up in cpu_start_secondary,
+ * they will have the information needed to figure out who we are and
+ * proceed.
  */
 
 vaddr_t cpustacks[MAXCPUS];

kern/arch/sys161/dev/lamebus_machdep.c

@@ -42,6 +42,7 @@
 #include <mainbus.h>
 #include <sys161/bus.h>
 #include <lamebus/lamebus.h>
+#include <lamebus/ltrace.h>
 #include "autoconf.h"
 
 /*
@@ -275,6 +276,15 @@ mainbus_send_ipi(struct cpu *target)
 	lamebus_assert_ipi(lamebus, target);
 }
 
+/*
+ * Trigger the debugger.
+ */
+void
+mainbus_debugger(void)
+{
+	ltrace_stop(0);
+}
+
 /*
  * Interrupt dispatcher.
  */

kern/conf/DUMBVM

@@ -3,7 +3,9 @@
 
 include conf/conf.kern		# get definitions of available options
 
-debug				# Compile with debug info.
+debug				# Compile with debug info and -Og.
+#debugonly			# Compile with debug info only (no -Og).
+options hangman 		# Deadlock detection. (off by default)
 
 #
 # Device drivers for hardware.

kern/conf/DUMBVM-OPT

@@ -7,6 +7,7 @@
 include conf/conf.kern		# get definitions of available options
 
 #debug				# Optimizing compile (no debug).
+#debugonly
 options noasserts		# Disable assertions.
 
 #

kern/conf/GENERIC

@@ -5,6 +5,8 @@
 include conf/conf.kern		# get definitions of available options
 
 debug				# Compile with debug info.
+#debugonly			# Compile with debug info only (no -Og).
+#options hangman 		# Deadlock detection. (off by default)
 
 #
 # Device drivers for hardware.