1 /*
   2  * This file and its contents are supplied under the terms of the
   3  * Common Development and Distribution License ("CDDL"), version 1.0.
   4  * You may only use this file in accordance with the terms of version
   5  * 1.0 of the CDDL.
   6  *
   7  * A full copy of the text of the CDDL should have accompanied this
   8  * source.  A copy of the CDDL is also available via the Internet at
   9  * http://www.illumos.org/license/CDDL.
  10  */
  11 
  12 /*
  13  * Copyright 2023 Oxide Computer Company
  14  */
  15 
  16 /*
  17  * This program pairs with the xregs_dump.32 and xregs_dump.64 program. It's
  18  * main purpose is to use /proc to overwrite the FPU contents right before our
  19  * target program calls xsu_getfpu().
  20  *
  21  * To accomplish this we end up using libproc for some mischief via support
  22  * routines. In particular we go through the following to logically accomplish
  23  * this:
  24  *
  25  *   o Generate the target FPU contents that we'll write (seeded from the CLI)
  26  *   o Explicitly create the process, which will be stopped.
  27  *   o Set it to be killed if we die.
  28  *   o Find the xsu_getfpu() symbol in the target and set a breakpoint.
  29  *   o Resume execution of the process.
  30  *   o When the break point hits, use libproc to set the FPU.
  31  *   o Delete the breakpoint and resume the process, which will print the FPU
  32  *     regs to a designated file.
  33  *   o Verify the process successfully terminates and returns 0.
  34  *
  35  * A critical assumption here is that our hardware support is not going to
  36  * change between processes (something that may be mucked around with via
  37  * environment variables for rtld).
  38  */
  39 
  40 #include <err.h>
  41 #include <stdlib.h>
  42 #include <errno.h>
  43 #include <sys/types.h>
  44 #include <sys/wait.h>
  45 #include <string.h>
  46 
  47 #include "xsave_util.h"
  48 
  49 static xsu_fpu_t fpu;
  50 
  51 int
  52 main(int argc, char *argv[])
  53 {
  54         uint32_t seed, hwsup;
  55         unsigned long ul;
  56         char *eptr;
  57         prxregset_t *prx;
  58         size_t prx_len;
  59         xsu_proc_t xp;
  60 
  61         if (argc != 5) {
  62                 errx(EXIT_FAILURE, "missing args: <prog> <output file> "
  63                     "<seed> <func>");
  64         }
  65 
  66         errno = 0;
  67         ul = strtoul(argv[3], &eptr, 0);
  68         if (errno != 0 || *eptr != '\0') {
  69                 errx(EXIT_FAILURE, "seed value is bad: %s", argv[3]);
  70         }
  71 
  72 #if defined(_LP64)
  73         if (ul > UINT32_MAX) {
  74                 errx(EXIT_FAILURE, "seed %s, exceeds [0, UINT32_MAX]", argv[3]);
  75         }
  76 #endif
  77 
  78         seed = (uint32_t)ul;
  79         hwsup = xsu_hwsupport();
  80         xsu_fill(&fpu, hwsup, seed);
  81         xsu_fpu_to_xregs(&fpu, hwsup, &prx, &prx_len);
  82 
  83         (void) memset(&xp, 0, sizeof (xsu_proc_t));
  84         xp.xp_prog = argv[1];
  85         xp.xp_arg = argv[2];
  86         xp.xp_object = "a.out";
  87         xp.xp_symname = argv[4];
  88 
  89         xsu_proc_bkpt(&xp);
  90         /* We know that libc always creates a default thread with id of 1 */
  91         if (Plwp_setxregs(xp.xp_proc, 1, prx, prx_len) != 0) {
  92                 err(EXIT_FAILURE, "failed to set target's xregs");
  93         }
  94 
  95         xsu_proc_finish(&xp);
  96 
  97         if (WEXITSTATUS(xp.xp_wait) != EXIT_SUCCESS) {
  98                 errx(EXIT_FAILURE, "our target process didn't exit non-zero, "
  99                     "got %d", WEXITSTATUS(xp.xp_wait));
 100         }
 101 
 102         return (EXIT_SUCCESS);
 103 }