cputlb: don't cpu_abort() if guest tries to execute outside RAM or RAM

In get_page_addr_code(), if the guest program counter turns out not to
be in ROM or RAM, we can't handle executing from it, and we call
cpu_abort(). This results in the message
  qemu: fatal: Trying to execute code outside RAM or ROM at 0x08000000
followed by a guest register dump, and then QEMU dumps core.

This situation happens in one of two cases:
 (1) a guest kernel bug, where it jumped off into nowhere
 (2) a user command line mistake, where they tried to run an image for
     board A on a QEMU model of board B, or where they didn't provide
     an image at all, and QEMU executed through a ROM or RAM full of
     NOP instructions and then fell off the end

In either case, a core dump of QEMU itself is entirely useless, and
only confuses users into thinking that this is a bug in QEMU rather
than a bug in the guest or a problem with their command line. (This
is a variation on the general idea that we shouldn't assert() on
something the user can accidentally provoke.)

Replace the cpu_abort() with something that explains the situation
a bit better and exits QEMU without dumping core.

(See LP:1062220 for several examples of confused users.)

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson  <rth@twiddle.net>
Message-id: 1466442425-11885-1-git-send-email-peter.maydell@linaro.org
1 file changed
tree: 32669ea07c5e5eef4be73601b2fbcac41416a1cd
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  23. po/
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  33. target-alpha/
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  62. accel.c
  63. aio-posix.c
  64. aio-win32.c
  65. arch_init.c
  66. async.c
  67. balloon.c
  68. block.c
  69. blockdev-nbd.c
  70. blockdev.c
  71. blockjob.c
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  73. bt-host.c
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  75. Changelog
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  80. cpu-exec-common.c
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  82. cpus.c
  83. cputlb.c
  84. device-hotplug.c
  85. device_tree.c
  86. disas.c
  87. dma-helpers.c
  88. dump.c
  89. exec.c
  90. gdbstub.c
  91. HACKING
  92. hmp-commands-info.hx
  93. hmp-commands.hx
  94. hmp.c
  95. hmp.h
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  112. os-posix.c
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  114. page_cache.c
  115. qapi-schema.json
  116. qdev-monitor.c
  117. qdict-test-data.txt
  118. qemu-bridge-helper.c
  119. qemu-char.c
  120. qemu-doc.texi
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  122. qemu-img-cmds.hx
  123. qemu-img.c
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  126. qemu-io.c
  127. qemu-nbd.c
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  129. qemu-options-wrapper.h
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  133. qemu-tech.texi
  134. qemu-timer.c
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  138. qmp.c
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  144. tcg-runtime.c
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  147. thunk.c
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  160. xen-hvm.c
  161. xen-mapcache.c