[Bug 1918302] Re: qemu-system-arm segfaults while servicing SYS_HEAPINFO

[Alex Bennée]

I think this was fixed earlier by:

commit 095f8c029319b79cce487e3b566cd826b93da3e6
Author: Keith Packard <keithp@keithp.com>
Date:   Fri Jan 8 22:42:51 2021 +0000

    semihosting: Support SYS_HEAPINFO when env->boot_info is not set

    env->boot_info is only set in some ARM startup paths, so we cannot
    rely on it to support the SYS_HEAPINFO semihosting function. When not
    available, fallback to finding a RAM memory region containing the
    current stack and use the base of that.

    Signed-off-by: Keith Packard <keithp@keithp.com>
    Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
    Message-Id: <20210107170717.2098982-5-keithp@keithp.com>
    Message-Id: <20210108224256.2321-16-alex.bennee@linaro.org>

Not withstanding the other fix to the ARG usage.

** Changed in: qemu
       Status: New => In Progress

** Changed in: qemu
     Assignee: (unassigned) => Alex Bennée (ajbennee)

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https://bugs.launchpad.net/bugs/1918302

Title:
  qemu-system-arm segfaults while servicing SYS_HEAPINFO

Status in QEMU:
  In Progress

Bug description:
  I compiled QEMU version 5.2.0 from source on Ubuntu 18.04, and tried
  to use it to run the attached bare-metal Arm hello-world image, using
  the command line

  qemu-system-arm -M microbit -semihosting -nographic -device
  loader,file=hello.hex

  The result was that qemu-system-arm itself died of a segfault.
  Compiling it for debugging, the location of the segfault was in
  target/arm/arm-semi.c, in the case handler for the semihosting call
  TARGET_SYS_HEAPINFO, on line 1020 which assigns to 'rambase':

              const struct arm_boot_info *info = env->boot_info;
              target_ulong rambase = info->loader_start;

  and the problem seems to be that 'info', aka env->boot_info, is NULL
  in this context.

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