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Re: [PATCH] linux-user: Add an argument QEMU_MMAP_BASE to set custom mma


From: Lirong Yuan
Subject: Re: [PATCH] linux-user: Add an argument QEMU_MMAP_BASE to set custom mmap base address in qemu user mode
Date: Fri, 28 Feb 2020 16:43:24 -0800

On Fri, Feb 21, 2020 at 5:09 PM Lirong Yuan <address@hidden> wrote:
>
> This change allows us to set custom base address for guest programs. It is 
> needed to allow qemu to work with Thread Sanitizer (TSan), which has specific 
> boundary definitions for memory mappings on different platforms:
> https://github.com/llvm/llvm-project/blob/master/compiler-rt/lib/tsan/rtl/tsan_platform.h
>
> Signed-off-by: Lirong Yuan <address@hidden>
> ---
>  linux-user/main.c | 12 ++++++++++++
>  linux-user/mmap.c |  3 ++-
>  linux-user/qemu.h |  5 +++++
>  3 files changed, 19 insertions(+), 1 deletion(-)
>
> diff --git a/linux-user/main.c b/linux-user/main.c
> index fba833aac9..c01af6bfee 100644
> --- a/linux-user/main.c
> +++ b/linux-user/main.c
> @@ -336,6 +336,16 @@ static void handle_arg_guest_base(const char *arg)
>      have_guest_base = 1;
>  }
>
> +static void handle_arg_mmap_base(const char *arg)
> +{
> +    int err = qemu_strtoul(arg, NULL, 0, &mmap_base);
> +    if (err) {
> +        fprintf(stderr, "Invalid mmap_base: %s, err: %d\n", arg, err);
> +        exit(EXIT_FAILURE);
> +    }
> +    mmap_next_start = mmap_base;
> +}
> +
>  static void handle_arg_reserved_va(const char *arg)
>  {
>      char *p;
> @@ -440,6 +450,8 @@ static const struct qemu_argument arg_table[] = {
>       "uname",      "set qemu uname release string to 'uname'"},
>      {"B",          "QEMU_GUEST_BASE",  true,  handle_arg_guest_base,
>       "address",    "set guest_base address to 'address'"},
> +    {"mmap_base",  "QEMU_MMAP_BASE",   true,  handle_arg_mmap_base,
> +     "",           "begin allocating guest pages at this host address"},
>      {"R",          "QEMU_RESERVED_VA", true,  handle_arg_reserved_va,
>       "size",       "reserve 'size' bytes for guest virtual address space"},
>      {"d",          "QEMU_LOG",         true,  handle_arg_log,
> diff --git a/linux-user/mmap.c b/linux-user/mmap.c
> index 8685f02e7e..3f35543acf 100644
> --- a/linux-user/mmap.c
> +++ b/linux-user/mmap.c
> @@ -189,6 +189,7 @@ static int mmap_frag(abi_ulong real_start,
>  # define TASK_UNMAPPED_BASE  0x40000000
>  #endif
>  abi_ulong mmap_next_start = TASK_UNMAPPED_BASE;
> +abi_ulong mmap_base = TASK_UNMAPPED_BASE;
>
>  unsigned long last_brk;
>
> @@ -299,7 +300,7 @@ abi_ulong mmap_find_vma(abi_ulong start, abi_ulong size, 
> abi_ulong align)
>
>              if ((addr & (align - 1)) == 0) {
>                  /* Success.  */
> -                if (start == mmap_next_start && addr >= TASK_UNMAPPED_BASE) {
> +                if (start == mmap_next_start && addr >= mmap_base) {
>                      mmap_next_start = addr + size;
>                  }
>                  return addr;
> diff --git a/linux-user/qemu.h b/linux-user/qemu.h
> index 560a68090e..83c00cfea2 100644
> --- a/linux-user/qemu.h
> +++ b/linux-user/qemu.h
> @@ -161,6 +161,11 @@ void task_settid(TaskState *);
>  void stop_all_tasks(void);
>  extern const char *qemu_uname_release;
>  extern unsigned long mmap_min_addr;
> +/*
> + * mmap_base is minimum address to use when allocating guest pages. All guest
> + * pages will be allocated at this (guest) address or higher addresses.
> + */
> +extern abi_ulong mmap_base;
>
>  /* ??? See if we can avoid exposing so much of the loader internals.  */
>
> --
> 2.25.0.265.gbab2e86ba0-goog
>

Friendly ping~

Link to the page for the patch on patchwork:
http://patchwork.ozlabs.org/patch/1242370/



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