Re: [PATCH] linux-user: Add an argument QEMU_MMAP_BASE to set custom mmap base address in qemu user mode

[Laurent Vivier]

Le 29/02/2020 à 01:43, Lirong Yuan a écrit :
> 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

Could you give more details and some examples?

Thanks,
Laurent

>> 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/
>