Re: [PATCH v3] Implement "info proc mappings" for NetBSD

Kamil Rytarowski
2020-04-11T21:29:44Z

On 11.04.2020 23:05, Simon Marchi wrote:
> On 2020-04-06 5:37 a.m., Kamil Rytarowski wrote:
>> @@ -39,3 +42,148 @@ nbsd_nat_target::pid_to_exec_file (int pid)
>> return NULL;
>> return buf;
>> }
>> +
>> +/* Retrieve all the memory regions in the specified process. */
>> +
>> +static gdb::unique_xmalloc_ptr<struct kinfo_vmentry[]>
>> +nbsd_kinfo_get_vmmap (pid_t pid, size_t *size)
>> +{
>> + int mib[5] = {CTL_VM, VM_PROC, VM_PROC_MAP, pid,
>> + sizeof (struct kinfo_vmentry)};
>> +
>> + size_t length = 0;
>> + if (sysctl (mib, ARRAY_SIZE (mib), NULL, &length, NULL, 0))
>> + {
>> + *size = 0;
>> + return NULL;
>> + }
>> +
>> + /* Prereserve more space. */
>> + length = length * 5 / 3;
>
> Why is this needed?
>

This length is volatile and can be larger on the 2nd sysctl(3) call. We
can call this function against a running process that can enlarge its
usage of address space in this time window.

>> +
>> + gdb::unique_xmalloc_ptr<struct kinfo_vmentry[]> kiv
>> + ((struct kinfo_vmentry *) xcalloc (length, 1));
>
> Let's use XCNEWVAR here. It doesn't matter in this case, but for consistency. It does
> check that we are not trying to allocate space for a non-POD type. You can use like:
>
> XCNEWVAR (kinfo_vmentry, length)
>
> You can also use XNEWVAR if you don't care about the buffer being initialized to zeros.
>

OK.

>> diff --git a/gdb/nbsd-tdep.h b/gdb/nbsd-tdep.h
>> index c99a8b537b6..81bdb2510f5 100644
>> --- a/gdb/nbsd-tdep.h
>> +++ b/gdb/nbsd-tdep.h
>> @@ -25,4 +25,22 @@ struct link_map_offsets *nbsd_lp64_solib_svr4_fetch_link_map_offsets (void);
>>
>> int nbsd_pc_in_sigtramp (CORE_ADDR, const char *);
>>
>> +/* Output the header for "info proc mappings". ADDR_BIT is the size
>> + of a virtual address in bits. */
>> +
>> +extern void nbsd_info_proc_mappings_header (int addr_bit);
>> +
>> +/* Output description of a single memory range for "info proc
>> + mappings". ADDR_BIT is the size of a virtual address in bits. The
>> + KVE_START, KVE_END, KVE_OFFSET, KVE_FLAGS, and KVE_PROTECTION
>> + parameters should contain the value of the corresponding fields in
>> + a 'struct kinfo_vmentry'. The KVE_PATH parameter should contain a
>> + pointer to the 'kve_path' field in a 'struct kinfo_vmentry'. */
>> +
>> +extern void nbsd_info_proc_mappings_entry (int addr_bit, ULONGEST kve_start,
>> + ULONGEST kve_end,
>> + ULONGEST kve_offset,
>> + int kve_flags, int kve_protection,
>> + const void *kve_path);
>
> I'd make the last parameter a `const char *` directly, since this is what the function
> expects to receive. And remove the reinterpret_casts.
>

OK.

> Simon
>