[Lldb-commits] [lldb] [lldb] Add SBProcess methods for get/set/use address masks (PR #83095)

[Jason Molenda via lldb-commits]

================
@@ -407,6 +407,117 @@ class LLDB_API SBProcess {
   ///     the process isn't loaded from a core file.
   lldb::SBFileSpec GetCoreFile();
 
+  /// \{
+  /// \group Mask Address Methods
+  ///
+  /// \a type
+  /// All of the methods in this group take \a type argument
+  /// which is an AddressMaskType enum value.
+  /// There can be different address masks for code addresses and
+  /// data addresses, this argument can select which to get/set,
+  /// or to use when clearing non-addressable bits from an address.
+  /// On AArch32 code with arm+thumb code, where instructions start
+  /// on even addresses, the 0th bit may be used to indicate that
+  /// a function is thumb code.  On such a target, the eAddressMaskTypeCode
+  /// may clear the 0th bit from an address to get the actual address.
+  ///
+  /// \a addr_range
+  /// Many of the methods in this group take an \a addr_range argument
+  /// which is an AddressMaskRange enum value.
+  /// Needing to specify the address range is highly unusual, and the
+  /// default argument can be used in nearly all circumstances.
+  /// On some architectures like AArch64, it is possible to have
+  /// different page table setups for low and high memory, so different
+  /// numbers of bits relevant to addressing. It is possible to have
+  /// a program running in one half of memory and accessing the other
+  /// as heap, so we need to maintain two different sets of address masks
+  /// to debug this correctly.
+
+  /// Get the current address mask that will be applied to addresses
+  /// before reading from memory.
+  ///
+  /// \param[in] type
+  ///     See \ref Mask Address Methods descripton of this argument.
+  ///     eAddressMaskTypeAny is often a suitable value when code and
+  ///     data masks are the same on a given target.
+  ///
+  /// \param[in] addr_range
+  ///     See \ref Mask Address Methods descripton of this argument.
+  ///     This will default to eAddressMaskRangeLow which is the
+  ///     only set of masks used normally.
+  ///
+  /// \return
+  ///     The address mask currently in use.  Bits which are not used
+  ///     for addressing will be set to 1 in the mask.
+  lldb::addr_t GetAddressMask(
+      lldb::AddressMaskType type,
+      lldb::AddressMaskRange addr_range = lldb::eAddressMaskRangeLow);
+
+  /// Set the current address mask that can be applied to addresses
+  /// before reading from memory.
+  ///
+  /// \param[in] type
+  ///     See \ref Mask Address Methods descripton of this argument.
+  ///     eAddressMaskTypeAll is often a suitable value when the
+  ///     same mask is being set for both code and data.
+  ///
+  /// \param[in] mask
+  ///     The address mask to set.  Bits which are not used for addressing
+  ///     should be set to 1 in the mask.
+  ///
+  /// \param[in] addr_range
+  ///     See \ref Mask Address Methods descripton of this argument.
+  ///     This will default to eAddressMaskRangeLow which is the
+  ///     only set of masks used normally.
+  void SetAddressMask(
+      lldb::AddressMaskType type, lldb::addr_t mask,
+      lldb::AddressMaskRange addr_range = lldb::eAddressMaskRangeLow);
+
+  /// Set the number of bits used for addressing in this Process.
+  ///
+  /// In some environments, the number of bits that are used for addressing
+  /// is the natural representation instead of a mask, but lldb
+  /// internally represents this as a mask.  This method calculates
+  /// the addressing mask that lldb uses that number of addressable bits.
----------------
jasonmolenda wrote:

Thanks, let me rewrite it to say "darwin likes addressable bits" directly :) 
On Linux the kernel provides a mask to apply to addresses to remove metadata, it's the most general representation so that's what we use internally in lldb.  But with Darwin on AArch64, we're only concerned with the low order number of bits that are used for addressing -- the addressable bits.  It's possible to calculate the mask incorrectly (I'm fixing my own bug with addressable-bits==64 in this patch), so I want to provide API for environments like Darwin where that's what the data they'll have from the OS etc.

https://github.com/llvm/llvm-project/pull/83095