Re: [RFA Darwin]: Add push_dummy_call for i386

Mark Kettenis
2009-07-03T16:49:58Z

> Date: Fri, 3 Jul 2009 17:51:52 +0200
> From: Tristan Gingold <gingold@adacore.com>
>
> Hi,
>
> Darwin i386 ABI is slightly different from the SVR4 one. In particular
> stack alignment is 16. As a consquence, i386 Darwin can't use the standard
> i386-tdeo.c push_dummy_call and this patch provides a Darwin version of this
> call.
>
> Regtested on i386 Darwin.
> Tristan.

Tristan, can you provide unified diffs instead of context diffs? It's much easier to read the unified ones.

> 2009-07-03 Tristan Gingold <gingold@adacore.com>
>
> * i386-darwin-tdep.c (i386_m128_p): New function.
> (i386_darwin_arg_type_alignment): Ditto.
> (i386_darwin_push_dummy_call): Ditto.
> (i386_darwin_init_abi): Define Darwin specific push_dummy_call.
> Adjust long_double size. Adjust pc offset in setjump buffer.
>
> Index: i386-darwin-tdep.c
> ===================================================================
> RCS file: /cvs/src/src/gdb/i386-darwin-tdep.c,v
> retrieving revision 1.6
> diff -c -p -r1.6 i386-darwin-tdep.c
> *** i386-darwin-tdep.c 3 Jul 2009 12:06:36 -0000 1.6
> --- i386-darwin-tdep.c 3 Jul 2009 15:48:55 -0000
> *************** darwin_dwarf_signal_frame_p (struct gdba
> *** 109,114 ****
> --- 109,241 ----
> return i386_sigtramp_p (this_frame);
> }
>
> + /* Check wether TYPE is a 128-bit vector (__m128, __m128d or __m128i). */
> +
> + static inline int
> + i386_m128_p (struct type *type)
> + {
> + return TYPE_CODE (type) == TYPE_CODE_ARRAY && TYPE_VECTOR (type)
> + && TYPE_LENGTH (type) == 16;
> + }

Any reason why this function must be inline? Ever since the bright
folks in the ISO committee decided to adpot different rules for things
like static inline and extern inline than GCC, the use of inline makes
me nervous. And I believe modern compilers are very well capable
themselves of deciding if static functions should be inlined or not.

> + /* Check whether TYPE must be 16-byte-aligned when passed as a
> + function argument. 16-byte vectors, _Decimal128 and structures or
> + unions containing such types must be 16-byte-aligned; other
> + arguments are 4-byte-aligned. */

Hmm, this function actually returns the alignment (as a number of
bytes), but the comment suggests it's a predicate. Can you adjust the
comment?

> + static int
> + i386_darwin_arg_type_alignment (struct type *type)
> + {
> + type = check_typedef (type);
> + /* Passing arguments.
> + 5. The caller places 64-bit vectors (__m64) on the parameter area,
> + aligned to 8-byte boundaries.

"on the parameter area"? Probably a type.

> + 6. [...] The caller aligns 128-bit vectors in the parameter area to
> + 16-byte boundaries. */
> + if (TYPE_CODE (type) == TYPE_CODE_ARRAY && TYPE_VECTOR (type))
> + return TYPE_LENGTH (type);
> + /* 2. The caller aligns nonvector arguments to 4-byte boundaries. */
> + return 4;
> + }
> +
> + static CORE_ADDR
> + i386_darwin_push_dummy_call (struct gdbarch *gdbarch, struct value *function,
> + struct regcache *regcache, CORE_ADDR bp_addr,
> + int nargs, struct value **args, CORE_ADDR sp,
> + int struct_return, CORE_ADDR struct_addr)
> + {
> + struct gdbarch_tdep *tdep = gdbarch_tdep (gdbarch);
> + enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
> + gdb_byte buf[4];
> + int i;
> + int write_pass;
> +
> + /* Determine the total space required for arguments and struct
> + return address in a first pass (allowing for 16-byte-aligned
> + arguments), then push arguments in a second pass. */
> +
> + for (write_pass = 0; write_pass < 2; write_pass++)
> + {
> + int args_space = 0;
> + int nbr_m128 = 0;

nbr_m128? Is that supposed to mean number of m128's? If so, would
you be so kind to reanem this variable num_m128?

> +
> + if (struct_return)
> + {
> + if (write_pass)
> + {
> + /* Push value address. */
> + store_unsigned_integer (buf, 4, byte_order, struct_addr);
> + write_memory (sp, buf, 4);
> + }
> + args_space += 4;
> + }
> +
> + for (i = 0; i < nargs; i++)
> + {
> + struct type *arg_type = value_enclosing_type (args[i]);
> +
> + if (i386_m128_p (arg_type) && nbr_m128 < 4)
> + {
> + if (write_pass)
> + {
> + const gdb_byte *val = value_contents_all (args[i]);
> + regcache_raw_write
> + (regcache, I387_MM0_REGNUM(tdep) + nbr_m128, val);
> + }
> + nbr_m128++;
> + }
> + else
> + {
> + int len = TYPE_LENGTH (arg_type);
> + int align = i386_darwin_arg_type_alignment (arg_type);
> +
> + args_space = align_up (args_space, align);
> + if (write_pass)
> + write_memory (sp + args_space,
> + value_contents_all (args[i]), len);
> +
> + /* The System V ABI says that:
> +
> + "An argument's size is increased, if necessary, to make it a
> + multiple of [32-bit] words. This may require tail padding,
> + depending on the size of the argument."
> +
> + This makes sure the stack stays word-aligned. */
> + args_space += align_up (len, 4);
> + }
> + }
> +
> + /* Darwin i386 ABI:
> + 1. The caller ensures that the stack is 16-byte aligned at the point
> + of the function call. */
> + if (!write_pass)
> + sp = align_down (sp - args_space, 16);
> + }
> +
> + /* Store return address. */
> + sp -= 4;
> + store_unsigned_integer (buf, 4, byte_order, bp_addr);
> + write_memory (sp, buf, 4);
> +
> + /* Finally, update the stack pointer... */
> + store_unsigned_integer (buf, 4, byte_order, sp);
> + regcache_cooked_write (regcache, I386_ESP_REGNUM, buf);
> +
> + /* ...and fake a frame pointer. */
> + regcache_cooked_write (regcache, I386_EBP_REGNUM, buf);
> +
> + /* MarkK wrote: This "+ 8" is all over the place:
> + (i386_frame_this_id, i386_sigtramp_frame_this_id,
> + i386_dummy_id). It's there, since all frame unwinders for
> + a given target have to agree (within a certain margin) on the
> + definition of the stack address of a frame. Otherwise frame id
> + comparison might not work correctly. Since DWARF2/GCC uses the
> + stack address *before* the function call as a frame's CFA. On
> + the i386, when %ebp is used as a frame pointer, the offset
> + between the contents %ebp and the CFA as defined by GCC. */
> + return sp + 8;
> + }
> +
> static void
> i386_darwin_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch)
> {
> *************** i386_darwin_init_abi (struct gdbarch_inf
> *** 119,124 ****
> --- 246,252 ----
> set_gdbarch_num_regs (gdbarch, I386_SSE_NUM_REGS);
>
> dwarf2_frame_set_signal_frame_p (gdbarch, darwin_dwarf_signal_frame_p);
> + set_gdbarch_push_dummy_call (gdbarch, i386_darwin_push_dummy_call);
>
> tdep->struct_return = reg_struct_return;
>
> *************** i386_darwin_init_abi (struct gdbarch_inf
> *** 127,133 ****
> tdep->sc_reg_offset = i386_darwin_thread_state_reg_offset;
> tdep->sc_num_regs = i386_darwin_thread_state_num_regs;
>
> ! tdep->jb_pc_offset = 20;
>
> set_solib_ops (gdbarch, &darwin_so_ops);
> }
> --- 255,266 ----
> tdep->sc_reg_offset = i386_darwin_thread_state_reg_offset;
> tdep->sc_num_regs = i386_darwin_thread_state_num_regs;
>
> ! tdep->jb_pc_offset = 48;
> !
> ! /* Although the i387 extended floating-point has only 80 significant
> ! bits, a `long double' actually takes up 128, probably to enforce
> ! alignment. */
> ! set_gdbarch_long_double_bit (gdbarch, 128);

This is true for the 32-bit Darwin ABI as well?