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Re: RFA: Fix tracepoints for LOC_COMPUTED - sort of
Looks good to me!
Daniel Jacobowitz <drow at mvista dot com> writes:
> On Mon, Feb 24, 2003 at 04:50:27PM -0500, Jim Blandy wrote:
> >
> > Daniel Jacobowitz <drow at mvista dot com> writes:
> > > Like the description function, this is pretty minimal; I don't have time to
> > > write a full evaluator right now, and I don't have access to a tracepoint
> > > stub, so I suggest someone who does implement this properly. For now,
> > > though, this handles the most likely types: DW_OP_reg and DW_OP_fbreg. It's
> > > enough to fix the test failures; it's correct as far as it goes; and it
> > > properly raises an error if it gets confused.
> > >
> > > Is this OK? Should I file a PR about the need for a proper
> > > evaluator?
> >
> > Well, the problem is likely to sit around indefinitely:
> > 1) I don't think anyone's using tracepoints at the moment.
> > 2) Compiling Dwarf 2 bytecodes into ax bytecodes is, in general, not
> > a simple thing at all.
> >
> > So its importance and difficulty both work against it. Would a
> > comment be better in this sort of situation? I don't know.
>
> I went for a comment, because I'm a comment sort of person.
>
> > You know, dwarf2read.c's read_{un,}signed_leb128 don't actually need
> > their BFD argument for anything. The call to bfd_get_8 ignores it;
> > it's just a char fetch anyway. In the future, I wonder if we could
> > just use those everywhere.
>
> Probably. There's a set in dwarf2cfi.c too; it would be nice to cut
> them down.
>
> > Gotta have a better error message, dude. It only takes a few
> > seconsd. Think of the poor user.
>
> > You should check that that's actually the end of the expression, too.
>
> OK, even I am kind of ashamed of the error messages in the last
> version... thanks for keeping me honest. How's this?
>
> --
> Daniel Jacobowitz
> MontaVista Software Debian GNU/Linux Developer
>
> 2003-02-26 Daniel Jacobowitz <drow at mvista dot com>
>
> * Makefile.in (dwarf2loc.o): Update dependencies.
> * ax-gdb.c (gen_var_ref): Handle LOC_COMPUTED and LOC_COMPUTED_ARG.
> * dwarf2expr.c (read_uleb128, read_sleb128): Make non-static.
> * dwarf2expr.h (read_uleb128, read_sleb128): Add prototypes.
> * dwarf2loc.c: Include "ax.h" and "ax-gdb.h".
> (locexpr_tracepoint_var_ref): New function.
> (dwarf2_locexpr_funcs): Add locexpr_tracepoint_var_ref.
>
> Index: Makefile.in
> ===================================================================
> RCS file: /cvs/src/src/gdb/Makefile.in,v
> retrieving revision 1.335
> diff -u -p -r1.335 Makefile.in
> --- Makefile.in 21 Feb 2003 15:24:17 -0000 1.335
> +++ Makefile.in 26 Feb 2003 21:30:44 -0000
> @@ -1639,7 +1639,7 @@ dwarf2expr.o: dwarf2expr.c $(defs_h) $(s
> $(gdbcore_h) $(dwarf2expr_h)
> dwarf2loc.o: dwarf2loc.c $(defs_h) $(ui_out_h) $(value_h) $(frame_h) \
> $(gdbcore_h) $(target_h) $(inferior_h) $(dwarf2expr_h) \
> - $(dwarf2loc_h) $(gdb_string_h)
> + $(dwarf2loc_h) $(ax_h) $(ax_gdb_h) $(gdb_string_h)
> dwarf2read.o: dwarf2read.c $(defs_h) $(bfd_h) $(symtab_h) $(gdbtypes_h) \
> $(symfile_h) $(objfiles_h) $(elf_dwarf2_h) $(buildsym_h) \
> $(demangle_h) $(expression_h) $(filenames_h) $(macrotab_h) \
> Index: ax-gdb.c
> ===================================================================
> RCS file: /cvs/src/src/gdb/ax-gdb.c,v
> retrieving revision 1.20
> diff -u -p -r1.20 ax-gdb.c
> --- ax-gdb.c 25 Feb 2003 21:36:16 -0000 1.20
> +++ ax-gdb.c 26 Feb 2003 21:30:44 -0000
> @@ -618,6 +618,11 @@ gen_var_ref (struct agent_expr *ax, stru
> }
> break;
>
> + case LOC_COMPUTED:
> + case LOC_COMPUTED_ARG:
> + (*SYMBOL_LOCATION_FUNCS (var)->tracepoint_var_ref) (var, ax, value);
> + break;
> +
> case LOC_OPTIMIZED_OUT:
> error ("The variable `%s' has been optimized out.",
> SYMBOL_PRINT_NAME (var));
> Index: dwarf2expr.c
> ===================================================================
> RCS file: /cvs/src/src/gdb/dwarf2expr.c,v
> retrieving revision 1.1
> diff -u -p -r1.1 dwarf2expr.c
> --- dwarf2expr.c 21 Feb 2003 15:24:17 -0000 1.1
> +++ dwarf2expr.c 26 Feb 2003 21:30:44 -0000
> @@ -115,7 +115,7 @@ dwarf_expr_eval (struct dwarf_expr_conte
> by R, and return the new value of BUF. Verify that it doesn't extend
> past BUF_END. */
>
> -static unsigned char *
> +unsigned char *
> read_uleb128 (unsigned char *buf, unsigned char *buf_end, ULONGEST * r)
> {
> unsigned shift = 0;
> @@ -141,7 +141,7 @@ read_uleb128 (unsigned char *buf, unsign
> by R, and return the new value of BUF. Verify that it doesn't extend
> past BUF_END. */
>
> -static unsigned char *
> +unsigned char *
> read_sleb128 (unsigned char *buf, unsigned char *buf_end, LONGEST * r)
> {
> unsigned shift = 0;
> Index: dwarf2expr.h
> ===================================================================
> RCS file: /cvs/src/src/gdb/dwarf2expr.h,v
> retrieving revision 1.1
> diff -u -p -r1.1 dwarf2expr.h
> --- dwarf2expr.h 21 Feb 2003 15:24:17 -0000 1.1
> +++ dwarf2expr.h 26 Feb 2003 21:30:44 -0000
> @@ -94,4 +94,10 @@ void dwarf_expr_eval (struct dwarf_expr_
> size_t len);
> CORE_ADDR dwarf_expr_fetch (struct dwarf_expr_context *ctx, int n);
>
> +
> +unsigned char *read_uleb128 (unsigned char *buf, unsigned char *buf_end,
> + ULONGEST * r);
> +unsigned char *read_sleb128 (unsigned char *buf, unsigned char *buf_end,
> + LONGEST * r);
> +
> #endif
> Index: dwarf2loc.c
> ===================================================================
> RCS file: /cvs/src/src/gdb/dwarf2loc.c,v
> retrieving revision 1.1
> diff -u -p -r1.1 dwarf2loc.c
> --- dwarf2loc.c 21 Feb 2003 15:24:17 -0000 1.1
> +++ dwarf2loc.c 26 Feb 2003 21:30:44 -0000
> @@ -26,6 +26,8 @@
> #include "gdbcore.h"
> #include "target.h"
> #include "inferior.h"
> +#include "ax.h"
> +#include "ax-gdb.h"
>
> #include "elf/dwarf2.h"
> #include "dwarf2expr.h"
> @@ -277,11 +279,73 @@ locexpr_describe_location (struct symbol
> return 1;
> }
>
> +
> +/* Describe the location of SYMBOL as an agent value in VALUE, generating
> + any necessary bytecode in AX.
> +
> + NOTE drow/2003-02-26: This function is extremely minimal, because
> + doing it correctly is extremely complicated and there is no
> + publicly available stub with tracepoint support for me to test
> + against. When there is one this function should be revisited. */
> +
> +void
> +locexpr_tracepoint_var_ref (struct symbol * symbol, struct agent_expr * ax,
> + struct axs_value * value)
> +{
> + struct dwarf2_locexpr_baton *dlbaton = SYMBOL_LOCATION_BATON (symbol);
> +
> + if (dlbaton->size == 0)
> + error ("Symbol \"%s\" has been optimized out.",
> + SYMBOL_PRINT_NAME (symbol));
> +
> + if (dlbaton->size == 1
> + && dlbaton->data[0] >= DW_OP_reg0
> + && dlbaton->data[0] <= DW_OP_reg31)
> + {
> + value->kind = axs_lvalue_register;
> + value->u.reg = dlbaton->data[0] - DW_OP_reg0;
> + }
> + else if (dlbaton->data[0] == DW_OP_regx)
> + {
> + ULONGEST reg;
> + read_uleb128 (dlbaton->data + 1, dlbaton->data + dlbaton->size,
> + ®);
> + value->kind = axs_lvalue_register;
> + value->u.reg = reg;
> + }
> + else if (dlbaton->data[0] == DW_OP_fbreg)
> + {
> + /* And this is worse than just minimal; we should honor the frame base
> + as above. */
> + int frame_reg;
> + LONGEST frame_offset;
> + char *buf_end;
> +
> + buf_end = read_sleb128 (dlbaton->data + 1, dlbaton->data + dlbaton->size,
> + &frame_offset);
> + if (buf_end != dlbaton->data + dlbaton->size)
> + error ("Unexpected opcode after DW_OP_fbreg for symbol \"%s\".",
> + SYMBOL_PRINT_NAME (symbol));
> +
> + TARGET_VIRTUAL_FRAME_POINTER (ax->scope, &frame_reg, &frame_offset);
> + ax_reg (ax, frame_reg);
> + ax_const_l (ax, frame_offset);
> + ax_simple (ax, aop_add);
> +
> + ax_const_l (ax, frame_offset);
> + ax_simple (ax, aop_add);
> + value->kind = axs_lvalue_memory;
> + }
> + else
> + error ("Unsupported DWARF opcode in the location of \"%s\".",
> + SYMBOL_PRINT_NAME (symbol));
> +}
> +
> /* The set of location functions used with the DWARF-2 expression
> evaluator. */
> struct location_funcs dwarf2_locexpr_funcs = {
> locexpr_read_variable,
> locexpr_read_needs_frame,
> locexpr_describe_location,
> - NULL
> + locexpr_tracepoint_var_ref
> };