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Re: RFA: Fix tracepoints for LOC_COMPUTED - sort of
Thanks, checked in (with a warning I accidentally introduced fixed).
On Fri, Feb 28, 2003 at 02:45:29PM -0500, Jim Blandy wrote:
>
> 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
> > };
>
--
Daniel Jacobowitz
MontaVista Software Debian GNU/Linux Developer