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[powerpc] breakpoint inserted past function end

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On powerpc, the prologue scanner reads instruction after instruction,
and just skips instructions that do not affect a frame.  This means
that it does not stop if if finds and unexpected instruction (which
could possibly happen with optimization, I presume). To avoid scanning
too many instructions, it tries to establish an upper limit.

The upper limit is first computed using the debugging (line) info,
but if that fails, it falls back on an arbitrary 100 bytes (or 25
instructions).  The problem is that, if the function is shorter than
those 25 instructions, we run the risk of skipping the entire function
and returning a PC that's outside our function.

In the event where we can find a symbol for a given PC (and therefore
can determine function start and end addresses), but cannot find an
upper limit using skip_prologue_using_sal, then we can at least limit
make sure that the 25 instructions do not put us beyour our function.
If it does, then further reduce the upper-limit to the end of the function.

gdb/ChangeLog:

        * rs6000-tdep.c (rs6000_skip_prologue): Make sure that the prologue
        upper limit address is not greater than the function end address
        when the upper limit could not be computed using the debugging
        info.
This commit is contained in:
Joel Brobecker 2011-01-18 16:18:26 +00:00
parent 752573b292
commit e3acb1155b
2 changed files with 14 additions and 2 deletions
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7
gdb/ChangeLog
View file

@ -1,3 +1,10 @@
2011-01-18 Joel Brobecker <brobecker@adacore.com>
* rs6000-tdep.c (rs6000_skip_prologue): Make sure that the prologue
upper limit address is not greater than the function end address
when the upper limit could not be computed using the debugging
info.
2011-01-17 Tom Tromey <tromey@redhat.com>
* cli/cli-cmds.c (apropos_command): Free the compiled regex. Use

9
gdb/rs6000-tdep.c
View file

@ -2090,12 +2090,12 @@ static CORE_ADDR
rs6000_skip_prologue (struct gdbarch *gdbarch, CORE_ADDR pc)
{
struct rs6000_framedata frame;
CORE_ADDR limit_pc, func_addr;
CORE_ADDR limit_pc, func_addr, func_end_addr = 0;
/* See if we can determine the end of the prologue via the symbol table.
If so, then return either PC, or the PC after the prologue, whichever
is greater. */
if (find_pc_partial_function (pc, NULL, &func_addr, NULL))
if (find_pc_partial_function (pc, NULL, &func_addr, &func_end_addr))
{
CORE_ADDR post_prologue_pc
= skip_prologue_using_sal (gdbarch, func_addr);
@ -2113,6 +2113,11 @@ rs6000_skip_prologue (struct gdbarch *gdbarch, CORE_ADDR pc)
if (limit_pc == 0)
limit_pc = pc + 100; /* Magic. */
/* Do not allow limit_pc to be past the function end, if we know
where that end is... */
if (func_end_addr && limit_pc > func_end_addr)
limit_pc = func_end_addr;
pc = skip_prologue (gdbarch, pc, limit_pc, &frame);
return pc;
}