RFA: general prologue analysis framework

Jim Blandy
2005-10-07T20:39:12Z

This code has been in use for around two years by two uncontributed
Red Hat ports. I'd like to contribute one of them, the Renesas M32C
port, so I'm putting this out for review first. I originally wrote it
for the S/390; the code below has been cleaned up, generalized a bit,
and extended. (If this code is accepted, then s390-tdep.c's analyzer
could be trimmed a lot.)

In my experience, prologue analyzers written using this framework are
much more robust than the processor-specific ones. For example, if
GCC decides to stop generating:

addi sp, -42

and instead say:

movi r1, -42
add sp, r1

the analyzer just handles it, with no changes needed. And the
analyzers themselves become simpler: they're just interpreters of
machine code, limited to instructions that appear in prologues.

Fortunately, we've managed to pass off the whole problem to the
compiler these days, by depending on Dwarf CFI for most cases. But as
long as we're still going to have prologue analyzers in GDB, I think
this makes them simpler and more robust.

If folks are interested, I can post the m32c prologue analyzer that
uses these functions, as an example of how they can be used.

2005-10-06 Jim Blandy <jimb@redhat.com>

* prologue-value.c, prologue-value.h: New files.
* Makefile.in (prologue_value_h): New variable.
(HFILES_NO_SRCDIR): List prologue-value.h.
(ALLDEPFILES): List prologue-value.c.
(prologue-value.o): New rule.

Index: gdb/prologue-value.h
===================================================================
RCS file: gdb/prologue-value.h
diff -N gdb/prologue-value.h
*** gdb/prologue-value.h 1 Jan 1970 00:00:00 -0000
--- gdb/prologue-value.h 6 Oct 2005 23:24:04 -0000
***************
*** 0 ****
--- 1,293 ----
+ /* Interface to prologue value handling for GDB.
+ Copyright 2003, 2004, 2005 Free Software Foundation, Inc.
+
+ This file is part of GDB.
+
+ This program is free software; you can redistribute it and/or modify
+ it under the terms of the GNU General Public License as published by
+ the Free Software Foundation; either version 2 of the License, or
+ (at your option) any later version.
+
+ This program is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with this program; if not, write to:
+
+ Free Software Foundation, Inc.
+ 51 Franklin St - Fifth Floor
+ Boston, MA 02110-1301
+ USA */
+
+ #ifndef PROLOGUE_VALUE_H
+ #define PROLOGUE_VALUE_H
+
+ /* When we analyze a prologue, we're really doing 'abstract
+ interpretation' or 'pseudo-evaluation': running the function's code
+ in simulation, but using conservative approximations of the values
+ it would have when it actually runs. For example, if our function
+ starts with the instruction:
+
+ addi r1, 42 # add 42 to r1
+
+ we don't know exactly what value will be in r1 after executing this
+ instruction, but we do know it'll be 42 greater than its original
+ value.
+
+ If we then see an instruction like:
+
+ addi r1, 22 # add 22 to r1
+
+ we still don't know what r1's value is, but again, we can say it is
+ now 64 greater than its original value.
+
+ If the next instruction were:
+
+ mov r2, r1 # set r2 to r1's value
+
+ then we can say that r2's value is now the original value of r1
+ plus 64.
+
+ It's common for prologues to save registers on the stack, so we'll
+ need to track the values of stack frame slots, as well as the
+ registers. So after an instruction like this:
+
+ mov (fp+4), r2
+
+ Then we'd know that the stack slot four bytes above the frame
+ pointer holds the original value of r1 plus 64.
+
+ And so on.
+
+ Of course, this can only go so far before it gets unreasonable. If
+ we wanted to be able to say anything about the value of r1 after
+ the instruction:
+
+ xor r1, r3 # exclusive-or r1 and r3, place result in r1
+
+ then things would get pretty complex. But remember, we're just
+ doing a conservative approximation; if exclusive-or instructions
+ aren't relevant to prologues, we can just say r1's value is now
+ 'unknown'. We can ignore things that are too complex, if that loss
+ of information is acceptable for our application.
+
+ So when I say "conservative approximation" here, what I mean is an
+ approximation that is either accurate, or marked "unknown", but
+ never inaccurate.
+
+ Once you've reached the current PC, or an instruction that you
+ don't know how to simulate, you stop. Now you can examine the
+ state of the registers and stack slots you've kept track of.
+
+ - To see how large your stack frame is, just check the value of the
+ stack pointer register; if it's the original value of the SP
+ minus a constant, then that constant is the stack frame's size.
+ If the SP's value has been marked as 'unknown', then that means
+ the prologue has done something too complex for us to track, and
+ we don't know the frame size.
+
+ - To see where we've saved the previous frame's registers, we just
+ search the values we've tracked --- stack slots, usually, but
+ registers, too, if you want --- for something equal to the
+ register's original value. If the ABI suggests a standard place
+ to save a given register, then we can check there first, but
+ really, anything that will get us back the original value will
+ probably work.
+
+ Sure, this takes some work. But prologue analyzers aren't
+ quick-and-simple pattern patching to recognize a few fixed prologue
+ forms any more; they're big, hairy functions. Along with inferior
+ function calls, prologue analysis accounts for a substantial
+ portion of the time needed to stabilize a GDB port. So I think
+ it's worthwhile to look for an approach that will be easier to
+ understand and maintain. In the approach used here:
+
+ - It's easier to see that the analyzer is correct: you just see
+ whether the analyzer properly (albiet conservatively) simulates
+ the effect of each instruction.
+
+ - It's easier to extend the analyzer: you can add support for new
+ instructions, and know that you haven't broken anything that
+ wasn't already broken before.
+
+ - It's orthogonal: to gather new information, you don't need to
+ complicate the code for each instruction. As long as your domain
+ of conservative values is already detailed enough to tell you
+ what you need, then all the existing instruction simulations are
+ already gathering the right data for you.
+
+ A 'struct prologue_value' is a conservative approximation of the
+ real value the register or stack slot will have. */
+
+ struct prologue_value {
+
+ /* What sort of value is this? This determines the interpretation
+ of subsequent fields. */
+ enum {
+
+ /* We don't know anything about the value. This is also used for
+ values we could have kept track of, when doing so would have
+ been too complex and we don't want to bother. The bottom of
+ our lattice. */
+ pvk_unknown,
+
+ /* A known constant. K is its value. */
+ pvk_constant,
+
+ /* The value that register REG originally had *UPON ENTRY TO THE
+ FUNCTION*, plus K. If K is zero, this means, obviously, just
+ the value REG had upon entry to the function. REG is a GDB
+ register number. Before we start interpreting, we initialize
+ every register R to { pvk_register, R, 0 }. */
+ pvk_register,
+
+ } kind;
+
+ /* The meanings of the following fields depend on 'kind'; see the
+ comments for the specific 'kind' values. */
+ int reg;
+ CORE_ADDR k;
+ };
+
+ typedef struct prologue_value pv_t;
+
+
+ /* Return the unknown prologue value --- { pvk_unknown, ?, ? }. */
+ pv_t pv_unknown (void);
+
+ /* Return the prologue value representing the constant K. */
+ pv_t pv_constant (CORE_ADDR k);
+
+ /* Return the prologue value representing the original value of
+ register REG, plus the constant K. */
+ pv_t pv_register (int reg, CORE_ADDR k);
+
+
+ /* Return conservative approximations of the results of the following
+ operations. */
+ pv_t pv_add (pv_t a, pv_t b); /* a + b */
+ pv_t pv_add_constant (pv_t v, CORE_ADDR k); /* a + k */
+ pv_t pv_subtract (pv_t a, pv_t b); /* a - b */
+ pv_t pv_logical_and (pv_t a, pv_t b); /* a & b */
+
+
+ /* Return non-zero iff A and B are identical expressions.
+
+ This is not the same as asking if the two values are equal; the
+ result of such a comparison would have to be a pv_boolean, and
+ asking whether two 'unknown' values were equal would give you
+ pv_maybe. Same for comparing, say, { pvk_register, R1, 0 } and {
+ pvk_register, R2, 0}.
+
+ Instead, this function asks whether the two representations are the
+ same. */
+ int pv_is_identical (pv_t a, pv_t b);
+
+
+ /* Return non-zero if A is known to be a constant. */
+ int pv_is_constant (pv_t a);
+
+ /* Return non-zero if A is the original value of register number R
+ plus some constant, zero otherwise. */
+ int pv_is_register (pv_t a, int r);
+
+
+ /* Return non-zero if A is the original value of register R plus the
+ constant K. */
+ int pv_is_register_k (pv_t a, int r, CORE_ADDR k);
+
+ /* A conservative boolean type, including "maybe", when we can't
+ figure out whether something is true or not. */
+ enum pv_boolean {
+ pv_maybe,
+ pv_definite_yes,
+ pv_definite_no,
+ };
+
+
+ /* Decide whether a reference to SIZE bytes at ADDR refers exactly to
+ an element of an array. The array starts at ARRAY_ADDR, and has
+ ARRAY_LEN values of ELT_SIZE bytes each. If ADDR definitely does
+ refer to an array element, set *I to the index of the referenced
+ element in the array, and return pv_definite_yes. If it definitely
+ doesn't, return pv_definite_no. If we can't tell, return pv_maybe.
+
+ If the reference does touch the array, but doesn't fall exactly on
+ an element boundary, or doesn't refer to the whole element, return
+ pv_maybe. */
+ enum pv_boolean pv_is_array_ref (pv_t addr, CORE_ADDR size,
+ pv_t array_addr, CORE_ADDR array_len,
+ CORE_ADDR elt_size,
+ int *i);
+
+
+ /* A 'struct pv_area' keeps track of values stored in a particular
+ region of memory. */
+ struct pv_area;
+
+ /* Create a new area, tracking stores relative to BASE_REG. Stores to
+ constant addresses, unknown addresses, or to addresses relative to
+ registers other than BASE_REG will trash this area; see
+ pv_area_store_would_trash. */
+ struct pv_area *make_pv_area (int base_reg);
+
+ /* Free AREA. */
+ void free_pv_area (struct pv_area *area);
+
+
+ /* Register a cleanup to free AREA. */
+ struct cleanup *make_cleanup_free_pv_area (struct pv_area *area);
+
+
+ /* Store the SIZE-byte value VALUE at ADDR in AREA.
+
+ If ADDR is not relative to the same base register we used in
+ creating AREA, then we can't tell which values here the stored
+ value might overlap, and we'll have to mark everything as
+ unknown. */
+ void pv_area_store (struct pv_area *area,
+ pv_t addr,
+ CORE_ADDR size,
+ pv_t value);
+
+ /* Return the SIZE-byte value at ADDR in AREA. This may return
+ pv_unknown (). */
+ pv_t pv_area_fetch (struct pv_area *area, pv_t addr, CORE_ADDR size);
+
+ /* Return true if storing to address ADDR in AREA would force us to
+ mark the contents of the entire area as unknown. This could happen
+ if, say, ADDR is unknown, since we could be storing anywhere. Or,
+ it could happen if ADDR is relative to a different register than
+ the other stores base register, since we don't know the relative
+ values of the two registers.
+
+ If you've reached such a store, it may be better to simply stop the
+ prologue analysis, and return the information you've gathered,
+ instead of losing all that information, most of which is probably
+ okay. */
+ int pv_area_store_would_trash (struct pv_area *area, pv_t addr);
+
+
+ /* Search AREA for the original value of REGISTER. If we can't find
+ it, return zero; if we can find it, return a non-zero value, and if
+ OFFSET_P is non-zero, set *OFFSET_P to the register's offset within
+ AREA. GDBARCH is the architecture of which REGISTER is a member. */
+ int pv_area_find_reg (struct pv_area *area,
+ struct gdbarch *gdbarch,
+ int register,
+ CORE_ADDR *offset_p);
+
+
+ /* For every part of AREA whose value we know, apply FUNC to CLOSURE,
+ the value's address, its size, and the value itself. */
+ void pv_area_scan (struct pv_area *area,
+ void (*func) (void *closure,
+ pv_t addr,
+ CORE_ADDR size,
+ pv_t value),
+ void *closure);
+
+
+ #endif /* PROLOGUE_VALUE_H */
Index: gdb/prologue-value.c
===================================================================
RCS file: gdb/prologue-value.c
diff -N gdb/prologue-value.c
*** gdb/prologue-value.c 1 Jan 1970 00:00:00 -0000
--- gdb/prologue-value.c 6 Oct 2005 23:24:04 -0000
***************
*** 0 ****
--- 1,591 ----
+ /* Prologue value handling for GDB.
+ Copyright 2003, 2004, 2005 Free Software Foundation, Inc.
+
+ This file is part of GDB.
+
+ This program is free software; you can redistribute it and/or modify
+ it under the terms of the GNU General Public License as published by
+ the Free Software Foundation; either version 2 of the License, or
+ (at your option) any later version.
+
+ This program is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with this program; if not, write to:
+
+ Free Software Foundation, Inc.
+ 51 Franklin St - Fifth Floor
+ Boston, MA 02110-1301
+ USA */
+
+ #include "defs.h"
+ #include "gdb_string.h"
+ #include "gdb_assert.h"
+ #include "prologue-value.h"
+ #include "regcache.h"
+
+ \f
+ /* Constructors. */
+
+ pv_t
+ pv_unknown (void)
+ {
+ pv_t v = { pvk_unknown, 0, 0 };
+
+ return v;
+ }
+
+
+ pv_t
+ pv_constant (CORE_ADDR k)
+ {
+ pv_t v;
+
+ v.kind = pvk_constant;
+ v.reg = -1; /* for debugging */
+ v.k = k;
+
+ return v;
+ }
+
+
+ pv_t
+ pv_register (int reg, CORE_ADDR k)
+ {
+ pv_t v;
+
+ v.kind = pvk_register;
+ v.reg = reg;
+ v.k = k;
+
+ return v;
+ }
+
+
+ \f
+ /* Arithmetic operations. */
+
+ /* If one of *A and *B is a constant, and the other isn't, swap the
+ values as necessary to ensure that *B is the constant. This can
+ reduce the number of cases we need to analyze in the functions
+ below. */
+ static void
+ constant_last (pv_t *a, pv_t *b)
+ {
+ if (a->kind == pvk_constant
+ && b->kind != pvk_constant)
+ {
+ pv_t temp = *a;
+ *a = *b;
+ *b = temp;
+ }
+ }
+
+
+ pv_t
+ pv_add (pv_t a, pv_t b)
+ {
+ constant_last (&a, &b);
+
+ /* We can add a constant to a register. */
+ if (a.kind == pvk_register
+ && b.kind == pvk_constant)
+ return pv_register (a.reg, a.k + b.k);
+
+ /* We can add a constant to another constant. */
+ else if (a.kind == pvk_constant
+ && b.kind == pvk_constant)
+ return pv_constant (a.k + b.k);
+
+ /* Anything else we don't know how to add. We don't have a
+ representation for, say, the sum of two registers, or a multiple
+ of a register's value (adding a register to itself). */
+ else
+ return pv_unknown ();
+ }
+
+
+ pv_t
+ pv_add_constant (pv_t v, CORE_ADDR k)
+ {
+ /* Rather than thinking of all the cases we can and can't handle,
+ we'll just let pv_add take care of that for us. */
+ return pv_add (v, pv_constant (k));
+ }
+
+
+ pv_t
+ pv_subtract (pv_t a, pv_t b)
+ {
+ /* This isn't quite the same as negating B and adding it to A, since
+ we don't have a representation for the negation of anything but a
+ constant. For example, we can't negate { pvk_register, R1, 10 },
+ but we do know that { pvk_register, R1, 10 } minus { pvk_register,
+ R1, 5 } is { pvk_constant, <ignored>, 5 }.
+
+ This means, for example, that we could subtract two stack
+ addresses; they're both relative to the original SP. Since the
+ frame pointer is set based on the SP, its value will be the
+ original SP plus some constant (probably zero), so we can use its
+ value just fine, too. */
+
+ constant_last (&a, &b);
+
+ /* We can subtract two constants. */
+ if (a.kind == pvk_constant
+ && b.kind == pvk_constant)
+ return pv_constant (a.k - b.k);
+
+ /* We can subtract a constant from a register. */
+ else if (a.kind == pvk_register
+ && b.kind == pvk_constant)
+ return pv_register (a.reg, a.k - b.k);
+
+ /* We can subtract a register from itself, yielding a constant. */
+ else if (a.kind == pvk_register
+ && b.kind == pvk_register
+ && a.reg == b.reg)
+ return pv_constant (a.k - b.k);
+
+ /* We don't know how to subtract anything else. */
+ else
+ return pv_unknown ();
+ }
+
+
+ pv_t
+ pv_logical_and (pv_t a, pv_t b)
+ {
+ constant_last (&a, &b);
+
+ /* We can 'and' two constants. */
+ if (a.kind == pvk_constant
+ && b.kind == pvk_constant)
+ return pv_constant (a.k & b.k);
+
+ /* We can 'and' anything with the constant zero. */
+ else if (b.kind == pvk_constant
+ && b.k == 0)
+ return pv_constant (0);
+
+ /* We can 'and' anything with ~0. */
+ else if (b.kind == pvk_constant
+ && b.k == ~ (CORE_ADDR) 0)
+ return a;
+
+ /* We can 'and' a register with itself. */
+ else if (a.kind == pvk_register
+ && b.kind == pvk_register
+ && a.reg == b.reg
+ && a.k == b.k)
+ return a;
+
+ /* Otherwise, we don't know. */
+ else
+ return pv_unknown ();
+ }
+
+
+ \f
+ /* Examining prologue values. */
+
+ int
+ pv_is_identical (pv_t a, pv_t b)
+ {
+ if (a.kind != b.kind)
+ return 0;
+
+ switch (a.kind)
+ {
+ case pvk_unknown:
+ return 1;
+ case pvk_constant:
+ return (a.k == b.k);
+ case pvk_register:
+ return (a.reg == b.reg && a.k == b.k);
+ default:
+ gdb_assert (0);
+ }
+ }
+
+
+ int
+ pv_is_constant (pv_t a)
+ {
+ return (a.kind == pvk_constant);
+ }
+
+
+ int
+ pv_is_register (pv_t a, int r)
+ {
+ return (a.kind == pvk_register
+ && a.reg == r);
+ }
+
+
+ int
+ pv_is_register_k (pv_t a, int r, CORE_ADDR k)
+ {
+ return (a.kind == pvk_register
+ && a.reg == r
+ && a.k == k);
+ }
+
+
+ enum pv_boolean
+ pv_is_array_ref (pv_t addr, CORE_ADDR size,
+ pv_t array_addr, CORE_ADDR array_len,
+ CORE_ADDR elt_size,
+ int *i)
+ {
+ /* Note that, since .k is a CORE_ADDR, and CORE_ADDR is unsigned, if
+ addr is *before* the start of the array, then this isn't going to
+ be negative... */
+ pv_t offset = pv_subtract (addr, array_addr);
+
+ if (offset.kind == pvk_constant)
+ {
+ /* This is a rather odd test. We want to know if the SIZE bytes
+ at ADDR don't overlap the array at all, so you'd expect it to
+ be an || expression: "if we're completely before || we're
+ completely after". But with unsigned arithmetic, things are
+ different: since it's a number circle, not a number line, the
+ right values for offset.k are actually one contiguous range. */
+ if (offset.k <= -size
+ && offset.k >= array_len * elt_size)
+ return pv_definite_no;
+ else if (offset.k % elt_size != 0
+ || size != elt_size)
+ return pv_maybe;
+ else
+ {
+ *i = offset.k / elt_size;
+ return pv_definite_yes;
+ }
+ }
+ else
+ return pv_maybe;
+ }
+
+
+ \f
+ /* Areas. */
+
+
+ /* A particular value known to be stored in an area.
+
+ Entries form a ring, sorted by unsigned offset from the area's base
+ register's value. Since entries can straddle the wrap-around point,
+ unsigned offsets form a circle, not a number line, so the list
+ itself is structured the same way --- there is no inherent head.
+ The entry with the lowest offset simply follows the entry with the
+ highest offset. Entries may abut, but never overlap. The area's
+ 'entry' pointer points to an arbitrary node in the ring. */
+ struct area_entry
+ {
+ /* Links in the doubly-linked ring. */
+ struct area_entry *prev, *next;
+
+ /* Offset of this entry's address from the value of the base
+ register. */
+ CORE_ADDR offset;
+
+ /* The size of this entry. Note that an entry may wrap around from
+ the end of the address space to the beginning. */
+ CORE_ADDR size;
+
+ /* The value stored here. */
+ pv_t value;
+ };
+
+
+ struct pv_area
+ {
+ /* This area's base register. */
+ int base_reg;
+
+ /* The mask to apply to addresses, to make the wrap-around happen at
+ the right place. */
+ CORE_ADDR addr_mask;
+
+ /* An element of the doubly-linked ring of entries, or zero if we
+ have none. */
+ struct area_entry *entry;
+ };
+
+
+ struct pv_area *
+ make_pv_area (int base_reg)
+ {
+ struct pv_area *a = (struct pv_area *) xmalloc (sizeof (*a));
+
+ memset (a, 0, sizeof (*a));
+
+ a->base_reg = base_reg;
+ a->entry = 0;
+
+ /* Remember that shift amounts equal to the type's width are
+ undefined. */
+ a->addr_mask = ((((CORE_ADDR) 1 << (TARGET_ADDR_BIT - 1)) - 1) << 1) | 1;
+
+ return a;
+ }
+
+
+ /* Delete all entries from AREA. */
+ static void
+ clear_entries (struct pv_area *area)
+ {
+ struct area_entry *e = area->entry;
+
+ if (e)
+ {
+ /* This needs to be a do-while loop, in order to actually
+ process the node being checked for in the terminating
+ condition. */
+ do
+ {
+ struct area_entry *next = e->next;
+ xfree (e);
+ }
+ while (e != area->entry);
+
+ area->entry = 0;
+ }
+ }
+
+
+ void
+ free_pv_area (struct pv_area *area)
+ {
+ clear_entries (area);
+ xfree (area);
+ }
+
+
+ static void
+ do_free_pv_area_cleanup (void *arg)
+ {
+ free_pv_area ((struct pv_area *) arg);
+ }
+
+
+ struct cleanup *
+ make_cleanup_free_pv_area (struct pv_area *area)
+ {
+ return make_cleanup (do_free_pv_area_cleanup, (void *) area);
+ }
+
+
+ int
+ pv_area_store_would_trash (struct pv_area *area, pv_t addr)
+ {
+ /* It may seem odd that pvk_constant appears here --- after all,
+ that's the case where we know the most about the address! But
+ pv_areas are always relative to a register, and we don't know the
+ value of the register, so we can't compare entry addresses to
+ constants. */
+ return (addr.kind == pvk_unknown
+ || addr.kind == pvk_constant
+ || (addr.kind == pvk_register && addr.reg != area->base_reg));
+ }
+
+
+ /* Return a pointer to the first entry we hit in AREA starting at
+ OFFSET and going forward.
+
+ This may return zero, if AREA has no entries.
+
+ And since the entries are a ring, this may return an entry that
+ entirely preceeds OFFSET. This is the correct behavior: depending
+ on the sizes involved, we could still overlap such an area, with
+ wrap-around. */
+ static struct area_entry *
+ find_entry (struct pv_area *area, CORE_ADDR offset)
+ {
+ struct area_entry *e = area->entry;
+
+ if (! e)
+ return 0;
+
+ /* If the next entry would be better than the current one, then scan
+ forward. Since we use '<' in this loop, it always terminates.
+
+ Note that, even setting aside the addr_mask stuff, we must not
+ simplify this, in high school algebra fashion, to
+ (e->next->offset < e->offset), because of the way < interacts
+ with wrap-around. We have to subtract offset from both sides to
+ make sure both things we're comparing are on the same side of the
+ discontinuity. */
+ while (((e->next->offset - offset) & area->addr_mask)
+ < ((e->offset - offset) & area->addr_mask))
+ e = e->next;
+
+ /* If the previous entry would be better than the current one, then
+ scan backwards. */
+ while (((e->prev->offset - offset) & area->addr_mask)
+ < ((e->offset - offset) & area->addr_mask))
+ e = e->prev;
+
+ /* In case there's some locality to the searches, set the area's
+ pointer to the entry we've found. */
+ area->entry = e;
+
+ return e;
+ }
+
+
+ /* Return non-zero if the SIZE bytes at OFFSET would overlap ENTRY;
+ return zero otherwise. AREA is the area to which ENTRY belongs. */
+ static int
+ overlaps (struct pv_area *area,
+ struct area_entry *entry,
+ CORE_ADDR offset,
+ CORE_ADDR size)
+ {
+ /* Think carefully about wrap-around before simplifying this. */
+ return (((entry->offset - offset) & area->addr_mask) < size
+ || ((offset - entry->offset) & area->addr_mask) < entry->size);
+ }
+
+
+ void
+ pv_area_store (struct pv_area *area,
+ pv_t addr,
+ CORE_ADDR size,
+ pv_t value)
+ {
+ /* Remove any (potentially) overlapping entries. */
+ if (pv_area_store_would_trash (area, addr))
+ clear_entries (area);
+ else
+ {
+ CORE_ADDR offset = addr.k;
+ struct area_entry *e = find_entry (area, offset);
+
+ /* Delete all entries that we would overlap. */
+ while (e && overlaps (area, e, offset, size))
+ {
+ struct area_entry *next = (e->next == e) ? 0 : e->next;
+ e->prev->next = e->next;
+ e->next->prev = e->prev;
+
+ xfree (e);
+ e = next;
+ }
+
+ /* Move the area's pointer to the next remaining entry. This
+ will also zero the pointer if we've deleted all the entries. */
+ area->entry = e;
+ }
+
+ /* Now, there are no entries overlapping us, and area->entry is
+ either zero or pointing at the closest entry after us. We can
+ just insert ourselves before that.
+
+ But if we're storing an unknown value, don't bother --- that's
+ the default. */
+ if (value.kind == pvk_unknown)
+ return;
+ else
+ {
+ CORE_ADDR offset = addr.k;
+ struct area_entry *e = (struct area_entry *) xmalloc (sizeof (*e));
+ e->offset = offset;
+ e->size = size;
+ e->value = value;
+
+ if (area->entry)
+ {
+ e->prev = area->entry->prev;
+ e->next = area->entry;
+ e->prev->next = e->next->prev = e;
+ }
+ else
+ {
+ e->prev = e->next = e;
+ area->entry = e;
+ }
+ }
+ }
+
+
+ pv_t
+ pv_area_fetch (struct pv_area *area, pv_t addr, CORE_ADDR size)
+ {
+ /* If we have no entries, or we can't decide how ADDR relates to the
+ entries we do have, then the value is unknown. */
+ if (! area->entry
+ || pv_area_store_would_trash (area, addr))
+ return pv_unknown ();
+ else
+ {
+ CORE_ADDR offset = addr.k;
+ struct area_entry *e = find_entry (area, offset);
+
+ /* If this entry exactly matches what we're looking for, then
+ we're set. Otherwise, say it's unknown. */
+ if (e->offset == offset && e->size == size)
+ return e->value;
+ else
+ return pv_unknown ();
+ }
+ }
+
+
+ int
+ pv_area_find_reg (struct pv_area *area,
+ struct gdbarch *gdbarch,
+ int reg,
+ CORE_ADDR *offset_p)
+ {
+ struct area_entry *e = area->entry;
+
+ if (e)
+ do
+ {
+ if (e->value.kind == pvk_register
+ && e->value.reg == reg
+ && e->value.k == 0
+ && e->size == register_size (gdbarch, reg))
+ {
+ if (offset_p)
+ *offset_p = e->offset;
+ return 1;
+ }
+
+ e = e->next;
+ }
+ while (e != area->entry);
+
+ return 0;
+ }
+
+
+ void
+ pv_area_scan (struct pv_area *area,
+ void (*func) (void *closure,
+ pv_t addr,
+ CORE_ADDR size,
+ pv_t value),
+ void *closure)
+ {
+ struct area_entry *e = area->entry;
+ pv_t addr;
+
+ addr.kind = pvk_register;
+ addr.reg = area->base_reg;
+
+ if (e)
+ do
+ {
+ addr.k = e->offset;
+ func (closure, addr, e->size, e->value);
+ e = e->next;
+ }
+ while (e != area->entry);
+ }
Index: gdb/Makefile.in
===================================================================
RCS file: /cvs/src/src/gdb/Makefile.in,v
retrieving revision 1.755
diff -c -p -r1.755 Makefile.in
*** gdb/Makefile.in 28 Sep 2005 02:55:41 -0000 1.755
--- gdb/Makefile.in 6 Oct 2005 23:24:05 -0000
*************** ppcnbsd_tdep_h = ppcnbsd-tdep.h
*** 750,755 ****
--- 751,757 ----
ppcobsd_tdep_h = ppcobsd-tdep.h
ppc_tdep_h = ppc-tdep.h
proc_utils_h = proc-utils.h
+ prologue_value_h = prologue-value.h
regcache_h = regcache.h
reggroups_h = reggroups.h
regset_h = regset.h
*************** HFILES_NO_SRCDIR = bcache.h buildsym.h c
*** 857,862 ****
--- 859,865 ----
symfile.h stabsread.h target.h terminal.h typeprint.h \
xcoffsolib.h \
macrotab.h macroexp.h macroscope.h \
+ prologue-value.h \
ada-lang.h c-lang.h f-lang.h \
jv-lang.h \
m2-lang.h p-lang.h \
*************** ALLDEPFILES = \
*** 1430,1435 ****
--- 1433,1439 ----
ppcnbsd-nat.c ppcnbsd-tdep.c \
ppcobsd-nat.c ppcobsd-tdep.c \
procfs.c \
+ prologue-value.c \
remote-e7000.c \
remote-hms.c remote-m32r-sdi.c remote-mips.c \
remote-rdp.c remote-sim.c \
*************** procfs.o: procfs.c $(defs_h) $(inferior_
*** 2413,2418 ****
--- 2419,2426 ----
proc-service.o: proc-service.c $(defs_h) $(gdb_proc_service_h) $(inferior_h) \
$(symtab_h) $(target_h) $(gregset_h)
proc-why.o: proc-why.c $(defs_h) $(proc_utils_h)
+ prologue-value.o: prologue-value.c $(defs_h) $(gdb_string_h) $(gdb_assert_h) \
+ $(prologue_value_h) $(regcache_h)
p-typeprint.o: p-typeprint.c $(defs_h) $(gdb_obstack_h) $(bfd_h) $(symtab_h) \
$(gdbtypes_h) $(expression_h) $(value_h) $(gdbcore_h) $(target_h) \
$(language_h) $(p_lang_h) $(typeprint_h) $(gdb_string_h)