123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100101102103104105106107108109110111112113114115116117118119120121122123124125126127128129130131132133134135136137138139140141142143144145146147148149150151152153154155156157158159160161162163164165166167168169170171172173174175176177178179180181182183184185186187188189190191192193194195196197198199200201202203204205206207208209210211212213214215216217218219220221222223224225226227228229230231232233234235236237238239240241242243244245246247248249250251252253254255256257258259260261262263264265266267268269270271272273274275276277278279280281282283284285286287288289290291292293294295296297298299300301302303304305306307308309310311312313314315316317318319320321322323324325326327328329330331332333334335336337338339340341342343344345346347348349350351352353354355356357358359360361362363364365366367368369370371372373374375376377378379380381382383384385386387388389390391392393394395396397398399400401402403404405406407408409410411412413414415416417418419420421422423424425426427428429430431432433434435436437438439440441442443444445446447448449450451452453454455456457458459460461462463464465466467468469470471472473474475476477478479480481482483484485486487488489490491492493494495496497498499500501502503504505506507508509510511512513514515516517518519520521522523524525526527528529530531532533534535536537538539540541542543544 |
- /* Prologue value handling for GDB.
- Copyright (C) 2003-2022 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 3 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, see <http://www.gnu.org/licenses/>. */
- #include "defs.h"
- #include "prologue-value.h"
- #include "regcache.h"
- /* 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;
- }
- /* 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 ();
- }
- /* 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_not_reached ("unexpected prologue value kind");
- }
- }
- 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;
- }
- /* 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 pv_area::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;
- };
- /* See prologue-value.h. */
- pv_area::pv_area (int base_reg, int addr_bit)
- : m_base_reg (base_reg),
- /* Remember that shift amounts equal to the type's width are
- undefined. */
- m_addr_mask (((((CORE_ADDR) 1 << (addr_bit - 1)) - 1) << 1) | 1),
- m_entry (nullptr)
- {
- }
- /* See prologue-value.h. */
- void
- pv_area::clear_entries ()
- {
- struct area_entry *e = m_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);
- e = next;
- }
- while (e != m_entry);
- m_entry = 0;
- }
- }
- pv_area::~pv_area ()
- {
- clear_entries ();
- }
- /* See prologue-value.h. */
- bool
- pv_area::store_would_trash (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 != m_base_reg));
- }
- /* See prologue-value.h. */
- struct pv_area::area_entry *
- pv_area::find_entry (CORE_ADDR offset)
- {
- struct area_entry *e = m_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) & m_addr_mask)
- < ((e->offset - offset) & m_addr_mask))
- e = e->next;
- /* If the previous entry would be better than the current one, then
- scan backwards. */
- while (((e->prev->offset - offset) & m_addr_mask)
- < ((e->offset - offset) & m_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. */
- m_entry = e;
- return e;
- }
- /* See prologue-value.h. */
- int
- pv_area::overlaps (struct area_entry *entry, CORE_ADDR offset, CORE_ADDR size)
- {
- /* Think carefully about wrap-around before simplifying this. */
- return (((entry->offset - offset) & m_addr_mask) < size
- || ((offset - entry->offset) & m_addr_mask) < entry->size);
- }
- /* See prologue-value.h. */
- void
- pv_area::store (pv_t addr, CORE_ADDR size, pv_t value)
- {
- /* Remove any (potentially) overlapping entries. */
- if (store_would_trash (addr))
- clear_entries ();
- else
- {
- CORE_ADDR offset = addr.k;
- struct area_entry *e = find_entry (offset);
- /* Delete all entries that we would overlap. */
- while (e && overlaps (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. */
- m_entry = e;
- }
- /* Now, there are no entries overlapping us, and m_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 = XNEW (struct area_entry);
- e->offset = offset;
- e->size = size;
- e->value = value;
- if (m_entry)
- {
- e->prev = m_entry->prev;
- e->next = m_entry;
- e->prev->next = e->next->prev = e;
- }
- else
- {
- e->prev = e->next = e;
- m_entry = e;
- }
- }
- }
- /* See prologue-value.h. */
- pv_t
- pv_area::fetch (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 (! m_entry
- || store_would_trash (addr))
- return pv_unknown ();
- else
- {
- CORE_ADDR offset = addr.k;
- struct area_entry *e = find_entry (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 ();
- }
- }
- /* See prologue-value.h. */
- bool
- pv_area::find_reg (struct gdbarch *gdbarch, int reg, CORE_ADDR *offset_p)
- {
- struct area_entry *e = m_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 true;
- }
- e = e->next;
- }
- while (e != m_entry);
- return false;
- }
- /* See prologue-value.h. */
- void
- pv_area::scan (void (*func) (void *closure,
- pv_t addr,
- CORE_ADDR size,
- pv_t value),
- void *closure)
- {
- struct area_entry *e = m_entry;
- pv_t addr;
- addr.kind = pvk_register;
- addr.reg = m_base_reg;
- if (e)
- do
- {
- addr.k = e->offset;
- func (closure, addr, e->size, e->value);
- e = e->next;
- }
- while (e != m_entry);
- }
|