From: Simon Marchi <simon.marchi@polymtl.ca>
To: gdb-patches@sourceware.org
Cc: Simon Marchi <simon.marchi@efficios.com>
Subject: [PATCH 06/24] gdb: fix bugs in {get,put}_frame_register_bytes
Date: Wed, 8 Nov 2023 00:00:50 -0500 [thread overview]
Message-ID: <20231108051222.1275306-7-simon.marchi@polymtl.ca> (raw)
In-Reply-To: <20231108051222.1275306-1-simon.marchi@polymtl.ca>
From: Simon Marchi <simon.marchi@efficios.com>
I found this only by inspection: the myaddr pointer in
{get,put}_frame_register_bytes is reset to `buffer.data ()` at each
iteration. This means that we will always use the bytes at the
beginning of `buffer` to read or write to the registers, instead of
progressing in `buffer`.
Fix this by re-writing the functions to chip away the beginning of the
buffer array_view as we progress in reading or writing the data.
These bugs was introduced almost 3 years ago [1], and yet nobody
complained. I'm wondering which architecture relies on that register
"overflow" behavior (reading or writing multiple consecutive registers
with one {get,put}_frame_register_bytes calls), and in which situation.
I find these functions a bit dangerous, if a caller mis-calculates
things, it could end up silently reading or writing to the next
register, even if it's not the intent.
If I could change it, I would prefer to have functions specifically made
for that ({get,put}_frame_register_bytes_consecutive or something like
that) and make {get,put}_frame_register_bytes only able to write within
a single register (which I presume represents most of the use cases of
the current {get,put}_frame_register_bytes). If a caller mis-calculates
things and an overflow occurs while calling
{get,put}_frame_register_bytes, it would hit an assert. The problem is
knowing which callers rely on the overflow behavior and which don't.
[1] https://gitlab.com/gnutools/binutils-gdb/-/commit/bdec2917b1e94c7198ba39919f45060067952f43
Change-Id: I43bd4a9f7fa8419d388a2b20bdc57d652688ddf8
---
gdb/frame.c | 63 +++++++++++++++++++----------------------------------
1 file changed, 23 insertions(+), 40 deletions(-)
diff --git a/gdb/frame.c b/gdb/frame.c
index afadb8ac4e73..b3d99163b4dc 100644
--- a/gdb/frame.c
+++ b/gdb/frame.c
@@ -1482,9 +1482,6 @@ get_frame_register_bytes (frame_info_ptr frame, int regnum,
int *optimizedp, int *unavailablep)
{
struct gdbarch *gdbarch = get_frame_arch (frame);
- int i;
- int maxsize;
- int numregs;
/* Skip registers wholly inside of OFFSET. */
while (offset >= register_size (gdbarch, regnum))
@@ -1495,9 +1492,9 @@ get_frame_register_bytes (frame_info_ptr frame, int regnum,
/* Ensure that we will not read beyond the end of the register file.
This can only ever happen if the debug information is bad. */
- maxsize = -offset;
- numregs = gdbarch_num_cooked_regs (gdbarch);
- for (i = regnum; i < numregs; i++)
+ int maxsize = -offset;
+ int numregs = gdbarch_num_cooked_regs (gdbarch);
+ for (int i = regnum; i < numregs; i++)
{
int thissize = register_size (gdbarch, i);
@@ -1506,20 +1503,15 @@ get_frame_register_bytes (frame_info_ptr frame, int regnum,
maxsize += thissize;
}
- int len = buffer.size ();
- if (len > maxsize)
+ if (buffer.size () > maxsize)
error (_("Bad debug information detected: "
- "Attempt to read %d bytes from registers."), len);
+ "Attempt to read %zu bytes from registers."), buffer.size ());
/* Copy the data. */
- while (len > 0)
+ while (!buffer.empty ())
{
- int curr_len = register_size (gdbarch, regnum) - offset;
-
- if (curr_len > len)
- curr_len = len;
-
- gdb_byte *myaddr = buffer.data ();
+ int curr_len = std::min<int> (register_size (gdbarch, regnum) - offset,
+ buffer.size ());
if (curr_len == register_size (gdbarch, regnum))
{
@@ -1527,8 +1519,8 @@ get_frame_register_bytes (frame_info_ptr frame, int regnum,
CORE_ADDR addr;
int realnum;
- frame_register (frame, regnum, optimizedp, unavailablep,
- &lval, &addr, &realnum, myaddr);
+ frame_register (frame, regnum, optimizedp, unavailablep, &lval,
+ &addr, &realnum, buffer.data ());
if (*optimizedp || *unavailablep)
return false;
}
@@ -1547,13 +1539,12 @@ get_frame_register_bytes (frame_info_ptr frame, int regnum,
return false;
}
- memcpy (myaddr, value->contents_all ().data () + offset,
- curr_len);
+ copy (value->contents_all ().slice (offset, curr_len),
+ buffer.slice (0, curr_len));
release_value (value);
}
- myaddr += curr_len;
- len -= curr_len;
+ buffer = buffer.slice (curr_len);
offset = 0;
regnum++;
}
@@ -1578,36 +1569,28 @@ put_frame_register_bytes (frame_info_ptr frame, int regnum,
regnum++;
}
- int len = buffer.size ();
/* Copy the data. */
- while (len > 0)
+ while (!buffer.empty ())
{
- int curr_len = register_size (gdbarch, regnum) - offset;
+ int curr_len = std::min<int> (register_size (gdbarch, regnum) - offset,
+ buffer.size ());
- if (curr_len > len)
- curr_len = len;
-
- const gdb_byte *myaddr = buffer.data ();
if (curr_len == register_size (gdbarch, regnum))
- {
- put_frame_register (frame, regnum, myaddr);
- }
+ put_frame_register (frame, regnum, buffer.data ());
else
{
- struct value *value
+ value *value
= frame_unwind_register_value (frame_info_ptr (frame->next),
regnum);
- gdb_assert (value != NULL);
+ gdb_assert (value != nullptr);
- memcpy ((char *) value->contents_writeable ().data () + offset,
- myaddr, curr_len);
- put_frame_register (frame, regnum,
- value->contents_raw ().data ());
+ copy (buffer.slice (0, curr_len),
+ value->contents_writeable ().slice (offset, curr_len));
+ put_frame_register (frame, regnum, value->contents_raw ().data ());
release_value (value);
}
- myaddr += curr_len;
- len -= curr_len;
+ buffer = buffer.slice (curr_len);
offset = 0;
regnum++;
}
--
2.42.1
next prev parent reply other threads:[~2023-11-08 5:21 UTC|newest]
Thread overview: 51+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-11-08 5:00 [PATCH 00/24] Fix reading and writing pseudo registers in non-current frames Simon Marchi
2023-11-08 5:00 ` [PATCH 01/24] gdb: don't handle i386 k registers as pseudo registers Simon Marchi
2023-11-11 19:29 ` John Baldwin
2023-11-08 5:00 ` [PATCH 02/24] gdb: use reg_buffer_common throughout gdbsupport/common-regcache.h Simon Marchi
2023-11-11 19:42 ` John Baldwin
2023-11-08 5:00 ` [PATCH 03/24] gdb: make store_integer take an array_view Simon Marchi
2023-11-08 5:00 ` [PATCH 04/24] gdb: simplify conditions in regcache::{read,write,raw_collect,raw_supply}_part Simon Marchi
2023-11-08 5:00 ` [PATCH 05/24] gdb: change regcache interface to use array_view Simon Marchi
2023-11-13 13:43 ` Andrew Burgess
2023-11-13 14:00 ` Andrew Burgess
2023-11-13 16:47 ` Simon Marchi
2023-11-08 5:00 ` Simon Marchi [this message]
2023-11-13 15:00 ` [PATCH 06/24] gdb: fix bugs in {get,put}_frame_register_bytes Andrew Burgess
2023-11-13 19:51 ` Simon Marchi
2023-11-08 5:00 ` [PATCH 07/24] gdb: make put_frame_register take an array_view Simon Marchi
2023-11-08 5:00 ` [PATCH 08/24] gdb: change value_of_register and value_of_register_lazy to take the next frame Simon Marchi
2023-11-08 5:00 ` [PATCH 09/24] gdb: remove frame_register Simon Marchi
2023-11-08 5:00 ` [PATCH 10/24] gdb: make put_frame_register take the next frame Simon Marchi
2023-11-08 5:00 ` [PATCH 11/24] gdb: make put_frame_register_bytes " Simon Marchi
2023-11-08 5:00 ` [PATCH 12/24] gdb: make get_frame_register_bytes " Simon Marchi
2023-11-08 5:00 ` [PATCH 13/24] gdb: add value::allocate_register Simon Marchi
2023-11-08 5:00 ` [PATCH 14/24] gdb: read pseudo register through frame Simon Marchi
2023-11-11 20:11 ` John Baldwin
2023-11-08 5:00 ` [PATCH 15/24] gdb: change parameter name in frame_unwind_register_unsigned declaration Simon Marchi
2023-11-08 5:01 ` [PATCH 16/24] gdb: rename gdbarch_pseudo_register_write to gdbarch_deprecated_pseudo_register_write Simon Marchi
2023-11-14 12:12 ` Andrew Burgess
2023-11-14 15:16 ` Simon Marchi
2023-11-08 5:01 ` [PATCH 17/24] gdb: add gdbarch_pseudo_register_write that takes a frame Simon Marchi
2023-11-14 12:20 ` Andrew Burgess
2023-11-14 15:20 ` Simon Marchi
2023-11-08 5:01 ` [PATCH 18/24] gdb: migrate i386 and amd64 to the new gdbarch_pseudo_register_write Simon Marchi
2023-11-11 20:16 ` John Baldwin
2023-11-13 2:59 ` Simon Marchi
2023-11-08 5:01 ` [PATCH 19/24] gdb: make aarch64_za_offsets_from_regnum return za_offsets Simon Marchi
2023-11-08 5:01 ` [PATCH 20/24] gdb: add missing raw register read in aarch64_sme_pseudo_register_write Simon Marchi
2023-11-08 5:01 ` [PATCH 21/24] gdb: migrate aarch64 to new gdbarch_pseudo_register_write Simon Marchi
2023-11-08 5:01 ` [PATCH 22/24] gdb: migrate arm to gdbarch_pseudo_register_read_value Simon Marchi
2023-11-08 5:01 ` [PATCH 23/24] gdb: migrate arm to new gdbarch_pseudo_register_write Simon Marchi
2023-11-08 5:01 ` [PATCH 24/24] gdb/testsuite: add tests for unwinding of pseudo registers Simon Marchi
2023-11-08 5:16 ` [PATCH 00/24] Fix reading and writing pseudo registers in non-current frames Simon Marchi
2023-11-09 3:05 ` Simon Marchi
2023-11-08 11:57 ` Luis Machado
2023-11-08 15:47 ` Simon Marchi
2023-11-08 17:08 ` Luis Machado
2023-11-08 19:34 ` Simon Marchi
2023-11-09 19:04 ` Simon Marchi
2023-11-13 13:10 ` Luis Machado
2023-11-13 15:08 ` Luis Machado
2023-11-11 20:26 ` John Baldwin
2023-11-13 3:03 ` Simon Marchi
2023-12-01 16:27 Simon Marchi
2023-12-01 16:27 ` [PATCH 06/24] gdb: fix bugs in {get,put}_frame_register_bytes Simon Marchi
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