From: Gustavo Romero <gustavo.romero@linaro.org>
To: gdb-patches@sourceware.org
Cc: luis.machado@arm.com, thiago.bauermann@linaro.org, eliz@gnu.org,
tom@tromey.com, gustavo.romero@linaro.org
Subject: [PATCH v6 6/8] gdb: Add qIsAddressTagged packet
Date: Thu, 18 Apr 2024 20:10:37 +0000 [thread overview]
Message-ID: <20240418201039.236867-7-gustavo.romero@linaro.org> (raw)
In-Reply-To: <20240418201039.236867-1-gustavo.romero@linaro.org>
This commit adds a new packet, qIsAddressTagged, allowing GDB remote
targets to use it to query the stub if a given address is tagged.
Currently, the memory tagging address check is done via a read query,
where the contents of /proc/<PID>/smaps is read and the flags are
inspected for memory tagging-related flags that indicate the address is
in a memory tagged region.
This is not ideal, for example, for QEMU stub and other cases, such as
on bare-metal, where there is no notion of an OS file like 'smaps.'
Hence, the introduction of qIsAddressTagged packet allows checking
if an address is tagged in an agnostic way.
The is_address_tagged target hook in remote.c attempts to use the
qIsAddressTagged packet first for checking if an address is tagged and
if the stub does not support such a packet (reply is empty) it falls
back to using the current mechanism that reads the contents of
/proc/<PID>/smaps via vFile requests.
Signed-off-by: Gustavo Romero <gustavo.romero@linaro.org>
---
gdb/remote.c | 75 ++++++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 75 insertions(+)
diff --git a/gdb/remote.c b/gdb/remote.c
index cd271c4b493..3d034bb1ef8 100644
--- a/gdb/remote.c
+++ b/gdb/remote.c
@@ -337,6 +337,9 @@ enum {
packets and the tag violation stop replies. */
PACKET_memory_tagging_feature,
+ /* Support for the qIsAddressTagged packet. */
+ PACKET_qIsAddressTagged,
+
PACKET_MAX
};
@@ -15535,6 +15538,50 @@ create_store_memtags_request (gdb::char_vector &packet, CORE_ADDR address,
strcpy (packet.data (), request.c_str ());
}
+static void
+create_is_address_tagged_request (gdbarch *gdbarch, gdb::char_vector &packet,
+ CORE_ADDR address)
+{
+ int addr_size;
+ std::string request;
+
+ addr_size = gdbarch_addr_bit (gdbarch) / 8;
+ request = string_printf ("qIsAddressTagged:%s", phex_nz (address, addr_size));
+
+ if (packet.size () < request.length () + 1)
+ error (_("Contents too big for packet qIsAddressTagged."));
+
+ strcpy (packet.data (), request.c_str ());
+}
+
+static bool
+check_is_address_tagged_reply (remote_target *remote, gdb::char_vector &packet,
+ bool &tagged)
+{
+ gdb_assert (remote != nullptr);
+ /* Check reply and disable qIsAddressTagged usage if it's not supported. */
+ packet_result result = remote->m_features.packet_ok (packet,
+ PACKET_qIsAddressTagged);
+
+ /* Return false on error (Exx), empty reply (packet not supported), or reply
+ size doesn't match 2 hex digits. */
+ if ((result.status () != PACKET_OK) || (strlen (packet.data ()) != 2))
+ return false;
+
+ gdb_byte reply;
+ /* Convert only 2 hex digits, i.e. 1 byte in hex format. */
+ hex2bin (packet.data (), &reply, 1);
+
+ if (reply == 0x00 || reply == 0x01)
+ {
+ tagged = !!reply;
+ return true;
+ }
+
+ /* Invalid reply. */
+ return false;
+}
+
/* Implement the "fetch_memtags" target_ops method. */
bool
@@ -15581,6 +15628,31 @@ remote_target::store_memtags (CORE_ADDR address, size_t len,
bool
remote_target::is_address_tagged (gdbarch *gdbarch, CORE_ADDR address)
{
+ /* Firstly, attempt to check the address using the qIsAddressTagged
+ packet. */
+ if (m_features.packet_support (PACKET_qIsAddressTagged) != PACKET_DISABLE)
+ {
+ remote_target *remote = get_current_remote_target ();
+ struct remote_state *rs = get_remote_state ();
+ bool is_addr_tagged;
+
+ create_is_address_tagged_request (gdbarch, rs->buf, address);
+
+ putpkt (rs->buf);
+ getpkt (&rs->buf);
+
+ /* If qIsAddressTagged is not supported PACKET_qIsAddressTagged will be
+ set to PACKET_DISABLE so no further attempt is made to check addresses
+ using this packet and the fallback mechanism below will be used
+ instead. Also, if the check fails due to an error (Exx reply) the
+ fallback is used too. Otherwise, the qIsAddressTagged query succeeded
+ and is_addr_tagged is valid. */
+ if (check_is_address_tagged_reply (remote, rs->buf, is_addr_tagged))
+ return is_addr_tagged;
+ }
+
+ /* Fallback to arch-specific method of checking whether an address is tagged
+ in case check via qIsAddressTagged fails. */
return gdbarch_tagged_address_p (gdbarch, address);
}
@@ -16070,6 +16142,9 @@ Show the maximum size of the address (in bits) in a memory packet."), NULL,
add_packet_config_cmd (PACKET_memory_tagging_feature,
"memory-tagging-feature", "memory-tagging-feature", 0);
+ add_packet_config_cmd (PACKET_qIsAddressTagged,
+ "qIsAddressTagged", "memory-tagging-address-check", 0);
+
/* Assert that we've registered "set remote foo-packet" commands
for all packet configs. */
{
--
2.34.1
next prev parent reply other threads:[~2024-04-18 20:11 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-18 20:10 [PATCH v6 0/8] Add another way to check tagged addresses on remote targets Gustavo Romero
2024-04-18 20:10 ` [PATCH v6 1/8] gdb: aarch64: Remove MTE address checking from get_memtag Gustavo Romero
2024-04-18 20:10 ` [PATCH v6 2/8] gdb: aarch64: Move MTE address check out of set_memtag Gustavo Romero
2024-04-18 20:10 ` [PATCH v6 3/8] gdb: aarch64: Remove MTE address checking from memtag_matches_p Gustavo Romero
2024-04-18 20:10 ` [PATCH v6 4/8] gdb: Use passed gdbarch instead of calling current_inferior Gustavo Romero
2024-04-18 20:10 ` [PATCH v6 5/8] gdb: Introduce is_address_tagged target hook Gustavo Romero
2024-04-18 20:10 ` Gustavo Romero [this message]
2024-04-19 7:52 ` [PATCH v6 6/8] gdb: Add qIsAddressTagged packet Luis Machado
2024-04-18 20:10 ` [PATCH v6 7/8] gdb/testsuite: Add unit tests for " Gustavo Romero
2024-04-19 7:53 ` Luis Machado
2024-04-19 14:00 ` Gustavo Romero
2024-04-19 14:31 ` Luis Machado
2024-04-18 20:10 ` [PATCH v6 8/8] gdb: Document " Gustavo Romero
2024-04-19 6:07 ` Eli Zaretskii
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