From: "Alex Bennée" <alex.bennee@linaro.org>
To: TaiseiIto <taisei1212@outlook.jp>
Cc: qemu-devel@nongnu.org, f4bug@amsat.org
Subject: Re: [PATCH] gdb-xml: Fix size of EFER register on i386 architecture when debugged by GDB
Date: Thu, 03 Nov 2022 15:59:24 +0000 [thread overview]
Message-ID: <87sfj0jadm.fsf@linaro.org> (raw)
In-Reply-To: <TY0PR0101MB4285F637209075C9F65FCDA6A4479@TY0PR0101MB4285.apcprd01.prod.exchangelabs.com>
TaiseiIto <taisei1212@outlook.jp> writes:
> Before this commit, there were contradictory descriptions about size of EFER
> register.
> Line 113 says the size is 8 bytes.
> Line 129 says the size is 4 bytes.
>
> As a result, when GDB is debugging an OS running on QEMU, the GDB cannot
> read 'g' packets correctly. This 'g' packet transmits values of each
> registers of machine emulated by QEMU to GDB. QEMU, the packet sender,
> assign 4 bytes for EFER in 'g' packet based on the line 113.
> GDB, the packet receiver, extract 8 bytes for EFER in 'g' packet based on
> the line 129. Therefore, all registers located behind EFER in 'g' packet
> has been shifted 4 bytes in GDB.
I can't get the failure to read in my case:
./qemu-system-i386 -monitor none -display none \
-chardev stdio,id=out -device isa-debugcon,chardev=out \
-device isa-debug-exit,iobase=0xf4,iosize=0x4 \
-kernel ./tests/tcg/i386-softmmu/memory -s -S
and then with gdb:
➜ gdb ./tests/tcg/i386-softmmu/memory -ex "target remote localhost:1234"
Reading symbols from ./tests/tcg/i386-softmmu/memory...
Remote debugging using localhost:1234
0x0000fff0 in ?? ()
(gdb) info registers efer
efer 0x0 [ ]
What am I missing?
>
> After this commit, GDB can read 'g' packets correctly.
>
> Signed-off-by: TaiseiIto <taisei1212@outlook.jp>
> ---
> gdb-xml/i386-32bit.xml | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/gdb-xml/i386-32bit.xml b/gdb-xml/i386-32bit.xml
> index 872fcea9c2..7a66a02b67 100644
> --- a/gdb-xml/i386-32bit.xml
> +++ b/gdb-xml/i386-32bit.xml
> @@ -110,7 +110,7 @@
> <field name="PKE" start="22" end="22"/>
> </flags>
>
> - <flags id="i386_efer" size="8">
> + <flags id="i386_efer" size="4">
> <field name="TCE" start="15" end="15"/>
> <field name="FFXSR" start="14" end="14"/>
> <field name="LMSLE" start="13" end="13"/>
--
Alex Bennée
next prev parent reply other threads:[~2022-11-03 16:01 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-09-13 12:06 [PATCH] gdb-xml: Fix size of EFER register on i386 architecture when debugged by GDB TaiseiIto
2022-10-10 2:46 ` [PATCH] [PING] " TaiseiIto
2022-10-22 2:14 ` [PATCH] [PING^2] " TaiseiIto
2022-11-03 15:59 ` Alex Bennée [this message]
2022-11-05 3:14 ` [PATCH] " 伊藤 太清
2022-11-03 18:38 ` Paolo Bonzini
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