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[PATCH] gdb-xml: Fix size of EFER register on i386 architecture when deb


From: TaiseiIto
Subject: [PATCH] gdb-xml: Fix size of EFER register on i386 architecture when debugged by GDB
Date: Tue, 13 Sep 2022 12:06:00 +0000

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.

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"/>
-- 
2.34.1




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