[PATCH] tools/gdbsx: fix 'g' packet response for 64bit guests

* [PATCH] tools/gdbsx: fix 'g' packet response for 64bit guests
@ 2018-07-31  2:30 Marek Marczykowski-Górecki
  2018-07-31  8:01 ` Jan Beulich
  2018-07-31  9:00 ` Wei Liu
  0 siblings, 2 replies; 11+ messages in thread
From: Marek Marczykowski-Górecki @ 2018-07-31  2:30 UTC (permalink / raw)
  To: xen-devel
  Cc: Elena Ufimtseva, Wei Liu, Ian Jackson,
	Marek Marczykowski-Górecki, xen-devel

gdb 8.0 fixed bounds checking for 'g' packet (commit
9dc193c3be85aafa60ceff57d3b0430af607b4ce "Check for truncated
registers in process_g_packet"). This revealed that gdbsx did
not properly formatted 'g' packet - segment registers and eflags are
expected to be 32-bit fields in the response (according to
gdb/features/i386/64bit-core.xml in gdb sources). Specific error is:

    Truncated register 26 in remote 'g' packet

instead of silently truncating part of register.

Additionally, it looks like segment registers of 64bit guests were never
reported correctly, because of type mismatch.

Signed-off-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com>
---
 tools/debugger/gdbsx/gx/gx_local.c  |  6 +++---
 tools/debugger/gdbsx/xg/xg_main.c   | 20 ++++++++++----------
 tools/debugger/gdbsx/xg/xg_public.h | 18 +++++++++---------
 3 files changed, 22 insertions(+), 22 deletions(-)

diff --git a/tools/debugger/gdbsx/gx/gx_local.c b/tools/debugger/gdbsx/gx/gx_local.c
index 1bec03d49c..33556a582d 100644
--- a/tools/debugger/gdbsx/gx/gx_local.c
+++ b/tools/debugger/gdbsx/gx/gx_local.c
@@ -45,8 +45,8 @@ prnt_32regs(struct xg_gdb_regs32 *r32p)
 static void
 prnt_64regs(struct xg_gdb_regs64 *r64p)
 {
-    printf("rip:"XGF64" rsp:"XGF64" flags:"XGF64"\n", r64p->rip, r64p->rsp,
-           r64p->rflags);
+    printf("rip:"XGF64" rsp:"XGF64" flags:%08x\n", r64p->rip, r64p->rsp,
+           r64p->eflags);
     printf("rax:"XGF64" rbx:"XGF64" rcx:"XGF64"\n", r64p->rax, r64p->rbx,
            r64p->rcx);
     printf("rdx:"XGF64" rsi:"XGF64" rdi:"XGF64"\n", r64p->rdx, r64p->rsi,
@@ -57,7 +57,7 @@ prnt_64regs(struct xg_gdb_regs64 *r64p)
            r64p->r13);
     printf("r14:"XGF64" r15:"XGF64" rbp:"XGF64"\n", r64p->r14, r64p->r15,
            r64p->rbp);
-    printf("cs:"XGF64" ds:"XGF64" fs:"XGF64" gs:"XGF64"\n", r64p->cs, 
+    printf("cs:%08x ds:%08x fs:%08x gs:%08x\n", r64p->cs,
            r64p->ds, r64p->fs, r64p->gs);
     printf("\n");
 }
diff --git a/tools/debugger/gdbsx/xg/xg_main.c b/tools/debugger/gdbsx/xg/xg_main.c
index cc640d1d82..a4e8653168 100644
--- a/tools/debugger/gdbsx/xg/xg_main.c
+++ b/tools/debugger/gdbsx/xg/xg_main.c
@@ -580,14 +580,14 @@ _cp_64ctxt_to_64gdb(struct cpu_user_regs_x86_64 *cp, struct xg_gdb_regs64 *rp)
     rp->rax = cp->rax;
     rp->rip = cp->rip;         
     rp->rsp = cp->rsp;      
-    rp->rflags = cp->rflags;
-
-    rp->cs = (uint64_t)cp->cs;            
-    rp->ss = (uint64_t)cp->ss;
-    rp->es = (uint64_t)cp->es;            
-    rp->ds = (uint64_t)cp->ds;
-    rp->fs = (uint64_t)cp->fs;            
-    rp->gs = (uint64_t)cp->gs;
+    rp->eflags = cp->rflags;
+
+    rp->cs = cp->cs;
+    rp->ss = cp->ss;
+    rp->es = cp->es;
+    rp->ds = cp->ds;
+    rp->fs = cp->fs;
+    rp->gs = cp->gs;
 #if 0
     printf("cp:%llx bp:%llx rip:%llx\n", rp->rsp, rp->rbp, rp->rip);
     printf("rax:%llx rbx:%llx\n", rp->rax, rp->rbx);
@@ -635,7 +635,7 @@ _cp_32gdb_to_64ctxt(struct xg_gdb_regs32 *rp, struct cpu_user_regs_x86_64 *cp)
     cp->ds = rp->ds;       
     cp->fs = rp->fs;       
     cp->gs = rp->gs;
-    cp->rflags = rp->eflags;
+    cp->eflags = rp->eflags;
 }
 
 static void
@@ -658,7 +658,7 @@ _cp_64gdb_to_64ctxt(struct xg_gdb_regs64 *rp, struct cpu_user_regs_x86_64 *cp)
     cp->rax = rp->rax;
     cp->rip = rp->rip;
     cp->rsp = rp->rsp;
-    cp->rflags = rp->rflags;
+    cp->rflags = rp->eflags;
 
     cp->cs = (uint16_t)rp->cs;
     cp->ss = (uint16_t)rp->ss;
diff --git a/tools/debugger/gdbsx/xg/xg_public.h b/tools/debugger/gdbsx/xg/xg_public.h
index 3f905a2f0d..cffb2f7532 100644
--- a/tools/debugger/gdbsx/xg/xg_public.h
+++ b/tools/debugger/gdbsx/xg/xg_public.h
@@ -61,7 +61,7 @@ struct xg_gdb_regs32 {
     uint32_t  gs;
 };  
 
-/* this from: regformats/reg-x86-64.dat in gdbserver */
+/* based on gdb/features/i386/64bit-core.xml in gdb */
 struct xg_gdb_regs64 {
     uint64_t  rax;
     uint64_t  rbx;
@@ -80,14 +80,14 @@ struct xg_gdb_regs64 {
     uint64_t  r14;
     uint64_t  r15;
     uint64_t  rip;
-    uint64_t  rflags;
-    uint64_t  cs;
-    uint64_t  ss;
-    uint64_t  ds;
-    uint64_t  es;
-    uint64_t  fs;
-    uint64_t  gs;
-};
+    uint32_t  eflags;
+    uint32_t  cs;
+    uint32_t  ss;
+    uint32_t  ds;
+    uint32_t  es;
+    uint32_t  fs;
+    uint32_t  gs;
+} __attribute__((__packed__));
 
 union xg_gdb_regs {
     struct xg_gdb_regs32 gregs_32;
-- 
2.17.1


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