Commit 56aebc891674cd2d07b3f64183415697be200084 changed gdbstub in way
that debugging 32 or 16-bit guest code is no longer possible with qemu
for x86_64 guest CPUs. Since that commit, qemu only provides registers
sets for 64-bit, forcing current and foreseeable gdb to also switch its
architecture to 64-bit. And this breaks if the inferior is 32 or 16 bit.
No question, this is a gdb issue. But, as it was confirmed in several
discusssions with gdb people, it is a non-trivial thing to fix. So until
qemu finds a gdb version attach with a rework x86 support, we have to
work around it by switching the register layout as the guest switches
its execution mode between 16/32 and 64 bit.
Signed-off-by: Jan Kiszka <jan.kiszka@xxxxxxxxxxx>
---
Sent to qemu-kvm for inclusion on Avi's request as this workaround is
still disliked upstream.
Note: qemu-kvm's gdbstub support in kvm mode is currently borken in git
- I'm bisecting...
gdbstub.c | 55 ++++++++++++++++++++++++++++++++++++++++-------------
target-i386/cpu.h | 7 +++++--
2 files changed, 47 insertions(+), 15 deletions(-)
diff --git a/gdbstub.c b/gdbstub.c
index c9304cd..a33aba0 100644
--- a/gdbstub.c
+++ b/gdbstub.c
@@ -506,8 +506,9 @@ static const int gpr_map[16] = {
8, 9, 10, 11, 12, 13, 14, 15
};
#else
-static const int gpr_map[8] = {0, 1, 2, 3, 4, 5, 6, 7};
+#define gpr_map gpr_map32
#endif
+static const int gpr_map32[8] = { 0, 1, 2, 3, 4, 5, 6, 7 };
#define NUM_CORE_REGS (CPU_NB_REGS * 2 + 25)
@@ -521,7 +522,11 @@ static const int gpr_map[8] = {0, 1, 2, 3, 4, 5, 6, 7};
static int cpu_gdb_read_register(CPUState *env, uint8_t *mem_buf, int n)
{
if (n < CPU_NB_REGS) {
- GET_REGL(env->regs[gpr_map[n]]);
+ if (TARGET_LONG_BITS == 64 && env->hflags & HF_CS64_MASK) {
+ GET_REG64(env->regs[gpr_map[n]]);
+ } else if (n < CPU_NB_REGS32) {
+ GET_REG32(env->regs[gpr_map32[n]]);
+ }
} else if (n >= IDX_FP_REGS && n < IDX_FP_REGS + 8) {
#ifdef USE_X86LDOUBLE
/* FIXME: byteswap float values - after fixing fpregs layout. */
@@ -532,12 +537,20 @@ static int cpu_gdb_read_register(CPUState *env, uint8_t *mem_buf, int n)
return 10;
} else if (n >= IDX_XMM_REGS && n < IDX_XMM_REGS + CPU_NB_REGS) {
n -= IDX_XMM_REGS;
- stq_p(mem_buf, env->xmm_regs[n].XMM_Q(0));
- stq_p(mem_buf + 8, env->xmm_regs[n].XMM_Q(1));
- return 16;
+ if (n < CPU_NB_REGS32 ||
+ (TARGET_LONG_BITS == 64 && env->hflags & HF_CS64_MASK)) {
+ stq_p(mem_buf, env->xmm_regs[n].XMM_Q(0));
+ stq_p(mem_buf + 8, env->xmm_regs[n].XMM_Q(1));
+ return 16;
+ }
} else {
switch (n) {
- case IDX_IP_REG: GET_REGL(env->eip);
+ case IDX_IP_REG:
+ if (TARGET_LONG_BITS == 64 && env->hflags & HF_CS64_MASK) {
+ GET_REG64(env->eip);
+ } else {
+ GET_REG32(env->eip);
+ }
case IDX_FLAGS_REG: GET_REG32(env->eflags);
case IDX_SEG_REGS: GET_REG32(env->segs[R_CS].selector);
@@ -593,8 +606,15 @@ static int cpu_gdb_write_register(CPUState *env, uint8_t *mem_buf, int n)
uint32_t tmp;
if (n < CPU_NB_REGS) {
- env->regs[gpr_map[n]] = ldtul_p(mem_buf);
- return sizeof(target_ulong);
+ if (TARGET_LONG_BITS == 64 && env->hflags & HF_CS64_MASK) {
+ env->regs[gpr_map[n]] = ldtul_p(mem_buf);
+ return sizeof(target_ulong);
+ } else if (n < CPU_NB_REGS32) {
+ n = gpr_map32[n];
+ env->regs[n] &= ~0xffffffffUL;
+ env->regs[n] |= (uint32_t)ldl_p(mem_buf);
+ return 4;
+ }
} else if (n >= IDX_FP_REGS && n < IDX_FP_REGS + 8) {
#ifdef USE_X86LDOUBLE
/* FIXME: byteswap float values - after fixing fpregs layout. */
@@ -603,14 +623,23 @@ static int cpu_gdb_write_register(CPUState *env, uint8_t *mem_buf, int n)
return 10;
} else if (n >= IDX_XMM_REGS && n < IDX_XMM_REGS + CPU_NB_REGS) {
n -= IDX_XMM_REGS;
- env->xmm_regs[n].XMM_Q(0) = ldq_p(mem_buf);
- env->xmm_regs[n].XMM_Q(1) = ldq_p(mem_buf + 8);
- return 16;
+ if (n < CPU_NB_REGS32 ||
+ (TARGET_LONG_BITS == 64 && env->hflags & HF_CS64_MASK)) {
+ env->xmm_regs[n].XMM_Q(0) = ldq_p(mem_buf);
+ env->xmm_regs[n].XMM_Q(1) = ldq_p(mem_buf + 8);
+ return 16;
+ }
} else {
switch (n) {
case IDX_IP_REG:
- env->eip = ldtul_p(mem_buf);
- return sizeof(target_ulong);
+ if (TARGET_LONG_BITS == 64 && env->hflags & HF_CS64_MASK) {
+ env->eip = ldq_p(mem_buf);
+ return 8;
+ } else {
+ env->eip &= ~0xffffffffUL;
+ env->eip |= (uint32_t)ldl_p(mem_buf);
+ return 4;
+ }
case IDX_FLAGS_REG:
env->eflags = ldl_p(mem_buf);
return 4;
diff --git a/target-i386/cpu.h b/target-i386/cpu.h
index b9a6392..4506d73 100644
--- a/target-i386/cpu.h
+++ b/target-i386/cpu.h
@@ -555,10 +555,13 @@ typedef union {
#endif
#define MMX_Q(n) q
+#define CPU_NB_REGS64 16
+#define CPU_NB_REGS32 8
+
#ifdef TARGET_X86_64
-#define CPU_NB_REGS 16
+#define CPU_NB_REGS CPU_NB_REGS64
#else
-#define CPU_NB_REGS 8
+#define CPU_NB_REGS CPU_NB_REGS32
#endif
#define NB_MMU_MODES 2
--
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