Am 21. Dezember 2024 05:45:49 UTC schrieb Davidson Francis
<davidsond...@gmail.com>:
>Debugging 16-bit/real mode code in QEMU+GDB is challenging due to
>incorrect architecture detection and segmented memory addressing issues.
>
>This patch improves the debugging experience by reporting i8086
>architecture to GDB when in real mode and converting segmented addresses
>(CS:EIP, SS:ESP) to their physical equivalents when reporting to GDB.
>This enables proper instruction disassembly and stack inspection without
>complex workarounds.
>
>Note: Mode switches after GDB attachment still require manual
>architecture change, as GDB RSP does not support runtime architecture
>switches.
>
>Signed-off-by: Davidson Francis <davidsond...@gmail.com>
>---
> target/i386/cpu.c | 8 +++++++-
> target/i386/gdbstub.c | 15 +++++++++++++--
> 2 files changed, 20 insertions(+), 3 deletions(-)
Ping
I don't feel confident reviewing this patch. Paolo? Zhao?
Best regards,
Bernhard
>
>diff --git a/target/i386/cpu.c b/target/i386/cpu.c
>index 5253399459..65bdc48cc0 100644
>--- a/target/i386/cpu.c
>+++ b/target/i386/cpu.c
>@@ -6404,7 +6404,13 @@ static const gchar *x86_gdb_arch_name(CPUState *cs)
> #ifdef TARGET_X86_64
> return "i386:x86-64";
> #else
>- return "i386";
>+ X86CPU *cpu = X86_CPU(cs);
>+ CPUX86State *env = &cpu->env;
>+ if (env->cr[0] & 1) {
>+ return "i386";
>+ } else {
>+ return "i8086";
>+ }
> #endif
> }
>
>diff --git a/target/i386/gdbstub.c b/target/i386/gdbstub.c
>index 04c49e802d..d600aee953 100644
>--- a/target/i386/gdbstub.c
>+++ b/target/i386/gdbstub.c
>@@ -136,7 +136,13 @@ int x86_cpu_gdb_read_register(CPUState *cs, GByteArray
>*mem_buf, int n)
> return gdb_get_regl(mem_buf, 0);
> }
> } else {
>- return gdb_get_reg32(mem_buf, env->regs[gpr_map32[n]]);
>+ if (n != R_ESP || (env->cr[0] & 1)) {
>+ return gdb_get_reg32(mem_buf, env->regs[gpr_map32[n]]);
>+ } else {
>+ return gdb_get_reg32(mem_buf,
>+ (env->segs[R_SS].selector << 4) +
>+ env->regs[gpr_map32[n]]);
>+ }
> }
> } else if (n >= IDX_FP_REGS && n < IDX_FP_REGS + 8) {
> int st_index = n - IDX_FP_REGS;
>@@ -155,7 +161,12 @@ int x86_cpu_gdb_read_register(CPUState *cs, GByteArray
>*mem_buf, int n)
> } else {
> switch (n) {
> case IDX_IP_REG:
>- return gdb_get_reg(env, mem_buf, env->eip);
>+ if (TARGET_LONG_BITS != 32 || (env->cr[0] & 1)) {
>+ return gdb_get_reg(env, mem_buf, env->eip);
>+ } else {
>+ return gdb_get_reg(env, mem_buf,
>+ (env->segs[R_CS].selector << 4) +
>env->eip);
>+ }
> case IDX_FLAGS_REG:
> return gdb_get_reg32(mem_buf, env->eflags);
>
