On 27/2/26 14:09, Philippe Mathieu-Daudé wrote:
On 27/2/26 10:58, Philippe Mathieu-Daudé wrote:
Hi Florian,
on current master (d8a9d97317d03190b34498741f98f22e2a9afe3e), the basic
gdb stub test fails for ppc-linux-user when running "make check-tcg".
I've debugged around a bit but I don't know my way around the gdbstub
internals enough to propose a patch right away, so I'll just summarize
what I figured out so far.
1. Due to cc->gdb_num_core_regs not being set explicitly anymore, it is
set to 0 at the end of gdbstub/gdbstub.c:gdb_init_cpu(). In the same
function, cpu->gdb_num_regs gets set to 70.
2. When the test tries to read a register in gdbstub/
gdbstub.c:gdb_read_register(),
the first condition of "reg < cc->gdb_num_core_regs" is always
false.
Also, the register number for fpscr passed to the function is is
103,
and cpu->gdb_num_regs is also 103. If the register number is
supposed
to be an index (as I understand it), this would indicate an
off-by-one error somewhere.
If you have some pointers on where to look / what to check out for
fixing this, I'll happily try to work on a patch. But I suppose that
somebody more experienced with this could probably fix this much faster
than I can.
I'll have a look.
Short term, this seems to fix it:
Series for the generic fix posted:
https://lore.kernel.org/qemu-devel/[email protected]/
-- >8 --
diff --git a/gdbstub/gdbstub.c b/gdbstub/gdbstub.c
index 90f4b95135b..0b0a5d1e044 100644
--- a/gdbstub/gdbstub.c
+++ b/gdbstub/gdbstub.c
@@ -610,6 +610,10 @@ void gdb_register_coprocessor(CPUState *cpu,
guint i;
int base_reg = cpu->gdb_num_regs;
+ if (g_pos && g_pos != base_reg) {
+ base_reg = g_pos;
+ }
+
for (i = 0; i < cpu->gdb_regs->len; i++) {
/* Check for duplicates. */
s = &g_array_index(cpu->gdb_regs, GDBRegisterState, i);
@@ -622,14 +626,7 @@ void gdb_register_coprocessor(CPUState *cpu,
/* Add to end of list. */
cpu->gdb_num_regs += feature->num_regs;
- if (g_pos) {
- if (g_pos != base_reg) {
- error_report("Error: Bad gdb register numbering for '%s', "
- "expected %d got %d", feature->xml, g_pos,
base_reg);
- } else {
- cpu->gdb_num_g_regs = cpu->gdb_num_regs;
- }
- }
+ cpu->gdb_num_g_regs = cpu->gdb_num_regs;
}
void gdb_unregister_coprocessor_all(CPUState *cpu)
diff --git a/target/ppc/gdbstub.c b/target/ppc/gdbstub.c
index e0aae9c9eaf..51b14b95b9f 100644
--- a/target/ppc/gdbstub.c
+++ b/target/ppc/gdbstub.c
@@ -502,7 +502,7 @@ void ppc_gdb_init(CPUState *cs, PowerPCCPUClass *pcc)
{
if (pcc->insns_flags & PPC_FLOAT) {
gdb_register_coprocessor(cs, gdb_get_float_reg,
gdb_set_float_reg,
- gdb_find_static_feature("power-fpu.xml"), 0);
+ gdb_find_static_feature("power-fpu.xml"), 71);
}
if (pcc->insns_flags & PPC_ALTIVEC) {
gdb_register_coprocessor(cs, gdb_get_avr_reg, gdb_set_avr_reg,
---
