| Message ID | TY0PR0101MB42855925D8414E4773D6FA36A41D9@TY0PR0101MB4285.apcprd01.prod.exchangelabs.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | target/i386/gdbstub: Fix a bug about order of FPU stack in 'g' packets. | expand |
On 12/8/22 04:30, TaiseiIto wrote: > Before this commit, when GDB attached an OS working on QEMU, order of FPU > stack registers printed by GDB command 'info float' was wrong. There was a > bug causing the problem in 'g' packets sent by QEMU to GDB. The packets have > values of registers of machine emulated by QEMU containing FPU stack > registers. There are 2 ways to specify a x87 FPU stack register. The first > is specifying by absolute indexed register names (R0, ..., R7). The second > is specifying by stack top relative indexed register names (ST0, ..., ST7). > Values of the FPU stack registers should be located in 'g' packet and be > ordered by the relative index. But QEMU had located these registers ordered > by the absolute index. After this commit, when QEMU reads registers to make > a 'g' packet, QEMU specifies FPU stack registers by the relative index. > Then, the registers are ordered correctly in the packet. As a result, GDB, > the packet receiver, can print FPU stack registers in the correct order. > > Signed-off-by: TaiseiIto <taisei1212@outlook.jp> > --- > target/i386/gdbstub.c | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > diff --git a/target/i386/gdbstub.c b/target/i386/gdbstub.c > index c3a2cf6f28..6109ad166d 100644 > --- a/target/i386/gdbstub.c > +++ b/target/i386/gdbstub.c > @@ -121,7 +121,9 @@ int x86_cpu_gdb_read_register(CPUState *cs, GByteArray *mem_buf, int n) > return gdb_get_reg32(mem_buf, env->regs[gpr_map32[n]]); > } > } else if (n >= IDX_FP_REGS && n < IDX_FP_REGS + 8) { > - floatx80 *fp = (floatx80 *) &env->fpregs[n - IDX_FP_REGS]; > + int st_index = n - IDX_FP_REGS; > + int r_index = (st_index + env->fpstt) % 8; > + floatx80 *fp = (floatx80 *) &env->fpregs[r_index]; Reviewed-by: Richard Henderson <richard.henderson@linaro.org> Note that the cast can be dropped by taking the address of the ".d" union member. r~
diff --git a/target/i386/gdbstub.c b/target/i386/gdbstub.c index c3a2cf6f28..6109ad166d 100644 --- a/target/i386/gdbstub.c +++ b/target/i386/gdbstub.c @@ -121,7 +121,9 @@ int x86_cpu_gdb_read_register(CPUState *cs, GByteArray *mem_buf, int n) return gdb_get_reg32(mem_buf, env->regs[gpr_map32[n]]); } } else if (n >= IDX_FP_REGS && n < IDX_FP_REGS + 8) { - floatx80 *fp = (floatx80 *) &env->fpregs[n - IDX_FP_REGS]; + int st_index = n - IDX_FP_REGS; + int r_index = (st_index + env->fpstt) % 8; + floatx80 *fp = (floatx80 *) &env->fpregs[r_index]; int len = gdb_get_reg64(mem_buf, cpu_to_le64(fp->low)); len += gdb_get_reg16(mem_buf, cpu_to_le16(fp->high)); return len;
Before this commit, when GDB attached an OS working on QEMU, order of FPU stack registers printed by GDB command 'info float' was wrong. There was a bug causing the problem in 'g' packets sent by QEMU to GDB. The packets have values of registers of machine emulated by QEMU containing FPU stack registers. There are 2 ways to specify a x87 FPU stack register. The first is specifying by absolute indexed register names (R0, ..., R7). The second is specifying by stack top relative indexed register names (ST0, ..., ST7). Values of the FPU stack registers should be located in 'g' packet and be ordered by the relative index. But QEMU had located these registers ordered by the absolute index. After this commit, when QEMU reads registers to make a 'g' packet, QEMU specifies FPU stack registers by the relative index. Then, the registers are ordered correctly in the packet. As a result, GDB, the packet receiver, can print FPU stack registers in the correct order. Signed-off-by: TaiseiIto <taisei1212@outlook.jp> --- target/i386/gdbstub.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)