===================================================================
@@ -198,8 +198,8 @@ struct arch_lwp_info
/* Pseudo registers can not be read. ptrace does not provide a way to
read (or set) PS_REGNUM, and there's no point in reading or setting
- ZERO_REGNUM. We also can not set BADVADDR, CAUSE, or FCRIR via
- ptrace(). */
+ ZERO_REGNUM, it's always 0. We also can not set BADVADDR, CAUSE,
+ or FCRIR via ptrace(). */
static int
mips_cannot_fetch_register (int regno)
@@ -242,6 +242,20 @@ mips_cannot_store_register (int regno)
return 0;
}
+static int
+mips_fetch_register (struct regcache *regcache, int regno)
+{
+ const struct target_desc *tdesc = current_process ()->tdesc;
+
+ if (find_regno (tdesc, "r0") == regno)
+ {
+ supply_register_zeroed (regcache, regno);
+ return 1;
+ }
+
+ return 0;
+}
+
static CORE_ADDR
mips_get_pc (struct regcache *regcache)
{
@@ -750,7 +764,9 @@ mips_store_gregset (struct regcache *reg
use_64bit = (register_size (regcache->tdesc, 0) == 8);
- for (i = 0; i < 32; i++)
+ supply_register_by_name_zeroed (regcache, "r0");
+
+ for (i = 1; i < 32; i++)
mips_supply_register (regcache, use_64bit, i, regset + i);
mips_supply_register (regcache, use_64bit,
@@ -879,7 +895,7 @@ struct linux_target_ops the_low_target =
mips_regs_info,
mips_cannot_fetch_register,
mips_cannot_store_register,
- NULL, /* fetch_register */
+ mips_fetch_register,
mips_get_pc,
mips_set_pc,
NULL, /* breakpoint_kind_from_pc */
Consistently supply hardwired $zero as a zeroed register, correcting issues with the PTRACE_GETREGS path that currently copies the value of $restart into $zero as illustrated by this program: $ cat read.c #include <unistd.h> int main (void) { char buf[1024]; ssize_t size; size = read (0, buf, sizeof (buf)); return size; } $ and this corresponding debug session: (gdb) break main Breakpoint 1 at 0x120000970: file read.c, line 9. (gdb) target remote :2346 Remote debugging using :2346 Reading symbols from .../sysroot/mips-r2-hard/lib64/ld.so.1...done. 0x000000fff7fca5a0 in __start () from .../sysroot/mips-r2-hard/lib64/ld.so.1 (gdb) continue Continuing. Breakpoint 1, main () at read.c:9 9 size = read (0, buf, sizeof (buf)); (gdb) info registers zero at v0 v1 R0 0000000000000000 0000000000000001 000000fff7ffe710 0000000000000000 a0 a1 a2 a3 R4 0000000000000001 000000ffffffeb88 000000ffffffeb98 0000000000000000 a4 a5 a6 a7 R8 000000fff7fc8800 000000fff7fc38f0 000000ffffffeb80 2f2f2f2f2f2f2f2f t0 t1 t2 t3 R12 0000000000000437 0000000000000002 000000fff7ffd000 0000000120000a00 s0 s1 s2 s3 R16 000000fff7fc7068 0000000120000b90 0000000000000000 0000000000000000 s4 s5 s6 s7 R20 0000000000521d88 0000000000522608 0000000000000000 0000000000000000 t8 t9 k0 k1 R24 0000000000000000 0000000120000970 0000000000000000 0000000000000000 gp sp s8 ra R28 000000fff7fc8800 000000ffffffea50 0000000000000000 000000fff7e4088c status lo hi badvaddr 0000000000109cf3 0000000000005ea5 0000000000000211 000000fff7eadf00 cause pc 0000000000800024 0000000120000970 fcsr fir restart 00000000 00f30000 0000000000000000 (gdb) continue Continuing. ^C Program received signal SIGINT, Interrupt. 0x000000fff7f084ac in __GI___libc_read (fd=0, buf=0xffffffe640, nbytes=1024) at ../sysdeps/unix/sysv/linux/read.c:27 27 return SYSCALL_CANCEL (read, fd, buf, nbytes); (gdb) info registers zero at v0 v1 R0 0000000000001388 0000000000000001 0000000000000200 000000fff7ffe710 a0 a1 a2 a3 R4 0000000000000000 000000ffffffe640 0000000000000400 0000000000000001 a4 a5 a6 a7 R8 000000fff7fc8800 000000fff7fc38f0 000000ffffffeb80 2f2f2f2f2f2f2f2f t0 t1 t2 t3 R12 00000000000005e3 0000000000000002 000000fff7ffd000 000000012000099c s0 s1 s2 s3 R16 000000fff7fc7068 0000000120000b90 0000000000000000 0000000000000000 s4 s5 s6 s7 R20 0000000000521d88 0000000000522608 0000000000000000 0000000000000000 t8 t9 k0 k1 R24 0000000000000000 000000fff7f2da20 0000000000000000 0000000000000000 gp sp s8 ra R28 000000fff7fc8800 000000ffffffe600 0000000000000000 000000012000099c status lo hi badvaddr 0000000000109cf3 00000000000001e6 00000000000000be 000000fff7f08470 cause pc 0000000000800020 000000fff7f084ac fcsr fir restart 00000000 00f30000 0000000000001388 (gdb) and with the PTRACE_PEEKUSR path that does not supply this register at all, causing issues analogous to ones addressed for the native MIPS backend with commit 4e6ff0e1b86f ("MIPS/Linux/native: Supply $zero for the !PTRACE_GETREGS case"): (gdb) info registers zero at v0 v1 R0 <unavailable> 0000000000000001 0000000000000001 0000000000000000 a0 a1 a2 a3 R4 00000001200212b0 0000000000000000 0000000000000021 000000012001a260 a4 a5 a6 a7 R8 000000012001a260 0000000000000004 800000010cab1680 fffffffffffffff8 t0 t1 t2 t3 R12 0000000000000000 000000fff7edab68 0000000000000001 0000000000000000 s0 s1 s2 s3 R16 000000fff7ee2068 0000000120008b80 0000000000000000 0000000000000000 s4 s5 s6 s7 R20 000000000052e5c8 000000000052f008 0000000000000000 0000000000000000 t8 t9 k0 k1 R24 0000000000000000 00000001200027c0 0000000000000000 0000000000000000 gp sp s8 ra R28 00000001200212b0 000000ffffffc880 000000ffffffc880 0000000120005ee8 status lo hi badvaddr <unavailable> 0000000000943efe 000000000000000e 000000012001a008 cause pc 0000000000800024 0000000120005ee8 fcsr fir restart 0e800000 00f30000 0000000000000000 (gdb) and (under certain circumstances): (gdb) next Register 0 is not available (gdb) The problem with PTRACE_GETREGS happens because `mips_store_gregset' supplies the contents of register slot #0, occupied by $restart, to $zero. The problem with PTRACE_PEEKUSR happens because for $zero `mips_cannot_fetch_register' returns one, and no alternative way to supply that register has been defined. Correct `mips_store_gregset' then for the PTRACE_GETREGS case and add `mips_fetch_register' for the PTRACE_PEEKUSR case. gdb/gdbserver/ * linux-mips-low.c (mips_fetch_register): New function. Update preceding comment. (mips_store_gregset): Supply 0 rather than $restart for $zero. (the_low_target): Wire `mips_fetch_register'. --- Hi, No regressions with o32 or n64 native-gdbserver testing, and numerous progressions with `gdbserver' strapped for PTRACE_PEEKUSR/PTRACE_POKEUSR use. Committed. Maciej --- gdb/gdbserver/linux-mips-low.c | 24 ++++++++++++++++++++---- 1 file changed, 20 insertions(+), 4 deletions(-) gdb-mips-gdbserver-zero-regno.diff