[for-9.1,v2,1/2] target/riscv/debug: set tval=pc in breakpoint exceptions

Commit Message

Daniel Henrique Barboza April 16, 2024, 7:41 p.m. UTC

We're not setting (s/m)tval when triggering breakpoints of type 2
(mcontrol) and 6 (mcontrol6). According to the debug spec section
5.7.12, "Match Control Type 6":

"The Privileged Spec says that breakpoint exceptions that occur on
instruction fetches, loads, or stores update the tval CSR with either
zero or the faulting virtual address. The faulting virtual address for
an mcontrol6 trigger with action = 0 is the address being accessed and
which caused that trigger to fire."

A similar text is also found in the Debug spec section 5.7.11 w.r.t.
mcontrol.

Note that what we're doing ATM is not violating the spec, but it's
simple enough to set mtval/stval and it makes life easier for any
software that relies on this info.

Given that we always use action = 0, save the faulting address for the
mcontrol and mcontrol6 trigger breakpoints into env->badaddr, which is
used as as scratch area for traps with address information. 'tval' is
then set during riscv_cpu_do_interrupt().

Signed-off-by: Daniel Henrique Barboza <[e-mail]>
---
 target/riscv/cpu_helper.c | 1 +
 target/riscv/debug.c      | 3 +++
 2 files changed, 4 insertions(+)

Patch

diff --git a/target/riscv/cpu_helper.c b/target/riscv/cpu_helper.c
index fc090d729a..f9c6d7053b 100644
--- a/target/riscv/cpu_helper.c
+++ b/target/riscv/cpu_helper.c
@@ -1717,6 +1717,7 @@  void riscv_cpu_do_interrupt(CPUState *cs)
             tval = env->bins;
             break;
         case RISCV_EXCP_BREAKPOINT:
+            tval = env->badaddr;
             if (cs->watchpoint_hit) {
                 tval = cs->watchpoint_hit->hitaddr;
                 cs->watchpoint_hit = NULL;
diff --git a/target/riscv/debug.c b/target/riscv/debug.c
index e30d99cc2f..b110370ea6 100644
--- a/target/riscv/debug.c
+++ b/target/riscv/debug.c
@@ -798,6 +798,7 @@  bool riscv_cpu_debug_check_breakpoint(CPUState *cs)
                 if ((ctrl & TYPE2_EXEC) && (bp->pc == pc)) {
                     /* check U/S/M bit against current privilege level */
                     if ((ctrl >> 3) & BIT(env->priv)) {
+                        env->badaddr = pc;
                         return true;
                     }
                 }
@@ -810,11 +811,13 @@  bool riscv_cpu_debug_check_breakpoint(CPUState *cs)
                     if (env->virt_enabled) {
                         /* check VU/VS bit against current privilege level */
                         if ((ctrl >> 23) & BIT(env->priv)) {
+                            env->badaddr = pc;
                             return true;
                         }
                     } else {
                         /* check U/S/M bit against current privilege level */
                         if ((ctrl >> 3) & BIT(env->priv)) {
+                            env->badaddr = pc;
                             return true;
                         }
                     }