[PATCH v3 0/5] Add stub to handle Xfer:siginfo:read query

[PATCH v3 0/5] Add stub to handle Xfer:siginfo:read query

[Gustavo Romero]

Xfer:siginfo:read query is received, usually, when GDB catches a signal
and needs additional info about it, like the si_code and the si_addr, so
GDB can show the user interesting info about the signal. This query can
also be received when an user explicitly asks for more information via
printing GBD's special purpose variable '$_siginfo'.

This series adds the stub to handle Xfer:siginfo:read queries.

To achieve this, it is first necessary to stash the target-specific
siginfo in the gdbstub server state struct when handling a signal, so it
requires modifying the gdb_handlesig function to accept the target's
siginfo struct and its length.

Later, when replying to a Xfer:siginfo:read query (i.e., after a
signal is caught), the query handler utilizes the stashed siginfo to
form the packet for replying to the query.

Finally, a test is added to check if the stub correctly responds to the
query when a simple binary causes a SIGSEGV. Since the si_addr must be
available in the case of a SIGSEGV, the value of si_addr is checked
against the expected faulting address, corresponding to the dereferenced
pointer value in the binary.

v1:
https://lists.gnu.org/archive/html/qemu-devel/2024-03/msg00423.html

v2:
https://lists.gnu.org/archive/html/qemu-devel/2024-03/msg01858.html


Cheers,
Gustavo

Gustavo Romero (5):
  gdbstub: Rename back gdb_handlesig
  linux-user: Move tswap_siginfo out of target code
  gdbstub: Save target's siginfo
  gdbstub: Add Xfer:siginfo:read stub
  tests/tcg: Add multiarch test for Xfer:siginfo:read stub

 bsd-user/main.c                               |  2 +-
 bsd-user/signal.c                             |  5 +-
 gdbstub/gdbstub.c                             |  8 ++++
 gdbstub/internals.h                           |  1 +
 gdbstub/user.c                                | 46 +++++++++++++++++--
 include/gdbstub/user.h                        | 19 +++-----
 linux-user/aarch64/signal.c                   |  2 +-
 linux-user/alpha/signal.c                     |  2 +-
 linux-user/arm/signal.c                       |  2 +-
 linux-user/hexagon/signal.c                   |  2 +-
 linux-user/hppa/signal.c                      |  2 +-
 linux-user/i386/signal.c                      |  6 +--
 linux-user/loongarch64/signal.c               |  2 +-
 linux-user/m68k/signal.c                      |  4 +-
 linux-user/main.c                             |  2 +-
 linux-user/microblaze/signal.c                |  2 +-
 linux-user/mips/signal.c                      |  4 +-
 linux-user/nios2/signal.c                     |  2 +-
 linux-user/openrisc/signal.c                  |  2 +-
 linux-user/ppc/signal.c                       |  4 +-
 linux-user/riscv/signal.c                     |  2 +-
 linux-user/s390x/signal.c                     |  2 +-
 linux-user/sh4/signal.c                       |  2 +-
 linux-user/signal-common.h                    |  2 -
 linux-user/signal.c                           | 15 ++++--
 linux-user/sparc/signal.c                     |  2 +-
 linux-user/xtensa/signal.c                    |  2 +-
 tests/tcg/multiarch/Makefile.target           | 10 +++-
 .../gdbstub/test-qxfer-siginfo-read.py        | 26 +++++++++++
 tests/tcg/multiarch/segfault.c                | 14 ++++++
 30 files changed, 147 insertions(+), 49 deletions(-)
 create mode 100644 tests/tcg/multiarch/gdbstub/test-qxfer-siginfo-read.py
 create mode 100644 tests/tcg/multiarch/segfault.c

-- 
2.34.1

[PATCH v3 1/5] gdbstub: Rename back gdb_handlesig

[Gustavo Romero]

Rename gdb_handlesig_reason back to gdb_handlesig. There is no need to
add a wrapper for gdb_handlesig and rename it when a new parameter is
added.

Signed-off-by: Gustavo Romero <gustavo.romero@linaro.org>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
---
 gdbstub/user.c         |  8 ++++----
 include/gdbstub/user.h | 15 ++-------------
 linux-user/main.c      |  2 +-
 linux-user/signal.c    |  2 +-
 4 files changed, 8 insertions(+), 19 deletions(-)

diff --git a/gdbstub/user.c b/gdbstub/user.c
index 14918d1a21..a157e67f95 100644
--- a/gdbstub/user.c
+++ b/gdbstub/user.c
@@ -131,7 +131,7 @@ void gdb_qemu_exit(int code)
     exit(code);
 }
 
-int gdb_handlesig_reason(CPUState *cpu, int sig, const char *reason)
+int gdb_handlesig(CPUState *cpu, int sig, const char *reason)
 {
     char buf[256];
     int n;
@@ -510,7 +510,7 @@ void gdb_breakpoint_remove_all(CPUState *cs)
 void gdb_syscall_handling(const char *syscall_packet)
 {
     gdb_put_packet(syscall_packet);
-    gdb_handlesig(gdbserver_state.c_cpu, 0);
+    gdb_handlesig(gdbserver_state.c_cpu, 0, NULL);
 }
 
 static bool should_catch_syscall(int num)
@@ -528,7 +528,7 @@ void gdb_syscall_entry(CPUState *cs, int num)
 {
     if (should_catch_syscall(num)) {
         g_autofree char *reason = g_strdup_printf("syscall_entry:%x;", num);
-        gdb_handlesig_reason(cs, gdb_target_sigtrap(), reason);
+        gdb_handlesig(cs, gdb_target_sigtrap(), reason);
     }
 }
 
@@ -536,7 +536,7 @@ void gdb_syscall_return(CPUState *cs, int num)
 {
     if (should_catch_syscall(num)) {
         g_autofree char *reason = g_strdup_printf("syscall_return:%x;", num);
-        gdb_handlesig_reason(cs, gdb_target_sigtrap(), reason);
+        gdb_handlesig(cs, gdb_target_sigtrap(), reason);
     }
 }
 
diff --git a/include/gdbstub/user.h b/include/gdbstub/user.h
index 68b6534130..6647af2123 100644
--- a/include/gdbstub/user.h
+++ b/include/gdbstub/user.h
@@ -10,7 +10,7 @@
 #define GDBSTUB_USER_H
 
 /**
- * gdb_handlesig_reason() - yield control to gdb
+ * gdb_handlesig() - yield control to gdb
  * @cpu: CPU
  * @sig: if non-zero, the signal number which caused us to stop
  * @reason: stop reason for stop reply packet or NULL
@@ -25,18 +25,7 @@
  * or 0 if no signal should be delivered, ie the signal that caused
  * us to stop should be ignored.
  */
-int gdb_handlesig_reason(CPUState *, int, const char *);
-
-/**
- * gdb_handlesig() - yield control to gdb
- * @cpu CPU
- * @sig: if non-zero, the signal number which caused us to stop
- * @see gdb_handlesig_reason()
- */
-static inline int gdb_handlesig(CPUState *cpu, int sig)
-{
-    return gdb_handlesig_reason(cpu, sig, NULL);
-}
+int gdb_handlesig(CPUState *, int, const char *);
 
 /**
  * gdb_signalled() - inform remote gdb of sig exit
diff --git a/linux-user/main.c b/linux-user/main.c
index 551acf1661..049fd85a2a 100644
--- a/linux-user/main.c
+++ b/linux-user/main.c
@@ -1014,7 +1014,7 @@ int main(int argc, char **argv, char **envp)
                     gdbstub);
             exit(EXIT_FAILURE);
         }
-        gdb_handlesig(cpu, 0);
+        gdb_handlesig(cpu, 0, NULL);
     }
 
 #ifdef CONFIG_SEMIHOSTING
diff --git a/linux-user/signal.c b/linux-user/signal.c
index d3e62ab030..a57c45de35 100644
--- a/linux-user/signal.c
+++ b/linux-user/signal.c
@@ -1180,7 +1180,7 @@ static void handle_pending_signal(CPUArchState *cpu_env, int sig,
     /* dequeue signal */
     k->pending = 0;
 
-    sig = gdb_handlesig(cpu, sig);
+    sig = gdb_handlesig(cpu, sig, NULL);
     if (!sig) {
         sa = NULL;
         handler = TARGET_SIG_IGN;
-- 
2.34.1

[PATCH v3 2/5] linux-user: Move tswap_siginfo out of target code

[Gustavo Romero]

Move tswap_siginfo from target code to handle_pending_signal. This will
allow some cleanups and having the siginfo ready to be used in gdbstub.

Signed-off-by: Gustavo Romero <gustavo.romero@linaro.org>
Suggested-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
---
 linux-user/aarch64/signal.c     |  2 +-
 linux-user/alpha/signal.c       |  2 +-
 linux-user/arm/signal.c         |  2 +-
 linux-user/hexagon/signal.c     |  2 +-
 linux-user/hppa/signal.c        |  2 +-
 linux-user/i386/signal.c        |  6 +++---
 linux-user/loongarch64/signal.c |  2 +-
 linux-user/m68k/signal.c        |  4 ++--
 linux-user/microblaze/signal.c  |  2 +-
 linux-user/mips/signal.c        |  4 ++--
 linux-user/nios2/signal.c       |  2 +-
 linux-user/openrisc/signal.c    |  2 +-
 linux-user/ppc/signal.c         |  4 ++--
 linux-user/riscv/signal.c       |  2 +-
 linux-user/s390x/signal.c       |  2 +-
 linux-user/sh4/signal.c         |  2 +-
 linux-user/signal-common.h      |  2 --
 linux-user/signal.c             | 10 ++++++++--
 linux-user/sparc/signal.c       |  2 +-
 linux-user/xtensa/signal.c      |  2 +-
 20 files changed, 31 insertions(+), 27 deletions(-)

diff --git a/linux-user/aarch64/signal.c b/linux-user/aarch64/signal.c
index a1e22d526d..bc7a13800d 100644
--- a/linux-user/aarch64/signal.c
+++ b/linux-user/aarch64/signal.c
@@ -670,7 +670,7 @@ static void target_setup_frame(int usig, struct target_sigaction *ka,
     aarch64_set_svcr(env, 0, R_SVCR_SM_MASK | R_SVCR_ZA_MASK);
 
     if (info) {
-        tswap_siginfo(&frame->info, info);
+        frame->info = *info;
         env->xregs[1] = frame_addr + offsetof(struct target_rt_sigframe, info);
         env->xregs[2] = frame_addr + offsetof(struct target_rt_sigframe, uc);
     }
diff --git a/linux-user/alpha/signal.c b/linux-user/alpha/signal.c
index 4ec42994d4..896c2c148a 100644
--- a/linux-user/alpha/signal.c
+++ b/linux-user/alpha/signal.c
@@ -173,7 +173,7 @@ void setup_rt_frame(int sig, struct target_sigaction *ka,
         goto give_sigsegv;
     }
 
-    tswap_siginfo(&frame->info, info);
+    frame->info = *info;
 
     __put_user(0, &frame->uc.tuc_flags);
     __put_user(0, &frame->uc.tuc_link);
diff --git a/linux-user/arm/signal.c b/linux-user/arm/signal.c
index f77f692c63..420fc04cfa 100644
--- a/linux-user/arm/signal.c
+++ b/linux-user/arm/signal.c
@@ -357,7 +357,7 @@ void setup_rt_frame(int usig, struct target_sigaction *ka,
 
     info_addr = frame_addr + offsetof(struct rt_sigframe, info);
     uc_addr = frame_addr + offsetof(struct rt_sigframe, sig.uc);
-    tswap_siginfo(&frame->info, info);
+    frame->info = *info;
 
     setup_sigframe(&frame->sig.uc, set, env);
 
diff --git a/linux-user/hexagon/signal.c b/linux-user/hexagon/signal.c
index 60fa7e1bce..492b51f155 100644
--- a/linux-user/hexagon/signal.c
+++ b/linux-user/hexagon/signal.c
@@ -162,7 +162,7 @@ void setup_rt_frame(int sig, struct target_sigaction *ka,
     }
 
     setup_ucontext(&frame->uc, env, set);
-    tswap_siginfo(&frame->info, info);
+    frame->info = *info;
     /*
      * The on-stack signal trampoline is no longer executed;
      * however, the libgcc signal frame unwinding code checks
diff --git a/linux-user/hppa/signal.c b/linux-user/hppa/signal.c
index d08a97dae6..8960175da3 100644
--- a/linux-user/hppa/signal.c
+++ b/linux-user/hppa/signal.c
@@ -127,7 +127,7 @@ void setup_rt_frame(int sig, struct target_sigaction *ka,
         goto give_sigsegv;
     }
 
-    tswap_siginfo(&frame->info, info);
+    frame->info = *info;
     frame->uc.tuc_flags = 0;
     frame->uc.tuc_link = 0;
 
diff --git a/linux-user/i386/signal.c b/linux-user/i386/signal.c
index bc5d45302e..cfe70fc5cf 100644
--- a/linux-user/i386/signal.c
+++ b/linux-user/i386/signal.c
@@ -430,7 +430,7 @@ void setup_frame(int sig, struct target_sigaction *ka,
     setup_sigcontext(&frame->sc, &frame->fpstate, env, set->sig[0],
             frame_addr + offsetof(struct sigframe, fpstate));
 
-    for(i = 1; i < TARGET_NSIG_WORDS; i++) {
+    for (i = 1; i < TARGET_NSIG_WORDS; i++) {
         __put_user(set->sig[i], &frame->extramask[i - 1]);
     }
 
@@ -490,7 +490,7 @@ void setup_rt_frame(int sig, struct target_sigaction *ka,
     __put_user(addr, &frame->puc);
 #endif
     if (ka->sa_flags & TARGET_SA_SIGINFO) {
-        tswap_siginfo(&frame->info, info);
+        frame->info = *info;
     }
 
     /* Create the ucontext.  */
@@ -504,7 +504,7 @@ void setup_rt_frame(int sig, struct target_sigaction *ka,
     setup_sigcontext(&frame->uc.tuc_mcontext, &frame->fpstate, env,
             set->sig[0], frame_addr + offsetof(struct rt_sigframe, fpstate));
 
-    for(i = 0; i < TARGET_NSIG_WORDS; i++) {
+    for (i = 0; i < TARGET_NSIG_WORDS; i++) {
         __put_user(set->sig[i], &frame->uc.tuc_sigmask.sig[i]);
     }
 
diff --git a/linux-user/loongarch64/signal.c b/linux-user/loongarch64/signal.c
index 39ea82c814..1a322f9697 100644
--- a/linux-user/loongarch64/signal.c
+++ b/linux-user/loongarch64/signal.c
@@ -376,7 +376,7 @@ void setup_rt_frame(int sig, struct target_sigaction *ka,
         extctx.end.haddr = (void *)frame + (extctx.end.gaddr - frame_addr);
     }
 
-    tswap_siginfo(&frame->rs_info, info);
+    frame->rs_info = *info;
 
     __put_user(0, &frame->rs_uc.tuc_flags);
     __put_user(0, &frame->rs_uc.tuc_link);
diff --git a/linux-user/m68k/signal.c b/linux-user/m68k/signal.c
index 5f35354487..77555781aa 100644
--- a/linux-user/m68k/signal.c
+++ b/linux-user/m68k/signal.c
@@ -295,7 +295,7 @@ void setup_rt_frame(int sig, struct target_sigaction *ka,
     uc_addr = frame_addr + offsetof(struct target_rt_sigframe, uc);
     __put_user(uc_addr, &frame->puc);
 
-    tswap_siginfo(&frame->info, info);
+    frame->info = *info;
 
     /* Create the ucontext */
 
@@ -307,7 +307,7 @@ void setup_rt_frame(int sig, struct target_sigaction *ka,
     if (err)
         goto give_sigsegv;
 
-    for(i = 0; i < TARGET_NSIG_WORDS; i++) {
+    for (i = 0; i < TARGET_NSIG_WORDS; i++) {
         __put_user(set->sig[i], &frame->uc.tuc_sigmask.sig[i]);
     }
 
diff --git a/linux-user/microblaze/signal.c b/linux-user/microblaze/signal.c
index 5188d74025..f6d47d76ff 100644
--- a/linux-user/microblaze/signal.c
+++ b/linux-user/microblaze/signal.c
@@ -147,7 +147,7 @@ void setup_rt_frame(int sig, struct target_sigaction *ka,
         return;
     }
 
-    tswap_siginfo(&frame->info, info);
+    frame->info = *info;
 
     __put_user(0, &frame->uc.tuc_flags);
     __put_user(0, &frame->uc.tuc_link);
diff --git a/linux-user/mips/signal.c b/linux-user/mips/signal.c
index 58a9d7a8a3..d69a5d73dd 100644
--- a/linux-user/mips/signal.c
+++ b/linux-user/mips/signal.c
@@ -303,7 +303,7 @@ void setup_rt_frame(int sig, struct target_sigaction *ka,
         goto give_sigsegv;
     }
 
-    tswap_siginfo(&frame->rs_info, info);
+    frame->rs_info = *info;
 
     __put_user(0, &frame->rs_uc.tuc_flags);
     __put_user(0, &frame->rs_uc.tuc_link);
@@ -311,7 +311,7 @@ void setup_rt_frame(int sig, struct target_sigaction *ka,
 
     setup_sigcontext(env, &frame->rs_uc.tuc_mcontext);
 
-    for(i = 0; i < TARGET_NSIG_WORDS; i++) {
+    for (i = 0; i < TARGET_NSIG_WORDS; i++) {
         __put_user(set->sig[i], &frame->rs_uc.tuc_sigmask.sig[i]);
     }
 
diff --git a/linux-user/nios2/signal.c b/linux-user/nios2/signal.c
index 32b3dc99c6..64c345f409 100644
--- a/linux-user/nios2/signal.c
+++ b/linux-user/nios2/signal.c
@@ -157,7 +157,7 @@ void setup_rt_frame(int sig, struct target_sigaction *ka,
         return;
     }
 
-    tswap_siginfo(&frame->info, info);
+    frame->info = *info;
 
     /* Create the ucontext.  */
     __put_user(0, &frame->uc.tuc_flags);
diff --git a/linux-user/openrisc/signal.c b/linux-user/openrisc/signal.c
index be8b68784a..cb74a9fe5e 100644
--- a/linux-user/openrisc/signal.c
+++ b/linux-user/openrisc/signal.c
@@ -103,7 +103,7 @@ void setup_rt_frame(int sig, struct target_sigaction *ka,
     }
 
     if (ka->sa_flags & SA_SIGINFO) {
-        tswap_siginfo(&frame->info, info);
+        frame->info = *info;
     }
 
     __put_user(0, &frame->uc.tuc_flags);
diff --git a/linux-user/ppc/signal.c b/linux-user/ppc/signal.c
index 7e7302823b..0ebfc0b26b 100644
--- a/linux-user/ppc/signal.c
+++ b/linux-user/ppc/signal.c
@@ -493,7 +493,7 @@ void setup_rt_frame(int sig, struct target_sigaction *ka,
     if (!lock_user_struct(VERIFY_WRITE, rt_sf, rt_sf_addr, 1))
         goto sigsegv;
 
-    tswap_siginfo(&rt_sf->info, info);
+    rt_sf->info = *info;
 
     __put_user(0, &rt_sf->uc.tuc_flags);
     __put_user(0, &rt_sf->uc.tuc_link);
@@ -502,7 +502,7 @@ void setup_rt_frame(int sig, struct target_sigaction *ka,
     __put_user(h2g (&rt_sf->uc.tuc_mcontext),
                &rt_sf->uc.tuc_regs);
 #endif
-    for(i = 0; i < TARGET_NSIG_WORDS; i++) {
+    for (i = 0; i < TARGET_NSIG_WORDS; i++) {
         __put_user(set->sig[i], &rt_sf->uc.tuc_sigmask.sig[i]);
     }
 
diff --git a/linux-user/riscv/signal.c b/linux-user/riscv/signal.c
index 941eadce87..358fa1d82d 100644
--- a/linux-user/riscv/signal.c
+++ b/linux-user/riscv/signal.c
@@ -125,7 +125,7 @@ void setup_rt_frame(int sig, struct target_sigaction *ka,
     }
 
     setup_ucontext(&frame->uc, env, set);
-    tswap_siginfo(&frame->info, info);
+    frame->info = *info;
 
     env->pc = ka->_sa_handler;
     env->gpr[xSP] = frame_addr;
diff --git a/linux-user/s390x/signal.c b/linux-user/s390x/signal.c
index b40f738a70..df49c24708 100644
--- a/linux-user/s390x/signal.c
+++ b/linux-user/s390x/signal.c
@@ -267,7 +267,7 @@ void setup_rt_frame(int sig, struct target_sigaction *ka,
     }
 
     /* Create siginfo on the signal stack. */
-    tswap_siginfo(&frame->info, info);
+    frame->info = *info;
 
     /* Create ucontext on the signal stack. */
     uc_flags = 0;
diff --git a/linux-user/sh4/signal.c b/linux-user/sh4/signal.c
index c16c2c2d57..9ecc026fae 100644
--- a/linux-user/sh4/signal.c
+++ b/linux-user/sh4/signal.c
@@ -233,7 +233,7 @@ void setup_rt_frame(int sig, struct target_sigaction *ka,
         goto give_sigsegv;
     }
 
-    tswap_siginfo(&frame->info, info);
+    frame->info = *info;
 
     /* Create the ucontext.  */
     __put_user(0, &frame->uc.tuc_flags);
diff --git a/linux-user/signal-common.h b/linux-user/signal-common.h
index 3e2dc604c2..f02d2b6b64 100644
--- a/linux-user/signal-common.h
+++ b/linux-user/signal-common.h
@@ -43,8 +43,6 @@ void host_to_target_sigset_internal(target_sigset_t *d,
                                     const sigset_t *s);
 void target_to_host_sigset_internal(sigset_t *d,
                                     const target_sigset_t *s);
-void tswap_siginfo(target_siginfo_t *tinfo,
-                   const target_siginfo_t *info);
 void set_sigmask(const sigset_t *set);
 void force_sig(int sig);
 void force_sigsegv(int oldsig);
diff --git a/linux-user/signal.c b/linux-user/signal.c
index a57c45de35..7a4c8e416e 100644
--- a/linux-user/signal.c
+++ b/linux-user/signal.c
@@ -409,8 +409,8 @@ static inline void host_to_target_siginfo_noswap(target_siginfo_t *tinfo,
     tinfo->si_code = deposit32(si_code, 16, 16, si_type);
 }
 
-void tswap_siginfo(target_siginfo_t *tinfo,
-                   const target_siginfo_t *info)
+static void tswap_siginfo(target_siginfo_t *tinfo,
+                          const target_siginfo_t *info)
 {
     int si_type = extract32(info->si_code, 16, 16);
     int si_code = sextract32(info->si_code, 0, 16);
@@ -1180,6 +1180,12 @@ static void handle_pending_signal(CPUArchState *cpu_env, int sig,
     /* dequeue signal */
     k->pending = 0;
 
+    /*
+     * Writes out siginfo values byteswapped, accordingly to the target. It also
+     * cleans the si_type from si_code making it correct for the target.
+     */
+    tswap_siginfo(&k->info, &k->info);
+
     sig = gdb_handlesig(cpu, sig, NULL);
     if (!sig) {
         sa = NULL;
diff --git a/linux-user/sparc/signal.c b/linux-user/sparc/signal.c
index c2dc1000e2..f164b74032 100644
--- a/linux-user/sparc/signal.c
+++ b/linux-user/sparc/signal.c
@@ -333,7 +333,7 @@ void setup_rt_frame(int sig, struct target_sigaction *ka,
 
     __put_user(0, &sf->rwin_save);  /* TODO: save_rwin_state */
 
-    tswap_siginfo(&sf->info, info);
+    sf->info = *info;
     tswap_sigset(&sf->mask, set);
     target_save_altstack(&sf->stack, env);
 
diff --git a/linux-user/xtensa/signal.c b/linux-user/xtensa/signal.c
index 32dcfa5229..11e60c3c82 100644
--- a/linux-user/xtensa/signal.c
+++ b/linux-user/xtensa/signal.c
@@ -184,7 +184,7 @@ void setup_rt_frame(int sig, struct target_sigaction *ka,
     }
 
     if (ka->sa_flags & SA_SIGINFO) {
-        tswap_siginfo(&frame->info, info);
+        frame->info = *info;
     }
 
     __put_user(0, &frame->uc.tuc_flags);
-- 
2.34.1

[PATCH v3 3/5] gdbstub: Save target's siginfo

[Gustavo Romero]

Save target's siginfo into gdbserver_state so it can be used later, for
example, in any stub that requires the target's si_signo and si_code.

This change affects only linux-user mode.

Signed-off-by: Gustavo Romero <gustavo.romero@linaro.org>
Suggested-by: Richard Henderson <richard.henderson@linaro.org>
---
 bsd-user/main.c        |  2 +-
 bsd-user/signal.c      |  5 ++++-
 gdbstub/user.c         | 23 +++++++++++++++++++----
 include/gdbstub/user.h |  6 +++++-
 linux-user/main.c      |  2 +-
 linux-user/signal.c    |  5 ++++-
 6 files changed, 34 insertions(+), 9 deletions(-)

diff --git a/bsd-user/main.c b/bsd-user/main.c
index 512d4ab69f..04b18eee27 100644
--- a/bsd-user/main.c
+++ b/bsd-user/main.c
@@ -601,7 +601,7 @@ int main(int argc, char **argv)
 
     if (gdbstub) {
         gdbserver_start(gdbstub);
-        gdb_handlesig(cpu, 0);
+        gdb_handlesig(cpu, 0, NULL, NULL, 0);
     }
     cpu_loop(env);
     /* never exits */
diff --git a/bsd-user/signal.c b/bsd-user/signal.c
index f4352e4530..ad738def70 100644
--- a/bsd-user/signal.c
+++ b/bsd-user/signal.c
@@ -27,6 +27,9 @@
 #include "hw/core/tcg-cpu-ops.h"
 #include "host-signal.h"
 
+/* target_siginfo_t must fit in gdbstub's siginfo save area. */
+QEMU_BUILD_BUG_ON(sizeof(target_siginfo_t) > MAX_SIGINFO_LENGTH);
+
 static struct target_sigaction sigact_table[TARGET_NSIG];
 static void host_signal_handler(int host_sig, siginfo_t *info, void *puc);
 static void target_to_host_sigset_internal(sigset_t *d,
@@ -890,7 +893,7 @@ static void handle_pending_signal(CPUArchState *env, int sig,
 
     k->pending = 0;
 
-    sig = gdb_handlesig(cpu, sig);
+    sig = gdb_handlesig(cpu, sig, NULL, &k->info, sizeof(k->info));
     if (!sig) {
         sa = NULL;
         handler = TARGET_SIG_IGN;
diff --git a/gdbstub/user.c b/gdbstub/user.c
index a157e67f95..df040c6ffa 100644
--- a/gdbstub/user.c
+++ b/gdbstub/user.c
@@ -36,6 +36,8 @@ typedef struct {
      */
     bool catch_all_syscalls;
     GDBSyscallsMask catch_syscalls_mask;
+    uint8_t siginfo[MAX_SIGINFO_LENGTH];
+    unsigned long siginfo_len;
 } GDBUserState;
 
 static GDBUserState gdbserver_user_state;
@@ -131,7 +133,8 @@ void gdb_qemu_exit(int code)
     exit(code);
 }
 
-int gdb_handlesig(CPUState *cpu, int sig, const char *reason)
+int gdb_handlesig(CPUState *cpu, int sig, const char *reason, void *siginfo,
+                  int siginfo_len)
 {
     char buf[256];
     int n;
@@ -140,6 +143,18 @@ int gdb_handlesig(CPUState *cpu, int sig, const char *reason)
         return sig;
     }
 
+    if (siginfo) {
+        /*
+         * Save target-specific siginfo.
+         *
+         * siginfo size, i.e. siginfo_len, is asserted at compile-time to fit in
+         * gdbserver_user_state.siginfo, usually in the source file calling
+         * gdb_handlesig. See, for instance, {linux,bsd}-user/signal.c.
+         */
+        memcpy(gdbserver_user_state.siginfo, siginfo, siginfo_len);
+        gdbserver_user_state.siginfo_len = siginfo_len;
+    }
+
     /* disable single step if it was enabled */
     cpu_single_step(cpu, 0);
     tb_flush(cpu);
@@ -510,7 +525,7 @@ void gdb_breakpoint_remove_all(CPUState *cs)
 void gdb_syscall_handling(const char *syscall_packet)
 {
     gdb_put_packet(syscall_packet);
-    gdb_handlesig(gdbserver_state.c_cpu, 0, NULL);
+    gdb_handlesig(gdbserver_state.c_cpu, 0, NULL, NULL, 0);
 }
 
 static bool should_catch_syscall(int num)
@@ -528,7 +543,7 @@ void gdb_syscall_entry(CPUState *cs, int num)
 {
     if (should_catch_syscall(num)) {
         g_autofree char *reason = g_strdup_printf("syscall_entry:%x;", num);
-        gdb_handlesig(cs, gdb_target_sigtrap(), reason);
+        gdb_handlesig(cs, gdb_target_sigtrap(), reason, NULL, 0);
     }
 }
 
@@ -536,7 +551,7 @@ void gdb_syscall_return(CPUState *cs, int num)
 {
     if (should_catch_syscall(num)) {
         g_autofree char *reason = g_strdup_printf("syscall_return:%x;", num);
-        gdb_handlesig(cs, gdb_target_sigtrap(), reason);
+        gdb_handlesig(cs, gdb_target_sigtrap(), reason, NULL, 0);
     }
 }
 
diff --git a/include/gdbstub/user.h b/include/gdbstub/user.h
index 6647af2123..0ec9a7e596 100644
--- a/include/gdbstub/user.h
+++ b/include/gdbstub/user.h
@@ -9,11 +9,15 @@
 #ifndef GDBSTUB_USER_H
 #define GDBSTUB_USER_H
 
+#define MAX_SIGINFO_LENGTH 128
+
 /**
  * gdb_handlesig() - yield control to gdb
  * @cpu: CPU
  * @sig: if non-zero, the signal number which caused us to stop
  * @reason: stop reason for stop reply packet or NULL
+ * @siginfo: target-specific siginfo struct
+ * @siginfo_len: target-specific siginfo struct length
  *
  * This function yields control to gdb, when a user-mode-only target
  * needs to stop execution. If @sig is non-zero, then we will send a
@@ -25,7 +29,7 @@
  * or 0 if no signal should be delivered, ie the signal that caused
  * us to stop should be ignored.
  */
-int gdb_handlesig(CPUState *, int, const char *);
+int gdb_handlesig(CPUState *, int, const char *, void *, int);
 
 /**
  * gdb_signalled() - inform remote gdb of sig exit
diff --git a/linux-user/main.c b/linux-user/main.c
index 049fd85a2a..3187be48d6 100644
--- a/linux-user/main.c
+++ b/linux-user/main.c
@@ -1014,7 +1014,7 @@ int main(int argc, char **argv, char **envp)
                     gdbstub);
             exit(EXIT_FAILURE);
         }
-        gdb_handlesig(cpu, 0, NULL);
+        gdb_handlesig(cpu, 0, NULL, NULL, 0);
     }
 
 #ifdef CONFIG_SEMIHOSTING
diff --git a/linux-user/signal.c b/linux-user/signal.c
index 7a4c8e416e..98d1eacffe 100644
--- a/linux-user/signal.c
+++ b/linux-user/signal.c
@@ -34,6 +34,9 @@
 #include "user/safe-syscall.h"
 #include "tcg/tcg.h"
 
+/* target_siginfo_t must fit in gdbstub's siginfo save area. */
+QEMU_BUILD_BUG_ON(sizeof(target_siginfo_t) > MAX_SIGINFO_LENGTH);
+
 static struct target_sigaction sigact_table[TARGET_NSIG];
 
 static void host_signal_handler(int host_signum, siginfo_t *info,
@@ -1186,7 +1189,7 @@ static void handle_pending_signal(CPUArchState *cpu_env, int sig,
      */
     tswap_siginfo(&k->info, &k->info);
 
-    sig = gdb_handlesig(cpu, sig, NULL);
+    sig = gdb_handlesig(cpu, sig, NULL, &k->info, sizeof(k->info));
     if (!sig) {
         sa = NULL;
         handler = TARGET_SIG_IGN;
-- 
2.34.1

[PATCH v3 4/5] gdbstub: Add Xfer:siginfo:read stub

[Gustavo Romero]

Add stub to handle Xfer:siginfo:read packet query that requests the
machine's siginfo data.

This is used when GDB user executes 'print $_siginfo' and when the
machine stops due to a signal, for instance, on SIGSEGV. The information
in siginfo allows GDB to determiner further details on the signal, like
the fault address/insn when the SIGSEGV is caught.

Signed-off-by: Gustavo Romero <gustavo.romero@linaro.org>
---
 gdbstub/gdbstub.c   |  8 ++++++++
 gdbstub/internals.h |  1 +
 gdbstub/user.c      | 23 +++++++++++++++++++++++
 3 files changed, 32 insertions(+)

diff --git a/gdbstub/gdbstub.c b/gdbstub/gdbstub.c
index 2909bc8c69..ab38cea46b 100644
--- a/gdbstub/gdbstub.c
+++ b/gdbstub/gdbstub.c
@@ -1651,6 +1651,8 @@ static void handle_query_supported(GArray *params, void *user_ctx)
         g_string_append(gdbserver_state.str_buf, ";qXfer:auxv:read+");
     }
     g_string_append(gdbserver_state.str_buf, ";QCatchSyscalls+");
+
+    g_string_append(gdbserver_state.str_buf, ";qXfer:siginfo:read+");
 #endif
     g_string_append(gdbserver_state.str_buf, ";qXfer:exec-file:read+");
 #endif
@@ -1799,6 +1801,12 @@ static const GdbCmdParseEntry gdb_gen_query_table[] = {
         .cmd_startswith = 1,
         .schema = "l,l0"
     },
+    {
+        .handler = gdb_handle_query_xfer_siginfo,
+        .cmd = "Xfer:siginfo:read::",
+        .cmd_startswith = 1,
+        .schema = "l,l0"
+     },
 #endif
     {
         .handler = gdb_handle_query_xfer_exec_file,
diff --git a/gdbstub/internals.h b/gdbstub/internals.h
index 56b7c13b75..fcfe7c2d26 100644
--- a/gdbstub/internals.h
+++ b/gdbstub/internals.h
@@ -190,6 +190,7 @@ typedef union GdbCmdVariant {
 void gdb_handle_query_rcmd(GArray *params, void *user_ctx); /* softmmu */
 void gdb_handle_query_offsets(GArray *params, void *user_ctx); /* user */
 void gdb_handle_query_xfer_auxv(GArray *params, void *user_ctx); /*user */
+void gdb_handle_query_xfer_siginfo(GArray *params, void *user_ctx); /*user */
 void gdb_handle_v_file_open(GArray *params, void *user_ctx); /* user */
 void gdb_handle_v_file_close(GArray *params, void *user_ctx); /* user */
 void gdb_handle_v_file_pread(GArray *params, void *user_ctx); /* user */
diff --git a/gdbstub/user.c b/gdbstub/user.c
index df040c6ffa..5e175b5d62 100644
--- a/gdbstub/user.c
+++ b/gdbstub/user.c
@@ -616,3 +616,26 @@ void gdb_handle_set_catch_syscalls(GArray *params, void *user_ctx)
 err:
     gdb_put_packet("E00");
 }
+
+void gdb_handle_query_xfer_siginfo(GArray *params, void *user_ctx)
+{
+    unsigned long offset, len;
+    uint8_t *siginfo_offset;
+
+    offset = get_param(params, 0)->val_ul;
+    len = get_param(params, 1)->val_ul;
+
+    if (offset + len > gdbserver_user_state.siginfo_len) {
+        /* Invalid offset and/or requested length. */
+        gdb_put_packet("E01");
+        return;
+    }
+
+    siginfo_offset = (uint8_t *)gdbserver_user_state.siginfo + offset;
+
+    /* Reply */
+    g_string_assign(gdbserver_state.str_buf, "l");
+    gdb_memtox(gdbserver_state.str_buf, (const char *)siginfo_offset, len);
+    gdb_put_packet_binary(gdbserver_state.str_buf->str,
+                          gdbserver_state.str_buf->len, true);
+}
-- 
2.34.1

[PATCH v3 5/5] tests/tcg: Add multiarch test for Xfer:siginfo:read stub

[Gustavo Romero]

Add multiarch test for testing if Xfer:siginfo:read query is properly
handled by gdbstub.

Signed-off-by: Gustavo Romero <gustavo.romero@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
---
 tests/tcg/multiarch/Makefile.target           | 10 ++++++-
 .../gdbstub/test-qxfer-siginfo-read.py        | 26 +++++++++++++++++++
 tests/tcg/multiarch/segfault.c                | 14 ++++++++++
 3 files changed, 49 insertions(+), 1 deletion(-)
 create mode 100644 tests/tcg/multiarch/gdbstub/test-qxfer-siginfo-read.py
 create mode 100644 tests/tcg/multiarch/segfault.c

diff --git a/tests/tcg/multiarch/Makefile.target b/tests/tcg/multiarch/Makefile.target
index f11f3b084d..5ab4ba89b2 100644
--- a/tests/tcg/multiarch/Makefile.target
+++ b/tests/tcg/multiarch/Makefile.target
@@ -71,6 +71,13 @@ run-gdbstub-qxfer-auxv-read: sha1
 		--bin $< --test $(MULTIARCH_SRC)/gdbstub/test-qxfer-auxv-read.py, \
 	basic gdbstub qXfer:auxv:read support)
 
+run-gdbstub-qxfer-siginfo-read: segfault
+	$(call run-test, $@, $(GDB_SCRIPT) \
+		--gdb $(GDB) \
+		--qemu $(QEMU) --qargs "$(QEMU_OPTS)" \
+		--bin "$< -s" --test $(MULTIARCH_SRC)/gdbstub/test-qxfer-siginfo-read.py, \
+	basic gdbstub qXfer:siginfo:read support)
+
 run-gdbstub-proc-mappings: sha1
 	$(call run-test, $@, $(GDB_SCRIPT) \
 		--gdb $(GDB) \
@@ -113,7 +120,8 @@ endif
 EXTRA_RUNS += run-gdbstub-sha1 run-gdbstub-qxfer-auxv-read \
 	      run-gdbstub-proc-mappings run-gdbstub-thread-breakpoint \
 	      run-gdbstub-registers run-gdbstub-prot-none \
-	      run-gdbstub-catch-syscalls
+	      run-gdbstub-catch-syscalls \
+	      run-gdbstub-qxfer-siginfo-read
 
 # ARM Compatible Semi Hosting Tests
 #
diff --git a/tests/tcg/multiarch/gdbstub/test-qxfer-siginfo-read.py b/tests/tcg/multiarch/gdbstub/test-qxfer-siginfo-read.py
new file mode 100644
index 0000000000..862596b07a
--- /dev/null
+++ b/tests/tcg/multiarch/gdbstub/test-qxfer-siginfo-read.py
@@ -0,0 +1,26 @@
+from __future__ import print_function
+#
+# Test gdbstub Xfer:siginfo:read stub.
+#
+# The test runs a binary that causes a SIGSEGV and then looks for additional
+# info about the signal through printing GDB's '$_siginfo' special variable,
+# which sends a Xfer:siginfo:read query to the gdbstub.
+#
+# The binary causes a SIGSEGV at dereferencing a pointer with value 0xdeadbeef,
+# so the test looks for and checks if this address is correctly reported by the
+# gdbstub.
+#
+# This is launched via tests/guest-debug/run-test.py
+#
+
+import gdb
+from test_gdbstub import main, report
+
+def run_test():
+    "Run through the test"
+
+    gdb.execute("continue", False, True)
+    resp = gdb.execute("print/x $_siginfo", False, True)
+    report(resp.find("si_addr = 0xdeadbeef"), "Found fault address.")
+
+main(run_test)
diff --git a/tests/tcg/multiarch/segfault.c b/tests/tcg/multiarch/segfault.c
new file mode 100644
index 0000000000..e6c8ff31ca
--- /dev/null
+++ b/tests/tcg/multiarch/segfault.c
@@ -0,0 +1,14 @@
+#include <stdio.h>
+#include <string.h>
+
+/* Cause a segfault for testing purposes. */
+
+int main(int argc, char *argv[])
+{
+    int *ptr = (void *)0xdeadbeef;
+
+    if (argc == 2 && strcmp(argv[1], "-s") == 0) {
+        /* Cause segfault. */
+        printf("%d\n", *ptr);
+    }
+}
-- 
2.34.1

Re: [PATCH v3 0/5] Add stub to handle Xfer:siginfo:read query

[Alex Bennée]

Gustavo Romero <gustavo.romero@linaro.org> writes:

> Xfer:siginfo:read query is received, usually, when GDB catches a signal
> and needs additional info about it, like the si_code and the si_addr, so
> GDB can show the user interesting info about the signal. This query can
> also be received when an user explicitly asks for more information via
> printing GBD's special purpose variable '$_siginfo'.

Queued to gdbstub/next, thanks.

-- 
Alex Bennée
Virtualisation Tech Lead @ Linaro

Re: [PATCH v3 3/5] gdbstub: Save target's siginfo

[Richard Henderson]

On 3/8/24 17:08, Gustavo Romero wrote:
> Save target's siginfo into gdbserver_state so it can be used later, for
> example, in any stub that requires the target's si_signo and si_code.
> 
> This change affects only linux-user mode.
> 
> Signed-off-by: Gustavo Romero<gustavo.romero@linaro.org>
> Suggested-by: Richard Henderson<richard.henderson@linaro.org>
> ---
>   bsd-user/main.c        |  2 +-
>   bsd-user/signal.c      |  5 ++++-
>   gdbstub/user.c         | 23 +++++++++++++++++++----
>   include/gdbstub/user.h |  6 +++++-
>   linux-user/main.c      |  2 +-
>   linux-user/signal.c    |  5 ++++-
>   6 files changed, 34 insertions(+), 9 deletions(-)

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>

r~

Re: [PATCH v3 4/5] gdbstub: Add Xfer:siginfo:read stub

[Richard Henderson]

On 3/8/24 17:09, Gustavo Romero wrote:
> Add stub to handle Xfer:siginfo:read packet query that requests the
> machine's siginfo data.
> 
> This is used when GDB user executes 'print $_siginfo' and when the
> machine stops due to a signal, for instance, on SIGSEGV. The information
> in siginfo allows GDB to determiner further details on the signal, like
> the fault address/insn when the SIGSEGV is caught.
> 
> Signed-off-by: Gustavo Romero<gustavo.romero@linaro.org>
> ---
>   gdbstub/gdbstub.c   |  8 ++++++++
>   gdbstub/internals.h |  1 +
>   gdbstub/user.c      | 23 +++++++++++++++++++++++
>   3 files changed, 32 insertions(+)

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>

r~