[binutils-gdb] Fix-for-multiple-thread-detection-in-AIX.

[Ulrich Weigand <uweigand@sourceware.org>]

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=80d362484999634e11d2b9f9e6d69e2cd4fdba12

commit 80d362484999634e11d2b9f9e6d69e2cd4fdba12
Author: Aditya Vidyadhar Kamath <Aditya.Kamath1@ibm.com>
Date:   Fri Aug 5 09:07:37 2022 -0500

    Fix-for-multiple-thread-detection-in-AIX.
    
    In AIX multiple threads were not added. This patch is a fix for the same
    
    When we create a pthread debug session we have callbacks to read
    symbols and memory.  One of those call backs is pdc_read_data.
    
    Before we come into aix-thread wait() we switch to no thread and
    therefore the current thread is null.
    
    When we get into pdc_read_data we have a dependency that we need to
    be in the correct current thread that has caused an event of new
    thread, inorder to read memory.
    
    Hence we switch to the correct thread.
    
    This is done by passing the pid in the pthdb_user_t user_current_pid
    parameter in every call back.

Diff:
---
 gdb/aix-thread.c | 63 +++++++++++++++++++++++++++++++-------------------------
 1 file changed, 35 insertions(+), 28 deletions(-)

diff --git a/gdb/aix-thread.c b/gdb/aix-thread.c
index 4c9195a7f12..57e5756e144 100644
--- a/gdb/aix-thread.c
+++ b/gdb/aix-thread.c
@@ -72,11 +72,6 @@ static bool debug_aix_thread;
 
 #define PD_TID(ptid)	(pd_active && ptid.tid () != 0)
 
-/* pthdb_user_t value that we pass to pthdb functions.  0 causes
-   PTHDB_BAD_USER errors, so use 1.  */
-
-#define PD_USER	1
-
 /* Success and failure values returned by pthdb callbacks.  */
 
 #define PDC_SUCCESS	PTHDB_SUCCESS
@@ -331,7 +326,7 @@ pid_to_prc (ptid_t *ptidp)
    the address of SYMBOLS[<i>].name.  */
 
 static int
-pdc_symbol_addrs (pthdb_user_t user, pthdb_symbol_t *symbols, int count)
+pdc_symbol_addrs (pthdb_user_t user_current_pid, pthdb_symbol_t *symbols, int count)
 {
   struct bound_minimal_symbol ms;
   int i;
@@ -339,8 +334,8 @@ pdc_symbol_addrs (pthdb_user_t user, pthdb_symbol_t *symbols, int count)
 
   if (debug_aix_thread)
     gdb_printf (gdb_stdlog,
-		"pdc_symbol_addrs (user = %ld, symbols = 0x%lx, count = %d)\n",
-		user, (long) symbols, count);
+		"pdc_symbol_addrs (user_current_pid = %ld, symbols = 0x%lx, count = %d)\n",
+		user_current_pid, (long) symbols, count);
 
   for (i = 0; i < count; i++)
     {
@@ -378,7 +373,7 @@ pdc_symbol_addrs (pthdb_user_t user, pthdb_symbol_t *symbols, int count)
    If successful return 0, else non-zero is returned.  */
 
 static int
-pdc_read_regs (pthdb_user_t user, 
+pdc_read_regs (pthdb_user_t user_current_pid,
 	       pthdb_tid_t tid,
 	       unsigned long long flags,
 	       pthdb_context_t *context)
@@ -450,7 +445,7 @@ pdc_read_regs (pthdb_user_t user,
    If successful return 0, else non-zero is returned.  */
 
 static int
-pdc_write_regs (pthdb_user_t user,
+pdc_write_regs (pthdb_user_t user_current_pid,
 		pthdb_tid_t tid,
 		unsigned long long flags,
 		pthdb_context_t *context)
@@ -500,17 +495,29 @@ pdc_write_regs (pthdb_user_t user,
 /* pthdb callback: read LEN bytes from process ADDR into BUF.  */
 
 static int
-pdc_read_data (pthdb_user_t user, void *buf, 
+pdc_read_data (pthdb_user_t user_current_pid, void *buf,
 	       pthdb_addr_t addr, size_t len)
 {
   int status, ret;
 
   if (debug_aix_thread)
     gdb_printf (gdb_stdlog,
-		"pdc_read_data (user = %ld, buf = 0x%lx, addr = %s, len = %ld)\n",
-		user, (long) buf, hex_string (addr), len);
+		"pdc_read_data (user_current_pid = %ld, buf = 0x%lx, addr = %s, len = %ld)\n",
+		user_current_pid, (long) buf, hex_string (addr), len);
 
-  status = target_read_memory (addr, (gdb_byte *) buf, len);
+  /* This is needed to eliminate the dependency of current thread
+     which is null so that thread reads the correct target memory.  */
+  {
+    scoped_restore_current_thread restore_current_thread;
+    /* Before the first inferior is added, we pass inferior_ptid.pid ()
+       from pd_enable () which is 0.  There is no need to switch threads
+       during first initialisation.  In the rest of the callbacks the
+       current thread needs to be correct.  */
+    if (user_current_pid != 0)
+      switch_to_thread (current_inferior ()->process_target (),
+			ptid_t (user_current_pid));
+    status = target_read_memory (addr, (gdb_byte *) buf, len);
+  }
   ret = status == 0 ? PDC_SUCCESS : PDC_FAILURE;
 
   if (debug_aix_thread)
@@ -522,15 +529,15 @@ pdc_read_data (pthdb_user_t user, void *buf,
 /* pthdb callback: write LEN bytes from BUF to process ADDR.  */
 
 static int
-pdc_write_data (pthdb_user_t user, void *buf, 
+pdc_write_data (pthdb_user_t user_current_pid, void *buf,
 		pthdb_addr_t addr, size_t len)
 {
   int status, ret;
 
   if (debug_aix_thread)
     gdb_printf (gdb_stdlog,
-		"pdc_write_data (user = %ld, buf = 0x%lx, addr = %s, len = %ld)\n",
-		user, (long) buf, hex_string (addr), len);
+		"pdc_write_data (user_current_pid = %ld, buf = 0x%lx, addr = %s, len = %ld)\n",
+		user_current_pid, (long) buf, hex_string (addr), len);
 
   status = target_write_memory (addr, (gdb_byte *) buf, len);
   ret = status == 0 ? PDC_SUCCESS : PDC_FAILURE;
@@ -545,12 +552,12 @@ pdc_write_data (pthdb_user_t user, void *buf,
    in BUFP.  */
 
 static int
-pdc_alloc (pthdb_user_t user, size_t len, void **bufp)
+pdc_alloc (pthdb_user_t user_current_pid, size_t len, void **bufp)
 {
   if (debug_aix_thread)
     gdb_printf (gdb_stdlog,
-		"pdc_alloc (user = %ld, len = %ld, bufp = 0x%lx)\n",
-		user, len, (long) bufp);
+		"pdc_alloc (user_current_pid = %ld, len = %ld, bufp = 0x%lx)\n",
+		user_current_pid, len, (long) bufp);
   *bufp = xmalloc (len);
   if (debug_aix_thread)
     gdb_printf (gdb_stdlog, 
@@ -567,12 +574,12 @@ pdc_alloc (pthdb_user_t user, size_t len, void **bufp)
    pointer to the result in BUFP.  */
 
 static int
-pdc_realloc (pthdb_user_t user, void *buf, size_t len, void **bufp)
+pdc_realloc (pthdb_user_t user_current_pid, void *buf, size_t len, void **bufp)
 {
   if (debug_aix_thread)
     gdb_printf (gdb_stdlog,
-		"pdc_realloc (user = %ld, buf = 0x%lx, len = %ld, bufp = 0x%lx)\n",
-		user, (long) buf, len, (long) bufp);
+		"pdc_realloc (user_current_pid = %ld, buf = 0x%lx, len = %ld, bufp = 0x%lx)\n",
+		user_current_pid, (long) buf, len, (long) bufp);
   *bufp = xrealloc (buf, len);
   if (debug_aix_thread)
     gdb_printf (gdb_stdlog, 
@@ -584,11 +591,11 @@ pdc_realloc (pthdb_user_t user, void *buf, size_t len, void **bufp)
    realloc callback.  */
 
 static int
-pdc_dealloc (pthdb_user_t user, void *buf)
+pdc_dealloc (pthdb_user_t user_current_pid, void *buf)
 {
   if (debug_aix_thread)
     gdb_printf (gdb_stdlog, 
-		"pdc_free (user = %ld, buf = 0x%lx)\n", user,
+		"pdc_free (user_current_pid = %ld, buf = 0x%lx)\n", user_current_pid,
 		(long) buf);
   xfree (buf);
   return PDC_SUCCESS;
@@ -912,7 +919,7 @@ pd_activate (int pid)
 {
   int status;
 		
-  status = pthdb_session_init (PD_USER, arch64 ? PEM_64BIT : PEM_32BIT,
+  status = pthdb_session_init (pid, arch64 ? PEM_64BIT : PEM_32BIT,
 			       PTHDB_FLAG_REGS, &pd_callbacks, 
 			       &pd_session);
   if (status != PTHDB_SUCCESS)
@@ -955,7 +962,7 @@ pd_enable (void)
 
   /* Check whether the application is pthreaded.  */
   stub_name = NULL;
-  status = pthdb_session_pthreaded (PD_USER, PTHDB_FLAG_REGS,
+  status = pthdb_session_pthreaded (inferior_ptid.pid (), PTHDB_FLAG_REGS,
 				    &pd_callbacks, &stub_name);
   if ((status != PTHDB_SUCCESS
        && status != PTHDB_NOT_PTHREADED) || !stub_name)
@@ -976,7 +983,7 @@ pd_enable (void)
   /* If we're debugging a core file or an attached inferior, the
      pthread library may already have been initialized, so try to
      activate thread debugging.  */
-  pd_activate (1);
+  pd_activate (inferior_ptid.pid ());
 }
 
 /* Undo the effects of pd_enable().  */