gdbserver: Add PID parameter to linux_get_auxv and linux_get_hwcap

This patch doesn't change gdbserver behaviour, but after later changes are
made it avoids a null pointer dereference when HWCAP needs to be obtained
for a specific process while current_thread is nullptr.

Fixing linux_read_auxv, linux_get_hwcap and linux_get_hwcap2 to take a PID
parameter seems more correct than setting current_thread in one particular
code path.

Changes are propagated to allow passing the new parameter through the call
chain.

Approved-By: Simon Marchi <simon.marchi@efficios.com>

gdbserver/linux-aarch64-low.cc

@@ -846,12 +846,13 @@ aarch64_target::low_arch_setup ()
   if (is_elf64)
     {
       struct aarch64_features features;
+      int pid = current_thread->id.pid ();
 
       features.vq = aarch64_sve_get_vq (tid);
       /* A-profile PAC is 64-bit only.  */
-      features.pauth = linux_get_hwcap (8) & AARCH64_HWCAP_PACA;
+      features.pauth = linux_get_hwcap (pid, 8) & AARCH64_HWCAP_PACA;
       /* A-profile MTE is 64-bit only.  */
-      features.mte = linux_get_hwcap2 (8) & HWCAP2_MTE;
+      features.mte = linux_get_hwcap2 (pid, 8) & HWCAP2_MTE;
       features.tls = aarch64_tls_register_count (tid);
 
       current_process ()->tdesc = aarch64_linux_read_description (features);
@@ -3322,7 +3323,7 @@ aarch64_target::supports_memory_tagging ()
 #endif
     }
 
-  return (linux_get_hwcap2 (8) & HWCAP2_MTE) != 0;
+  return (linux_get_hwcap2 (current_thread->id.pid (), 8) & HWCAP2_MTE) != 0;
 }
 
 bool

gdbserver/linux-arm-low.cc

@@ -958,7 +958,7 @@ get_next_pcs_syscall_next_pc (struct arm_get_next_pcs *self)
 static const struct target_desc *
 arm_read_description (void)
 {
-  unsigned long arm_hwcap = linux_get_hwcap (4);
+  unsigned long arm_hwcap = linux_get_hwcap (current_thread->id.pid (), 4);
 
   if (arm_hwcap & HWCAP_IWMMXT)
     return arm_linux_read_description (ARM_FP_TYPE_IWMMXT);

gdbserver/linux-low.cc

@@ -5483,12 +5483,11 @@ linux_process_target::supports_read_auxv ()
    to debugger memory starting at MYADDR.  */
 
 int
-linux_process_target::read_auxv (CORE_ADDR offset, unsigned char *myaddr,
-				 unsigned int len)
+linux_process_target::read_auxv (int pid, CORE_ADDR offset,
+				 unsigned char *myaddr, unsigned int len)
 {
   char filename[PATH_MAX];
   int fd, n;
-  int pid = lwpid_of (current_thread);
 
   xsnprintf (filename, sizeof filename, "/proc/%d/auxv", pid);
 
@@ -6982,14 +6981,15 @@ linux_get_pc_64bit (struct regcache *regcache)
 /* See linux-low.h.  */
 
 int
-linux_get_auxv (int wordsize, CORE_ADDR match, CORE_ADDR *valp)
+linux_get_auxv (int pid, int wordsize, CORE_ADDR match, CORE_ADDR *valp)
 {
   gdb_byte *data = (gdb_byte *) alloca (2 * wordsize);
   int offset = 0;
 
   gdb_assert (wordsize == 4 || wordsize == 8);
 
-  while (the_target->read_auxv (offset, data, 2 * wordsize) == 2 * wordsize)
+  while (the_target->read_auxv (pid, offset, data, 2 * wordsize)
+	 == 2 * wordsize)
     {
       if (wordsize == 4)
 	{
@@ -7019,20 +7019,20 @@ linux_get_auxv (int wordsize, CORE_ADDR match, CORE_ADDR *valp)
 /* See linux-low.h.  */
 
 CORE_ADDR
-linux_get_hwcap (int wordsize)
+linux_get_hwcap (int pid, int wordsize)
 {
   CORE_ADDR hwcap = 0;
-  linux_get_auxv (wordsize, AT_HWCAP, &hwcap);
+  linux_get_auxv (pid, wordsize, AT_HWCAP, &hwcap);
   return hwcap;
 }
 
 /* See linux-low.h.  */
 
 CORE_ADDR
-linux_get_hwcap2 (int wordsize)
+linux_get_hwcap2 (int pid, int wordsize)
 {
   CORE_ADDR hwcap2 = 0;
-  linux_get_auxv (wordsize, AT_HWCAP2, &hwcap2);
+  linux_get_auxv (pid, wordsize, AT_HWCAP2, &hwcap2);
   return hwcap2;
 }
 

gdbserver/linux-low.h

@@ -178,7 +178,7 @@ public:
 
   bool supports_read_auxv () override;
 
-  int read_auxv (CORE_ADDR offset, unsigned char *myaddr,
+  int read_auxv (int pid, CORE_ADDR offset, unsigned char *myaddr,
 		 unsigned int len) override;
 
   int insert_point (enum raw_bkpt_type type, CORE_ADDR addr,
@@ -941,22 +941,21 @@ bool thread_db_thread_handle (ptid_t ptid, gdb_byte **handle, int *handle_len);
 
 extern int have_ptrace_getregset;
 
-/* Search for the value with type MATCH in the auxv vector with
-   entries of length WORDSIZE bytes.  If found, store the value in
-   *VALP and return 1.  If not found or if there is an error, return
-   0.  */
+/* Search for the value with type MATCH in the auxv vector, with entries of
+   length WORDSIZE bytes, of process with pid PID.  If found, store the
+   value in *VALP and return 1.  If not found or if there is an error,
+   return 0.  */
 
-int linux_get_auxv (int wordsize, CORE_ADDR match,
-		    CORE_ADDR *valp);
+int linux_get_auxv (int pid, int wordsize, CORE_ADDR match, CORE_ADDR *valp);
 
 /* Fetch the AT_HWCAP entry from the auxv vector, where entries are length
-   WORDSIZE.  If no entry was found, return zero.  */
+   WORDSIZE, of process with pid PID.  If no entry was found, return 0.  */
 
-CORE_ADDR linux_get_hwcap (int wordsize);
+CORE_ADDR linux_get_hwcap (int pid, int wordsize);
 
 /* Fetch the AT_HWCAP2 entry from the auxv vector, where entries are length
-   WORDSIZE.  If no entry was found, return zero.  */
+   WORDSIZE, of process with pid PID.  If no entry was found, return 0.  */
 
-CORE_ADDR linux_get_hwcap2 (int wordsize);
+CORE_ADDR linux_get_hwcap2 (int pid, int wordsize);
 
 #endif /* GDBSERVER_LINUX_LOW_H */

gdbserver/linux-ppc-low.cc

@@ -894,8 +894,8 @@ ppc_target::low_arch_setup ()
 
   /* The value of current_process ()->tdesc needs to be set for this
      call.  */
-  ppc_hwcap = linux_get_hwcap (features.wordsize);
-  ppc_hwcap2 = linux_get_hwcap2 (features.wordsize);
+  ppc_hwcap = linux_get_hwcap (current_thread->id.pid (), features.wordsize);
+  ppc_hwcap2 = linux_get_hwcap2 (current_thread->id.pid (), features.wordsize);
 
   features.isa205 = ppc_linux_has_isa205 (ppc_hwcap);
 
@@ -1097,7 +1097,7 @@ is_elfv2_inferior (void)
   const struct target_desc *tdesc = current_process ()->tdesc;
   int wordsize = register_size (tdesc, 0);
 
-  if (!linux_get_auxv (wordsize, AT_PHDR, &phdr))
+  if (!linux_get_auxv (current_thread->id.pid (), wordsize, AT_PHDR, &phdr))
     return def_res;
 
   /* Assume ELF header is at the beginning of the page where program headers

gdbserver/linux-s390-low.cc

@@ -592,7 +592,7 @@ s390_target::low_arch_setup ()
   /* Determine word size and HWCAP.  */
   int pid = pid_of (current_thread);
   int wordsize = s390_get_wordsize (pid);
-  unsigned long hwcap = linux_get_hwcap (wordsize);
+  unsigned long hwcap = linux_get_hwcap (pid, wordsize);
 
   /* Check whether the kernel supports extra register sets.  */
   int have_regset_last_break

gdbserver/netbsd-low.cc

@@ -581,11 +581,9 @@ netbsd_read_auxv(pid_t pid, void *offs, void *addr, size_t len)
    to debugger memory starting at MYADDR.  */
 
 int
-netbsd_process_target::read_auxv (CORE_ADDR offset,
+netbsd_process_target::read_auxv (int pid, CORE_ADDR offset,
 				  unsigned char *myaddr, unsigned int len)
 {
-  pid_t pid = pid_of (current_thread);
-
   return netbsd_read_auxv (pid, (void *) (intptr_t) offset, myaddr, len);
 }
 

gdbserver/netbsd-low.h

@@ -77,7 +77,7 @@ public:
 
   bool supports_read_auxv () override;
 
-  int read_auxv (CORE_ADDR offset, unsigned char *myaddr,
+  int read_auxv (int pid, CORE_ADDR offset, unsigned char *myaddr,
 		 unsigned int len) override;
 
   bool supports_hardware_single_step () override;

gdbserver/server.cc

@@ -1443,7 +1443,8 @@ handle_qxfer_auxv (const char *annex,
   if (annex[0] != '\0' || current_thread == NULL)
     return -1;
 
-  return the_target->read_auxv (offset, readbuf, len);
+  return the_target->read_auxv (current_thread->id.pid (), offset, readbuf,
+				len);
 }
 
 /* Handle qXfer:exec-file:read.  */

gdbserver/target.cc

@@ -346,8 +346,8 @@ process_stratum_target::supports_read_auxv ()
 }
 
 int
-process_stratum_target::read_auxv (CORE_ADDR offset, unsigned char *myaddr,
-				   unsigned int len)
+process_stratum_target::read_auxv (int pid, CORE_ADDR offset,
+				   unsigned char *myaddr, unsigned int len)
 {
   gdb_assert_not_reached ("target op read_auxv not supported");
 }

gdbserver/target.h

@@ -172,10 +172,10 @@ public:
   /* Return true if the read_auxv target op is supported.  */
   virtual bool supports_read_auxv ();
 
-  /* Read auxiliary vector data from the inferior process.
+  /* Read auxiliary vector data from the process with pid PID.
 
      Read LEN bytes at OFFSET into a buffer at MYADDR.  */
-  virtual int read_auxv (CORE_ADDR offset, unsigned char *myaddr,
+  virtual int read_auxv (int pid, CORE_ADDR offset, unsigned char *myaddr,
 			 unsigned int len);
 
   /* Returns true if GDB Z breakpoint type TYPE is supported, false