[PATCH v3 2/8] gdbserver: Add PID parameter to linux_get_auxv and linux_get_hwcap

Thiago Jung Bauermann via Gdb-patches
2023-01-30T04:46:10Z

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 | 7 ++++---
gdbserver/linux-arm-low.cc | 2 +-
gdbserver/linux-low.cc | 18 +++++++++---------
gdbserver/linux-low.h | 9 ++++-----
gdbserver/linux-ppc-low.cc | 6 +++---
gdbserver/linux-s390-low.cc | 2 +-
gdbserver/netbsd-low.cc | 4 +---
gdbserver/netbsd-low.h | 2 +-
gdbserver/server.cc | 3 ++-
gdbserver/target.cc | 4 ++--
gdbserver/target.h | 4 ++--
11 files changed, 30 insertions(+), 31 deletions(-)

diff --git a/gdbserver/linux-aarch64-low.cc b/gdbserver/linux-aarch64-low.cc
index 3c09e086afee..2ed6e95562c5 100644
--- a/gdbserver/linux-aarch64-low.cc
+++ b/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
diff --git a/gdbserver/linux-arm-low.cc b/gdbserver/linux-arm-low.cc
index 98ba0e02524b..5975b44af0ae 100644
--- a/gdbserver/linux-arm-low.cc
+++ b/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);
diff --git a/gdbserver/linux-low.cc b/gdbserver/linux-low.cc
index 7e1de3978933..5cd22824e470 100644
--- a/gdbserver/linux-low.cc
+++ b/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;
}

diff --git a/gdbserver/linux-low.h b/gdbserver/linux-low.h
index aebfe05707e5..221de85aa2ee 100644
--- a/gdbserver/linux-low.h
+++ b/gdbserver/linux-low.h
@@ -178,7 +178,7 @@ class linux_process_target : public process_stratum_target

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,
@@ -946,17 +946,16 @@ extern int have_ptrace_getregset;
*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. */

-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. */

-CORE_ADDR linux_get_hwcap2 (int wordsize);
+CORE_ADDR linux_get_hwcap2 (int pid, int wordsize);

#endif /* GDBSERVER_LINUX_LOW_H */
diff --git a/gdbserver/linux-ppc-low.cc b/gdbserver/linux-ppc-low.cc
index fdf74727e392..f8dd770b8eb3 100644
--- a/gdbserver/linux-ppc-low.cc
+++ b/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
diff --git a/gdbserver/linux-s390-low.cc b/gdbserver/linux-s390-low.cc
index b3ccdff3e57f..48f64ef7bb3b 100644
--- a/gdbserver/linux-s390-low.cc
+++ b/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
diff --git a/gdbserver/netbsd-low.cc b/gdbserver/netbsd-low.cc
index 15afa36d1152..4defd79eee47 100644
--- a/gdbserver/netbsd-low.cc
+++ b/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);
}

diff --git a/gdbserver/netbsd-low.h b/gdbserver/netbsd-low.h
index daefc302785e..050b43fc54f4 100644
--- a/gdbserver/netbsd-low.h
+++ b/gdbserver/netbsd-low.h
@@ -77,7 +77,7 @@ class netbsd_process_target : public process_stratum_target

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;
diff --git a/gdbserver/server.cc b/gdbserver/server.cc
index d802e8b4a341..21fb51a45d16 100644
--- a/gdbserver/server.cc
+++ b/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. */
diff --git a/gdbserver/target.cc b/gdbserver/target.cc
index 24b8e2160138..b4f8e9f1efb6 100644
--- a/gdbserver/target.cc
+++ b/gdbserver/target.cc
@@ -344,8 +344,8 @@ 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");
}
diff --git a/gdbserver/target.h b/gdbserver/target.h
index eea651c30b4b..1b0caa98c56a 100644
--- a/gdbserver/target.h
+++ b/gdbserver/target.h
@@ -172,10 +172,10 @@ class process_stratum_target
/* 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