[PATCH 2/2] gdbserver: Add linux_get_hwcap
Alan Hayward
Alan.Hayward@arm.com
Tue Mar 26 13:17:00 GMT 2019
> On 25 Mar 2019, at 15:41, Simon Marchi <simark@simark.ca> wrote:
>
> On 2019-03-25 8:05 a.m., Alan Hayward wrote:
>> In gdbserver, Tidy up calls to read HWCAP (and HWCAP2) by adding common
>> functions, removing the Arm, AArch64, PPC and S390 specific versions.
>> No functionality differences.
>> [ I wasn't sure in gdbserver when to use CORE_ADDR and when to use int/long.
>> I'm assuming CORE_ADDR is fairly recent to gdbserver? ]
>
> I don't know if CORE_ADDR is a recent addition to gdbserver. But I suppose CORE_ADDR was chosen as the return type for functions reading arbitrary AUXV values, since some of them may be pointers. With CORE_ADDR, we know those values will fit in the data type. When we return the HWCAP value, we know it won't be a pointer though, so returning a CORE_ADDR is a bit confusing, IMO. Those functions returning the HWCAP value could return something else, an uint64_t maybe. But then I would change it in the gdb version as well to match.
I’ve been flipping back and too in my head to change CORE_ADDR to uint64_t.
On a 32bit build, CORE_ADDR is 32bits. So it would be making a difference. Not sure if that really matters or not?
Left this change out of the update below for now.
>
>> /* Implementation of linux_target_ops method "arch_setup". */
>> static void
>> @@ -545,8 +521,8 @@ aarch64_arch_setup (void)
>> if (is_elf64)
>> {
>> uint64_t vq = aarch64_sve_get_vq (tid);
>> - unsigned long hwcap = 0;
>> - bool pauth_p = aarch64_get_hwcap (&hwcap) && (hwcap & AARCH64_HWCAP_PACA);
>> + unsigned long hwcap = linux_get_hwcap (8);
>> + bool pauth_p = hwcap & AARCH64_HWCAP_PACA;
>
> Just wondering, can the linux-aarch64-low.c code be used to debug a process
"gdbserver :2345 a.out” works on an AArch64 box if that’s what you're asking?
The code above is used to detect point auth.
>
>> diff --git a/gdb/gdbserver/linux-low.c b/gdb/gdbserver/linux-low.c
>> index 6f703f589f..481919c205 100644
>> --- a/gdb/gdbserver/linux-low.c
>> +++ b/gdb/gdbserver/linux-low.c
>> @@ -7423,6 +7423,64 @@ linux_get_pc_64bit (struct regcache *regcache)
>> return pc;
>> }
>> +/* Extract the auxiliary vector entry with a_type matching MATCH, storing the
>> + value in VALP and returning true. If no entry was found, return false. */
>> +
>> +static bool
>> +linux_get_auxv (int wordsize, CORE_ADDR match, CORE_ADDR *valp)
>
> I think this function could return the result (CORE_ADDR) directly,
> returning 0 on failure.
Done. Agreed that given that this function is now static, there is really no need to
keep the unused error.
With this changed, I almost changed linux_get_hwcap and linux_get_hwcap2 into inline
functions in the header. But that means adding extra includes into the header (for
the AT_HWCAP defines) and reliving the static from linux_get_auxv.
>
> If 4 and 8 are the only supported wordsize values, I would suggest adding an assert to verify it.
Done.
>
>> +{
>> + gdb_byte *data = (gdb_byte *) alloca (2 * wordsize);
>> + int offset = 0;
>> +
>> + while ((*the_target->read_auxv) (offset, data, 2 * wordsize) == 2 * wordsize)
>> + {
>> + if (wordsize == 4)
>> + {
>> + unsigned int *data_p = (unsigned int *)data;
>> + if (data_p[0] == match)
>> + {
>> + *valp = data_p[1];
>> + return true;
>> + }
>> + }
>> + else
>> + {
>> + unsigned long *data_p = (unsigned long *)data;
>> + if (data_p[0] == match)
>> + {
>> + *valp = data_p[1];
>> + return true;
>> + }
>> + }
>
> I am a bit worried about relying on the size of the "int" and "long" types in architecture-independent code. Could we use uint32_t and uint64_t instead?
>
Done.
> Simon
Updated patch below. Will push if you have no more comments.
Alan.
diff --git a/gdb/gdbserver/linux-aarch64-low.c b/gdb/gdbserver/linux-aarch64-low.c
index 20c75493b0..dc4ee81d2a 100644
--- a/gdb/gdbserver/linux-aarch64-low.c
+++ b/gdb/gdbserver/linux-aarch64-low.c
@@ -505,30 +505,6 @@ aarch64_linux_new_fork (struct process_info *parent,
/* Matches HWCAP_PACA in kernel header arch/arm64/include/uapi/asm/hwcap.h. */
#define AARCH64_HWCAP_PACA (1 << 30)
-/* Fetch the AT_HWCAP entry from the auxv vector. */
-
-static bool
-aarch64_get_hwcap (unsigned long *valp)
-{
- unsigned char *data = (unsigned char *) alloca (16);
- int offset = 0;
-
- while ((*the_target->read_auxv) (offset, data, 16) == 16)
- {
- unsigned long *data_p = (unsigned long *)data;
- if (data_p[0] == AT_HWCAP)
- {
- *valp = data_p[1];
- return true;
- }
-
- offset += 16;
- }
-
- *valp = 0;
- return false;
-}
-
/* Implementation of linux_target_ops method "arch_setup". */
static void
@@ -545,8 +521,8 @@ aarch64_arch_setup (void)
if (is_elf64)
{
uint64_t vq = aarch64_sve_get_vq (tid);
- unsigned long hwcap = 0;
- bool pauth_p = aarch64_get_hwcap (&hwcap) && (hwcap & AARCH64_HWCAP_PACA);
+ unsigned long hwcap = linux_get_hwcap (8);
+ bool pauth_p = hwcap & AARCH64_HWCAP_PACA;
current_process ()->tdesc = aarch64_linux_read_description (vq, pauth_p);
}
diff --git a/gdb/gdbserver/linux-arm-low.c b/gdb/gdbserver/linux-arm-low.c
index 8cad5c5fd4..ff72a489cb 100644
--- a/gdb/gdbserver/linux-arm-low.c
+++ b/gdb/gdbserver/linux-arm-low.c
@@ -847,40 +847,15 @@ get_next_pcs_syscall_next_pc (struct arm_get_next_pcs *self)
return next_pc;
}
-static int
-arm_get_hwcap (unsigned long *valp)
-{
- unsigned char *data = (unsigned char *) alloca (8);
- int offset = 0;
-
- while ((*the_target->read_auxv) (offset, data, 8) == 8)
- {
- unsigned int *data_p = (unsigned int *)data;
- if (data_p[0] == AT_HWCAP)
- {
- *valp = data_p[1];
- return 1;
- }
-
- offset += 8;
- }
-
- *valp = 0;
- return 0;
-}
-
static const struct target_desc *
arm_read_description (void)
{
int pid = lwpid_of (current_thread);
- unsigned long arm_hwcap = 0;
+ unsigned long arm_hwcap = linux_get_hwcap (4);
/* Query hardware watchpoint/breakpoint capabilities. */
arm_linux_init_hwbp_cap (pid);
- if (arm_get_hwcap (&arm_hwcap) == 0)
- return tdesc_arm;
-
if (arm_hwcap & HWCAP_IWMMXT)
return tdesc_arm_with_iwmmxt;
diff --git a/gdb/gdbserver/linux-low.c b/gdb/gdbserver/linux-low.c
index 6f703f589f..7158a6798c 100644
--- a/gdb/gdbserver/linux-low.c
+++ b/gdb/gdbserver/linux-low.c
@@ -7423,6 +7423,53 @@ linux_get_pc_64bit (struct regcache *regcache)
return pc;
}
+/* Fetch the entry MATCH from the auxv vector, where entries are length
+ WORDSIZE. If no entry was found, return zero. */
+
+static CORE_ADDR
+linux_get_auxv (int wordsize, CORE_ADDR match)
+{
+ gdb_byte *data = (gdb_byte *) alloca (2 * wordsize);
+ int offset = 0;
@@ -7423,6 +7423,53 @@ linux_get_pc_64bit (struct regcache *regcache)
return pc;
}
+/* Fetch the entry MATCH from the auxv vector, where entries are length
+ WORDSIZE. If no entry was found, return zero. */
+
+static CORE_ADDR
+linux_get_auxv (int wordsize, CORE_ADDR match)
+{
+ 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)
+ {
+ if (wordsize == 4)
+ {
+ uint32_t *data_p = (uint32_t *)data;
+ if (data_p[0] == match)
+ return data_p[1];
+ }
+ else
+ {
+ uint64_t *data_p = (uint64_t *)data;
+ if (data_p[0] == match)
+ return data_p[1];
+ }
+
+ offset += 2 * wordsize;
+ }
+
+ return 0;
+}
+
+/* See linux-low.h. */
+
+CORE_ADDR
+linux_get_hwcap (int wordsize)
+{
+ return linux_get_auxv (wordsize, AT_HWCAP);
+}
+
+/* See linux-low.h. */
+
+CORE_ADDR
+linux_get_hwcap2 (int wordsize)
+{
+ return linux_get_auxv (wordsize, AT_HWCAP2);
+}
static struct target_ops linux_target_ops = {
linux_create_inferior,
diff --git a/gdb/gdbserver/linux-low.h b/gdb/gdbserver/linux-low.h
index 1ade35d648..d825184835 100644
--- a/gdb/gdbserver/linux-low.h
+++ b/gdb/gdbserver/linux-low.h
@@ -435,4 +435,14 @@ bool thread_db_thread_handle (ptid_t ptid, gdb_byte **handle, int *handle_len);
extern int have_ptrace_getregset;
+/* 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);
+
+/* 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);
+
#endif /* GDBSERVER_LINUX_LOW_H */
diff --git a/gdb/gdbserver/linux-ppc-low.c b/gdb/gdbserver/linux-ppc-low.c
index 1b695e53fe..8deb0ce068 100644
--- a/gdb/gdbserver/linux-ppc-low.c
+++ b/gdb/gdbserver/linux-ppc-low.c
@@ -323,43 +323,6 @@ ppc_set_pc (struct regcache *regcache, CORE_ADDR pc)
}
}
-
-static int
-ppc_get_auxv (unsigned long type, unsigned long *valp)
-{
- const struct target_desc *tdesc = current_process ()->tdesc;
- int wordsize = register_size (tdesc, 0);
- unsigned char *data = (unsigned char *) alloca (2 * wordsize);
- int offset = 0;
-
- while ((*the_target->read_auxv) (offset, data, 2 * wordsize) == 2 * wordsize)
- {
- if (wordsize == 4)
- {
- unsigned int *data_p = (unsigned int *)data;
- if (data_p[0] == type)
- {
- *valp = data_p[1];
- return 1;
- }
- }
- else
- {
- unsigned long *data_p = (unsigned long *)data;
- if (data_p[0] == type)
- {
- *valp = data_p[1];
- return 1;
- }
- }
-
- offset += 2 * wordsize;
- }
-
- *valp = 0;
- return 0;
-}
-
#ifndef __powerpc64__
static int ppc_regmap_adjusted;
#endif
@@ -944,8 +907,8 @@ ppc_arch_setup (void)
/* The value of current_process ()->tdesc needs to be set for this
call. */
- ppc_get_auxv (AT_HWCAP, &ppc_hwcap);
- ppc_get_auxv (AT_HWCAP2, &ppc_hwcap2);
+ ppc_hwcap = linux_get_hwcap (features.wordsize);
+ ppc_hwcap2 = linux_get_hwcap2 (features.wordsize);
features.isa205 = ppc_linux_has_isa205 (ppc_hwcap);
diff --git a/gdb/gdbserver/linux-s390-low.c b/gdb/gdbserver/linux-s390-low.c
index edbef77fe9..f65a1ec38e 100644
--- a/gdb/gdbserver/linux-s390-low.c
+++ b/gdb/gdbserver/linux-s390-low.c
@@ -467,36 +467,6 @@ s390_set_pc (struct regcache *regcache, CORE_ADDR newpc)
}
}
-/* Get HWCAP from AUXV, using the given WORDSIZE. Return the HWCAP, or
- zero if not found. */
-
-static unsigned long
-s390_get_hwcap (int wordsize)
-{
- gdb_byte *data = (gdb_byte *) alloca (2 * wordsize);
- int offset = 0;
-
- while ((*the_target->read_auxv) (offset, data, 2 * wordsize) == 2 * wordsize)
- {
- if (wordsize == 4)
- {
- unsigned int *data_p = (unsigned int *)data;
- if (data_p[0] == AT_HWCAP)
- return data_p[1];
- }
- else
- {
- unsigned long *data_p = (unsigned long *)data;
- if (data_p[0] == AT_HWCAP)
- return data_p[1];
- }
-
- offset += 2 * wordsize;
- }
-
- return 0;
-}
-
/* Determine the word size for the given PID, in bytes. */
#ifdef __s390x__
@@ -548,7 +518,7 @@ s390_arch_setup (void)
/* Determine word size and HWCAP. */
int pid = pid_of (current_thread);
int wordsize = s390_get_wordsize (pid);
- unsigned long hwcap = s390_get_hwcap (wordsize);
+ unsigned long hwcap = linux_get_hwcap (wordsize);
/* Check whether the kernel supports extra register sets. */
int have_regset_last_break
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