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[PATCH 08/12] powerpc: Refactor vsyscall internal macros
- From: Adhemerval Zanella <adhemerval dot zanella at linaro dot org>
- To: libc-alpha at sourceware dot org
- Date: Fri, 14 Jun 2019 12:29:04 -0300
- Subject: [PATCH 08/12] powerpc: Refactor vsyscall internal macros
- References: <20190614152908.8101-1-adhemerval.zanella@linaro.org>
As described in libc-vdso.h, the powerpc64 vDSO does not provide the
function descriptor required by ELFv1 ABI. It requires the architecture
to emulate function calls through INTERNAL_VSYSCALL_CALL without odp
entries.
Another issue is for direct optimized iFUNC calls, where the ifunc goes
directly to vDSO instead of a libc wrapper, the libc must create an
function table itself (since the program will use the default function
call ABI).
This patch follows the previous Linux vDSO refactor to make the internal
vDSO pointer as the only proxy to access the vDSO. The get_vdso_symbol
and get_vdso_mangle_symbol calls are changed for powerpc64 elfv1 to
generate the required ODP entries. This allows removes all the internal
macros and simplify the code, where compile is free to generate itself
a function call when the vDSO is called.
Checked on powerpc-linux-gnu, powerpcp64-linux-gnu, and
powerpc64le-linux-gnu.
* sysdeps/unix/sysv/linux/powerpc/dl-vdso.h: New file.
* sysdeps/unix/sysv/linux/powerpc/get_timebase_freq.c
(get_timebase_freq_fallback): New symbol.
(__get_timebase_freq): Call vDSO as a function pointer instead of
arch-specific macros.
* .../unix/sysv/linux/powerpc/gettimeofday.c (gettimeofday): Use
get_vdso_symbol.
* sysdeps/unix/sysv/linux/powerpc/time.c (time): Likewise.
* sysdeps/unix/sysv/linux/powerpc/libc-vdso.h (VDSO_IFUNC_RET): Move
definition to dl-vdso.h.
* sysdeps/unix/sysv/linux/powerpc/powerpc32/sysdep.h
(INTERNAL_VSYSCALL_CALL_TYPE, INTERNAL_VSYSCALL_CALL): Remove.
* .../sysv/linux/powerpc/powerpc64/sysdep.h
(INTERNAL_VSYSCALL_NO_SYSCALL_FALLBACK, INTERNAL_VSYSCALL_CALL_TYPE,
INTERNAL_VSYSCALL_CALL): Likewise.
* sysdeps/unix/sysv/linux/powerpc/sysdep.h (INTERNAL_VSYSCALL_CALL):
Define.
---
sysdeps/unix/sysv/linux/powerpc/dl-vdso.h | 69 +++++++++++++++++++
.../sysv/linux/powerpc/get_timebase_freq.c | 22 +++---
.../unix/sysv/linux/powerpc/gettimeofday.c | 4 +-
sysdeps/unix/sysv/linux/powerpc/libc-vdso.h | 30 --------
.../sysv/linux/powerpc/powerpc32/sysdep.h | 37 ----------
.../sysv/linux/powerpc/powerpc64/sysdep.h | 52 +-------------
sysdeps/unix/sysv/linux/powerpc/sysdep.h | 10 +++
sysdeps/unix/sysv/linux/powerpc/time.c | 4 +-
8 files changed, 97 insertions(+), 131 deletions(-)
create mode 100644 sysdeps/unix/sysv/linux/powerpc/dl-vdso.h
diff --git a/sysdeps/unix/sysv/linux/powerpc/dl-vdso.h b/sysdeps/unix/sysv/linux/powerpc/dl-vdso.h
new file mode 100644
index 0000000000..f6858f02b2
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/powerpc/dl-vdso.h
@@ -0,0 +1,69 @@
+/* ELF symbol resolve functions for VDSO objects. PowerPC version.
+ Copyright (C) 2005-2019 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, see
+ <http://www.gnu.org/licenses/>. */
+
+#ifndef _DL_VDSO_POWERPC_H
+#define _DL_VDSO_POWERPC_H 1
+
+#if (defined(__PPC64__) || defined(__powerpc64__)) && _CALL_ELF != 2
+
+# include <dl-machine.h>
+# define get_vdso_symbol __get_vdso_symbol
+# define get_vdso_mangle_symbol __get_vdso_mangle_symbol
+# include_next <dl-vdso.h>
+# undef get_vdso_symbol
+# undef get_vdso_mangle_symbol
+
+/* The correct solution is for _dl_vdso_vsym to return the address of the OPD
+ for the kernel VDSO function. That address would then be stored in the
+ __vdso_* variables and returned as the result of the IFUNC resolver function.
+ Yet, the kernel does not contain any OPD entries for the VDSO functions
+ (incomplete implementation). However, PLT relocations for IFUNCs still expect
+ the address of an OPD to be returned from the IFUNC resolver function (since
+ PLT entries on PPC64 are just copies of OPDs). The solution for now is to
+ create an artificial static OPD for each VDSO function returned by a resolver
+ function. The TOC value is set to a non-zero value to avoid triggering lazy
+ symbol resolution via .glink0/.plt0 for a zero TOC (requires thread-safe PLT
+ sequences) when the dynamic linker isn't prepared for it e.g. RTLD_NOW. None
+ of the kernel VDSO routines use the TOC or AUX values so any non-zero value
+ will work. Note that function pointer comparisons will not use this artificial
+ static OPD since those are resolved via ADDR64 relocations and will point at
+ the non-IFUNC default OPD for the symbol. Lastly, because the IFUNC relocations
+ are processed immediately at startup the resolver functions and this code need
+ not be thread-safe, but if the caller writes to a PLT slot it must do so in a
+ thread-safe manner with all the required barriers. */
+#define get_vdso_symbol(symbol) \
+ ({ \
+ static Elf64_FuncDesc vdso_opd_##symbol = { .fd_toc = ~0x0 }; \
+ vdso_opd_##symbol.fd_func = (Elf64_Addr) __get_vdso_symbol (symbol); \
+ (void*)&vdso_opd_##symbol; \
+ })
+
+#define get_vdso_mangle_symbol(symbol) \
+ ({ \
+ static Elf64_FuncDesc vdso_opd_##symbol = { .fd_toc = ~0x0 }; \
+ vdso_opd_##symbol.fd_func = (Elf64_Addr) __get_vdso_symbol (symbol); \
+ void *vdsop = &vdso_opd_##symbol; \
+ PTR_MANGLE (vdsop); \
+ vdsop; \
+ })
+
+#else
+# include_next <dl-vdso.h>
+#endif
+
+#endif
diff --git a/sysdeps/unix/sysv/linux/powerpc/get_timebase_freq.c b/sysdeps/unix/sysv/linux/powerpc/get_timebase_freq.c
index 23e7694d87..b551412356 100644
--- a/sysdeps/unix/sysv/linux/powerpc/get_timebase_freq.c
+++ b/sysdeps/unix/sysv/linux/powerpc/get_timebase_freq.c
@@ -23,17 +23,11 @@
#include <not-cancel.h>
#include <libc-vdso.h>
-uint64_t
-__get_timebase_freq (void)
+static uint64_t
+get_timebase_freq_fallback (void)
{
hp_timing_t result = 0L;
-#ifdef SHARED
- /* The vDSO does not return an error (it clear cr0.so on returning). */
- INTERNAL_SYSCALL_DECL (err);
- result =
- INTERNAL_VSYSCALL_NO_SYSCALL_FALLBACK (get_tbfreq, err, uint64_t, 0);
-#else
/* We read the information from the /proc filesystem. /proc/cpuinfo
contains at least one line like:
timebase : 33333333
@@ -99,8 +93,18 @@ __get_timebase_freq (void)
}
}
}
-#endif
return result;
}
+
+uint64_t
+__get_timebase_freq (void)
+{
+ /* The vDSO does not have a fallback mechanism (such calling a syscall). */
+ __typeof (VDSO_SYMBOL (get_tbfreq)) vdsop = VDSO_SYMBOL (get_tbfreq);
+ if (vdsop == NULL)
+ return get_timebase_freq_fallback ();
+ PTR_DEMANGLE (vdsop);
+ return vdsop ();
+}
weak_alias (__get_timebase_freq, __ppc_get_timebase_freq)
diff --git a/sysdeps/unix/sysv/linux/powerpc/gettimeofday.c b/sysdeps/unix/sysv/linux/powerpc/gettimeofday.c
index 6b92e2807b..7a4e3cca0c 100644
--- a/sysdeps/unix/sysv/linux/powerpc/gettimeofday.c
+++ b/sysdeps/unix/sysv/linux/powerpc/gettimeofday.c
@@ -58,13 +58,13 @@ __gettimeofday_syscall (struct timeval *tv, struct timezone *tz)
}
# define INIT_ARCH() \
- void *vdso_gettimeofday = get_vdso_symbol ("__kernel_gettimeofday")
+ void *vdso_gettimeofday = get_vdso_symbol (HAVE_GETTIMEOFDAY_VSYSCALL)
/* If the vDSO is not available we fall back syscall. */
libc_ifunc_hidden (__redirect___gettimeofday, __gettimeofday,
vdso_gettimeofday
- ? VDSO_IFUNC_RET (vdso_gettimeofday)
+ ? vdso_gettimeofday
: (void *) __gettimeofday_syscall);
libc_hidden_def (__gettimeofday)
diff --git a/sysdeps/unix/sysv/linux/powerpc/libc-vdso.h b/sysdeps/unix/sysv/linux/powerpc/libc-vdso.h
index 47e925493b..c2da7bd7f1 100644
--- a/sysdeps/unix/sysv/linux/powerpc/libc-vdso.h
+++ b/sysdeps/unix/sysv/linux/powerpc/libc-vdso.h
@@ -32,34 +32,4 @@ extern void *VDSO_SYMBOL(sigtramp32);
extern void *VDSO_SYMBOL(sigtramp_rt32);
#endif
-#if (defined(__PPC64__) || defined(__powerpc64__)) && _CALL_ELF != 2
-/* The correct solution is for _dl_vdso_vsym to return the address of the OPD
- for the kernel VDSO function. That address would then be stored in the
- __vdso_* variables and returned as the result of the IFUNC resolver function.
- Yet, the kernel does not contain any OPD entries for the VDSO functions
- (incomplete implementation). However, PLT relocations for IFUNCs still expect
- the address of an OPD to be returned from the IFUNC resolver function (since
- PLT entries on PPC64 are just copies of OPDs). The solution for now is to
- create an artificial static OPD for each VDSO function returned by a resolver
- function. The TOC value is set to a non-zero value to avoid triggering lazy
- symbol resolution via .glink0/.plt0 for a zero TOC (requires thread-safe PLT
- sequences) when the dynamic linker isn't prepared for it e.g. RTLD_NOW. None
- of the kernel VDSO routines use the TOC or AUX values so any non-zero value
- will work. Note that function pointer comparisons will not use this artificial
- static OPD since those are resolved via ADDR64 relocations and will point at
- the non-IFUNC default OPD for the symbol. Lastly, because the IFUNC relocations
- are processed immediately at startup the resolver functions and this code need
- not be thread-safe, but if the caller writes to a PLT slot it must do so in a
- thread-safe manner with all the required barriers. */
-#define VDSO_IFUNC_RET(value) \
- ({ \
- static Elf64_FuncDesc vdso_opd = { .fd_toc = ~0x0 }; \
- vdso_opd.fd_func = (Elf64_Addr)value; \
- &vdso_opd; \
- })
-
-#else
-#define VDSO_IFUNC_RET(value) ((void *) (value))
-#endif
-
#endif /* _LIBC_VDSO_H */
diff --git a/sysdeps/unix/sysv/linux/powerpc/powerpc32/sysdep.h b/sysdeps/unix/sysv/linux/powerpc/powerpc32/sysdep.h
index f459543fcd..889c6ac117 100644
--- a/sysdeps/unix/sysv/linux/powerpc/powerpc32/sysdep.h
+++ b/sysdeps/unix/sysv/linux/powerpc/powerpc32/sysdep.h
@@ -34,43 +34,6 @@
# include <errno.h>
-/* Define a macro which expands inline into the wrapper code for a VDSO
- call. This use is for internal calls that do not need to handle errors
- normally. It will never touch errno.
- On powerpc a system call basically clobbers the same registers like a
- function call, with the exception of LR (which is needed for the
- "sc; bnslr+" sequence) and CR (where only CR0.SO is clobbered to signal
- an error return status). */
-# define INTERNAL_VSYSCALL_CALL_TYPE(funcptr, err, nr, type, args...) \
- ({ \
- register void *r0 __asm__ ("r0"); \
- register long int r3 __asm__ ("r3"); \
- register long int r4 __asm__ ("r4"); \
- register long int r5 __asm__ ("r5"); \
- register long int r6 __asm__ ("r6"); \
- register long int r7 __asm__ ("r7"); \
- register long int r8 __asm__ ("r8"); \
- register long int r9 __asm__ ("r9"); \
- register long int r10 __asm__ ("r10"); \
- register long int r11 __asm__ ("r11"); \
- register long int r12 __asm__ ("r12"); \
- register type rval __asm__ ("r3"); \
- LOADARGS_##nr (funcptr, args); \
- __asm__ __volatile__ \
- ("mtctr %0\n\t" \
- "bctrl\n\t" \
- "mfcr %0" \
- : "+r" (r0), "+r" (r3), "+r" (r4), "+r" (r5), "+r" (r6), "+r" (r7), \
- "+r" (r8), "+r" (r9), "+r" (r10), "+r" (r11), "+r" (r12) \
- : : "cr0", "ctr", "lr", "memory"); \
- err = (long int) r0; \
- __asm__ __volatile__ ("" : "=r" (rval) : "r" (r3), "r" (r4)); \
- rval; \
- })
-
-#define INTERNAL_VSYSCALL_CALL(funcptr, err, nr, args...) \
- INTERNAL_VSYSCALL_CALL_TYPE(funcptr, err, nr, long int, args)
-
# undef INLINE_SYSCALL
# define INLINE_SYSCALL(name, nr, args...) \
({ \
diff --git a/sysdeps/unix/sysv/linux/powerpc/powerpc64/sysdep.h b/sysdeps/unix/sysv/linux/powerpc/powerpc64/sysdep.h
index 06222f52e6..4e507db00d 100644
--- a/sysdeps/unix/sysv/linux/powerpc/powerpc64/sysdep.h
+++ b/sysdeps/unix/sysv/linux/powerpc/powerpc64/sysdep.h
@@ -45,59 +45,9 @@
#endif /* __ASSEMBLER__ */
-/* This version is for internal uses when there is no desire
- to set errno */
-#define INTERNAL_VSYSCALL_NO_SYSCALL_FALLBACK(name, err, type, nr, args...) \
- ({ \
- type sc_ret = ENOSYS; \
- \
- __typeof (__vdso_##name) vdsop = __vdso_##name; \
- PTR_DEMANGLE (vdsop); \
- if (vdsop != NULL) \
- sc_ret = \
- INTERNAL_VSYSCALL_CALL_TYPE (vdsop, err, type, nr, ##args); \
- else \
- err = 1 << 28; \
- sc_ret; \
- })
-
-/* Define a macro which expands inline into the wrapper code for a system
- call. This use is for internal calls that do not need to handle errors
- normally. It will never touch errno. This returns just what the kernel
- gave back in the non-error (CR0.SO cleared) case, otherwise (CR0.SO set)
- the negation of the return value in the kernel gets reverted. */
-
-#define INTERNAL_VSYSCALL_CALL_TYPE(funcptr, err, type, nr, args...) \
- ({ \
- register void *r0 __asm__ ("r0"); \
- register long int r3 __asm__ ("r3"); \
- register long int r4 __asm__ ("r4"); \
- register long int r5 __asm__ ("r5"); \
- register long int r6 __asm__ ("r6"); \
- register long int r7 __asm__ ("r7"); \
- register long int r8 __asm__ ("r8"); \
- register type rval __asm__ ("r3"); \
- LOADARGS_##nr (funcptr, args); \
- __asm__ __volatile__ \
- ("mtctr %0\n\t" \
- "bctrl\n\t" \
- "mfcr %0\n\t" \
- "0:" \
- : "+r" (r0), "+r" (r3), "+r" (r4), "+r" (r5), "+r" (r6), \
- "+r" (r7), "+r" (r8) \
- : : "r9", "r10", "r11", "r12", "cr0", "ctr", "lr", "memory"); \
- err = (long int) r0; \
- __asm__ __volatile__ ("" : "=r" (rval) : "r" (r3)); \
- rval; \
- })
-
-#define INTERNAL_VSYSCALL_CALL(funcptr, err, nr, args...) \
- INTERNAL_VSYSCALL_CALL_TYPE(funcptr, err, long int, nr, args)
-
-#undef INLINE_SYSCALL
-
/* This version is for kernels that implement system calls that
behave like function calls as far as register saving. */
+#undef INLINE_SYSCALL
#define INLINE_SYSCALL(name, nr, args...) \
({ \
INTERNAL_SYSCALL_DECL (sc_err); \
diff --git a/sysdeps/unix/sysv/linux/powerpc/sysdep.h b/sysdeps/unix/sysv/linux/powerpc/sysdep.h
index 20167615c8..cf967a8c33 100644
--- a/sysdeps/unix/sysv/linux/powerpc/sysdep.h
+++ b/sysdeps/unix/sysv/linux/powerpc/sysdep.h
@@ -24,6 +24,7 @@
#define HAVE_CLOCK_GETTIME_VSYSCALL "__kernel_clock_gettime"
#define HAVE_GETCPU_VSYSCALL "__kernel_getcpu"
#define HAVE_TIME_VSYSCALL "__kernel_time"
+#define HAVE_GETTIMEOFDAY_VSYSCALL "__kernel_gettimeofday"
#define HAVE_GET_TBFREQ "__kernel_get_tbfreq"
#if defined(__PPC64__) || defined(__powerpc64__)
@@ -32,3 +33,12 @@
# define HAVE_SIGTRAMP_32 "__kernel_sigtramp32"
# define HAVE_SIGTRAMP_RT32 "__kernel_sigtramp_rt32"
#endif
+
+#ifndef __ASSEMBLER__
+
+/* PowerPC vDSO symbols always succeed, so there is no need to emulate a
+ function call and check for CR0.SO value. */
+#define INTERNAL_VSYSCALL_CALL(funcptr, err, nr, args...) \
+ ({ err = 0; funcptr (args); })
+
+#endif /* __ASSEMBLER__ */
diff --git a/sysdeps/unix/sysv/linux/powerpc/time.c b/sysdeps/unix/sysv/linux/powerpc/time.c
index 53fd119b00..ca6721cf95 100644
--- a/sysdeps/unix/sysv/linux/powerpc/time.c
+++ b/sysdeps/unix/sysv/linux/powerpc/time.c
@@ -67,12 +67,12 @@ time_syscall (time_t *t)
}
# define INIT_ARCH() \
- void *vdso_time = get_vdso_symbol ("__kernel_time");
+ void *vdso_time = get_vdso_symbol (HAVE_TIME_VSYSCALL);
/* If the vDSO is not available we fall back to the syscall. */
libc_ifunc_hidden (__redirect_time, time,
vdso_time
- ? VDSO_IFUNC_RET (vdso_time)
+ ? vdso_time
: (void *) time_syscall);
libc_hidden_def (time)
--
2.17.1