* [musl] [PATCH V3 0/1] feat(x86_64): use wrfsbase if AT_HWCAP2 allows usage
@ 2022-03-29 12:24 Harald Hoyer
2022-03-29 12:24 ` [musl] [PATCH 1/1] " Harald Hoyer
0 siblings, 1 reply; 6+ messages in thread
From: Harald Hoyer @ 2022-03-29 12:24 UTC (permalink / raw)
To: musl; +Cc: Harald Hoyer
V2: Forgot to add `arch/x86_64/bits/hwcap.h`
V3: Tabified src/thread/x86_64/__set_thread_area.c
Harald Hoyer (1):
feat(x86_64): use wrfsbase if AT_HWCAP2 allows usage
arch/x86_64/bits/hwcap.h | 2 ++
ldso/dynlink.c | 1 +
src/env/__libc_start_main.c | 1 +
src/internal/libc.c | 1 +
src/internal/libc.h | 1 +
src/thread/x86_64/__set_thread_area.c | 14 ++++++++++++++
src/thread/x86_64/__set_thread_area.s | 11 -----------
7 files changed, 20 insertions(+), 11 deletions(-)
create mode 100644 arch/x86_64/bits/hwcap.h
create mode 100644 src/thread/x86_64/__set_thread_area.c
delete mode 100644 src/thread/x86_64/__set_thread_area.s
--
2.35.1
^ permalink raw reply [flat|nested] 6+ messages in thread
* [musl] [PATCH 1/1] feat(x86_64): use wrfsbase if AT_HWCAP2 allows usage
2022-03-29 12:24 [musl] [PATCH V3 0/1] feat(x86_64): use wrfsbase if AT_HWCAP2 allows usage Harald Hoyer
@ 2022-03-29 12:24 ` Harald Hoyer
2022-03-29 15:54 ` Rich Felker
0 siblings, 1 reply; 6+ messages in thread
From: Harald Hoyer @ 2022-03-29 12:24 UTC (permalink / raw)
To: musl; +Cc: Harald Hoyer
If `AT_HWCAP2` has `HWCAP2_FSGSBASE` set, then instead of calling
`arch_prctl()`, the `wrfsbase` instruction will be used.
This is helpful in SGX contexts, where inside the enclave no other
mechanism is possible.
Tested against `libc-test`.
Signed-off-by: Harald Hoyer <harald@profian.com>
---
arch/x86_64/bits/hwcap.h | 2 ++
ldso/dynlink.c | 1 +
src/env/__libc_start_main.c | 1 +
src/internal/libc.c | 1 +
src/internal/libc.h | 1 +
src/thread/x86_64/__set_thread_area.c | 14 ++++++++++++++
src/thread/x86_64/__set_thread_area.s | 11 -----------
7 files changed, 20 insertions(+), 11 deletions(-)
create mode 100644 arch/x86_64/bits/hwcap.h
create mode 100644 src/thread/x86_64/__set_thread_area.c
delete mode 100644 src/thread/x86_64/__set_thread_area.s
diff --git a/arch/x86_64/bits/hwcap.h b/arch/x86_64/bits/hwcap.h
new file mode 100644
index 00000000..eb962bce
--- /dev/null
+++ b/arch/x86_64/bits/hwcap.h
@@ -0,0 +1,2 @@
+#define HWCAP2_RING3MWAIT (1 << 0)
+#define HWCAP2_FSGSBASE (1 << 1)
diff --git a/ldso/dynlink.c b/ldso/dynlink.c
index 5b9c8be4..2d38ec63 100644
--- a/ldso/dynlink.c
+++ b/ldso/dynlink.c
@@ -1710,6 +1710,7 @@ void __dls2b(size_t *sp, size_t *auxv)
* use during dynamic linking. If possible it will also serve as the
* thread pointer at runtime. */
search_vec(auxv, &__hwcap, AT_HWCAP);
+ search_vec(auxv, &__hwcap2, AT_HWCAP2);
libc.auxv = auxv;
libc.tls_size = sizeof builtin_tls;
libc.tls_align = tls_align;
diff --git a/src/env/__libc_start_main.c b/src/env/__libc_start_main.c
index c5b277bd..38772bdb 100644
--- a/src/env/__libc_start_main.c
+++ b/src/env/__libc_start_main.c
@@ -28,6 +28,7 @@ void __init_libc(char **envp, char *pn)
libc.auxv = auxv = (void *)(envp+i+1);
for (i=0; auxv[i]; i+=2) if (auxv[i]<AUX_CNT) aux[auxv[i]] = auxv[i+1];
__hwcap = aux[AT_HWCAP];
+ __hwcap2 = aux[AT_HWCAP2];
if (aux[AT_SYSINFO]) __sysinfo = aux[AT_SYSINFO];
libc.page_size = aux[AT_PAGESZ];
diff --git a/src/internal/libc.c b/src/internal/libc.c
index cb051810..16e47633 100644
--- a/src/internal/libc.c
+++ b/src/internal/libc.c
@@ -3,6 +3,7 @@
struct __libc __libc;
size_t __hwcap;
+size_t __hwcap2;
char *__progname=0, *__progname_full=0;
weak_alias(__progname, program_invocation_short_name);
diff --git a/src/internal/libc.h b/src/internal/libc.h
index 619bba86..7d239626 100644
--- a/src/internal/libc.h
+++ b/src/internal/libc.h
@@ -47,6 +47,7 @@ hidden void __libc_exit_fini(void);
hidden void __fork_handler(int);
extern hidden size_t __hwcap;
+extern hidden size_t __hwcap2;
extern hidden size_t __sysinfo;
extern char *__progname, *__progname_full;
diff --git a/src/thread/x86_64/__set_thread_area.c b/src/thread/x86_64/__set_thread_area.c
new file mode 100644
index 00000000..dcc5d116
--- /dev/null
+++ b/src/thread/x86_64/__set_thread_area.c
@@ -0,0 +1,14 @@
+#include <libc.h>
+#include <syscall.h>
+#include <bits/hwcap.h>
+
+hidden int __set_thread_area(void *p)
+{
+ if (__hwcap2 & HWCAP2_FSGSBASE) {
+ __asm__ ("wrfsbase %0" :: "r" (p) : "memory");
+ return 0;
+ }
+
+ // arch_prctl(SET_FS, arg)
+ return syscall(__NR_arch_prctl, 0x1002, p);
+}
diff --git a/src/thread/x86_64/__set_thread_area.s b/src/thread/x86_64/__set_thread_area.s
deleted file mode 100644
index 7347ff4d..00000000
--- a/src/thread/x86_64/__set_thread_area.s
+++ /dev/null
@@ -1,11 +0,0 @@
-/* Copyright 2011-2012 Nicholas J. Kain, licensed under standard MIT license */
-.text
-.global __set_thread_area
-.hidden __set_thread_area
-.type __set_thread_area,@function
-__set_thread_area:
- mov %rdi,%rsi /* shift for syscall */
- movl $0x1002,%edi /* SET_FS register */
- movl $158,%eax /* set fs segment to */
- syscall /* arch_prctl(SET_FS, arg)*/
- ret
--
2.35.1
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [musl] [PATCH 1/1] feat(x86_64): use wrfsbase if AT_HWCAP2 allows usage
2022-03-29 12:24 ` [musl] [PATCH 1/1] " Harald Hoyer
@ 2022-03-29 15:54 ` Rich Felker
2022-03-30 6:57 ` Harald Hoyer
0 siblings, 1 reply; 6+ messages in thread
From: Rich Felker @ 2022-03-29 15:54 UTC (permalink / raw)
To: Harald Hoyer; +Cc: musl
On Tue, Mar 29, 2022 at 02:24:16PM +0200, Harald Hoyer wrote:
> If `AT_HWCAP2` has `HWCAP2_FSGSBASE` set, then instead of calling
> `arch_prctl()`, the `wrfsbase` instruction will be used.
>
> This is helpful in SGX contexts, where inside the enclave no other
> mechanism is possible.
Thanks for including this motivation, since otherwise I don't think it
makes any sense to use this feature. BTW what happens with other
syscalls in such a context (at least set_tid_address is called
unconditionally), and how does the process communicate any information
or even exit?
> diff --git a/src/thread/x86_64/__set_thread_area.c b/src/thread/x86_64/__set_thread_area.c
> new file mode 100644
> index 00000000..dcc5d116
> --- /dev/null
> +++ b/src/thread/x86_64/__set_thread_area.c
> @@ -0,0 +1,14 @@
> +#include <libc.h>
> +#include <syscall.h>
> +#include <bits/hwcap.h>
> +
> +hidden int __set_thread_area(void *p)
> +{
> + if (__hwcap2 & HWCAP2_FSGSBASE) {
> + __asm__ ("wrfsbase %0" :: "r" (p) : "memory");
> + return 0;
> + }
> +
> + // arch_prctl(SET_FS, arg)
> + return syscall(__NR_arch_prctl, 0x1002, p);
> +}
I'm guessing this breaks build on anything but recent assembler
versions, no? If so, it should probably be written with a .byte
directive or something.
There's also a question of whether the existence of the hwcap flag is
intended to document a contract for the kernel to permit the process
to perform this operation, and a contract for the kernel to accept it
being set this way (rather than creating a possible inconsistency
between the kernel's idea of the process's %fs base and the actual %fs
base that's active. Is this documented somewhere on the kernel side?
If so then this should be okay, but this needs checking before it can
be merged.
Rich
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [musl] [PATCH 1/1] feat(x86_64): use wrfsbase if AT_HWCAP2 allows usage
2022-03-29 15:54 ` Rich Felker
@ 2022-03-30 6:57 ` Harald Hoyer
2022-03-30 12:32 ` Rich Felker
0 siblings, 1 reply; 6+ messages in thread
From: Harald Hoyer @ 2022-03-30 6:57 UTC (permalink / raw)
To: Rich Felker; +Cc: musl
Am 29.03.22 um 17:54 schrieb Rich Felker:
> On Tue, Mar 29, 2022 at 02:24:16PM +0200, Harald Hoyer wrote:
>> If `AT_HWCAP2` has `HWCAP2_FSGSBASE` set, then instead of calling
>> `arch_prctl()`, the `wrfsbase` instruction will be used.
>>
>> This is helpful in SGX contexts, where inside the enclave no other
>> mechanism is possible.
>
> Thanks for including this motivation, since otherwise I don't think it
> makes any sense to use this feature. BTW what happens with other
> syscalls in such a context (at least set_tid_address is called
> unconditionally), and how does the process communicate any information
> or even exit?
In our project (enarx) we catch the `syscall` exception and handle it by proxying
it to the host (with filtering and sanity checks). Because `arch_prctl` sets a
hardware register, which is handled special in enclave context switching,
we can't do that for this syscall.
>
>> diff --git a/src/thread/x86_64/__set_thread_area.c b/src/thread/x86_64/__set_thread_area.c
>> new file mode 100644
>> index 00000000..dcc5d116
>> --- /dev/null
>> +++ b/src/thread/x86_64/__set_thread_area.c
>> @@ -0,0 +1,14 @@
>> +#include <libc.h>
>> +#include <syscall.h>
>> +#include <bits/hwcap.h>
>> +
>> +hidden int __set_thread_area(void *p)
>> +{
>> + if (__hwcap2 & HWCAP2_FSGSBASE) {
>> + __asm__ ("wrfsbase %0" :: "r" (p) : "memory");
>> + return 0;
>> + }
>> +
>> + // arch_prctl(SET_FS, arg)
>> + return syscall(__NR_arch_prctl, 0x1002, p);
>> +}
>
> I'm guessing this breaks build on anything but recent assembler
> versions, no? If so, it should probably be written with a .byte
> directive or something.
Is gcc-4.6.0 old enough?
commit 4ee89d5fb78b48b62b507a29d3a576c63ae22505
Author: H.J. Lu <hongjiu.lu@intel.com>
Date: Mon Jul 5 21:57:55 2010 +0000
or llvm 3.1.0?
commit 228d9131aad9f3553c9c69abf010f41ce43c8423
Author: Craig Topper <craig.topper@gmail.com>
Date: Sun Oct 30 19:57:21 2011 +0000
>
> There's also a question of whether the existence of the hwcap flag is
> intended to document a contract for the kernel to permit the process
> to perform this operation, and a contract for the kernel to accept it
> being set this way (rather than creating a possible inconsistency
> between the kernel's idea of the process's %fs base and the actual %fs
> base that's active. Is this documented somewhere on the kernel side?
> If so then this should be okay, but this needs checking before it can
> be merged.
>
> Rich
linux Documentation/x86/x86_64/fsgs.rst:
The kernel provides reliable information about the enabled state in the
ELF AUX vector. If the HWCAP2_FSGSBASE bit is set in the AUX vector, the
kernel has FSGSBASE instructions enabled and applications can use them.
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [musl] [PATCH 1/1] feat(x86_64): use wrfsbase if AT_HWCAP2 allows usage
2022-03-30 6:57 ` Harald Hoyer
@ 2022-03-30 12:32 ` Rich Felker
0 siblings, 0 replies; 6+ messages in thread
From: Rich Felker @ 2022-03-30 12:32 UTC (permalink / raw)
To: Harald Hoyer; +Cc: musl
On Wed, Mar 30, 2022 at 08:57:55AM +0200, Harald Hoyer wrote:
> Am 29.03.22 um 17:54 schrieb Rich Felker:
> >On Tue, Mar 29, 2022 at 02:24:16PM +0200, Harald Hoyer wrote:
> >>If `AT_HWCAP2` has `HWCAP2_FSGSBASE` set, then instead of calling
> >>`arch_prctl()`, the `wrfsbase` instruction will be used.
> >>
> >>This is helpful in SGX contexts, where inside the enclave no other
> >>mechanism is possible.
> >
> >Thanks for including this motivation, since otherwise I don't think it
> >makes any sense to use this feature. BTW what happens with other
> >syscalls in such a context (at least set_tid_address is called
> >unconditionally), and how does the process communicate any information
> >or even exit?
>
> In our project (enarx) we catch the `syscall` exception and handle it by proxying
> it to the host (with filtering and sanity checks). Because `arch_prctl` sets a
> hardware register, which is handled special in enclave context switching,
> we can't do that for this syscall.
Is there no way to make it jump the guest to a host-provided (ala
vdso) helper that would juse use the instruction?
> >>diff --git a/src/thread/x86_64/__set_thread_area.c b/src/thread/x86_64/__set_thread_area.c
> >>new file mode 100644
> >>index 00000000..dcc5d116
> >>--- /dev/null
> >>+++ b/src/thread/x86_64/__set_thread_area.c
> >>@@ -0,0 +1,14 @@
> >>+#include <libc.h>
> >>+#include <syscall.h>
> >>+#include <bits/hwcap.h>
> >>+
> >>+hidden int __set_thread_area(void *p)
> >>+{
> >>+ if (__hwcap2 & HWCAP2_FSGSBASE) {
> >>+ __asm__ ("wrfsbase %0" :: "r" (p) : "memory");
> >>+ return 0;
> >>+ }
> >>+
> >>+ // arch_prctl(SET_FS, arg)
> >>+ return syscall(__NR_arch_prctl, 0x1002, p);
> >>+}
> >
> >I'm guessing this breaks build on anything but recent assembler
> >versions, no? If so, it should probably be written with a .byte
> >directive or something.
>
> Is gcc-4.6.0 old enough?
>
> commit 4ee89d5fb78b48b62b507a29d3a576c63ae22505
> Author: H.J. Lu <hongjiu.lu@intel.com>
> Date: Mon Jul 5 21:57:55 2010 +0000
It's a matter of binutils not gcc. And I'm not sure. Previously I
don't think we've had any minimum required binutils version for
x86_64, so my leaning would be to do this a way that does not create a
dependency on the assembler knowing new insns from a -march greater
than what you're compiling for.
Using .byte does preclude letting the compiler pick an input register,
but "D"(p) instead of "r"(p) should be zero-cost anyway since p is
always going to be in the first argument register anyway.
> or llvm 3.1.0?
>
> commit 228d9131aad9f3553c9c69abf010f41ce43c8423
> Author: Craig Topper <craig.topper@gmail.com>
> Date: Sun Oct 30 19:57:21 2011 +0000
>
> >
> >There's also a question of whether the existence of the hwcap flag is
> >intended to document a contract for the kernel to permit the process
> >to perform this operation, and a contract for the kernel to accept it
> >being set this way (rather than creating a possible inconsistency
> >between the kernel's idea of the process's %fs base and the actual %fs
> >base that's active. Is this documented somewhere on the kernel side?
> >If so then this should be okay, but this needs checking before it can
> >be merged.
> >
> >Rich
>
> linux Documentation/x86/x86_64/fsgs.rst:
>
> The kernel provides reliable information about the enabled state in the
> ELF AUX vector. If the HWCAP2_FSGSBASE bit is set in the AUX vector, the
> kernel has FSGSBASE instructions enabled and applications can use them.
Thanks! I just found that myself, along with:
https://lwn.net/Articles/821723/
which explains some of the history and motivation.
Short of any concern others may raise that I'm not seeing, I think
this change is almost surely okay with care taken not to bump the
assembler version requirements. I'll plan to take this shortly after
release.
Rich
^ permalink raw reply [flat|nested] 6+ messages in thread
* [musl] [PATCH] feat(x86_64): use wrfsbase if AT_HWCAP2 allows usage
@ 2022-03-29 11:42 Harald Hoyer
2022-03-29 11:54 ` [musl] [PATCH V2 0/1] " Harald Hoyer
0 siblings, 1 reply; 6+ messages in thread
From: Harald Hoyer @ 2022-03-29 11:42 UTC (permalink / raw)
To: musl; +Cc: Harald Hoyer
If `AT_HWCAP2` has `HWCAP2_FSGSBASE` set, then instead of calling
`arch_prctl()`, the `wrfsbase` instruction will be used.
This is helpful in SGX contexts, where inside the enclave no other
mechanism is possible.
Tested against `libc-test`.
Signed-off-by: Harald Hoyer <harald@profian.com>
---
ldso/dynlink.c | 1 +
src/env/__libc_start_main.c | 1 +
src/internal/libc.c | 1 +
src/internal/libc.h | 1 +
src/thread/x86_64/__set_thread_area.c | 14 ++++++++++++++
src/thread/x86_64/__set_thread_area.s | 11 -----------
6 files changed, 18 insertions(+), 11 deletions(-)
create mode 100644 src/thread/x86_64/__set_thread_area.c
delete mode 100644 src/thread/x86_64/__set_thread_area.s
diff --git a/ldso/dynlink.c b/ldso/dynlink.c
index 5b9c8be4..2d38ec63 100644
--- a/ldso/dynlink.c
+++ b/ldso/dynlink.c
@@ -1710,6 +1710,7 @@ void __dls2b(size_t *sp, size_t *auxv)
* use during dynamic linking. If possible it will also serve as the
* thread pointer at runtime. */
search_vec(auxv, &__hwcap, AT_HWCAP);
+ search_vec(auxv, &__hwcap2, AT_HWCAP2);
libc.auxv = auxv;
libc.tls_size = sizeof builtin_tls;
libc.tls_align = tls_align;
diff --git a/src/env/__libc_start_main.c b/src/env/__libc_start_main.c
index c5b277bd..38772bdb 100644
--- a/src/env/__libc_start_main.c
+++ b/src/env/__libc_start_main.c
@@ -28,6 +28,7 @@ void __init_libc(char **envp, char *pn)
libc.auxv = auxv = (void *)(envp+i+1);
for (i=0; auxv[i]; i+=2) if (auxv[i]<AUX_CNT) aux[auxv[i]] = auxv[i+1];
__hwcap = aux[AT_HWCAP];
+ __hwcap2 = aux[AT_HWCAP2];
if (aux[AT_SYSINFO]) __sysinfo = aux[AT_SYSINFO];
libc.page_size = aux[AT_PAGESZ];
diff --git a/src/internal/libc.c b/src/internal/libc.c
index cb051810..16e47633 100644
--- a/src/internal/libc.c
+++ b/src/internal/libc.c
@@ -3,6 +3,7 @@
struct __libc __libc;
size_t __hwcap;
+size_t __hwcap2;
char *__progname=0, *__progname_full=0;
weak_alias(__progname, program_invocation_short_name);
diff --git a/src/internal/libc.h b/src/internal/libc.h
index 619bba86..7d239626 100644
--- a/src/internal/libc.h
+++ b/src/internal/libc.h
@@ -47,6 +47,7 @@ hidden void __libc_exit_fini(void);
hidden void __fork_handler(int);
extern hidden size_t __hwcap;
+extern hidden size_t __hwcap2;
extern hidden size_t __sysinfo;
extern char *__progname, *__progname_full;
diff --git a/src/thread/x86_64/__set_thread_area.c b/src/thread/x86_64/__set_thread_area.c
new file mode 100644
index 00000000..cd3a2519
--- /dev/null
+++ b/src/thread/x86_64/__set_thread_area.c
@@ -0,0 +1,14 @@
+#include <libc.h>
+#include <syscall.h>
+#include <bits/hwcap.h>
+
+hidden int __set_thread_area(void *p)
+{
+ if (__hwcap2 & HWCAP2_FSGSBASE) {
+ __asm__ ("wrfsbase %0" :: "r" (p) : "memory");
+ return 0;
+ }
+
+ // arch_prctl(SET_FS, arg)
+ return syscall(__NR_arch_prctl, 0x1002, p);
+}
diff --git a/src/thread/x86_64/__set_thread_area.s b/src/thread/x86_64/__set_thread_area.s
deleted file mode 100644
index 7347ff4d..00000000
--- a/src/thread/x86_64/__set_thread_area.s
+++ /dev/null
@@ -1,11 +0,0 @@
-/* Copyright 2011-2012 Nicholas J. Kain, licensed under standard MIT license */
-.text
-.global __set_thread_area
-.hidden __set_thread_area
-.type __set_thread_area,@function
-__set_thread_area:
- mov %rdi,%rsi /* shift for syscall */
- movl $0x1002,%edi /* SET_FS register */
- movl $158,%eax /* set fs segment to */
- syscall /* arch_prctl(SET_FS, arg)*/
- ret
--
2.35.1
^ permalink raw reply [flat|nested] 6+ messages in thread
* [musl] [PATCH V2 0/1] feat(x86_64): use wrfsbase if AT_HWCAP2 allows usage
2022-03-29 11:42 [musl] [PATCH] " Harald Hoyer
@ 2022-03-29 11:54 ` Harald Hoyer
2022-03-29 11:54 ` [musl] [PATCH 1/1] " Harald Hoyer
0 siblings, 1 reply; 6+ messages in thread
From: Harald Hoyer @ 2022-03-29 11:54 UTC (permalink / raw)
To: musl; +Cc: Harald Hoyer
Forgot to add `arch/x86_64/bits/hwcap.h`
Harald Hoyer (1):
feat(x86_64): use wrfsbase if AT_HWCAP2 allows usage
arch/x86_64/bits/hwcap.h | 2 ++
ldso/dynlink.c | 1 +
src/env/__libc_start_main.c | 1 +
src/internal/libc.c | 1 +
src/internal/libc.h | 1 +
src/thread/x86_64/__set_thread_area.c | 14 ++++++++++++++
src/thread/x86_64/__set_thread_area.s | 11 -----------
7 files changed, 20 insertions(+), 11 deletions(-)
create mode 100644 arch/x86_64/bits/hwcap.h
create mode 100644 src/thread/x86_64/__set_thread_area.c
delete mode 100644 src/thread/x86_64/__set_thread_area.s
--
2.35.1
^ permalink raw reply [flat|nested] 6+ messages in thread
* [musl] [PATCH 1/1] feat(x86_64): use wrfsbase if AT_HWCAP2 allows usage
2022-03-29 11:54 ` [musl] [PATCH V2 0/1] " Harald Hoyer
@ 2022-03-29 11:54 ` Harald Hoyer
0 siblings, 0 replies; 6+ messages in thread
From: Harald Hoyer @ 2022-03-29 11:54 UTC (permalink / raw)
To: musl; +Cc: Harald Hoyer
If `AT_HWCAP2` has `HWCAP2_FSGSBASE` set, then instead of calling
`arch_prctl()`, the `wrfsbase` instruction will be used.
This is helpful in SGX contexts, where inside the enclave no other
mechanism is possible.
Tested against `libc-test`.
Signed-off-by: Harald Hoyer <harald@profian.com>
---
arch/x86_64/bits/hwcap.h | 2 ++
ldso/dynlink.c | 1 +
src/env/__libc_start_main.c | 1 +
src/internal/libc.c | 1 +
src/internal/libc.h | 1 +
src/thread/x86_64/__set_thread_area.c | 14 ++++++++++++++
src/thread/x86_64/__set_thread_area.s | 11 -----------
7 files changed, 20 insertions(+), 11 deletions(-)
create mode 100644 arch/x86_64/bits/hwcap.h
create mode 100644 src/thread/x86_64/__set_thread_area.c
delete mode 100644 src/thread/x86_64/__set_thread_area.s
diff --git a/arch/x86_64/bits/hwcap.h b/arch/x86_64/bits/hwcap.h
new file mode 100644
index 00000000..804d41fa
--- /dev/null
+++ b/arch/x86_64/bits/hwcap.h
@@ -0,0 +1,2 @@
+#define HWCAP2_RING3MWAIT (1 << 0)
+#define HWCAP2_FSGSBASE (1 << 1)
diff --git a/ldso/dynlink.c b/ldso/dynlink.c
index 5b9c8be4..2d38ec63 100644
--- a/ldso/dynlink.c
+++ b/ldso/dynlink.c
@@ -1710,6 +1710,7 @@ void __dls2b(size_t *sp, size_t *auxv)
* use during dynamic linking. If possible it will also serve as the
* thread pointer at runtime. */
search_vec(auxv, &__hwcap, AT_HWCAP);
+ search_vec(auxv, &__hwcap2, AT_HWCAP2);
libc.auxv = auxv;
libc.tls_size = sizeof builtin_tls;
libc.tls_align = tls_align;
diff --git a/src/env/__libc_start_main.c b/src/env/__libc_start_main.c
index c5b277bd..38772bdb 100644
--- a/src/env/__libc_start_main.c
+++ b/src/env/__libc_start_main.c
@@ -28,6 +28,7 @@ void __init_libc(char **envp, char *pn)
libc.auxv = auxv = (void *)(envp+i+1);
for (i=0; auxv[i]; i+=2) if (auxv[i]<AUX_CNT) aux[auxv[i]] = auxv[i+1];
__hwcap = aux[AT_HWCAP];
+ __hwcap2 = aux[AT_HWCAP2];
if (aux[AT_SYSINFO]) __sysinfo = aux[AT_SYSINFO];
libc.page_size = aux[AT_PAGESZ];
diff --git a/src/internal/libc.c b/src/internal/libc.c
index cb051810..16e47633 100644
--- a/src/internal/libc.c
+++ b/src/internal/libc.c
@@ -3,6 +3,7 @@
struct __libc __libc;
size_t __hwcap;
+size_t __hwcap2;
char *__progname=0, *__progname_full=0;
weak_alias(__progname, program_invocation_short_name);
diff --git a/src/internal/libc.h b/src/internal/libc.h
index 619bba86..7d239626 100644
--- a/src/internal/libc.h
+++ b/src/internal/libc.h
@@ -47,6 +47,7 @@ hidden void __libc_exit_fini(void);
hidden void __fork_handler(int);
extern hidden size_t __hwcap;
+extern hidden size_t __hwcap2;
extern hidden size_t __sysinfo;
extern char *__progname, *__progname_full;
diff --git a/src/thread/x86_64/__set_thread_area.c b/src/thread/x86_64/__set_thread_area.c
new file mode 100644
index 00000000..cd3a2519
--- /dev/null
+++ b/src/thread/x86_64/__set_thread_area.c
@@ -0,0 +1,14 @@
+#include <libc.h>
+#include <syscall.h>
+#include <bits/hwcap.h>
+
+hidden int __set_thread_area(void *p)
+{
+ if (__hwcap2 & HWCAP2_FSGSBASE) {
+ __asm__ ("wrfsbase %0" :: "r" (p) : "memory");
+ return 0;
+ }
+
+ // arch_prctl(SET_FS, arg)
+ return syscall(__NR_arch_prctl, 0x1002, p);
+}
diff --git a/src/thread/x86_64/__set_thread_area.s b/src/thread/x86_64/__set_thread_area.s
deleted file mode 100644
index 7347ff4d..00000000
--- a/src/thread/x86_64/__set_thread_area.s
+++ /dev/null
@@ -1,11 +0,0 @@
-/* Copyright 2011-2012 Nicholas J. Kain, licensed under standard MIT license */
-.text
-.global __set_thread_area
-.hidden __set_thread_area
-.type __set_thread_area,@function
-__set_thread_area:
- mov %rdi,%rsi /* shift for syscall */
- movl $0x1002,%edi /* SET_FS register */
- movl $158,%eax /* set fs segment to */
- syscall /* arch_prctl(SET_FS, arg)*/
- ret
--
2.35.1
^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2022-03-30 12:32 UTC | newest]
Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2022-03-29 12:24 [musl] [PATCH V3 0/1] feat(x86_64): use wrfsbase if AT_HWCAP2 allows usage Harald Hoyer
2022-03-29 12:24 ` [musl] [PATCH 1/1] " Harald Hoyer
2022-03-29 15:54 ` Rich Felker
2022-03-30 6:57 ` Harald Hoyer
2022-03-30 12:32 ` Rich Felker
-- strict thread matches above, loose matches on Subject: below --
2022-03-29 11:42 [musl] [PATCH] " Harald Hoyer
2022-03-29 11:54 ` [musl] [PATCH V2 0/1] " Harald Hoyer
2022-03-29 11:54 ` [musl] [PATCH 1/1] " Harald Hoyer
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