The pax argument is unnecesary. Instead, store the RAX value directly
in regs.
Signed-off-by: Brian Gerst <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: "H. Peter Anvin" <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: Denys Vlasenko <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: [email protected]
Cc: [email protected]
---
arch/x86/ia32/ia32_signal.c | 17 ++++++-----------
arch/x86/include/asm/sighandling.h | 4 +---
arch/x86/kernel/signal.c | 22 ++++++++--------------
3 files changed, 15 insertions(+), 28 deletions(-)
diff --git a/arch/x86/ia32/ia32_signal.c b/arch/x86/ia32/ia32_signal.c
index 1f5e2b0..c81d35e6 100644
--- a/arch/x86/ia32/ia32_signal.c
+++ b/arch/x86/ia32/ia32_signal.c
@@ -161,8 +161,7 @@ int copy_siginfo_from_user32(siginfo_t *to, compat_siginfo_t __user *from)
}
static int ia32_restore_sigcontext(struct pt_regs *regs,
- struct sigcontext_ia32 __user *sc,
- unsigned int *pax)
+ struct sigcontext_ia32 __user *sc)
{
unsigned int tmpflags, err = 0;
void __user *buf;
@@ -184,7 +183,7 @@ static int ia32_restore_sigcontext(struct pt_regs *regs,
RELOAD_SEG(es);
COPY(di); COPY(si); COPY(bp); COPY(sp); COPY(bx);
- COPY(dx); COPY(cx); COPY(ip);
+ COPY(dx); COPY(cx); COPY(ip); COPY(ax);
/* Don't touch extended registers */
COPY_SEG_CPL3(cs);
@@ -197,8 +196,6 @@ static int ia32_restore_sigcontext(struct pt_regs *regs,
get_user_ex(tmp, &sc->fpstate);
buf = compat_ptr(tmp);
-
- get_user_ex(*pax, &sc->ax);
} get_user_catch(err);
err |= restore_xstate_sig(buf, 1);
@@ -213,7 +210,6 @@ asmlinkage long sys32_sigreturn(void)
struct pt_regs *regs = current_pt_regs();
struct sigframe_ia32 __user *frame = (struct sigframe_ia32 __user *)(regs->sp-8);
sigset_t set;
- unsigned int ax;
if (!access_ok(VERIFY_READ, frame, sizeof(*frame)))
goto badframe;
@@ -226,9 +222,9 @@ asmlinkage long sys32_sigreturn(void)
set_current_blocked(&set);
- if (ia32_restore_sigcontext(regs, &frame->sc, &ax))
+ if (ia32_restore_sigcontext(regs, &frame->sc))
goto badframe;
- return ax;
+ return regs->ax;
badframe:
signal_fault(regs, frame, "32bit sigreturn");
@@ -240,7 +236,6 @@ asmlinkage long sys32_rt_sigreturn(void)
struct pt_regs *regs = current_pt_regs();
struct rt_sigframe_ia32 __user *frame;
sigset_t set;
- unsigned int ax;
frame = (struct rt_sigframe_ia32 __user *)(regs->sp - 4);
@@ -251,13 +246,13 @@ asmlinkage long sys32_rt_sigreturn(void)
set_current_blocked(&set);
- if (ia32_restore_sigcontext(regs, &frame->uc.uc_mcontext, &ax))
+ if (ia32_restore_sigcontext(regs, &frame->uc.uc_mcontext))
goto badframe;
if (compat_restore_altstack(&frame->uc.uc_stack))
goto badframe;
- return ax;
+ return regs->ax;
badframe:
signal_fault(regs, frame, "32bit rt sigreturn");
diff --git a/arch/x86/include/asm/sighandling.h b/arch/x86/include/asm/sighandling.h
index 7a95816..89db467 100644
--- a/arch/x86/include/asm/sighandling.h
+++ b/arch/x86/include/asm/sighandling.h
@@ -13,9 +13,7 @@
X86_EFLAGS_CF | X86_EFLAGS_RF)
void signal_fault(struct pt_regs *regs, void __user *frame, char *where);
-
-int restore_sigcontext(struct pt_regs *regs, struct sigcontext __user *sc,
- unsigned long *pax);
+int restore_sigcontext(struct pt_regs *regs, struct sigcontext __user *sc);
int setup_sigcontext(struct sigcontext __user *sc, void __user *fpstate,
struct pt_regs *regs, unsigned long mask);
diff --git a/arch/x86/kernel/signal.c b/arch/x86/kernel/signal.c
index eaa2c5e..53cc408 100644
--- a/arch/x86/kernel/signal.c
+++ b/arch/x86/kernel/signal.c
@@ -61,8 +61,7 @@
regs->seg = GET_SEG(seg) | 3; \
} while (0)
-int restore_sigcontext(struct pt_regs *regs, struct sigcontext __user *sc,
- unsigned long *pax)
+int restore_sigcontext(struct pt_regs *regs, struct sigcontext __user *sc)
{
void __user *buf;
unsigned int tmpflags;
@@ -81,7 +80,7 @@ int restore_sigcontext(struct pt_regs *regs, struct sigcontext __user *sc,
#endif /* CONFIG_X86_32 */
COPY(di); COPY(si); COPY(bp); COPY(sp); COPY(bx);
- COPY(dx); COPY(cx); COPY(ip);
+ COPY(dx); COPY(cx); COPY(ip); COPY(ax);
#ifdef CONFIG_X86_64
COPY(r8);
@@ -102,8 +101,6 @@ int restore_sigcontext(struct pt_regs *regs, struct sigcontext __user *sc,
regs->orig_ax = -1; /* disable syscall checks */
get_user_ex(buf, &sc->fpstate);
-
- get_user_ex(*pax, &sc->ax);
} get_user_catch(err);
err |= restore_xstate_sig(buf, config_enabled(CONFIG_X86_32));
@@ -545,7 +542,6 @@ asmlinkage unsigned long sys_sigreturn(void)
{
struct pt_regs *regs = current_pt_regs();
struct sigframe __user *frame;
- unsigned long ax;
sigset_t set;
frame = (struct sigframe __user *)(regs->sp - 8);
@@ -559,9 +555,9 @@ asmlinkage unsigned long sys_sigreturn(void)
set_current_blocked(&set);
- if (restore_sigcontext(regs, &frame->sc, &ax))
+ if (restore_sigcontext(regs, &frame->sc))
goto badframe;
- return ax;
+ return regs->ax;
badframe:
signal_fault(regs, frame, "sigreturn");
@@ -574,7 +570,6 @@ asmlinkage long sys_rt_sigreturn(void)
{
struct pt_regs *regs = current_pt_regs();
struct rt_sigframe __user *frame;
- unsigned long ax;
sigset_t set;
frame = (struct rt_sigframe __user *)(regs->sp - sizeof(long));
@@ -585,13 +580,13 @@ asmlinkage long sys_rt_sigreturn(void)
set_current_blocked(&set);
- if (restore_sigcontext(regs, &frame->uc.uc_mcontext, &ax))
+ if (restore_sigcontext(regs, &frame->uc.uc_mcontext))
goto badframe;
if (restore_altstack(&frame->uc.uc_stack))
goto badframe;
- return ax;
+ return regs->ax;
badframe:
signal_fault(regs, frame, "rt_sigreturn");
@@ -786,7 +781,6 @@ asmlinkage long sys32_x32_rt_sigreturn(void)
struct pt_regs *regs = current_pt_regs();
struct rt_sigframe_x32 __user *frame;
sigset_t set;
- unsigned long ax;
frame = (struct rt_sigframe_x32 __user *)(regs->sp - 8);
@@ -797,13 +791,13 @@ asmlinkage long sys32_x32_rt_sigreturn(void)
set_current_blocked(&set);
- if (restore_sigcontext(regs, &frame->uc.uc_mcontext, &ax))
+ if (restore_sigcontext(regs, &frame->uc.uc_mcontext))
goto badframe;
if (compat_restore_altstack(&frame->uc.uc_stack))
goto badframe;
- return ax;
+ return regs->ax;
badframe:
signal_fault(regs, frame, "x32 rt_sigreturn");
--
2.1.0
* Brian Gerst <[email protected]> wrote:
> The pax argument is unnecesary. Instead, store the RAX value directly
> in regs.
>
> Signed-off-by: Brian Gerst <[email protected]>
> Cc: Ingo Molnar <[email protected]>
> Cc: "H. Peter Anvin" <[email protected]>
> Cc: Andy Lutomirski <[email protected]>
> Cc: Denys Vlasenko <[email protected]>
> Cc: Linus Torvalds <[email protected]>
> Cc: Borislav Petkov <[email protected]>
> Cc: [email protected]
> Cc: [email protected]
> ---
> arch/x86/ia32/ia32_signal.c | 17 ++++++-----------
> arch/x86/include/asm/sighandling.h | 4 +---
> arch/x86/kernel/signal.c | 22 ++++++++--------------
> 3 files changed, 15 insertions(+), 28 deletions(-)
>
> diff --git a/arch/x86/ia32/ia32_signal.c b/arch/x86/ia32/ia32_signal.c
> index 1f5e2b0..c81d35e6 100644
> --- a/arch/x86/ia32/ia32_signal.c
> +++ b/arch/x86/ia32/ia32_signal.c
> @@ -161,8 +161,7 @@ int copy_siginfo_from_user32(siginfo_t *to, compat_siginfo_t __user *from)
> }
>
> static int ia32_restore_sigcontext(struct pt_regs *regs,
> - struct sigcontext_ia32 __user *sc,
> - unsigned int *pax)
> + struct sigcontext_ia32 __user *sc)
> {
> unsigned int tmpflags, err = 0;
> void __user *buf;
> @@ -184,7 +183,7 @@ static int ia32_restore_sigcontext(struct pt_regs *regs,
> RELOAD_SEG(es);
>
> COPY(di); COPY(si); COPY(bp); COPY(sp); COPY(bx);
> - COPY(dx); COPY(cx); COPY(ip);
> + COPY(dx); COPY(cx); COPY(ip); COPY(ax);
> /* Don't touch extended registers */
>
> COPY_SEG_CPL3(cs);
> @@ -197,8 +196,6 @@ static int ia32_restore_sigcontext(struct pt_regs *regs,
>
> get_user_ex(tmp, &sc->fpstate);
> buf = compat_ptr(tmp);
> -
> - get_user_ex(*pax, &sc->ax);
> } get_user_catch(err);
Note that arch/x86/kernel/signal.c appears to have a similar pattern -
and there it could be removed as well?
I'm wondering what the original reason for adding the extra handling
of regs->ax was. Maybe something changed regs->ax - but I cannot find
such code path anymore.
It would be nice to try to do a bit of Git archeology to figure out
the origins of this complication - maybe it's something subtle - or
it's something that has changed meanwhile.
Thanks,
Ingo
On Sat, Apr 4, 2015 at 10:14 AM, Ingo Molnar <[email protected]> wrote:
>
> * Brian Gerst <[email protected]> wrote:
>
>> The pax argument is unnecesary. Instead, store the RAX value directly
>> in regs.
>>
>> Signed-off-by: Brian Gerst <[email protected]>
>> Cc: Ingo Molnar <[email protected]>
>> Cc: "H. Peter Anvin" <[email protected]>
>> Cc: Andy Lutomirski <[email protected]>
>> Cc: Denys Vlasenko <[email protected]>
>> Cc: Linus Torvalds <[email protected]>
>> Cc: Borislav Petkov <[email protected]>
>> Cc: [email protected]
>> Cc: [email protected]
>> ---
>> arch/x86/ia32/ia32_signal.c | 17 ++++++-----------
>> arch/x86/include/asm/sighandling.h | 4 +---
>> arch/x86/kernel/signal.c | 22 ++++++++--------------
>> 3 files changed, 15 insertions(+), 28 deletions(-)
>>
>> diff --git a/arch/x86/ia32/ia32_signal.c b/arch/x86/ia32/ia32_signal.c
>> index 1f5e2b0..c81d35e6 100644
>> --- a/arch/x86/ia32/ia32_signal.c
>> +++ b/arch/x86/ia32/ia32_signal.c
>> @@ -161,8 +161,7 @@ int copy_siginfo_from_user32(siginfo_t *to, compat_siginfo_t __user *from)
>> }
>>
>> static int ia32_restore_sigcontext(struct pt_regs *regs,
>> - struct sigcontext_ia32 __user *sc,
>> - unsigned int *pax)
>> + struct sigcontext_ia32 __user *sc)
>> {
>> unsigned int tmpflags, err = 0;
>> void __user *buf;
>> @@ -184,7 +183,7 @@ static int ia32_restore_sigcontext(struct pt_regs *regs,
>> RELOAD_SEG(es);
>>
>> COPY(di); COPY(si); COPY(bp); COPY(sp); COPY(bx);
>> - COPY(dx); COPY(cx); COPY(ip);
>> + COPY(dx); COPY(cx); COPY(ip); COPY(ax);
>> /* Don't touch extended registers */
>>
>> COPY_SEG_CPL3(cs);
>> @@ -197,8 +196,6 @@ static int ia32_restore_sigcontext(struct pt_regs *regs,
>>
>> get_user_ex(tmp, &sc->fpstate);
>> buf = compat_ptr(tmp);
>> -
>> - get_user_ex(*pax, &sc->ax);
>> } get_user_catch(err);
>
> Note that arch/x86/kernel/signal.c appears to have a similar pattern -
> and there it could be removed as well?
I'm guessing you didn't read the whole patch, because I did change it.
> I'm wondering what the original reason for adding the extra handling
> of regs->ax was. Maybe something changed regs->ax - but I cannot find
> such code path anymore.
>
> It would be nice to try to do a bit of Git archeology to figure out
> the origins of this complication - maybe it's something subtle - or
> it's something that has changed meanwhile.
On Sat, Apr 4, 2015 at 10:14 AM, Ingo Molnar <[email protected]> wrote:
>
> * Brian Gerst <[email protected]> wrote:
>
>> The pax argument is unnecesary. Instead, store the RAX value directly
>> in regs.
>>
>> Signed-off-by: Brian Gerst <[email protected]>
>> Cc: Ingo Molnar <[email protected]>
>> Cc: "H. Peter Anvin" <[email protected]>
>> Cc: Andy Lutomirski <[email protected]>
>> Cc: Denys Vlasenko <[email protected]>
>> Cc: Linus Torvalds <[email protected]>
>> Cc: Borislav Petkov <[email protected]>
>> Cc: [email protected]
>> Cc: [email protected]
>> ---
>> arch/x86/ia32/ia32_signal.c | 17 ++++++-----------
>> arch/x86/include/asm/sighandling.h | 4 +---
>> arch/x86/kernel/signal.c | 22 ++++++++--------------
>> 3 files changed, 15 insertions(+), 28 deletions(-)
>>
>> diff --git a/arch/x86/ia32/ia32_signal.c b/arch/x86/ia32/ia32_signal.c
>> index 1f5e2b0..c81d35e6 100644
>> --- a/arch/x86/ia32/ia32_signal.c
>> +++ b/arch/x86/ia32/ia32_signal.c
>> @@ -161,8 +161,7 @@ int copy_siginfo_from_user32(siginfo_t *to, compat_siginfo_t __user *from)
>> }
>>
>> static int ia32_restore_sigcontext(struct pt_regs *regs,
>> - struct sigcontext_ia32 __user *sc,
>> - unsigned int *pax)
>> + struct sigcontext_ia32 __user *sc)
>> {
>> unsigned int tmpflags, err = 0;
>> void __user *buf;
>> @@ -184,7 +183,7 @@ static int ia32_restore_sigcontext(struct pt_regs *regs,
>> RELOAD_SEG(es);
>>
>> COPY(di); COPY(si); COPY(bp); COPY(sp); COPY(bx);
>> - COPY(dx); COPY(cx); COPY(ip);
>> + COPY(dx); COPY(cx); COPY(ip); COPY(ax);
>> /* Don't touch extended registers */
>>
>> COPY_SEG_CPL3(cs);
>> @@ -197,8 +196,6 @@ static int ia32_restore_sigcontext(struct pt_regs *regs,
>>
>> get_user_ex(tmp, &sc->fpstate);
>> buf = compat_ptr(tmp);
>> -
>> - get_user_ex(*pax, &sc->ax);
>> } get_user_catch(err);
>
> Note that arch/x86/kernel/signal.c appears to have a similar pattern -
> and there it could be removed as well?
>
> I'm wondering what the original reason for adding the extra handling
> of regs->ax was. Maybe something changed regs->ax - but I cannot find
> such code path anymore.
>
> It would be nice to try to do a bit of Git archeology to figure out
> the origins of this complication - maybe it's something subtle - or
> it's something that has changed meanwhile.
It goes all the way back to 2.1.106pre1, when restore_sigcontext() was
changed to return an error code instead of EAX directly.
https://git.kernel.org/cgit/linux/kernel/git/history/history.git/diff/arch/i386/kernel/signal.c?id=9a8f8b7ca3f319bd668298d447bdf32730e51174
--
Brian Gerst
* Brian Gerst <[email protected]> wrote:
> On Sat, Apr 4, 2015 at 10:14 AM, Ingo Molnar <[email protected]> wrote:
> >
> > * Brian Gerst <[email protected]> wrote:
> >
> >> The pax argument is unnecesary. Instead, store the RAX value directly
> >> in regs.
> >>
> >> Signed-off-by: Brian Gerst <[email protected]>
> >> Cc: Ingo Molnar <[email protected]>
> >> Cc: "H. Peter Anvin" <[email protected]>
> >> Cc: Andy Lutomirski <[email protected]>
> >> Cc: Denys Vlasenko <[email protected]>
> >> Cc: Linus Torvalds <[email protected]>
> >> Cc: Borislav Petkov <[email protected]>
> >> Cc: [email protected]
> >> Cc: [email protected]
> >> ---
> >> arch/x86/ia32/ia32_signal.c | 17 ++++++-----------
> >> arch/x86/include/asm/sighandling.h | 4 +---
> >> arch/x86/kernel/signal.c | 22 ++++++++--------------
> >> 3 files changed, 15 insertions(+), 28 deletions(-)
> >>
> >> diff --git a/arch/x86/ia32/ia32_signal.c b/arch/x86/ia32/ia32_signal.c
> >> index 1f5e2b0..c81d35e6 100644
> >> --- a/arch/x86/ia32/ia32_signal.c
> >> +++ b/arch/x86/ia32/ia32_signal.c
> >> @@ -161,8 +161,7 @@ int copy_siginfo_from_user32(siginfo_t *to, compat_siginfo_t __user *from)
> >> }
> >>
> >> static int ia32_restore_sigcontext(struct pt_regs *regs,
> >> - struct sigcontext_ia32 __user *sc,
> >> - unsigned int *pax)
> >> + struct sigcontext_ia32 __user *sc)
> >> {
> >> unsigned int tmpflags, err = 0;
> >> void __user *buf;
> >> @@ -184,7 +183,7 @@ static int ia32_restore_sigcontext(struct pt_regs *regs,
> >> RELOAD_SEG(es);
> >>
> >> COPY(di); COPY(si); COPY(bp); COPY(sp); COPY(bx);
> >> - COPY(dx); COPY(cx); COPY(ip);
> >> + COPY(dx); COPY(cx); COPY(ip); COPY(ax);
> >> /* Don't touch extended registers */
> >>
> >> COPY_SEG_CPL3(cs);
> >> @@ -197,8 +196,6 @@ static int ia32_restore_sigcontext(struct pt_regs *regs,
> >>
> >> get_user_ex(tmp, &sc->fpstate);
> >> buf = compat_ptr(tmp);
> >> -
> >> - get_user_ex(*pax, &sc->ax);
> >> } get_user_catch(err);
> >
> > Note that arch/x86/kernel/signal.c appears to have a similar pattern -
> > and there it could be removed as well?
>
> I'm guessing you didn't read the whole patch, because I did change it.
Yes :-/
Ingo
* Brian Gerst <[email protected]> wrote:
> > I'm wondering what the original reason for adding the extra
> > handling of regs->ax was. Maybe something changed regs->ax - but I
> > cannot find such code path anymore.
> >
> > It would be nice to try to do a bit of Git archeology to figure
> > out the origins of this complication - maybe it's something subtle
> > - or it's something that has changed meanwhile.
>
> It goes all the way back to 2.1.106pre1, when restore_sigcontext()
> was changed to return an error code instead of EAX directly.
>
> https://git.kernel.org/cgit/linux/kernel/git/history/history.git/diff/arch/i386/kernel/signal.c?id=9a8f8b7ca3f319bd668298d447bdf32730e51174
Indeed: restore_sigcontext() used to return eax as a return value,
without copying it into regs->ax.
Then in 2007 sigaltstack syscall support was added, where the return
value of restore_sigcontext() was changed to carry the memory-copying
failure code. But instead of putting 'ax' into regs->ax, it was
carried in via a pointer and then returned, where the generic syscall
return code copied it to regs->ax.
So there was never any deeper reason for this suboptimal pattern, it
was simply never noticed after being introduced.
(Btw., the regs->ax we return will be copied back to regs->ax after
the syscall straight away once again - but I guess this cannot be
helped.)
I've added this information to the changelog.
Thanks,
Ingo
On Mon, Apr 6, 2015 at 3:03 AM, Ingo Molnar <[email protected]> wrote:
>
> * Brian Gerst <[email protected]> wrote:
>
>> > I'm wondering what the original reason for adding the extra
>> > handling of regs->ax was. Maybe something changed regs->ax - but I
>> > cannot find such code path anymore.
>> >
>> > It would be nice to try to do a bit of Git archeology to figure
>> > out the origins of this complication - maybe it's something subtle
>> > - or it's something that has changed meanwhile.
>>
>> It goes all the way back to 2.1.106pre1, when restore_sigcontext()
>> was changed to return an error code instead of EAX directly.
>>
>> https://git.kernel.org/cgit/linux/kernel/git/history/history.git/diff/arch/i386/kernel/signal.c?id=9a8f8b7ca3f319bd668298d447bdf32730e51174
>
> Indeed: restore_sigcontext() used to return eax as a return value,
> without copying it into regs->ax.
>
> Then in 2007
Version 2.1.106 was released on Jun 13, 1998.
> sigaltstack syscall support was added, where the return
> value of restore_sigcontext() was changed to carry the memory-copying
> failure code. But instead of putting 'ax' into regs->ax, it was
> carried in via a pointer and then returned, where the generic syscall
> return code copied it to regs->ax.
>
> So there was never any deeper reason for this suboptimal pattern, it
> was simply never noticed after being introduced.
>
> (Btw., the regs->ax we return will be copied back to regs->ax after
> the syscall straight away once again - but I guess this cannot be
> helped.)
The 64-bit stub could skip saving it back to regs. However 32-bit
does not have a special stub so sys_rt_sigreturn() still needs to
return regs->ax.
--
Brian Gerst
Commit-ID: 6a3713f001b3b53587e411ab0d3036ae9b0fb93b
Gitweb: http://git.kernel.org/tip/6a3713f001b3b53587e411ab0d3036ae9b0fb93b
Author: Brian Gerst <[email protected]>
AuthorDate: Sat, 4 Apr 2015 08:58:23 -0400
Committer: Ingo Molnar <[email protected]>
CommitDate: Mon, 6 Apr 2015 09:06:39 +0200
x86/signal: Remove pax argument from restore_sigcontext
The 'pax' argument is unnecesary. Instead, store the RAX value
directly in regs.
This pattern goes all the way back to 2.1.106pre1, when restore_sigcontext()
was changed to return an error code instead of EAX directly:
https://git.kernel.org/cgit/linux/kernel/git/history/history.git/diff/arch/i386/kernel/signal.c?id=9a8f8b7ca3f319bd668298d447bdf32730e51174
In 2007 sigaltstack syscall support was added, where the return
value of restore_sigcontext() was changed to carry the memory-copying
failure code.
But instead of putting 'ax' into regs->ax directly, it was carried
in via a pointer and then returned, where the generic syscall return
code copied it to regs->ax.
So there was never any deeper reason for this suboptimal pattern, it
was simply never noticed after being introduced.
Signed-off-by: Brian Gerst <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Denys Vlasenko <[email protected]>
Cc: H. Peter Anvin <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>
---
arch/x86/ia32/ia32_signal.c | 17 ++++++-----------
arch/x86/include/asm/sighandling.h | 4 +---
arch/x86/kernel/signal.c | 22 ++++++++--------------
3 files changed, 15 insertions(+), 28 deletions(-)
diff --git a/arch/x86/ia32/ia32_signal.c b/arch/x86/ia32/ia32_signal.c
index 1f5e2b0..c81d35e6 100644
--- a/arch/x86/ia32/ia32_signal.c
+++ b/arch/x86/ia32/ia32_signal.c
@@ -161,8 +161,7 @@ int copy_siginfo_from_user32(siginfo_t *to, compat_siginfo_t __user *from)
}
static int ia32_restore_sigcontext(struct pt_regs *regs,
- struct sigcontext_ia32 __user *sc,
- unsigned int *pax)
+ struct sigcontext_ia32 __user *sc)
{
unsigned int tmpflags, err = 0;
void __user *buf;
@@ -184,7 +183,7 @@ static int ia32_restore_sigcontext(struct pt_regs *regs,
RELOAD_SEG(es);
COPY(di); COPY(si); COPY(bp); COPY(sp); COPY(bx);
- COPY(dx); COPY(cx); COPY(ip);
+ COPY(dx); COPY(cx); COPY(ip); COPY(ax);
/* Don't touch extended registers */
COPY_SEG_CPL3(cs);
@@ -197,8 +196,6 @@ static int ia32_restore_sigcontext(struct pt_regs *regs,
get_user_ex(tmp, &sc->fpstate);
buf = compat_ptr(tmp);
-
- get_user_ex(*pax, &sc->ax);
} get_user_catch(err);
err |= restore_xstate_sig(buf, 1);
@@ -213,7 +210,6 @@ asmlinkage long sys32_sigreturn(void)
struct pt_regs *regs = current_pt_regs();
struct sigframe_ia32 __user *frame = (struct sigframe_ia32 __user *)(regs->sp-8);
sigset_t set;
- unsigned int ax;
if (!access_ok(VERIFY_READ, frame, sizeof(*frame)))
goto badframe;
@@ -226,9 +222,9 @@ asmlinkage long sys32_sigreturn(void)
set_current_blocked(&set);
- if (ia32_restore_sigcontext(regs, &frame->sc, &ax))
+ if (ia32_restore_sigcontext(regs, &frame->sc))
goto badframe;
- return ax;
+ return regs->ax;
badframe:
signal_fault(regs, frame, "32bit sigreturn");
@@ -240,7 +236,6 @@ asmlinkage long sys32_rt_sigreturn(void)
struct pt_regs *regs = current_pt_regs();
struct rt_sigframe_ia32 __user *frame;
sigset_t set;
- unsigned int ax;
frame = (struct rt_sigframe_ia32 __user *)(regs->sp - 4);
@@ -251,13 +246,13 @@ asmlinkage long sys32_rt_sigreturn(void)
set_current_blocked(&set);
- if (ia32_restore_sigcontext(regs, &frame->uc.uc_mcontext, &ax))
+ if (ia32_restore_sigcontext(regs, &frame->uc.uc_mcontext))
goto badframe;
if (compat_restore_altstack(&frame->uc.uc_stack))
goto badframe;
- return ax;
+ return regs->ax;
badframe:
signal_fault(regs, frame, "32bit rt sigreturn");
diff --git a/arch/x86/include/asm/sighandling.h b/arch/x86/include/asm/sighandling.h
index 7a95816..89db467 100644
--- a/arch/x86/include/asm/sighandling.h
+++ b/arch/x86/include/asm/sighandling.h
@@ -13,9 +13,7 @@
X86_EFLAGS_CF | X86_EFLAGS_RF)
void signal_fault(struct pt_regs *regs, void __user *frame, char *where);
-
-int restore_sigcontext(struct pt_regs *regs, struct sigcontext __user *sc,
- unsigned long *pax);
+int restore_sigcontext(struct pt_regs *regs, struct sigcontext __user *sc);
int setup_sigcontext(struct sigcontext __user *sc, void __user *fpstate,
struct pt_regs *regs, unsigned long mask);
diff --git a/arch/x86/kernel/signal.c b/arch/x86/kernel/signal.c
index eaa2c5e..53cc408 100644
--- a/arch/x86/kernel/signal.c
+++ b/arch/x86/kernel/signal.c
@@ -61,8 +61,7 @@
regs->seg = GET_SEG(seg) | 3; \
} while (0)
-int restore_sigcontext(struct pt_regs *regs, struct sigcontext __user *sc,
- unsigned long *pax)
+int restore_sigcontext(struct pt_regs *regs, struct sigcontext __user *sc)
{
void __user *buf;
unsigned int tmpflags;
@@ -81,7 +80,7 @@ int restore_sigcontext(struct pt_regs *regs, struct sigcontext __user *sc,
#endif /* CONFIG_X86_32 */
COPY(di); COPY(si); COPY(bp); COPY(sp); COPY(bx);
- COPY(dx); COPY(cx); COPY(ip);
+ COPY(dx); COPY(cx); COPY(ip); COPY(ax);
#ifdef CONFIG_X86_64
COPY(r8);
@@ -102,8 +101,6 @@ int restore_sigcontext(struct pt_regs *regs, struct sigcontext __user *sc,
regs->orig_ax = -1; /* disable syscall checks */
get_user_ex(buf, &sc->fpstate);
-
- get_user_ex(*pax, &sc->ax);
} get_user_catch(err);
err |= restore_xstate_sig(buf, config_enabled(CONFIG_X86_32));
@@ -545,7 +542,6 @@ asmlinkage unsigned long sys_sigreturn(void)
{
struct pt_regs *regs = current_pt_regs();
struct sigframe __user *frame;
- unsigned long ax;
sigset_t set;
frame = (struct sigframe __user *)(regs->sp - 8);
@@ -559,9 +555,9 @@ asmlinkage unsigned long sys_sigreturn(void)
set_current_blocked(&set);
- if (restore_sigcontext(regs, &frame->sc, &ax))
+ if (restore_sigcontext(regs, &frame->sc))
goto badframe;
- return ax;
+ return regs->ax;
badframe:
signal_fault(regs, frame, "sigreturn");
@@ -574,7 +570,6 @@ asmlinkage long sys_rt_sigreturn(void)
{
struct pt_regs *regs = current_pt_regs();
struct rt_sigframe __user *frame;
- unsigned long ax;
sigset_t set;
frame = (struct rt_sigframe __user *)(regs->sp - sizeof(long));
@@ -585,13 +580,13 @@ asmlinkage long sys_rt_sigreturn(void)
set_current_blocked(&set);
- if (restore_sigcontext(regs, &frame->uc.uc_mcontext, &ax))
+ if (restore_sigcontext(regs, &frame->uc.uc_mcontext))
goto badframe;
if (restore_altstack(&frame->uc.uc_stack))
goto badframe;
- return ax;
+ return regs->ax;
badframe:
signal_fault(regs, frame, "rt_sigreturn");
@@ -786,7 +781,6 @@ asmlinkage long sys32_x32_rt_sigreturn(void)
struct pt_regs *regs = current_pt_regs();
struct rt_sigframe_x32 __user *frame;
sigset_t set;
- unsigned long ax;
frame = (struct rt_sigframe_x32 __user *)(regs->sp - 8);
@@ -797,13 +791,13 @@ asmlinkage long sys32_x32_rt_sigreturn(void)
set_current_blocked(&set);
- if (restore_sigcontext(regs, &frame->uc.uc_mcontext, &ax))
+ if (restore_sigcontext(regs, &frame->uc.uc_mcontext))
goto badframe;
if (compat_restore_altstack(&frame->uc.uc_stack))
goto badframe;
- return ax;
+ return regs->ax;
badframe:
signal_fault(regs, frame, "x32 rt_sigreturn");
* Brian Gerst <[email protected]> wrote:
> On Mon, Apr 6, 2015 at 3:03 AM, Ingo Molnar <[email protected]> wrote:
> >
> > * Brian Gerst <[email protected]> wrote:
> >
> >> > I'm wondering what the original reason for adding the extra
> >> > handling of regs->ax was. Maybe something changed regs->ax - but I
> >> > cannot find such code path anymore.
> >> >
> >> > It would be nice to try to do a bit of Git archeology to figure
> >> > out the origins of this complication - maybe it's something subtle
> >> > - or it's something that has changed meanwhile.
> >>
> >> It goes all the way back to 2.1.106pre1, when restore_sigcontext()
> >> was changed to return an error code instead of EAX directly.
> >>
> >> https://git.kernel.org/cgit/linux/kernel/git/history/history.git/diff/arch/i386/kernel/signal.c?id=9a8f8b7ca3f319bd668298d447bdf32730e51174
> >
> > Indeed: restore_sigcontext() used to return eax as a return value,
> > without copying it into regs->ax.
> >
> > Then in 2007
>
> Version 2.1.106 was released on Jun 13, 1998.
Sigh, the Git timestamp of the historic tree threw me off :-)
> > sigaltstack syscall support was added, where the return value of
> > restore_sigcontext() was changed to carry the memory-copying
> > failure code. But instead of putting 'ax' into regs->ax, it was
> > carried in via a pointer and then returned, where the generic
> > syscall return code copied it to regs->ax.
> >
> > So there was never any deeper reason for this suboptimal pattern,
> > it was simply never noticed after being introduced.
> >
> > (Btw., the regs->ax we return will be copied back to regs->ax
> > after the syscall straight away once again - but I guess this
> > cannot be helped.)
>
> The 64-bit stub could skip saving it back to regs.
Yeah, but at the cost of having a duplicated entry stub, right?
Thanks,
Ingo