| Message ID | 20231103104900.409470-1-ubizjak@gmail.com (mailing list archive) |
|---|---|
| State | Handled Elsewhere, archived |
| Headers | show |
| Series | x86/acpi: Use %rip-relative addressing in wakeup_64.S | expand |
On Fri, Nov 3, 2023 at 11:49 AM Uros Bizjak <ubizjak@gmail.com> wrote: > > Instruction with %rip-relative address operand is one byte shorter than > its absolute address counterpart and is also compatible with position > independent executable (-fpie) build. > > No functional changes intended. I'm wondering what's the exact motivation for making this change. Any urgent need for it doesn't seem to be there. > Cc: "Rafael J. Wysocki" <rafael@kernel.org> > Cc: Len Brown <len.brown@intel.com> > Cc: Pavel Machek <pavel@ucw.cz> > Cc: Thomas Gleixner <tglx@linutronix.de> > Cc: Ingo Molnar <mingo@kernel.org> > Cc: Borislav Petkov <bp@alien8.de> > Cc: Dave Hansen <dave.hansen@linux.intel.com> > Cc: "H. Peter Anvin" <hpa@zytor.com> > Signed-off-by: Uros Bizjak <ubizjak@gmail.com> > --- > arch/x86/kernel/acpi/wakeup_64.S | 24 ++++++++++++------------ > 1 file changed, 12 insertions(+), 12 deletions(-) > > diff --git a/arch/x86/kernel/acpi/wakeup_64.S b/arch/x86/kernel/acpi/wakeup_64.S > index d5d8a352eafa..94ff83f3d3fe 100644 > --- a/arch/x86/kernel/acpi/wakeup_64.S > +++ b/arch/x86/kernel/acpi/wakeup_64.S > @@ -17,7 +17,7 @@ > * Hooray, we are in Long 64-bit mode (but still running in low memory) > */ > SYM_FUNC_START(wakeup_long64) > - movq saved_magic, %rax > + movq saved_magic(%rip), %rax > movq $0x123456789abcdef0, %rdx > cmpq %rdx, %rax > je 2f > @@ -33,14 +33,14 @@ SYM_FUNC_START(wakeup_long64) > movw %ax, %es > movw %ax, %fs > movw %ax, %gs > - movq saved_rsp, %rsp > + movq saved_rsp(%rip), %rsp > > - movq saved_rbx, %rbx > - movq saved_rdi, %rdi > - movq saved_rsi, %rsi > - movq saved_rbp, %rbp > + movq saved_rbx(%rip), %rbx > + movq saved_rdi(%rip), %rdi > + movq saved_rsi(%rip), %rsi > + movq saved_rbp(%rip), %rbp > > - movq saved_rip, %rax > + movq saved_rip(%rip), %rax > ANNOTATE_RETPOLINE_SAFE > jmp *%rax > SYM_FUNC_END(wakeup_long64) > @@ -72,11 +72,11 @@ SYM_FUNC_START(do_suspend_lowlevel) > > movq $.Lresume_point, saved_rip(%rip) > > - movq %rsp, saved_rsp > - movq %rbp, saved_rbp > - movq %rbx, saved_rbx > - movq %rdi, saved_rdi > - movq %rsi, saved_rsi > + movq %rsp, saved_rsp(%rip) > + movq %rbp, saved_rbp(%rip) > + movq %rbx, saved_rbx(%rip) > + movq %rdi, saved_rdi(%rip) > + movq %rsi, saved_rsi(%rip) > > addq $8, %rsp > movl $3, %edi > --
On Mon, Nov 6, 2023 at 3:14 PM Rafael J. Wysocki <rafael@kernel.org> wrote: > > On Fri, Nov 3, 2023 at 11:49 AM Uros Bizjak <ubizjak@gmail.com> wrote: > > > > Instruction with %rip-relative address operand is one byte shorter than > > its absolute address counterpart and is also compatible with position > > independent executable (-fpie) build. > > > > No functional changes intended. > > I'm wondering what's the exact motivation for making this change. Mainly to be consistent with what the compiler emits by default when a symbol is accessed. As said in the commit message, the %rip-relative access is also one byte shorter, and results in a position independent code. > Any urgent need for it doesn't seem to be there. True. It's mostly a nice-to-have change. Thanks, Uros. > > Cc: "Rafael J. Wysocki" <rafael@kernel.org> > > Cc: Len Brown <len.brown@intel.com> > > Cc: Pavel Machek <pavel@ucw.cz> > > Cc: Thomas Gleixner <tglx@linutronix.de> > > Cc: Ingo Molnar <mingo@kernel.org> > > Cc: Borislav Petkov <bp@alien8.de> > > Cc: Dave Hansen <dave.hansen@linux.intel.com> > > Cc: "H. Peter Anvin" <hpa@zytor.com> > > Signed-off-by: Uros Bizjak <ubizjak@gmail.com> > > --- > > arch/x86/kernel/acpi/wakeup_64.S | 24 ++++++++++++------------ > > 1 file changed, 12 insertions(+), 12 deletions(-) > > > > diff --git a/arch/x86/kernel/acpi/wakeup_64.S b/arch/x86/kernel/acpi/wakeup_64.S > > index d5d8a352eafa..94ff83f3d3fe 100644 > > --- a/arch/x86/kernel/acpi/wakeup_64.S > > +++ b/arch/x86/kernel/acpi/wakeup_64.S > > @@ -17,7 +17,7 @@ > > * Hooray, we are in Long 64-bit mode (but still running in low memory) > > */ > > SYM_FUNC_START(wakeup_long64) > > - movq saved_magic, %rax > > + movq saved_magic(%rip), %rax > > movq $0x123456789abcdef0, %rdx > > cmpq %rdx, %rax > > je 2f > > @@ -33,14 +33,14 @@ SYM_FUNC_START(wakeup_long64) > > movw %ax, %es > > movw %ax, %fs > > movw %ax, %gs > > - movq saved_rsp, %rsp > > + movq saved_rsp(%rip), %rsp > > > > - movq saved_rbx, %rbx > > - movq saved_rdi, %rdi > > - movq saved_rsi, %rsi > > - movq saved_rbp, %rbp > > + movq saved_rbx(%rip), %rbx > > + movq saved_rdi(%rip), %rdi > > + movq saved_rsi(%rip), %rsi > > + movq saved_rbp(%rip), %rbp > > > > - movq saved_rip, %rax > > + movq saved_rip(%rip), %rax > > ANNOTATE_RETPOLINE_SAFE > > jmp *%rax > > SYM_FUNC_END(wakeup_long64) > > @@ -72,11 +72,11 @@ SYM_FUNC_START(do_suspend_lowlevel) > > > > movq $.Lresume_point, saved_rip(%rip) > > > > - movq %rsp, saved_rsp > > - movq %rbp, saved_rbp > > - movq %rbx, saved_rbx > > - movq %rdi, saved_rdi > > - movq %rsi, saved_rsi > > + movq %rsp, saved_rsp(%rip) > > + movq %rbp, saved_rbp(%rip) > > + movq %rbx, saved_rbx(%rip) > > + movq %rdi, saved_rdi(%rip) > > + movq %rsi, saved_rsi(%rip) > > > > addq $8, %rsp > > movl $3, %edi > > --
On Mon, Nov 6, 2023 at 3:25 PM Uros Bizjak <ubizjak@gmail.com> wrote: > > On Mon, Nov 6, 2023 at 3:14 PM Rafael J. Wysocki <rafael@kernel.org> wrote: > > > > On Fri, Nov 3, 2023 at 11:49 AM Uros Bizjak <ubizjak@gmail.com> wrote: > > > > > > Instruction with %rip-relative address operand is one byte shorter than > > > its absolute address counterpart and is also compatible with position > > > independent executable (-fpie) build. > > > > > > No functional changes intended. > > > > I'm wondering what's the exact motivation for making this change. > > Mainly to be consistent with what the compiler emits by default when a > symbol is accessed. As said in the commit message, the %rip-relative > access is also one byte shorter, and results in a position independent > code. > > > Any urgent need for it doesn't seem to be there. > > True. It's mostly a nice-to-have change. OK, so Acked-by: Rafael J. Wysocki <rafael@kernel.org> and the decision what to do with it is up to the x86 folks. > > > Cc: "Rafael J. Wysocki" <rafael@kernel.org> > > > Cc: Len Brown <len.brown@intel.com> > > > Cc: Pavel Machek <pavel@ucw.cz> > > > Cc: Thomas Gleixner <tglx@linutronix.de> > > > Cc: Ingo Molnar <mingo@kernel.org> > > > Cc: Borislav Petkov <bp@alien8.de> > > > Cc: Dave Hansen <dave.hansen@linux.intel.com> > > > Cc: "H. Peter Anvin" <hpa@zytor.com> > > > Signed-off-by: Uros Bizjak <ubizjak@gmail.com> > > > --- > > > arch/x86/kernel/acpi/wakeup_64.S | 24 ++++++++++++------------ > > > 1 file changed, 12 insertions(+), 12 deletions(-) > > > > > > diff --git a/arch/x86/kernel/acpi/wakeup_64.S b/arch/x86/kernel/acpi/wakeup_64.S > > > index d5d8a352eafa..94ff83f3d3fe 100644 > > > --- a/arch/x86/kernel/acpi/wakeup_64.S > > > +++ b/arch/x86/kernel/acpi/wakeup_64.S > > > @@ -17,7 +17,7 @@ > > > * Hooray, we are in Long 64-bit mode (but still running in low memory) > > > */ > > > SYM_FUNC_START(wakeup_long64) > > > - movq saved_magic, %rax > > > + movq saved_magic(%rip), %rax > > > movq $0x123456789abcdef0, %rdx > > > cmpq %rdx, %rax > > > je 2f > > > @@ -33,14 +33,14 @@ SYM_FUNC_START(wakeup_long64) > > > movw %ax, %es > > > movw %ax, %fs > > > movw %ax, %gs > > > - movq saved_rsp, %rsp > > > + movq saved_rsp(%rip), %rsp > > > > > > - movq saved_rbx, %rbx > > > - movq saved_rdi, %rdi > > > - movq saved_rsi, %rsi > > > - movq saved_rbp, %rbp > > > + movq saved_rbx(%rip), %rbx > > > + movq saved_rdi(%rip), %rdi > > > + movq saved_rsi(%rip), %rsi > > > + movq saved_rbp(%rip), %rbp > > > > > > - movq saved_rip, %rax > > > + movq saved_rip(%rip), %rax > > > ANNOTATE_RETPOLINE_SAFE > > > jmp *%rax > > > SYM_FUNC_END(wakeup_long64) > > > @@ -72,11 +72,11 @@ SYM_FUNC_START(do_suspend_lowlevel) > > > > > > movq $.Lresume_point, saved_rip(%rip) > > > > > > - movq %rsp, saved_rsp > > > - movq %rbp, saved_rbp > > > - movq %rbx, saved_rbx > > > - movq %rdi, saved_rdi > > > - movq %rsi, saved_rsi > > > + movq %rsp, saved_rsp(%rip) > > > + movq %rbp, saved_rbp(%rip) > > > + movq %rbx, saved_rbx(%rip) > > > + movq %rdi, saved_rdi(%rip) > > > + movq %rsi, saved_rsi(%rip) > > > > > > addq $8, %rsp > > > movl $3, %edi > > > --
diff --git a/arch/x86/kernel/acpi/wakeup_64.S b/arch/x86/kernel/acpi/wakeup_64.S index d5d8a352eafa..94ff83f3d3fe 100644 --- a/arch/x86/kernel/acpi/wakeup_64.S +++ b/arch/x86/kernel/acpi/wakeup_64.S @@ -17,7 +17,7 @@ * Hooray, we are in Long 64-bit mode (but still running in low memory) */ SYM_FUNC_START(wakeup_long64) - movq saved_magic, %rax + movq saved_magic(%rip), %rax movq $0x123456789abcdef0, %rdx cmpq %rdx, %rax je 2f @@ -33,14 +33,14 @@ SYM_FUNC_START(wakeup_long64) movw %ax, %es movw %ax, %fs movw %ax, %gs - movq saved_rsp, %rsp + movq saved_rsp(%rip), %rsp - movq saved_rbx, %rbx - movq saved_rdi, %rdi - movq saved_rsi, %rsi - movq saved_rbp, %rbp + movq saved_rbx(%rip), %rbx + movq saved_rdi(%rip), %rdi + movq saved_rsi(%rip), %rsi + movq saved_rbp(%rip), %rbp - movq saved_rip, %rax + movq saved_rip(%rip), %rax ANNOTATE_RETPOLINE_SAFE jmp *%rax SYM_FUNC_END(wakeup_long64) @@ -72,11 +72,11 @@ SYM_FUNC_START(do_suspend_lowlevel) movq $.Lresume_point, saved_rip(%rip) - movq %rsp, saved_rsp - movq %rbp, saved_rbp - movq %rbx, saved_rbx - movq %rdi, saved_rdi - movq %rsi, saved_rsi + movq %rsp, saved_rsp(%rip) + movq %rbp, saved_rbp(%rip) + movq %rbx, saved_rbx(%rip) + movq %rdi, saved_rdi(%rip) + movq %rsi, saved_rsi(%rip) addq $8, %rsp movl $3, %edi
Instruction with %rip-relative address operand is one byte shorter than its absolute address counterpart and is also compatible with position independent executable (-fpie) build. No functional changes intended. Cc: "Rafael J. Wysocki" <rafael@kernel.org> Cc: Len Brown <len.brown@intel.com> Cc: Pavel Machek <pavel@ucw.cz> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@kernel.org> Cc: Borislav Petkov <bp@alien8.de> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: "H. Peter Anvin" <hpa@zytor.com> Signed-off-by: Uros Bizjak <ubizjak@gmail.com> --- arch/x86/kernel/acpi/wakeup_64.S | 24 ++++++++++++------------ 1 file changed, 12 insertions(+), 12 deletions(-)