2020-03-08 23:54:04

by Thomas Gleixner

Subject: [patch part-III V2 05/23] x86/entry/32: Provide macro to emit IDT entry stubs

From: Thomas Gleixner <[email protected]>

32 and 64 bit have unnecessary different ways to populate the exception
entry code. Provide a idtentry macro which allows to consolidate all of
that.

Signed-off-by: Thomas Gleixner <[email protected]>
Reviewed-by: Alexandre Chartre <[email protected]>

---
arch/x86/entry/entry_32.S | 42 ++++++++++++++++++++++++++++++++++++++++++
1 file changed, 42 insertions(+)

--- a/arch/x86/entry/entry_32.S
+++ b/arch/x86/entry/entry_32.S
@@ -44,6 +44,7 @@
#include <asm/asm.h>
#include <asm/smap.h>
#include <asm/frame.h>
+#include <asm/trapnr.h>
#include <asm/nospec-branch.h>

#include "calling.h"
@@ -726,6 +727,47 @@

.Lend_\@:
.endm
+
+#ifdef CONFIG_X86_INVD_BUG
+.macro idtentry_push_func vector cfunc
+ .if \vector == X86_TRAP_XF
+ /* AMD 486 bug: invd from userspace calls exception 19 instead of #GP */
+ ALTERNATIVE "pushl $do_general_protection", \
+ "pushl $do_simd_coprocessor_error", \
+ X86_FEATURE_XMM
+ .else
+ pushl $\cfunc
+ .endif
+.endm
+#else
+.macro idtentry_push_func vector cfunc
+ pushl $\cfunc
+.endm
+#endif
+
+/**
+ * idtentry - Macro to generate entry stubs for simple IDT entries
+ * @vector: Vector number
+ * @asmsym: ASM symbol for the entry point
+ * @cfunc: C function to be called
+ * @has_error_code: Hardware pushed error code on stack
+ */
+.macro idtentry vector asmsym cfunc has_error_code:req
+SYM_CODE_START(\asmsym)
+ ASM_CLAC
+ cld
+
+ .if \has_error_code == 0
+ pushl $0 /* Clear the error code */
+ .endif
+
+ /* Push the C-function address into the GS slot */
+ idtentry_push_func \vector \cfunc
+ /* Invoke the common exception entry */
+ jmp common_exception
+SYM_CODE_END(\asmsym)
+.endm
+
/*
* %eax: prev task
* %edx: next task

2020-03-09 05:09:22

by Brian Gerst

Subject: Re: [patch part-III V2 05/23] x86/entry/32: Provide macro to emit IDT entry stubs

On Sun, Mar 8, 2020 at 7:24 PM Thomas Gleixner <[email protected]> wrote:
>
> From: Thomas Gleixner <[email protected]>
>
> 32 and 64 bit have unnecessary different ways to populate the exception
> entry code. Provide a idtentry macro which allows to consolidate all of
> that.
>
> Signed-off-by: Thomas Gleixner <[email protected]>
> Reviewed-by: Alexandre Chartre <[email protected]>
>
> ---
> arch/x86/entry/entry_32.S | 42 ++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 42 insertions(+)
>
> --- a/arch/x86/entry/entry_32.S
> +++ b/arch/x86/entry/entry_32.S
> @@ -44,6 +44,7 @@
> #include <asm/asm.h>
> #include <asm/smap.h>
> #include <asm/frame.h>
> +#include <asm/trapnr.h>
> #include <asm/nospec-branch.h>
>
> #include "calling.h"
> @@ -726,6 +727,47 @@
>
> .Lend_\@:
> .endm
> +
> +#ifdef CONFIG_X86_INVD_BUG
> +.macro idtentry_push_func vector cfunc
> + .if \vector == X86_TRAP_XF
> + /* AMD 486 bug: invd from userspace calls exception 19 instead of #GP */
> + ALTERNATIVE "pushl $do_general_protection", \
> + "pushl $do_simd_coprocessor_error", \
> + X86_FEATURE_XMM
> + .else
> + pushl $\cfunc
> + .endif
> +.endm
> +#else
> +.macro idtentry_push_func vector cfunc
> + pushl $\cfunc
> +.endm
> +#endif

IMHO it would be better to push this to the C code and not make the
asm more complicated. Something like:

dotraplinkage void
do_simd_coprocessor_error(struct pt_regs *regs, long error_code)
{
#ifdef CONFIG_X86_INVD_BUG
/* AMD 486 bug: invd from userspace calls exception 19 instead of #GP */
if (!static_cpu_has(X86_FEATURE_XMM)) {
do_general_protection(regs, error_code);
return;
}
#endif
RCU_LOCKDEP_WARN(!rcu_is_watching(), "entry code didn't wake RCU");
math_error(regs, error_code, X86_TRAP_XF);
}

--
Brian Gerst

2020-03-09 07:03:42

by Thomas Gleixner

Subject: Re: [patch part-III V2 05/23] x86/entry/32: Provide macro to emit IDT entry stubs

Brian Gerst <[email protected]> writes:
> On Sun, Mar 8, 2020 at 7:24 PM Thomas Gleixner <[email protected]> wrote:
>> +#ifdef CONFIG_X86_INVD_BUG
>> +.macro idtentry_push_func vector cfunc
>> + .if \vector == X86_TRAP_XF
>> + /* AMD 486 bug: invd from userspace calls exception 19 instead of #GP */
>> + ALTERNATIVE "pushl $do_general_protection", \
>> + "pushl $do_simd_coprocessor_error", \
>> + X86_FEATURE_XMM
>> + .else
>> + pushl $\cfunc
>> + .endif
>> +.endm
>> +#else
>> +.macro idtentry_push_func vector cfunc
>> + pushl $\cfunc
>> +.endm
>> +#endif
>
> IMHO it would be better to push this to the C code and not make the
> asm more complicated. Something like:
>
> dotraplinkage void
> do_simd_coprocessor_error(struct pt_regs *regs, long error_code)
> {
> #ifdef CONFIG_X86_INVD_BUG
> /* AMD 486 bug: invd from userspace calls exception 19 instead of #GP */
> if (!static_cpu_has(X86_FEATURE_XMM)) {
> do_general_protection(regs, error_code);
> return;
> }
> #endif
> RCU_LOCKDEP_WARN(!rcu_is_watching(), "entry code didn't wake RCU");
> math_error(regs, error_code, X86_TRAP_XF);
> }

That's too obvious :)

Thanks for catching that!

tglx