Clear RF on SYSCALL instruction

[Qemu-devel] [PATCH] Clear RF on SYSCALL instruction

Roman Kapl posted 1 patch 5 years, 6 months ago

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git fetch https://github.com/patchew-project/qemu tags/patchew/20181019122449.26387-1-rka@sysgo.com

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target/i386/seg_helper.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

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[Qemu-devel] [PATCH] Clear RF on SYSCALL instruction

Posted by Roman Kapl 5 years, 6 months ago

From: Rudolf Marek <rudolf.marek@sysgo.com>

Fix the SYSCALL instruction in 64-bit (long mode). The RF flag
should be cleared in R11 as well as in the RFLAGS. Intel
and AMD CPUs behave same. AMD has this documented in the
APM vol 3.

Signed-off-by: Roman Kapl <rka@sysgo.com>
Signed-off-by: Rudolf Marek <rudolf.marek@sysgo.com>
---
 target/i386/seg_helper.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/target/i386/seg_helper.c b/target/i386/seg_helper.c
index 33714bc6e1..63e265cb38 100644
--- a/target/i386/seg_helper.c
+++ b/target/i386/seg_helper.c
@@ -991,11 +991,11 @@ void helper_syscall(CPUX86State *env, int next_eip_addend)
         int code64;
 
         env->regs[R_ECX] = env->eip + next_eip_addend;
-        env->regs[11] = cpu_compute_eflags(env);
+        env->regs[11] = cpu_compute_eflags(env) & ~RF_MASK;
 
         code64 = env->hflags & HF_CS64_MASK;
 
-        env->eflags &= ~env->fmask;
+        env->eflags &= ~(env->fmask | RF_MASK);
         cpu_load_eflags(env, env->eflags, 0);
         cpu_x86_load_seg_cache(env, R_CS, selector & 0xfffc,
                            0, 0xffffffff,
-- 
2.11.0

Re: [Qemu-devel] [PATCH] Clear RF on SYSCALL instruction

Posted by Paolo Bonzini 5 years, 6 months ago

On 19/10/2018 14:24, Roman Kapl wrote:
> From: Rudolf Marek <rudolf.marek@sysgo.com>
> 
> Fix the SYSCALL instruction in 64-bit (long mode). The RF flag
> should be cleared in R11 as well as in the RFLAGS. Intel
> and AMD CPUs behave same. AMD has this documented in the
> APM vol 3.
> 
> Signed-off-by: Roman Kapl <rka@sysgo.com>
> Signed-off-by: Rudolf Marek <rudolf.marek@sysgo.com>
> ---
>  target/i386/seg_helper.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/target/i386/seg_helper.c b/target/i386/seg_helper.c
> index 33714bc6e1..63e265cb38 100644
> --- a/target/i386/seg_helper.c
> +++ b/target/i386/seg_helper.c
> @@ -991,11 +991,11 @@ void helper_syscall(CPUX86State *env, int next_eip_addend)
>          int code64;
>  
>          env->regs[R_ECX] = env->eip + next_eip_addend;
> -        env->regs[11] = cpu_compute_eflags(env);
> +        env->regs[11] = cpu_compute_eflags(env) & ~RF_MASK;
>  
>          code64 = env->hflags & HF_CS64_MASK;
>  
> -        env->eflags &= ~env->fmask;
> +        env->eflags &= ~(env->fmask | RF_MASK);
>          cpu_load_eflags(env, env->eflags, 0);
>          cpu_x86_load_seg_cache(env, R_CS, selector & 0xfffc,
>                             0, 0xffffffff,
> 

Queued, thanks.

Paolo