diff mbox series

[v3,05/49] semihosting: Add target_strlen for softmmu-uaccess.h

Message ID 20220521000400.454525-6-richard.henderson@linaro.org
State Superseded
Headers show
Series semihosting cleanup | expand

Commit Message

Richard Henderson May 21, 2022, 12:03 a.m. UTC
Mirror the interface of the user-only function of the same name.
Use probe_access_flags for the common case of ram, and
cpu_memory_rw_debug for the uncommon case of mmio.

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
v3: Use probe_access_flags (pmm)
---
 include/semihosting/softmmu-uaccess.h |  3 ++
 semihosting/uaccess.c                 | 49 +++++++++++++++++++++++++++
 2 files changed, 52 insertions(+)

Comments

Richard Henderson May 21, 2022, 4:51 a.m. UTC | #1
On 5/20/22 17:03, Richard Henderson wrote:
> Mirror the interface of the user-only function of the same name.
> Use probe_access_flags for the common case of ram, and
> cpu_memory_rw_debug for the uncommon case of mmio.
> 
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
> ---
> v3: Use probe_access_flags (pmm)

Ho hum.  MIPS still selects semihosting without TCG, which means that
probe_access_flags is not present.

At present I'm assuming that semihosting can't work with KVM, and that we should disable 
the feature.


r~

> ---
>   include/semihosting/softmmu-uaccess.h |  3 ++
>   semihosting/uaccess.c                 | 49 +++++++++++++++++++++++++++
>   2 files changed, 52 insertions(+)
> 
> diff --git a/include/semihosting/softmmu-uaccess.h b/include/semihosting/softmmu-uaccess.h
> index 03300376d3..4f08dfc098 100644
> --- a/include/semihosting/softmmu-uaccess.h
> +++ b/include/semihosting/softmmu-uaccess.h
> @@ -53,4 +53,7 @@ void softmmu_unlock_user(CPUArchState *env, void *p,
>                            target_ulong addr, target_ulong len);
>   #define unlock_user(s, args, len) softmmu_unlock_user(env, s, args, len)
>   
> +ssize_t softmmu_strlen_user(CPUArchState *env, target_ulong addr);
> +#define target_strlen(p) softmmu_strlen_user(env, p)
> +
>   #endif /* SEMIHOSTING_SOFTMMU_UACCESS_H */
> diff --git a/semihosting/uaccess.c b/semihosting/uaccess.c
> index 0d3b32b75d..51019b79ff 100644
> --- a/semihosting/uaccess.c
> +++ b/semihosting/uaccess.c
> @@ -8,6 +8,7 @@
>    */
>   
>   #include "qemu/osdep.h"
> +#include "exec/exec-all.h"
>   #include "semihosting/softmmu-uaccess.h"
>   
>   void *softmmu_lock_user(CPUArchState *env, target_ulong addr,
> @@ -23,6 +24,54 @@ void *softmmu_lock_user(CPUArchState *env, target_ulong addr,
>       return p;
>   }
>   
> +ssize_t softmmu_strlen_user(CPUArchState *env, target_ulong addr)
> +{
> +    int mmu_idx = cpu_mmu_index(env, false);
> +    size_t len = 0;
> +
> +    while (1) {
> +        size_t left_in_page;
> +        int flags;
> +        void *h;
> +
> +        /* Find the number of bytes remaining in the page. */
> +        left_in_page = -(addr | TARGET_PAGE_MASK);
> +
> +        flags = probe_access_flags(env, addr, MMU_DATA_LOAD,
> +                                   mmu_idx, true, &h, 0);
> +        if (flags & TLB_INVALID_MASK) {
> +            return -1;
> +        }
> +        if (flags & TLB_MMIO) {
> +            do {
> +                uint8_t c;
> +                if (cpu_memory_rw_debug(env_cpu(env), addr, &c, 1, 0)) {
> +                    return -1;
> +                }
> +                if (c == 0) {
> +                    return len;
> +                }
> +                addr++;
> +                len++;
> +                if (len > INT32_MAX) {
> +                    return -1;
> +                }
> +            } while (--left_in_page != 0);
> +        } else {
> +            char *p = memchr(h, 0, left_in_page);
> +            if (p) {
> +                len += p - (char *)h;
> +                return len <= INT32_MAX ? (ssize_t)len : -1;
> +            }
> +            addr += left_in_page;
> +            len += left_in_page;
> +            if (len > INT32_MAX) {
> +                return -1;
> +            }
> +        }
> +    }
> +}
> +
>   char *softmmu_lock_user_string(CPUArchState *env, target_ulong addr)
>   {
>       /* TODO: Make this something that isn't fixed size.  */
Peter Maydell May 23, 2022, 10:55 a.m. UTC | #2
On Sat, 21 May 2022 at 05:51, Richard Henderson
<richard.henderson@linaro.org> wrote:
>
> On 5/20/22 17:03, Richard Henderson wrote:
> > Mirror the interface of the user-only function of the same name.
> > Use probe_access_flags for the common case of ram, and
> > cpu_memory_rw_debug for the uncommon case of mmio.
> >
> > Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
> > ---
> > v3: Use probe_access_flags (pmm)
>
> Ho hum.  MIPS still selects semihosting without TCG, which means that
> probe_access_flags is not present.
>
> At present I'm assuming that semihosting can't work with KVM, and that we should disable
> the feature.
>
>
> r~
>
> > ---
> >   include/semihosting/softmmu-uaccess.h |  3 ++
> >   semihosting/uaccess.c                 | 49 +++++++++++++++++++++++++++
> >   2 files changed, 52 insertions(+)
> >
> > diff --git a/include/semihosting/softmmu-uaccess.h b/include/semihosting/softmmu-uaccess.h
> > index 03300376d3..4f08dfc098 100644
> > --- a/include/semihosting/softmmu-uaccess.h
> > +++ b/include/semihosting/softmmu-uaccess.h
> > @@ -53,4 +53,7 @@ void softmmu_unlock_user(CPUArchState *env, void *p,
> >                            target_ulong addr, target_ulong len);
> >   #define unlock_user(s, args, len) softmmu_unlock_user(env, s, args, len)
> >
> > +ssize_t softmmu_strlen_user(CPUArchState *env, target_ulong addr);
> > +#define target_strlen(p) softmmu_strlen_user(env, p)
> > +
> >   #endif /* SEMIHOSTING_SOFTMMU_UACCESS_H */
> > diff --git a/semihosting/uaccess.c b/semihosting/uaccess.c
> > index 0d3b32b75d..51019b79ff 100644
> > --- a/semihosting/uaccess.c
> > +++ b/semihosting/uaccess.c
> > @@ -8,6 +8,7 @@
> >    */
> >
> >   #include "qemu/osdep.h"
> > +#include "exec/exec-all.h"
> >   #include "semihosting/softmmu-uaccess.h"
> >
> >   void *softmmu_lock_user(CPUArchState *env, target_ulong addr,
> > @@ -23,6 +24,54 @@ void *softmmu_lock_user(CPUArchState *env, target_ulong addr,
> >       return p;
> >   }
> >
> > +ssize_t softmmu_strlen_user(CPUArchState *env, target_ulong addr)
> > +{
> > +    int mmu_idx = cpu_mmu_index(env, false);
> > +    size_t len = 0;
> > +
> > +    while (1) {
> > +        size_t left_in_page;
> > +        int flags;
> > +        void *h;
> > +
> > +        /* Find the number of bytes remaining in the page. */
> > +        left_in_page = -(addr | TARGET_PAGE_MASK);

This works but I'm never really a fan of expressions that mix
arithmetic and logical operations -- I always have to start writing
out bit patterns and checking what 2s-complement representation
involves in order to find out what they really do.

left_in_page = TARGET_PAGE_SIZE - (addr & ~TARGET_PAGE_MASK);

seems to me like it would be clearer.

You're correct that MIPS shouldn't be selecting semihosting in
a KVM-only compile -- there's no code to handle getting from the
guest executing the sdbbp insn to QEMU userspace to the code in
QEMU to deal with a semihosting call.

So for this patch:
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>

-- PMM
diff mbox series

Patch

diff --git a/include/semihosting/softmmu-uaccess.h b/include/semihosting/softmmu-uaccess.h
index 03300376d3..4f08dfc098 100644
--- a/include/semihosting/softmmu-uaccess.h
+++ b/include/semihosting/softmmu-uaccess.h
@@ -53,4 +53,7 @@  void softmmu_unlock_user(CPUArchState *env, void *p,
                          target_ulong addr, target_ulong len);
 #define unlock_user(s, args, len) softmmu_unlock_user(env, s, args, len)
 
+ssize_t softmmu_strlen_user(CPUArchState *env, target_ulong addr);
+#define target_strlen(p) softmmu_strlen_user(env, p)
+
 #endif /* SEMIHOSTING_SOFTMMU_UACCESS_H */
diff --git a/semihosting/uaccess.c b/semihosting/uaccess.c
index 0d3b32b75d..51019b79ff 100644
--- a/semihosting/uaccess.c
+++ b/semihosting/uaccess.c
@@ -8,6 +8,7 @@ 
  */
 
 #include "qemu/osdep.h"
+#include "exec/exec-all.h"
 #include "semihosting/softmmu-uaccess.h"
 
 void *softmmu_lock_user(CPUArchState *env, target_ulong addr,
@@ -23,6 +24,54 @@  void *softmmu_lock_user(CPUArchState *env, target_ulong addr,
     return p;
 }
 
+ssize_t softmmu_strlen_user(CPUArchState *env, target_ulong addr)
+{
+    int mmu_idx = cpu_mmu_index(env, false);
+    size_t len = 0;
+
+    while (1) {
+        size_t left_in_page;
+        int flags;
+        void *h;
+
+        /* Find the number of bytes remaining in the page. */
+        left_in_page = -(addr | TARGET_PAGE_MASK);
+
+        flags = probe_access_flags(env, addr, MMU_DATA_LOAD,
+                                   mmu_idx, true, &h, 0);
+        if (flags & TLB_INVALID_MASK) {
+            return -1;
+        }
+        if (flags & TLB_MMIO) {
+            do {
+                uint8_t c;
+                if (cpu_memory_rw_debug(env_cpu(env), addr, &c, 1, 0)) {
+                    return -1;
+                }
+                if (c == 0) {
+                    return len;
+                }
+                addr++;
+                len++;
+                if (len > INT32_MAX) {
+                    return -1;
+                }
+            } while (--left_in_page != 0);
+        } else {
+            char *p = memchr(h, 0, left_in_page);
+            if (p) {
+                len += p - (char *)h;
+                return len <= INT32_MAX ? (ssize_t)len : -1;
+            }
+            addr += left_in_page;
+            len += left_in_page;
+            if (len > INT32_MAX) {
+                return -1;
+            }
+        }
+    }
+}
+
 char *softmmu_lock_user_string(CPUArchState *env, target_ulong addr)
 {
     /* TODO: Make this something that isn't fixed size.  */