[Qemu-devel] Re: [PATCH] linux-user, x86: use target_mmap() to allocate idt, gdt and ldt tables

[Jan Kiszka <jan.kiszka@web.de>]

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Kirill A. Shutemov wrote:
> env->*dt.base should fits target address space, so we should use
> target_mmap to allocate it.

I just noticed that this bug is still unfixed upstream, was about to
repost my corresponding patch [1], but then found this even nicer
approach. Could someone please finally merge a fix?

Kirill, do you also have a patch for the problem [2] addresses in your
queue?

Last time I posted my series, Anthony remarked that the role of the
linux-user maintainer is vacant. My impression is that this is still the
case while at the same time Kirill is doing quite a good job now getting
this corner of qemu in shape again...... :->

Jan

[1] http://permalink.gmane.org/gmane.comp.emulators.qemu/28386
[2] http://permalink.gmane.org/gmane.comp.emulators.qemu/28385

> 
> Signed-off-by: Kirill A. Shutemov <kirill@shutemov.name>
> ---
>  linux-user/main.c    |   23 +++++++++++++++--------
>  linux-user/syscall.c |   10 ++++++----
>  2 files changed, 21 insertions(+), 12 deletions(-)
> 
> diff --git a/linux-user/main.c b/linux-user/main.c
> index 25b2867..61d497e 100644
> --- a/linux-user/main.c
> +++ b/linux-user/main.c
> @@ -23,6 +23,7 @@
>  #include <string.h>
>  #include <errno.h>
>  #include <unistd.h>
> +#include <sys/mman.h>
>  
>  #include "qemu.h"
>  #include "qemu-common.h"
> @@ -283,9 +284,8 @@ static void write_dt(void *ptr, unsigned long addr, unsigned long limit,
>      p[1] = tswap32(e2);
>  }
>  
> +uint64_t *idt_table;

This should become static...

>  #ifdef TARGET_X86_64
> -uint64_t idt_table[512];

...as this is now static as well.

> -
>  static void set_gate64(void *ptr, unsigned int type, unsigned int dpl,
>                         uint64_t addr, unsigned int sel)
>  {
> @@ -304,8 +304,6 @@ static void set_idt(int n, unsigned int dpl)
>      set_gate64(idt_table + n * 2, 0, dpl, 0, 0);
>  }
>  #else
> -uint64_t idt_table[256];
> -
>  static void set_gate(void *ptr, unsigned int type, unsigned int dpl,
>                       uint32_t addr, unsigned int sel)
>  {
> @@ -2500,8 +2498,15 @@ int main(int argc, char **argv, char **envp)
>  #endif
>  
>      /* linux interrupt setup */
> -    env->idt.base = h2g(idt_table);
> -    env->idt.limit = sizeof(idt_table) - 1;
> +#ifndef TARGET_ABI32
> +    env->idt.limit = 511;
> +#else
> +    env->idt.limit = 255;
> +#endif
> +    env->idt.base = target_mmap(0, sizeof(uint64_t) * (env->idt.limit + 1),
> +                                PROT_READ|PROT_WRITE,
> +                                MAP_ANONYMOUS|MAP_PRIVATE, -1, 0);
> +    idt_table = g2h(env->idt.base);
>      set_idt(0, 0);
>      set_idt(1, 0);
>      set_idt(2, 0);
> @@ -2527,9 +2532,11 @@ int main(int argc, char **argv, char **envp)
>      /* linux segment setup */
>      {
>          uint64_t *gdt_table;
> -        gdt_table = qemu_mallocz(sizeof(uint64_t) * TARGET_GDT_ENTRIES);
> -        env->gdt.base = h2g((unsigned long)gdt_table);
> +        env->gdt.base = target_mmap(0, sizeof(uint64_t) * TARGET_GDT_ENTRIES,
> +                                    PROT_READ|PROT_WRITE,
> +                                    MAP_ANONYMOUS|MAP_PRIVATE, -1, 0);
>          env->gdt.limit = sizeof(uint64_t) * TARGET_GDT_ENTRIES - 1;
> +        gdt_table = g2h(env->gdt.base);
>  #ifdef TARGET_ABI32
>          write_dt(&gdt_table[__USER_CS >> 3], 0, 0xfffff,
>                   DESC_G_MASK | DESC_B_MASK | DESC_P_MASK | DESC_S_MASK |
> diff --git a/linux-user/syscall.c b/linux-user/syscall.c
> index db3538b..27bd7e1 100644
> --- a/linux-user/syscall.c
> +++ b/linux-user/syscall.c
> @@ -2823,12 +2823,14 @@ static abi_long write_ldt(CPUX86State *env,
>      }
>      /* allocate the LDT */
>      if (!ldt_table) {
> -        ldt_table = malloc(TARGET_LDT_ENTRIES * TARGET_LDT_ENTRY_SIZE);
> -        if (!ldt_table)
> +        env->ldt.base = target_mmap(0, TARGET_LDT_ENTRIES * TARGET_LDT_ENTRY_SIZE,
> +                                    PROT_READ|PROT_WRITE,
> +                                    MAP_ANONYMOUS|MAP_PRIVATE, -1, 0);
> +        if (env->ldt.base == -1)
>              return -TARGET_ENOMEM;
> -        memset(ldt_table, 0, TARGET_LDT_ENTRIES * TARGET_LDT_ENTRY_SIZE);
> -        env->ldt.base = h2g((unsigned long)ldt_table);
> +        memset(g2h(env->ldt.base), 0, TARGET_LDT_ENTRIES * TARGET_LDT_ENTRY_SIZE);
>          env->ldt.limit = 0xffff;
> +        ldt_table = g2h(env->ldt.base);
>      }
>  
>      /* NOTE: same code as Linux kernel */



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