On Fri, Jan 12, 2018 at 12:37 PM, Alistair Francis <alistai...@gmail.com> wrote:
> On Thu, Oct 5, 2017 at 7:36 AM, Richard Henderson
> <richard.hender...@linaro.org> wrote:
>> From: Richard Henderson <r...@twiddle.net>
>>
>> We had a check using TARGET_VIRT_ADDR_SPACE_BITS to make sure
>> that the allocation coming in from the command-line option was
>> not too large, but that didn't include target-specific knowledge
>> about other restrictions on user-space.
>>
>> Remove several target-specific hacks in linux-user/main.c.
>>
>> For MIPS and Nios, we can replace them with proper adjustments
>> to the respective target's TARGET_VIRT_ADDR_SPACE_BITS definition.
>>
>> For ARM, we had no existing ifdef but I suspect that the current
>> default value of 0xf7000000 was chosen with this in mind. Define
>> a workable value in linux-user/arm/, and also document why the
>> special case is required.
>>
>> Signed-off-by: Richard Henderson <r...@twiddle.net>
>> Reviewed-by: Peter Maydell <peter.mayd...@linaro.org>
>> Message-Id: <20170708025030.15845-3-...@twiddle.net>
>
> Hey,
>
> I just had the arduous task of bisecting QEMU 2.10 and 2.11 to figure
> out that somehow this patch causes the Yocto webkitgtk build for x86
> to hang.
>
> Any ideas?
>
> My host is 64-bit x86 and I'm building for 32-bit x86. I'm going to
> test now to see if I see the same hang building for 64-bit. I am not
> sure yet where QEMU usermode is used, but apparently it is.
The hang only occurs if building for x86-32bit on a 64-bit machine.
Alistair
>
> Thanks,
> Alistair
>
>> ---
>> linux-user/arm/target_cpu.h | 4 ++++
>> target/mips/mips-defs.h | 6 +++++-
>> target/nios2/cpu.h | 6 +++++-
>> linux-user/main.c | 38 +++++++++++++++++++++++++-------------
>> 4 files changed, 39 insertions(+), 15 deletions(-)
>>
>> diff --git a/linux-user/arm/target_cpu.h b/linux-user/arm/target_cpu.h
>> index d888219150..c3eb4b243d 100644
>> --- a/linux-user/arm/target_cpu.h
>> +++ b/linux-user/arm/target_cpu.h
>> @@ -19,6 +19,10 @@
>> #ifndef ARM_TARGET_CPU_H
>> #define ARM_TARGET_CPU_H
>>
>> +/* We need to be able to map the commpage.
>> + See validate_guest_space in linux-user/elfload.c. */
>> +#define MAX_RESERVED_VA 0xffff0000ul
>> +
>> static inline void cpu_clone_regs(CPUARMState *env, target_ulong newsp)
>> {
>> if (newsp) {
>> diff --git a/target/mips/mips-defs.h b/target/mips/mips-defs.h
>> index 047554ee45..d239069975 100644
>> --- a/target/mips/mips-defs.h
>> +++ b/target/mips/mips-defs.h
>> @@ -15,7 +15,11 @@
>> #else
>> #define TARGET_LONG_BITS 32
>> #define TARGET_PHYS_ADDR_SPACE_BITS 40
>> -#define TARGET_VIRT_ADDR_SPACE_BITS 32
>> +# ifdef CONFIG_USER_ONLY
>> +# define TARGET_VIRT_ADDR_SPACE_BITS 31
>> +# else
>> +# define TARGET_VIRT_ADDR_SPACE_BITS 32
>> +#endif
>> #endif
>>
>> /* Masks used to mark instructions to indicate which ISA level they
>> diff --git a/target/nios2/cpu.h b/target/nios2/cpu.h
>> index 50d803a217..9119eee587 100644
>> --- a/target/nios2/cpu.h
>> +++ b/target/nios2/cpu.h
>> @@ -226,7 +226,11 @@ qemu_irq *nios2_cpu_pic_init(Nios2CPU *cpu);
>> void nios2_check_interrupts(CPUNios2State *env);
>>
>> #define TARGET_PHYS_ADDR_SPACE_BITS 32
>> -#define TARGET_VIRT_ADDR_SPACE_BITS 32
>> +#ifdef CONFIG_USER_ONLY
>> +# define TARGET_VIRT_ADDR_SPACE_BITS 31
>> +#else
>> +# define TARGET_VIRT_ADDR_SPACE_BITS 32
>> +#endif
>>
>> #define cpu_init(cpu_model) cpu_generic_init(TYPE_NIOS2_CPU, cpu_model)
>>
>> diff --git a/linux-user/main.c b/linux-user/main.c
>> index 829f974662..fd54d344bb 100644
>> --- a/linux-user/main.c
>> +++ b/linux-user/main.c
>> @@ -60,23 +60,38 @@ do {
>> \
>> } \
>> } while (0)
>>
>> -#if (TARGET_LONG_BITS == 32) && (HOST_LONG_BITS == 64)
>> /*
>> * When running 32-on-64 we should make sure we can fit all of the possible
>> * guest address space into a contiguous chunk of virtual host memory.
>> *
>> * This way we will never overlap with our own libraries or binaries or
>> stack
>> * or anything else that QEMU maps.
>> + *
>> + * Many cpus reserve the high bit (or more than one for some 64-bit cpus)
>> + * of the address for the kernel. Some cpus rely on this and user space
>> + * uses the high bit(s) for pointer tagging and the like. For them, we
>> + * must preserve the expected address space.
>> */
>> -# if defined(TARGET_MIPS) || defined(TARGET_NIOS2)
>> -/*
>> - * MIPS only supports 31 bits of virtual address space for user space.
>> - * Nios2 also only supports 31 bits.
>> - */
>> -unsigned long reserved_va = 0x77000000;
>> +#ifndef MAX_RESERVED_VA
>> +# if HOST_LONG_BITS > TARGET_VIRT_ADDR_SPACE_BITS
>> +# if TARGET_VIRT_ADDR_SPACE_BITS == 32 && \
>> + (TARGET_LONG_BITS == 32 || defined(TARGET_ABI32))
>> +/* There are a number of places where we assign reserved_va to a variable
>> + of type abi_ulong and expect it to fit. Avoid the last page. */
>> +# define MAX_RESERVED_VA (0xfffffffful & TARGET_PAGE_MASK)
>> +# else
>> +# define MAX_RESERVED_VA (1ul << TARGET_VIRT_ADDR_SPACE_BITS)
>> +# endif
>> # else
>> -unsigned long reserved_va = 0xf7000000;
>> +# define MAX_RESERVED_VA 0
>> # endif
>> +#endif
>> +
>> +/* That said, reserving *too* much vm space via mmap can run into problems
>> + with rlimits, oom due to page table creation, etc. We will still try it,
>> + if directed by the command-line option, but not by default. */
>> +#if HOST_LONG_BITS == 64 && TARGET_VIRT_ADDR_SPACE_BITS <= 32
>> +unsigned long reserved_va = MAX_RESERVED_VA;
>> #else
>> unsigned long reserved_va;
>> #endif
>> @@ -3978,11 +3993,8 @@ static void handle_arg_reserved_va(const char *arg)
>> unsigned long unshifted = reserved_va;
>> p++;
>> reserved_va <<= shift;
>> - if (((reserved_va >> shift) != unshifted)
>> -#if HOST_LONG_BITS > TARGET_VIRT_ADDR_SPACE_BITS
>> - || (reserved_va > (1ul << TARGET_VIRT_ADDR_SPACE_BITS))
>> -#endif
>> - ) {
>> + if (reserved_va >> shift != unshifted
>> + || (MAX_RESERVED_VA && reserved_va > MAX_RESERVED_VA)) {
>> fprintf(stderr, "Reserved virtual address too big\n");
>> exit(EXIT_FAILURE);
>> }
>> --
>> 2.13.6
>>
>>
