From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:43663) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1dTfpj-0001W3-U6 for qemu-devel@nongnu.org; Fri, 07 Jul 2017 22:51:01 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1dTfpi-00050b-PT for qemu-devel@nongnu.org; Fri, 07 Jul 2017 22:51:00 -0400 Sender: Richard Henderson From: Richard Henderson Date: Fri, 7 Jul 2017 16:50:29 -1000 Message-Id: <20170708025030.15845-3-rth@twiddle.net> In-Reply-To: <20170708025030.15845-1-rth@twiddle.net> References: <20170708025030.15845-1-rth@twiddle.net> Subject: [Qemu-devel] [PATCH 2/3] linux-user: Tidy and enforce reserved_va initialization List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: riku.voipio@iki.fi, laurent@vivier.eu, qemu-arm@nongnu.org, aurelien@aurel32.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 --- 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 d888219..c4f79eb 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 0xfff00000ul + 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 047554e..d239069 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 13931f3..da3f637 100644 --- a/target/nios2/cpu.h +++ b/target/nios2/cpu.h @@ -227,7 +227,11 @@ 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(cpu_nios2_init(cpu_model)) diff --git a/linux-user/main.c b/linux-user/main.c index ad03c9e..e000533 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 @@ -3975,11 +3990,8 @@ 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); } -- 2.9.4