From 12700c17fc286149324f92d6d380bc48e43f253d Mon Sep 17 00:00:00 2001 From: Arnd Bergmann Date: Tue, 15 Feb 2022 17:55:04 +0100 Subject: uaccess: generalize access_ok() There are many different ways that access_ok() is defined across architectures, but in the end, they all just compare against the user_addr_max() value or they accept anything. Provide one definition that works for most architectures, checking against TASK_SIZE_MAX for user processes or skipping the check inside of uaccess_kernel() sections. For architectures without CONFIG_SET_FS(), this should be the fastest check, as it comes down to a single comparison of a pointer against a compile-time constant, while the architecture specific versions tend to do something more complex for historic reasons or get something wrong. Type checking for __user annotations is handled inconsistently across architectures, but this is easily simplified as well by using an inline function that takes a 'const void __user *' argument. A handful of callers need an extra __user annotation for this. Some architectures had trick to use 33-bit or 65-bit arithmetic on the addresses to calculate the overflow, however this simpler version uses fewer registers, which means it can produce better object code in the end despite needing a second (statically predicted) branch. Reviewed-by: Christoph Hellwig Acked-by: Mark Rutland [arm64, asm-generic] Acked-by: Geert Uytterhoeven Acked-by: Stafford Horne Acked-by: Dinh Nguyen Signed-off-by: Arnd Bergmann --- arch/arm/include/asm/uaccess.h | 20 +------------------- 1 file changed, 1 insertion(+), 19 deletions(-) (limited to 'arch/arm/include') diff --git a/arch/arm/include/asm/uaccess.h b/arch/arm/include/asm/uaccess.h index d20d78c34b94..2fcbec9c306c 100644 --- a/arch/arm/include/asm/uaccess.h +++ b/arch/arm/include/asm/uaccess.h @@ -55,21 +55,6 @@ extern int __put_user_bad(void); #ifdef CONFIG_MMU -/* - * We use 33-bit arithmetic here. Success returns zero, failure returns - * addr_limit. We take advantage that addr_limit will be zero for KERNEL_DS, - * so this will always return success in that case. - */ -#define __range_ok(addr, size) ({ \ - unsigned long flag, roksum; \ - __chk_user_ptr(addr); \ - __asm__(".syntax unified\n" \ - "adds %1, %2, %3; sbcscc %1, %1, %0; movcc %0, #0" \ - : "=&r" (flag), "=&r" (roksum) \ - : "r" (addr), "Ir" (size), "0" (TASK_SIZE) \ - : "cc"); \ - flag; }) - /* * This is a type: either unsigned long, if the argument fits into * that type, or otherwise unsigned long long. @@ -241,15 +226,12 @@ extern int __put_user_8(void *, unsigned long long); #else /* CONFIG_MMU */ -#define __addr_ok(addr) ((void)(addr), 1) -#define __range_ok(addr, size) ((void)(addr), 0) - #define get_user(x, p) __get_user(x, p) #define __put_user_check __put_user_nocheck #endif /* CONFIG_MMU */ -#define access_ok(addr, size) (__range_ok(addr, size) == 0) +#include #ifdef CONFIG_CPU_SPECTRE /* -- cgit v1.2.3