From 425fc47adb5bb69f76285be77a09a3341a30799e Mon Sep 17 00:00:00 2001 From: Will Deacon Date: Mon, 14 Feb 2011 14:31:09 +0100 Subject: ARM: 6668/1: ptrace: remove single-step emulation code PTRACE_SINGLESTEP is a ptrace request designed to offer single-stepping support to userspace when the underlying architecture has hardware support for this operation. On ARM, we set arch_has_single_step() to 1 and attempt to emulate hardware single-stepping by disassembling the current instruction to determine the next pc and placing a software breakpoint on that location. Unfortunately this has the following problems: 1.) Only a subset of ARMv7 instructions are supported 2.) Thumb-2 is unsupported 3.) The code is not SMP safe We could try to fix this code, but it turns out that because of the above issues it is rarely used in practice. GDB, for example, uses PTRACE_POKETEXT and PTRACE_PEEKTEXT to manage breakpoints itself and does not require any kernel assistance. This patch removes the single-step emulation code from ptrace meaning that the PTRACE_SINGLESTEP request will return -EIO on ARM. Portable code must check the return value from a ptrace call and handle the failure gracefully. Acked-by: Nicolas Pitre Signed-off-by: Will Deacon Signed-off-by: Russell King --- arch/arm/include/asm/ptrace.h | 2 -- 1 file changed, 2 deletions(-) (limited to 'arch/arm/include/asm/ptrace.h') diff --git a/arch/arm/include/asm/ptrace.h b/arch/arm/include/asm/ptrace.h index 783d50f3261..a8ff22b2a39 100644 --- a/arch/arm/include/asm/ptrace.h +++ b/arch/arm/include/asm/ptrace.h @@ -130,8 +130,6 @@ struct pt_regs { #ifdef __KERNEL__ -#define arch_has_single_step() (1) - #define user_mode(regs) \ (((regs)->ARM_cpsr & 0xf) == 0) -- cgit v1.2.3-70-g09d2