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Date: Sun, 26 Feb 2012 21:47:55 +0530 From: Siddhesh Poyarekar <siddhesh.poyarekar@...il.com> To: x86@...nel.org Cc: KOSAKI Motohiro <kosaki.motohiro@...il.com>, linux-kernel@...r.kernel.org, Jamie Lokier <jamie@...reable.org>, Mike Frysinger <vapier@...too.org>, Andrew Morton <akpm@...ux-foundation.org>, Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, "H. Peter Anvin" <hpa@...or.com>, Siddhesh Poyarekar <siddhesh.poyarekar@...il.com> Subject: [PATCH] x86_64: Record stack pointer before task execution begins task->thread.usersp is unusable immediately after a binary is exec()'d until it undergoes a context switch cycle. The start_thread() function called during execve() saves the stack pointer into pt_regs and into old_rsp, but fails to record it into task->thread.usersp. Because of this, KSTK_ESP(task) returns an incorrect value for a 64-bit program until the task is switched out and back in since switch_to swaps %rsp values in and out into task->thread.usersp. Signed-off-by: Siddhesh Poyarekar <siddhesh.poyarekar@...il.com> --- arch/x86/kernel/process_64.c | 1 + 1 files changed, 1 insertions(+), 0 deletions(-) diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c index 9b9fe4a..702a3b9 100644 --- a/arch/x86/kernel/process_64.c +++ b/arch/x86/kernel/process_64.c @@ -341,6 +341,7 @@ start_thread_common(struct pt_regs *regs, unsigned long new_ip, loadsegment(es, _ds); loadsegment(ds, _ds); load_gs_index(0); + current->thread.usersp = new_sp; regs->ip = new_ip; regs->sp = new_sp; percpu_write(old_rsp, new_sp); -- 1.7.7.4 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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