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authorSiddhesh Poyarekar <siddhesh.poyarekar@gmail.com>2012-02-26 16:17:55 (GMT)
committerH. Peter Anvin <hpa@zytor.com>2012-02-26 20:59:04 (GMT)
commit42dfc43ee5999ac64284476ea0ac6c937587cf2b (patch)
tree4527353aa4f9cfedc09142f2a9da418c90b618e5 /arch/x86/kernel/process_64.c
parentb01543dfe67bb1d191998e90d20534dc354de059 (diff)
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@gmail.com> Link: http://lkml.kernel.org/r/1330273075-2949-1-git-send-email-siddhesh.poyarekar@gmail.com Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Diffstat (limited to 'arch/x86/kernel/process_64.c')
-rw-r--r--arch/x86/kernel/process_64.c1
1 files changed, 1 insertions, 0 deletions
diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c
index 1fd94bc..eb54dd0 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);

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