The patch titled
x86-64: ptrace ia32 BP fix
has been added to the -mm tree. Its filename is
x86-64-ptrace-ia32-bp-fix.patch
Patches currently in -mm which might be from [EMAIL PROTECTED] are
x86-64-ptrace-ia32-bp-fix.patch
kgdb-ga.patch
From: Roland McGrath <[EMAIL PROTECTED]>
When the 32-bit vDSO is used to make a system call, the %ebp register for
the 6th syscall arg has to be loaded from the user stack (where it's pushed
by the vDSO user code). The native i386 kernel always does this before
stopping for syscall tracing, so %ebp can be seen and modified via ptrace
to access the 6th syscall argument. The x86-64 kernel fails to do this,
presenting the stack address to ptrace instead. This makes the %rbp value
seen by 64-bit ptrace of a 32-bit process, and the %ebp value seen by a
32-bit caller of ptrace, both differ from the native i386 behavior.
This patch fixes the problem by putting the word loaded from the user stack
into %rbp before calling syscall_trace_enter, and reloading the 6th syscall
argument from there afterwards (so ptrace can change it). This makes the
behavior match that of i386 kernels.
Signed-off-by: Roland McGrath <[EMAIL PROTECTED]>
Cc: Andi Kleen <[EMAIL PROTECTED]>
Signed-off-by: Andrew Morton <[EMAIL PROTECTED]>
---
arch/x86_64/ia32/ia32entry.S | 17 ++++-------------
1 files changed, 4 insertions(+), 13 deletions(-)
diff -puN arch/x86_64/ia32/ia32entry.S~x86-64-ptrace-ia32-bp-fix
arch/x86_64/ia32/ia32entry.S
--- 25/arch/x86_64/ia32/ia32entry.S~x86-64-ptrace-ia32-bp-fix Wed Jul 6
13:23:35 2005
+++ 25-akpm/arch/x86_64/ia32/ia32entry.S Wed Jul 6 13:23:35 2005
@@ -102,6 +102,7 @@ sysenter_do_call:
.byte 0xf, 0x35
sysenter_tracesys:
+ movl %r9d,%ebp
SAVE_REST
CLEAR_RREGS
movq $-ENOSYS,RAX(%rsp) /* really needed? */
@@ -109,13 +110,7 @@ sysenter_tracesys:
call syscall_trace_enter
LOAD_ARGS ARGOFFSET /* reload args from stack in case ptrace changed
it */
RESTORE_REST
- movl %ebp, %ebp
- /* no need to do an access_ok check here because rbp has been
- 32bit zero extended */
-1: movl (%rbp),%r9d
- .section __ex_table,"a"
- .quad 1b,ia32_badarg
- .previous
+ movl %ebp,%r9d
jmp sysenter_do_call
CFI_ENDPROC
@@ -183,6 +178,7 @@ cstar_do_call:
sysretl
cstar_tracesys:
+ movl %r9d,%ebp
SAVE_REST
CLEAR_RREGS
movq $-ENOSYS,RAX(%rsp) /* really needed? */
@@ -191,12 +187,7 @@ cstar_tracesys:
LOAD_ARGS ARGOFFSET /* reload args from stack in case ptrace changed
it */
RESTORE_REST
movl RSP-ARGOFFSET(%rsp), %r8d
- /* no need to do an access_ok check here because r8 has been
- 32bit zero extended */
-1: movl (%r8),%r9d
- .section __ex_table,"a"
- .quad 1b,ia32_badarg
- .previous
+ movl %ebp,%r9d
jmp cstar_do_call
ia32_badarg:
_
-
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