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Subject[RFC][PATCH 06/22] x86: get rid of get_user_ex() in ia32_restore_sigcontext()
Date
From: Al Viro <viro@zeniv.linux.org.uk>

Just do copyin into a local struct and be done with that - we are
on a shallow stack here.

[reworked by tglx, removing the macro horrors while we are touching that]

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---
arch/x86/ia32/ia32_signal.c | 106 ++++++++++++++++++--------------------------
1 file changed, 44 insertions(+), 62 deletions(-)

diff --git a/arch/x86/ia32/ia32_signal.c b/arch/x86/ia32/ia32_signal.c
index c72025d615f8..23e2c55d8a59 100644
--- a/arch/x86/ia32/ia32_signal.c
+++ b/arch/x86/ia32/ia32_signal.c
@@ -36,70 +36,56 @@
#include <asm/sighandling.h>
#include <asm/smap.h>

+static inline void reload_segments(struct sigcontext_32 *sc)
+{
+ unsigned int cur;
+
+ savesegment(gs, cur);
+ if ((sc->gs | 0x03) != cur)
+ load_gs_index(sc->gs | 0x03);
+ savesegment(fs, cur);
+ if ((sc->fs | 0x03) != cur)
+ loadsegment(fs, sc->fs | 0x03);
+ savesegment(ds, cur);
+ if ((sc->ds | 0x03) != cur)
+ loadsegment(ds, sc->ds | 0x03);
+ savesegment(es, cur);
+ if ((sc->es | 0x03) != cur)
+ loadsegment(es, sc->es | 0x03);
+}
+
/*
* Do a signal return; undo the signal stack.
*/
-#define loadsegment_gs(v) load_gs_index(v)
-#define loadsegment_fs(v) loadsegment(fs, v)
-#define loadsegment_ds(v) loadsegment(ds, v)
-#define loadsegment_es(v) loadsegment(es, v)
-
-#define get_user_seg(seg) ({ unsigned int v; savesegment(seg, v); v; })
-#define set_user_seg(seg, v) loadsegment_##seg(v)
-
-#define COPY(x) { \
- get_user_ex(regs->x, &sc->x); \
-}
-
-#define GET_SEG(seg) ({ \
- unsigned short tmp; \
- get_user_ex(tmp, &sc->seg); \
- tmp; \
-})
-
-#define COPY_SEG_CPL3(seg) do { \
- regs->seg = GET_SEG(seg) | 3; \
-} while (0)
-
-#define RELOAD_SEG(seg) { \
- unsigned int pre = (seg) | 3; \
- unsigned int cur = get_user_seg(seg); \
- if (pre != cur) \
- set_user_seg(seg, pre); \
-}
-
static int ia32_restore_sigcontext(struct pt_regs *regs,
- struct sigcontext_32 __user *sc)
+ struct sigcontext_32 __user *usc)
{
- unsigned int tmpflags, err = 0;
- u16 gs, fs, es, ds;
- void __user *buf;
- u32 tmp;
+ struct sigcontext_32 sc;

/* Always make any pending restarted system calls return -EINTR */
current->restart_block.fn = do_no_restart_syscall;

- get_user_try {
- gs = GET_SEG(gs);
- fs = GET_SEG(fs);
- ds = GET_SEG(ds);
- es = GET_SEG(es);
-
- COPY(di); COPY(si); COPY(bp); COPY(sp); COPY(bx);
- COPY(dx); COPY(cx); COPY(ip); COPY(ax);
- /* Don't touch extended registers */
-
- COPY_SEG_CPL3(cs);
- COPY_SEG_CPL3(ss);
-
- get_user_ex(tmpflags, &sc->flags);
- regs->flags = (regs->flags & ~FIX_EFLAGS) | (tmpflags & FIX_EFLAGS);
- /* disable syscall checks */
- regs->orig_ax = -1;
+ if (unlikely(copy_from_user(&sc, usc, sizeof(sc))))
+ return -EFAULT;

- get_user_ex(tmp, &sc->fpstate);
- buf = compat_ptr(tmp);
- } get_user_catch(err);
+ /* Get only the ia32 registers. */
+ regs->bx = sc.bx;
+ regs->cx = sc.cx;
+ regs->dx = sc.dx;
+ regs->si = sc.si;
+ regs->di = sc.di;
+ regs->bp = sc.bp;
+ regs->ax = sc.ax;
+ regs->sp = sc.sp;
+ regs->ip = sc.ip;
+
+ /* Get CS/SS and force CPL3 */
+ regs->cs = sc.cs | 0x03;
+ regs->ss = sc.ss | 0x03;
+
+ regs->flags = (regs->flags & ~FIX_EFLAGS) | (sc.flags & FIX_EFLAGS);
+ /* disable syscall checks */
+ regs->orig_ax = -1;

/*
* Reload fs and gs if they have changed in the signal
@@ -107,14 +93,8 @@ static int ia32_restore_sigcontext(struct pt_regs *regs,
* the handler, but does not clobber them at least in the
* normal case.
*/
- RELOAD_SEG(gs);
- RELOAD_SEG(fs);
- RELOAD_SEG(ds);
- RELOAD_SEG(es);
-
- err |= fpu__restore_sig(buf, 1);
-
- return err;
+ reload_segments(&sc);
+ return fpu__restore_sig(compat_ptr(sc.fpstate), 1);
}

COMPAT_SYSCALL_DEFINE0(sigreturn)
@@ -172,6 +152,8 @@ COMPAT_SYSCALL_DEFINE0(rt_sigreturn)
* Set up a signal frame.
*/

+#define get_user_seg(seg) ({ unsigned int v; savesegment(seg, v); v; })
+
static int ia32_setup_sigcontext(struct sigcontext_32 __user *sc,
void __user *fpstate,
struct pt_regs *regs, unsigned int mask)
--
2.11.0
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