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Subject[RFC][PATCH 07/22] x86: get rid of get_user_ex() in 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/kernel/signal.c | 86 ++++++++++++++++++++----------------------------
1 file changed, 36 insertions(+), 50 deletions(-)

diff --git a/arch/x86/kernel/signal.c b/arch/x86/kernel/signal.c
index 53ac66b3fd9b..83563e98f0be 100644
--- a/arch/x86/kernel/signal.c
+++ b/arch/x86/kernel/signal.c
@@ -47,24 +47,6 @@
#include <asm/sigframe.h>
#include <asm/signal.h>

-#define COPY(x) do { \
- get_user_ex(regs->x, &sc->x); \
-} while (0)
-
-#define GET_SEG(seg) ({ \
- unsigned short tmp; \
- get_user_ex(tmp, &sc->seg); \
- tmp; \
-})
-
-#define COPY_SEG(seg) do { \
- regs->seg = GET_SEG(seg); \
-} while (0)
-
-#define COPY_SEG_CPL3(seg) do { \
- regs->seg = GET_SEG(seg) | 3; \
-} while (0)
-
#ifdef CONFIG_X86_64
/*
* If regs->ss will cause an IRET fault, change it. Otherwise leave it
@@ -92,53 +74,58 @@ static void force_valid_ss(struct pt_regs *regs)
ar != (AR_DPL3 | AR_S | AR_P | AR_TYPE_RWDATA_EXPDOWN))
regs->ss = __USER_DS;
}
+# define CONTEXT_COPY_SIZE offsetof(struct sigcontext, reserved1)
+#else
+# define CONTEXT_COPY_SIZE sizeof(struct sigcontext)
#endif

static int restore_sigcontext(struct pt_regs *regs,
- struct sigcontext __user *sc,
+ struct sigcontext __user *usc,
unsigned long uc_flags)
{
- unsigned long buf_val;
- void __user *buf;
- unsigned int tmpflags;
- unsigned int err = 0;
+ struct sigcontext sc;

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

- get_user_try {
+ if (copy_from_user(&sc, usc, CONTEXT_COPY_SIZE))
+ return -EFAULT;

#ifdef CONFIG_X86_32
- set_user_gs(regs, GET_SEG(gs));
- COPY_SEG(fs);
- COPY_SEG(es);
- COPY_SEG(ds);
+ set_user_gs(regs, sc.gs);
+ regs->fs = sc.fs;
+ regs->es = sc.es;
+ regs->ds = sc.ds;
#endif /* CONFIG_X86_32 */

- COPY(di); COPY(si); COPY(bp); COPY(sp); COPY(bx);
- COPY(dx); COPY(cx); COPY(ip); COPY(ax);
+ 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;

#ifdef CONFIG_X86_64
- COPY(r8);
- COPY(r9);
- COPY(r10);
- COPY(r11);
- COPY(r12);
- COPY(r13);
- COPY(r14);
- COPY(r15);
+ regs->r8 = sc.r8;
+ regs->r9 = sc.r9;
+ regs->r10 = sc.r10;
+ regs->r11 = sc.r11;
+ regs->r12 = sc.r12;
+ regs->r13 = sc.r13;
+ regs->r14 = sc.r14;
+ regs->r15 = sc.r15;
#endif /* CONFIG_X86_64 */

- COPY_SEG_CPL3(cs);
- COPY_SEG_CPL3(ss);
-
- get_user_ex(tmpflags, &sc->flags);
- regs->flags = (regs->flags & ~FIX_EFLAGS) | (tmpflags & FIX_EFLAGS);
- regs->orig_ax = -1; /* disable syscall checks */
+ /* Get CS/SS and force CPL3 */
+ regs->cs = sc.cs | 0x03;
+ regs->ss = sc.ss | 0x03;

- get_user_ex(buf_val, &sc->fpstate);
- buf = (void __user *)buf_val;
- } get_user_catch(err);
+ regs->flags = (regs->flags & ~FIX_EFLAGS) | (sc.flags & FIX_EFLAGS);
+ /* disable syscall checks */
+ regs->orig_ax = -1;

#ifdef CONFIG_X86_64
/*
@@ -149,9 +136,8 @@ static int restore_sigcontext(struct pt_regs *regs,
force_valid_ss(regs);
#endif

- err |= fpu__restore_sig(buf, IS_ENABLED(CONFIG_X86_32));
-
- return err;
+ return fpu__restore_sig((void __user *)sc.fpstate,
+ IS_ENABLED(CONFIG_X86_32));
}

int setup_sigcontext(struct sigcontext __user *sc, void __user *fpstate,
--
2.11.0
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