Update the trampoline code to match the kernel: this uses
sp-relative accesses rather than pc-relative.
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
linux-user/arm/target_signal.h | 2 +
linux-user/arm/signal.c | 177 ++++++++++++++++++++++++---------
2 files changed, 130 insertions(+), 49 deletions(-)
diff --git a/linux-user/arm/target_signal.h b/linux-user/arm/target_signal.h
index 0998dd6dfa..1e7fb0cecb 100644
--- a/linux-user/arm/target_signal.h
+++ b/linux-user/arm/target_signal.h
@@ -22,4 +22,6 @@ typedef struct target_sigaltstack {
#include "../generic/signal.h"
#define TARGET_ARCH_HAS_SETUP_FRAME
+#define TARGET_ARCH_HAS_SIGTRAMP_PAGE 1
+
#endif /* ARM_TARGET_SIGNAL_H */
diff --git a/linux-user/arm/signal.c b/linux-user/arm/signal.c
index ed7d1d80bb..ccfae43028 100644
--- a/linux-user/arm/signal.c
+++ b/linux-user/arm/signal.c
@@ -103,39 +103,52 @@ struct rt_sigframe
abi_ulong retcode[4];
};
-/*
- * For ARM syscalls, we encode the syscall number into the instruction.
- */
-#define SWI_SYS_SIGRETURN (0xef000000|(TARGET_NR_sigreturn + ARM_SYSCALL_BASE))
-#define SWI_SYS_RT_SIGRETURN (0xef000000|(TARGET_NR_rt_sigreturn + ARM_SYSCALL_BASE))
+static abi_ptr sigreturn_fdpic_tramp;
/*
- * For Thumb syscalls, we pass the syscall number via r7. We therefore
- * need two 16-bit instructions.
+ * EABI syscalls pass the number via r7.
+ * Note that the kernel still adds the OABI syscall number to the trap,
+ * presumably for backward ABI compatibility with unwinders.
*/
-#define SWI_THUMB_SIGRETURN (0xdf00 << 16 | 0x2700 | (TARGET_NR_sigreturn))
-#define SWI_THUMB_RT_SIGRETURN (0xdf00 << 16 | 0x2700 | (TARGET_NR_rt_sigreturn))
+#define ARM_MOV_R7_IMM(X) (0xe3a07000 | (X))
+#define ARM_SWI_SYS(X) (0xef000000 | (X) | ARM_SYSCALL_BASE)
-static const abi_ulong retcodes[4] = {
- SWI_SYS_SIGRETURN, SWI_THUMB_SIGRETURN,
- SWI_SYS_RT_SIGRETURN, SWI_THUMB_RT_SIGRETURN
-};
+#define THUMB_MOVS_R7_IMM(X) (0x2700 | (X))
+#define THUMB_SWI_SYS 0xdf00
+
+static void write_arm_sigreturn(uint32_t *rc, int syscall)
+{
+ __put_user(ARM_MOV_R7_IMM(syscall), rc);
+ __put_user(ARM_SWI_SYS(syscall), rc + 1);
+}
+
+static void write_thumb_sigreturn(uint32_t *rc, int syscall)
+{
+ __put_user(THUMB_SWI_SYS << 16 | THUMB_MOVS_R7_IMM(syscall), rc);
+}
/*
- * Stub needed to make sure the FD register (r9) contains the right
- * value.
+ * Stub needed to make sure the FD register (r9) contains the right value.
+ * Use the same instruction sequence as the kernel.
*/
-static const unsigned long sigreturn_fdpic_codes[3] = {
- 0xe59fc004, /* ldr r12, [pc, #4] to read function descriptor */
- 0xe59c9004, /* ldr r9, [r12, #4] to setup GOT */
- 0xe59cf000 /* ldr pc, [r12] to jump into restorer */
-};
+static void write_arm_fdpic_sigreturn(uint32_t *rc, int ofs)
+{
+ assert(ofs <= 0xfff);
+ __put_user(0xe59d3000 | ofs, rc + 0); /* ldr r3, [sp, #ofs] */
+ __put_user(0xe8930908, rc + 1); /* ldm r3, { r3, r9 } */
+ __put_user(0xe12fff13, rc + 2); /* bx r3 */
+}
-static const unsigned long sigreturn_fdpic_thumb_codes[3] = {
- 0xc008f8df, /* ldr r12, [pc, #8] to read function descriptor */
- 0x9004f8dc, /* ldr r9, [r12, #4] to setup GOT */
- 0xf000f8dc /* ldr pc, [r12] to jump into restorer */
-};
+static void write_thumb_fdpic_sigreturn(void *vrc, int ofs)
+{
+ uint16_t *rc = vrc;
+
+ assert((ofs & ~0x3fc) == 0);
+ __put_user(0x9b00 | (ofs >> 2), rc + 0); /* ldr r3, [sp, #ofs] */
+ __put_user(0xcb0c, rc + 1); /* ldm r3, { r2, r3 } */
+ __put_user(0x4699, rc + 2); /* mov r9, r3 */
+ __put_user(0x4710, rc + 3); /* bx r2 */
+}
static inline int valid_user_regs(CPUARMState *regs)
{
@@ -184,13 +197,12 @@ get_sigframe(struct target_sigaction *ka, CPUARMState *regs, int framesize)
static int
setup_return(CPUARMState *env, struct target_sigaction *ka,
- abi_ulong *rc, abi_ulong frame_addr, int usig, abi_ulong rc_addr)
+ abi_ulong *rc, abi_ulong frame_addr, int usig, abi_ulong rc_ofs)
{
abi_ulong handler = 0;
abi_ulong handler_fdpic_GOT = 0;
abi_ulong retcode;
-
- int thumb;
+ int thumb, retcode_idx;
int is_fdpic = info_is_fdpic(((TaskState *)thread_cpu->opaque)->info);
if (is_fdpic) {
@@ -208,6 +220,7 @@ setup_return(CPUARMState *env, struct target_sigaction *ka,
}
thumb = handler & 1;
+ retcode_idx = thumb + (ka->sa_flags & TARGET_SA_SIGINFO ? 2 : 0);
uint32_t cpsr = cpsr_read(env);
@@ -225,37 +238,39 @@ setup_return(CPUARMState *env, struct target_sigaction *ka,
if (ka->sa_flags & TARGET_SA_RESTORER) {
if (is_fdpic) {
- /* For FDPIC we ensure that the restorer is called with a
- * correct r9 value. For that we need to write code on
- * the stack that sets r9 and jumps back to restorer
- * value.
+ /*
+ * For FDPIC we ensure that the restorer is called with a
+ * correct r9 value. For that we need a special trampoline
+ * the reads the function descriptor from the frame,
+ * sets r9 and jumps back to restorer value.
+ *
+ * This on-stack code is unused but retained for ABI compliance.
*/
if (thumb) {
- __put_user(sigreturn_fdpic_thumb_codes[0], rc);
- __put_user(sigreturn_fdpic_thumb_codes[1], rc + 1);
- __put_user(sigreturn_fdpic_thumb_codes[2], rc + 2);
- __put_user((abi_ulong)ka->sa_restorer, rc + 3);
+ write_thumb_fdpic_sigreturn(rc, rc_ofs + 12);
} else {
- __put_user(sigreturn_fdpic_codes[0], rc);
- __put_user(sigreturn_fdpic_codes[1], rc + 1);
- __put_user(sigreturn_fdpic_codes[2], rc + 2);
- __put_user((abi_ulong)ka->sa_restorer, rc + 3);
+ write_arm_fdpic_sigreturn(rc, rc_ofs + 12);
}
+ __put_user((abi_ulong)ka->sa_restorer, &rc[3]);
- retcode = rc_addr + thumb;
+ /* Each trampoline variant consumes a 12-byte slot. */
+ retcode = sigreturn_fdpic_tramp + retcode_idx * 12 + thumb;
} else {
retcode = ka->sa_restorer;
}
} else {
- unsigned int idx = thumb;
+ int syscall = (ka->sa_flags & TARGET_SA_SIGINFO
+ ? TARGET_NR_rt_sigreturn : TARGET_NR_sigreturn);
- if (ka->sa_flags & TARGET_SA_SIGINFO) {
- idx += 2;
+ /* This on-stack code is unused but retained for ABI compliance. */
+ if (thumb) {
+ write_thumb_sigreturn(rc, syscall);
+ } else {
+ write_arm_sigreturn(rc, syscall);
}
- __put_user(retcodes[idx], rc);
-
- retcode = rc_addr + thumb;
+ /* Each trampoline variant consumes 8-byte slot. */
+ retcode = default_sigreturn + retcode_idx * 8 + thumb;
}
env->regs[0] = usig;
@@ -352,7 +367,7 @@ void setup_frame(int usig, struct target_sigaction *ka,
setup_sigframe(&frame->uc, set, regs);
if (setup_return(regs, ka, frame->retcode, frame_addr, usig,
- frame_addr + offsetof(struct sigframe, retcode))) {
+ offsetof(struct sigframe, retcode))) {
goto sigsegv;
}
@@ -383,7 +398,7 @@ void setup_rt_frame(int usig, struct target_sigaction *ka,
setup_sigframe(&frame->uc, set, env);
if (setup_return(env, ka, frame->retcode, frame_addr, usig,
- frame_addr + offsetof(struct rt_sigframe, retcode))) {
+ offsetof(struct rt_sigframe, retcode))) {
goto sigsegv;
}
@@ -591,3 +606,67 @@ badframe:
force_sig(TARGET_SIGSEGV);
return -TARGET_QEMU_ESIGRETURN;
}
+
+void setup_sigtramp(abi_ulong sigtramp_page)
+{
+ enum {
+ SIGFRAME_FDPIC_OFS = offsetof(struct sigframe, retcode[3]),
+ RT_SIGFRAME_FDPIC_OFS = offsetof(struct rt_sigframe, retcode[3]),
+ };
+
+ uint32_t total_size = 4 * 8 + 4 * 12;
+ uint32_t *tramp = lock_user(VERIFY_WRITE, sigtramp_page, total_size, 0);
+ uint32_t i = 0;
+
+ assert(tramp != NULL);
+
+ default_sigreturn = sigtramp_page;
+ write_arm_sigreturn(&tramp[i], TARGET_NR_sigreturn);
+ i += 2;
+ write_thumb_sigreturn(&tramp[i], TARGET_NR_sigreturn);
+ i += 2;
+ write_arm_sigreturn(&tramp[i], TARGET_NR_rt_sigreturn);
+ i += 2;
+ write_thumb_sigreturn(&tramp[i], TARGET_NR_rt_sigreturn);
+ i += 2;
+
+ /*
+ * FDPIC require trampolines to call sa_restorer, and different
+ * from the pc-relative versions we write to the stack.
+ *
+ * ARM versions use:
+ * ldr r3, [sp, #ofs]
+ * ldr r9, [r3, #4]
+ * ldr pc, [r3, #0]
+ *
+ * Thumb versions use:
+ * ldr r3, [sp, #ofs]
+ * ldmia r3, {r2, r3}
+ * mov r9, r3
+ * bx r2
+ */
+ sigreturn_fdpic_tramp = sigtramp_page + i * 4;
+
+ /* ARM sigframe */
+ write_arm_fdpic_sigreturn(tramp + i,
+ offsetof(struct sigframe, retcode[3]));
+ i += 3;
+
+ /* Thumb sigframe */
+ write_thumb_fdpic_sigreturn(tramp + i,
+ offsetof(struct sigframe, retcode[3]));
+ i += 3;
+
+ /* ARM rt_sigframe */
+ write_arm_fdpic_sigreturn(tramp + i,
+ offsetof(struct rt_sigframe, retcode[3]));
+ i += 3;
+
+ /* Thumb rt_sigframe */
+ write_thumb_fdpic_sigreturn(tramp + i,
+ offsetof(struct rt_sigframe, retcode[3]));
+ i += 3;
+
+ assert(i * 4 == total_size);
+ unlock_user(tramp, sigtramp_page, total_size);
+}
--
2.25.1