@@ -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 */
@@ -99,43 +99,21 @@ struct sigframe
struct rt_sigframe
{
struct target_siginfo info;
- struct target_ucontext uc;
- abi_ulong retcode[4];
+ struct sigframe sig;
};
+static abi_ptr sigreturn_fdpic_tramp;
+
/*
- * For ARM syscalls, we encode the syscall number into the instruction.
+ * Up to 3 words of 'retcode' in the sigframe are code,
+ * with retcode[3] being used by fdpic for the function descriptor.
+ * This code is not actually executed, but is retained for ABI compat.
+ *
+ * We will create a table of 8 retcode variants in the sigtramp page.
+ * Let each table entry use 3 words.
*/
-#define SWI_SYS_SIGRETURN (0xef000000|(TARGET_NR_sigreturn + ARM_SYSCALL_BASE))
-#define SWI_SYS_RT_SIGRETURN (0xef000000|(TARGET_NR_rt_sigreturn + ARM_SYSCALL_BASE))
-
-/*
- * For Thumb syscalls, we pass the syscall number via r7. We therefore
- * need two 16-bit instructions.
- */
-#define SWI_THUMB_SIGRETURN (0xdf00 << 16 | 0x2700 | (TARGET_NR_sigreturn))
-#define SWI_THUMB_RT_SIGRETURN (0xdf00 << 16 | 0x2700 | (TARGET_NR_rt_sigreturn))
-
-static const abi_ulong retcodes[4] = {
- SWI_SYS_SIGRETURN, SWI_THUMB_SIGRETURN,
- SWI_SYS_RT_SIGRETURN, SWI_THUMB_RT_SIGRETURN
-};
-
-/*
- * Stub needed to make sure the FD register (r9) contains the right
- * value.
- */
-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 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 */
-};
+#define RETCODE_WORDS 3
+#define RETCODE_BYTES (RETCODE_WORDS * 4)
static inline int valid_user_regs(CPUARMState *regs)
{
@@ -183,15 +161,15 @@ 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)
+setup_return(CPUARMState *env, struct target_sigaction *ka, int usig,
+ struct sigframe *frame, abi_ulong sp_addr)
{
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);
+ bool copy_retcode;
if (is_fdpic) {
/* In FDPIC mode, ka->_sa_handler points to a function
@@ -208,6 +186,7 @@ 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);
@@ -225,44 +204,29 @@ 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.
- */
- 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);
- } 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);
- }
-
- retcode = rc_addr + thumb;
+ __put_user((abi_ulong)ka->sa_restorer, &frame->retcode[3]);
+ retcode = (sigreturn_fdpic_tramp +
+ retcode_idx * RETCODE_BYTES + thumb);
+ copy_retcode = true;
} else {
retcode = ka->sa_restorer;
+ copy_retcode = false;
}
} else {
- unsigned int idx = thumb;
+ retcode = default_sigreturn + retcode_idx * RETCODE_BYTES + thumb;
+ copy_retcode = true;
+ }
- if (ka->sa_flags & TARGET_SA_SIGINFO) {
- idx += 2;
- }
-
- __put_user(retcodes[idx], rc);
-
- retcode = rc_addr + thumb;
+ /* Copy the code to the stack slot for ABI compatibility. */
+ if (copy_retcode) {
+ memcpy(frame->retcode, g2h_untagged(retcode & ~1), RETCODE_BYTES);
}
env->regs[0] = usig;
if (is_fdpic) {
env->regs[9] = handler_fdpic_GOT;
}
- env->regs[13] = frame_addr;
+ env->regs[13] = sp_addr;
env->regs[14] = retcode;
env->regs[15] = handler & (thumb ? ~1 : ~3);
cpsr_write(env, cpsr, CPSR_IT | CPSR_T | CPSR_E, CPSRWriteByInstr);
@@ -351,8 +315,7 @@ 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))) {
+ if (setup_return(regs, ka, usig, frame, frame_addr)) {
goto sigsegv;
}
@@ -377,13 +340,12 @@ void setup_rt_frame(int usig, struct target_sigaction *ka,
}
info_addr = frame_addr + offsetof(struct rt_sigframe, info);
- uc_addr = frame_addr + offsetof(struct rt_sigframe, uc);
+ uc_addr = frame_addr + offsetof(struct rt_sigframe, sig.uc);
tswap_siginfo(&frame->info, info);
- setup_sigframe(&frame->uc, set, env);
+ setup_sigframe(&frame->sig.uc, set, env);
- if (setup_return(env, ka, frame->retcode, frame_addr, usig,
- frame_addr + offsetof(struct rt_sigframe, retcode))) {
+ if (setup_return(env, ka, usig, &frame->sig, frame_addr)) {
goto sigsegv;
}
@@ -578,8 +540,8 @@ long do_rt_sigreturn(CPUARMState *env)
}
if (do_sigframe_return(env,
- frame_addr + offsetof(struct rt_sigframe, uc),
- &frame->uc)) {
+ frame_addr + offsetof(struct rt_sigframe, sig.uc),
+ &frame->sig.uc)) {
goto badframe;
}
@@ -591,3 +553,78 @@ badframe:
force_sig(TARGET_SIGSEGV);
return -TARGET_QEMU_ESIGRETURN;
}
+
+/*
+ * 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 ARM_MOV_R7_IMM(X) (0xe3a07000 | (X))
+#define ARM_SWI_SYS(X) (0xef000000 | (X) | ARM_SYSCALL_BASE)
+
+#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);
+ /* Wrote 8 of 12 bytes */
+}
+
+static void write_thm_sigreturn(uint32_t *rc, int syscall)
+{
+ __put_user(THUMB_SWI_SYS << 16 | THUMB_MOVS_R7_IMM(syscall), rc);
+ /* Wrote 4 of 12 bytes */
+}
+
+/*
+ * Stub needed to make sure the FD register (r9) contains the right value.
+ * Use the same instruction sequence as the kernel.
+ */
+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 */
+ /* Wrote 12 of 12 bytes */
+}
+
+static void write_thm_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 */
+ /* Wrote 8 of 12 bytes */
+}
+
+void setup_sigtramp(abi_ulong sigtramp_page)
+{
+ uint32_t total_size = 8 * RETCODE_BYTES;
+ uint32_t *tramp = lock_user(VERIFY_WRITE, sigtramp_page, total_size, 0);
+
+ assert(tramp != NULL);
+
+ default_sigreturn = sigtramp_page;
+ write_arm_sigreturn(&tramp[0 * RETCODE_WORDS], TARGET_NR_sigreturn);
+ write_thm_sigreturn(&tramp[1 * RETCODE_WORDS], TARGET_NR_sigreturn);
+ write_arm_sigreturn(&tramp[2 * RETCODE_WORDS], TARGET_NR_rt_sigreturn);
+ write_thm_sigreturn(&tramp[3 * RETCODE_WORDS], TARGET_NR_rt_sigreturn);
+
+ sigreturn_fdpic_tramp = sigtramp_page + 4 * RETCODE_BYTES;
+ write_arm_fdpic_sigreturn(tramp + 4 * RETCODE_WORDS,
+ offsetof(struct sigframe, retcode[3]));
+ write_thm_fdpic_sigreturn(tramp + 5 * RETCODE_WORDS,
+ offsetof(struct sigframe, retcode[3]));
+ write_arm_fdpic_sigreturn(tramp + 6 * RETCODE_WORDS,
+ offsetof(struct rt_sigframe, sig.retcode[3]));
+ write_thm_fdpic_sigreturn(tramp + 7 * RETCODE_WORDS,
+ offsetof(struct rt_sigframe, sig.retcode[3]));
+
+ unlock_user(tramp, sigtramp_page, total_size);
+}
Mirror what the kernel does in arch/arm/kernel/signal.h, using the old sigframe struct in the rt sigframe struct. Update the trampoline code to match the kernel: this uses sp-relative accesses rather than pc-relative. Copy the code into frame->retcode from the trampoline page. This minimises the different cases wrt arm vs thumb vs fdpic. Signed-off-by: Richard Henderson <richard.henderson@linaro.org> --- linux-user/arm/target_signal.h | 2 + linux-user/arm/signal.c | 181 ++++++++++++++++++++------------- 2 files changed, 111 insertions(+), 72 deletions(-) -- 2.25.1