linux-user/arm: Implement setup_sigtramp
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> Reviewed-by: Peter Maydell <peter.maydell@linaro.org> Message-Id: <20210929130553.121567-6-richard.henderson@linaro.org> Signed-off-by: Laurent Vivier <laurent@vivier.eu>
This commit is contained in:
Richard Henderson
Laurent Vivier
parent
b807a1087e
commit
b5d66e0dd8
@ -99,43 +99,21 @@ struct sigframe
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struct rt_sigframe
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{
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struct target_siginfo info;
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struct target_ucontext uc;
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abi_ulong retcode[4];
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struct sigframe sig;
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};
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static abi_ptr sigreturn_fdpic_tramp;
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/*
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* For ARM syscalls, we encode the syscall number into the instruction.
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* Up to 3 words of 'retcode' in the sigframe are code,
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* with retcode[3] being used by fdpic for the function descriptor.
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* This code is not actually executed, but is retained for ABI compat.
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*
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* We will create a table of 8 retcode variants in the sigtramp page.
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* Let each table entry use 3 words.
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*/
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#define SWI_SYS_SIGRETURN (0xef000000|(TARGET_NR_sigreturn + ARM_SYSCALL_BASE))
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#define SWI_SYS_RT_SIGRETURN (0xef000000|(TARGET_NR_rt_sigreturn + ARM_SYSCALL_BASE))
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/*
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* For Thumb syscalls, we pass the syscall number via r7. We therefore
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* need two 16-bit instructions.
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*/
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#define SWI_THUMB_SIGRETURN (0xdf00 << 16 | 0x2700 | (TARGET_NR_sigreturn))
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#define SWI_THUMB_RT_SIGRETURN (0xdf00 << 16 | 0x2700 | (TARGET_NR_rt_sigreturn))
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static const abi_ulong retcodes[4] = {
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SWI_SYS_SIGRETURN, SWI_THUMB_SIGRETURN,
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SWI_SYS_RT_SIGRETURN, SWI_THUMB_RT_SIGRETURN
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};
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/*
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* Stub needed to make sure the FD register (r9) contains the right
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* value.
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*/
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static const unsigned long sigreturn_fdpic_codes[3] = {
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0xe59fc004, /* ldr r12, [pc, #4] to read function descriptor */
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0xe59c9004, /* ldr r9, [r12, #4] to setup GOT */
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0xe59cf000 /* ldr pc, [r12] to jump into restorer */
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};
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static const unsigned long sigreturn_fdpic_thumb_codes[3] = {
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0xc008f8df, /* ldr r12, [pc, #8] to read function descriptor */
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0x9004f8dc, /* ldr r9, [r12, #4] to setup GOT */
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0xf000f8dc /* ldr pc, [r12] to jump into restorer */
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};
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#define RETCODE_WORDS 3
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#define RETCODE_BYTES (RETCODE_WORDS * 4)
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static inline int valid_user_regs(CPUARMState *regs)
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{
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@ -183,15 +161,15 @@ get_sigframe(struct target_sigaction *ka, CPUARMState *regs, int framesize)
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}
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static int
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setup_return(CPUARMState *env, struct target_sigaction *ka,
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abi_ulong *rc, abi_ulong frame_addr, int usig, abi_ulong rc_addr)
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setup_return(CPUARMState *env, struct target_sigaction *ka, int usig,
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struct sigframe *frame, abi_ulong sp_addr)
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{
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abi_ulong handler = 0;
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abi_ulong handler_fdpic_GOT = 0;
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abi_ulong retcode;
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int thumb;
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int thumb, retcode_idx;
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int is_fdpic = info_is_fdpic(((TaskState *)thread_cpu->opaque)->info);
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bool copy_retcode;
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if (is_fdpic) {
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/* In FDPIC mode, ka->_sa_handler points to a function
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@ -208,6 +186,7 @@ setup_return(CPUARMState *env, struct target_sigaction *ka,
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}
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thumb = handler & 1;
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retcode_idx = thumb + (ka->sa_flags & TARGET_SA_SIGINFO ? 2 : 0);
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uint32_t cpsr = cpsr_read(env);
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@ -225,44 +204,29 @@ setup_return(CPUARMState *env, struct target_sigaction *ka,
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if (ka->sa_flags & TARGET_SA_RESTORER) {
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if (is_fdpic) {
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/* For FDPIC we ensure that the restorer is called with a
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* correct r9 value. For that we need to write code on
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* the stack that sets r9 and jumps back to restorer
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* value.
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*/
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if (thumb) {
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__put_user(sigreturn_fdpic_thumb_codes[0], rc);
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__put_user(sigreturn_fdpic_thumb_codes[1], rc + 1);
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__put_user(sigreturn_fdpic_thumb_codes[2], rc + 2);
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__put_user((abi_ulong)ka->sa_restorer, rc + 3);
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} else {
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__put_user(sigreturn_fdpic_codes[0], rc);
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__put_user(sigreturn_fdpic_codes[1], rc + 1);
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__put_user(sigreturn_fdpic_codes[2], rc + 2);
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__put_user((abi_ulong)ka->sa_restorer, rc + 3);
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}
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retcode = rc_addr + thumb;
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__put_user((abi_ulong)ka->sa_restorer, &frame->retcode[3]);
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retcode = (sigreturn_fdpic_tramp +
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retcode_idx * RETCODE_BYTES + thumb);
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copy_retcode = true;
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} else {
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retcode = ka->sa_restorer;
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copy_retcode = false;
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}
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} else {
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unsigned int idx = thumb;
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if (ka->sa_flags & TARGET_SA_SIGINFO) {
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idx += 2;
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retcode = default_sigreturn + retcode_idx * RETCODE_BYTES + thumb;
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copy_retcode = true;
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}
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__put_user(retcodes[idx], rc);
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retcode = rc_addr + thumb;
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/* Copy the code to the stack slot for ABI compatibility. */
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if (copy_retcode) {
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memcpy(frame->retcode, g2h_untagged(retcode & ~1), RETCODE_BYTES);
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}
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env->regs[0] = usig;
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if (is_fdpic) {
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env->regs[9] = handler_fdpic_GOT;
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}
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env->regs[13] = frame_addr;
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env->regs[13] = sp_addr;
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env->regs[14] = retcode;
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env->regs[15] = handler & (thumb ? ~1 : ~3);
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cpsr_write(env, cpsr, CPSR_IT | CPSR_T | CPSR_E, CPSRWriteByInstr);
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@ -351,8 +315,7 @@ void setup_frame(int usig, struct target_sigaction *ka,
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setup_sigframe(&frame->uc, set, regs);
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if (setup_return(regs, ka, frame->retcode, frame_addr, usig,
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frame_addr + offsetof(struct sigframe, retcode))) {
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if (setup_return(regs, ka, usig, frame, frame_addr)) {
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goto sigsegv;
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}
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@ -377,13 +340,12 @@ void setup_rt_frame(int usig, struct target_sigaction *ka,
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}
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info_addr = frame_addr + offsetof(struct rt_sigframe, info);
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uc_addr = frame_addr + offsetof(struct rt_sigframe, uc);
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uc_addr = frame_addr + offsetof(struct rt_sigframe, sig.uc);
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tswap_siginfo(&frame->info, info);
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setup_sigframe(&frame->uc, set, env);
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setup_sigframe(&frame->sig.uc, set, env);
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if (setup_return(env, ka, frame->retcode, frame_addr, usig,
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frame_addr + offsetof(struct rt_sigframe, retcode))) {
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if (setup_return(env, ka, usig, &frame->sig, frame_addr)) {
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goto sigsegv;
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}
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@ -578,8 +540,8 @@ long do_rt_sigreturn(CPUARMState *env)
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}
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if (do_sigframe_return(env,
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frame_addr + offsetof(struct rt_sigframe, uc),
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&frame->uc)) {
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frame_addr + offsetof(struct rt_sigframe, sig.uc),
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&frame->sig.uc)) {
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goto badframe;
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}
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@ -591,3 +553,78 @@ badframe:
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force_sig(TARGET_SIGSEGV);
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return -TARGET_QEMU_ESIGRETURN;
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}
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/*
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* EABI syscalls pass the number via r7.
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* Note that the kernel still adds the OABI syscall number to the trap,
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* presumably for backward ABI compatibility with unwinders.
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*/
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#define ARM_MOV_R7_IMM(X) (0xe3a07000 | (X))
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#define ARM_SWI_SYS(X) (0xef000000 | (X) | ARM_SYSCALL_BASE)
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#define THUMB_MOVS_R7_IMM(X) (0x2700 | (X))
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#define THUMB_SWI_SYS 0xdf00
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static void write_arm_sigreturn(uint32_t *rc, int syscall)
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{
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__put_user(ARM_MOV_R7_IMM(syscall), rc);
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__put_user(ARM_SWI_SYS(syscall), rc + 1);
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/* Wrote 8 of 12 bytes */
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}
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static void write_thm_sigreturn(uint32_t *rc, int syscall)
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{
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__put_user(THUMB_SWI_SYS << 16 | THUMB_MOVS_R7_IMM(syscall), rc);
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/* Wrote 4 of 12 bytes */
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}
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/*
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* Stub needed to make sure the FD register (r9) contains the right value.
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* Use the same instruction sequence as the kernel.
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*/
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static void write_arm_fdpic_sigreturn(uint32_t *rc, int ofs)
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{
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assert(ofs <= 0xfff);
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__put_user(0xe59d3000 | ofs, rc + 0); /* ldr r3, [sp, #ofs] */
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__put_user(0xe8930908, rc + 1); /* ldm r3, { r3, r9 } */
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__put_user(0xe12fff13, rc + 2); /* bx r3 */
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/* Wrote 12 of 12 bytes */
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}
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static void write_thm_fdpic_sigreturn(void *vrc, int ofs)
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{
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uint16_t *rc = vrc;
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assert((ofs & ~0x3fc) == 0);
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__put_user(0x9b00 | (ofs >> 2), rc + 0); /* ldr r3, [sp, #ofs] */
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__put_user(0xcb0c, rc + 1); /* ldm r3, { r2, r3 } */
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__put_user(0x4699, rc + 2); /* mov r9, r3 */
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__put_user(0x4710, rc + 3); /* bx r2 */
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/* Wrote 8 of 12 bytes */
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}
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void setup_sigtramp(abi_ulong sigtramp_page)
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{
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uint32_t total_size = 8 * RETCODE_BYTES;
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uint32_t *tramp = lock_user(VERIFY_WRITE, sigtramp_page, total_size, 0);
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assert(tramp != NULL);
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default_sigreturn = sigtramp_page;
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write_arm_sigreturn(&tramp[0 * RETCODE_WORDS], TARGET_NR_sigreturn);
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write_thm_sigreturn(&tramp[1 * RETCODE_WORDS], TARGET_NR_sigreturn);
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write_arm_sigreturn(&tramp[2 * RETCODE_WORDS], TARGET_NR_rt_sigreturn);
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write_thm_sigreturn(&tramp[3 * RETCODE_WORDS], TARGET_NR_rt_sigreturn);
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sigreturn_fdpic_tramp = sigtramp_page + 4 * RETCODE_BYTES;
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write_arm_fdpic_sigreturn(tramp + 4 * RETCODE_WORDS,
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offsetof(struct sigframe, retcode[3]));
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write_thm_fdpic_sigreturn(tramp + 5 * RETCODE_WORDS,
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offsetof(struct sigframe, retcode[3]));
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write_arm_fdpic_sigreturn(tramp + 6 * RETCODE_WORDS,
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offsetof(struct rt_sigframe, sig.retcode[3]));
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write_thm_fdpic_sigreturn(tramp + 7 * RETCODE_WORDS,
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offsetof(struct rt_sigframe, sig.retcode[3]));
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unlock_user(tramp, sigtramp_page, total_size);
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}
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@ -22,4 +22,6 @@ typedef struct target_sigaltstack {
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#include "../generic/signal.h"
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#define TARGET_ARCH_HAS_SETUP_FRAME
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#define TARGET_ARCH_HAS_SIGTRAMP_PAGE 1
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#endif /* ARM_TARGET_SIGNAL_H */
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