[OpenWrt-Devel] [PATCH] generic: mips: exclude more dsemul code when fpu-emu is not enabled
Hauke Mehrtens
hauke at hauke-m.de
Sun Mar 29 11:33:46 EDT 2020
On 3/27/20 5:28 AM, Yousong Zhou wrote:
> The patch is backported from mips-next. In addition to minor reduction
> of code size and runtime memory use, the more apparent difference is
> that the delay slot emulation page will not be present for those targets
> with fpu emulation disabled (CONFIG_MIPS_FP_SUPPORT=n)
>
> Memory maps of busybox before and after this change
>
> root at OpenWrt:/# cat /proc/self/maps
> 00400000-00449000 r-xp 00000000 00:02 23 /bin/busybox
> 00458000-00459000 r-xp 00048000 00:02 23 /bin/busybox
> 00459000-0045a000 rwxp 00049000 00:02 23 /bin/busybox
> 77dc0000-77de2000 r-xp 00000000 00:02 273 /lib/libgcc_s.so.1
> 77de2000-77de3000 r-xp 00012000 00:02 273 /lib/libgcc_s.so.1
> 77de3000-77de4000 rwxp 00013000 00:02 273 /lib/libgcc_s.so.1
> 77de4000-77e7b000 r-xp 00000000 00:02 271 /lib/libc.so
> 77e8a000-77e8c000 rwxp 00096000 00:02 271 /lib/libc.so
> 77e8c000-77e8e000 rwxp 00000000 00:00 0
> 7fd86000-7fda7000 rw-p 00000000 00:00 0 [stack]
> 7fefd000-7fefe000 r-xp 00000000 00:00 0
> 7ffe6000-7ffe7000 r--p 00000000 00:00 0 [vvar]
> 7ffe7000-7ffe8000 r-xp 00000000 00:00 0 [vdso]
>
> root at OpenWrt:/# cat /proc/self/maps
> 00400000-00449000 r-xp 00000000 00:02 23 /bin/busybox
> 00458000-00459000 r-xp 00048000 00:02 23 /bin/busybox
> 00459000-0045a000 rwxp 00049000 00:02 23 /bin/busybox
> 77d55000-77d77000 r-xp 00000000 00:02 274 /lib/libgcc_s.so.1
> 77d77000-77d78000 r-xp 00012000 00:02 274 /lib/libgcc_s.so.1
> 77d78000-77d79000 rwxp 00013000 00:02 274 /lib/libgcc_s.so.1
> 77d79000-77e10000 r-xp 00000000 00:02 272 /lib/libc.so
> 77e1f000-77e21000 rwxp 00096000 00:02 272 /lib/libc.so
> 77e21000-77e23000 rwxp 00000000 00:00 0
> 7fe23000-7fe44000 rw-p 00000000 00:00 0 [stack]
> 7ff63000-7ff64000 r--p 00000000 00:00 0 [vvar]
> 7ff64000-7ff65000 r-xp 00000000 00:00 0 [vdso]
>
> Signed-off-by: Yousong Zhou <yszhou4tech at gmail.com>
Acked-by: Hauke Mehrtens <hauke at hauke-m.de>
> ---
> ...e-dsemul-code-when-CONFIG_MIPS_FP_SU.patch | 140 ++++++++++++++++++
> 1 file changed, 140 insertions(+)
> create mode 100644 target/linux/generic/backport-5.4/300-MIPS-Exclude-more-dsemul-code-when-CONFIG_MIPS_FP_SU.patch
>
> diff --git a/target/linux/generic/backport-5.4/300-MIPS-Exclude-more-dsemul-code-when-CONFIG_MIPS_FP_SU.patch b/target/linux/generic/backport-5.4/300-MIPS-Exclude-more-dsemul-code-when-CONFIG_MIPS_FP_SU.patch
> new file mode 100644
> index 0000000000..1be051e1df
> --- /dev/null
> +++ b/target/linux/generic/backport-5.4/300-MIPS-Exclude-more-dsemul-code-when-CONFIG_MIPS_FP_SU.patch
> @@ -0,0 +1,140 @@
> +From d96c3157f9ca177727fbad960fcf6f52f145f471 Mon Sep 17 00:00:00 2001
> +From: Yousong Zhou <yszhou4tech at gmail.com>
> +Date: Thu, 9 Jan 2020 11:33:19 +0800
> +Subject: [PATCH] MIPS: Exclude more dsemul code when CONFIG_MIPS_FP_SUPPORT=n
> +
> +This furthers what commit 42b10815d559 ("MIPS: Don't compile math-emu
> +when CONFIG_MIPS_FP_SUPPORT=n") has done
> +
> +Signed-off-by: Yousong Zhou <yszhou4tech at gmail.com>
> +---
> + arch/mips/include/asm/processor.h | 12 ++++++------
> + arch/mips/kernel/process.c | 10 ++++++++--
> + arch/mips/kernel/vdso.c | 26 +++++++++++++++-----------
> + 3 files changed, 29 insertions(+), 19 deletions(-)
> +
> +diff --git a/arch/mips/include/asm/processor.h b/arch/mips/include/asm/processor.h
> +index 7619ad319400..813ba94d87bb 100644
> +--- a/arch/mips/include/asm/processor.h
> ++++ b/arch/mips/include/asm/processor.h
> +@@ -253,13 +253,13 @@ struct thread_struct {
> + #ifdef CONFIG_MIPS_FP_SUPPORT
> + /* Saved fpu/fpu emulator stuff. */
> + struct mips_fpu_struct fpu FPU_ALIGN;
> +-#endif
> + /* Assigned branch delay slot 'emulation' frame */
> + atomic_t bd_emu_frame;
> + /* PC of the branch from a branch delay slot 'emulation' */
> + unsigned long bd_emu_branch_pc;
> + /* PC to continue from following a branch delay slot 'emulation' */
> + unsigned long bd_emu_cont_pc;
> ++#endif
> + #ifdef CONFIG_MIPS_MT_FPAFF
> + /* Emulated instruction count */
> + unsigned long emulated_fp;
> +@@ -302,7 +302,11 @@ struct thread_struct {
> + .fpr = {{{0,},},}, \
> + .fcr31 = 0, \
> + .msacsr = 0, \
> +- },
> ++ }, \
> ++ /* Delay slot emulation */ \
> ++ .bd_emu_frame = ATOMIC_INIT(BD_EMUFRAME_NONE), \
> ++ .bd_emu_branch_pc = 0, \
> ++ .bd_emu_cont_pc = 0,
> + #else
> + # define FPU_INIT
> + #endif
> +@@ -334,10 +338,6 @@ struct thread_struct {
> + * FPU affinity state (null if not FPAFF) \
> + */ \
> + FPAFF_INIT \
> +- /* Delay slot emulation */ \
> +- .bd_emu_frame = ATOMIC_INIT(BD_EMUFRAME_NONE), \
> +- .bd_emu_branch_pc = 0, \
> +- .bd_emu_cont_pc = 0, \
> + /* \
> + * Saved DSP stuff \
> + */ \
> +diff --git a/arch/mips/kernel/process.c b/arch/mips/kernel/process.c
> +index 339870ed92f7..b2a797557825 100644
> +--- a/arch/mips/kernel/process.c
> ++++ b/arch/mips/kernel/process.c
> +@@ -75,7 +75,9 @@ void start_thread(struct pt_regs * regs, unsigned long pc, unsigned long sp)
> + lose_fpu(0);
> + clear_thread_flag(TIF_MSA_CTX_LIVE);
> + clear_used_math();
> ++#ifdef CONFIG_MIPS_FP_SUPPORT
> + atomic_set(¤t->thread.bd_emu_frame, BD_EMUFRAME_NONE);
> ++#endif
> + init_dsp();
> + regs->cp0_epc = pc;
> + regs->regs[29] = sp;
> +@@ -176,7 +178,9 @@ int copy_thread_tls(unsigned long clone_flags, unsigned long usp,
> + clear_tsk_thread_flag(p, TIF_FPUBOUND);
> + #endif /* CONFIG_MIPS_MT_FPAFF */
> +
> ++#ifdef CONFIG_MIPS_FP_SUPPORT
> + atomic_set(&p->thread.bd_emu_frame, BD_EMUFRAME_NONE);
> ++#endif
> +
> + if (clone_flags & CLONE_SETTLS)
> + ti->tp_value = tls;
> +@@ -650,8 +654,10 @@ unsigned long mips_stack_top(void)
> + {
> + unsigned long top = TASK_SIZE & PAGE_MASK;
> +
> +- /* One page for branch delay slot "emulation" */
> +- top -= PAGE_SIZE;
> ++ if (IS_ENABLED(CONFIG_MIPS_FP_SUPPORT)) {
> ++ /* One page for branch delay slot "emulation" */
> ++ top -= PAGE_SIZE;
> ++ }
> +
> + /* Space for the VDSO, data page & GIC user page */
> + top -= PAGE_ALIGN(current->thread.abi->vdso->size);
> +diff --git a/arch/mips/kernel/vdso.c b/arch/mips/kernel/vdso.c
> +index bc35f8499111..3adb7354bc01 100644
> +--- a/arch/mips/kernel/vdso.c
> ++++ b/arch/mips/kernel/vdso.c
> +@@ -71,10 +71,12 @@ subsys_initcall(init_vdso);
> +
> + static unsigned long vdso_base(void)
> + {
> +- unsigned long base;
> ++ unsigned long base = STACK_TOP;
> +
> +- /* Skip the delay slot emulation page */
> +- base = STACK_TOP + PAGE_SIZE;
> ++ if (IS_ENABLED(CONFIG_MIPS_FP_SUPPORT)) {
> ++ /* Skip the delay slot emulation page */
> ++ base += PAGE_SIZE;
> ++ }
> +
> + if (current->flags & PF_RANDOMIZE) {
> + base += get_random_int() & (VDSO_RANDOMIZE_SIZE - 1);
> +@@ -95,14 +97,16 @@ int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
> + if (down_write_killable(&mm->mmap_sem))
> + return -EINTR;
> +
> +- /* Map delay slot emulation page */
> +- base = mmap_region(NULL, STACK_TOP, PAGE_SIZE,
> +- VM_READ | VM_EXEC |
> +- VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC,
> +- 0, NULL);
> +- if (IS_ERR_VALUE(base)) {
> +- ret = base;
> +- goto out;
> ++ if (IS_ENABLED(CONFIG_MIPS_FP_SUPPORT)) {
> ++ /* Map delay slot emulation page */
> ++ base = mmap_region(NULL, STACK_TOP, PAGE_SIZE,
> ++ VM_READ | VM_EXEC |
> ++ VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC,
> ++ 0, NULL);
> ++ if (IS_ERR_VALUE(base)) {
> ++ ret = base;
> ++ goto out;
> ++ }
> + }
> +
> + /*
>
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