ARM: 9079/1: ftrace: Add MODULE_PLTS support

commit 79f32b221b18c15a98507b101ef4beb52444cc6f upstream

Teach ftrace_make_call() and ftrace_make_nop() about PLTs.
Teach PLT code about FTRACE and all its callbacks.
Otherwise the following might happen:

------------[ cut here ]------------
WARNING: CPU: 14 PID: 2265 at .../arch/arm/kernel/insn.c:14 __arm_gen_branch+0x83/0x8c()
...
Hardware name: LSI Axxia AXM55XX
[<c0314a49>] (unwind_backtrace) from [<c03115e9>] (show_stack+0x11/0x14)
[<c03115e9>] (show_stack) from [<c0519f51>] (dump_stack+0x81/0xa8)
[<c0519f51>] (dump_stack) from [<c032185d>] (warn_slowpath_common+0x69/0x90)
[<c032185d>] (warn_slowpath_common) from [<c03218f3>] (warn_slowpath_null+0x17/0x1c)
[<c03218f3>] (warn_slowpath_null) from [<c03143cf>] (__arm_gen_branch+0x83/0x8c)
[<c03143cf>] (__arm_gen_branch) from [<c0314337>] (ftrace_make_nop+0xf/0x24)
[<c0314337>] (ftrace_make_nop) from [<c038ebcb>] (ftrace_process_locs+0x27b/0x3e8)
[<c038ebcb>] (ftrace_process_locs) from [<c0378d79>] (load_module+0x11e9/0x1a44)
[<c0378d79>] (load_module) from [<c037974d>] (SyS_finit_module+0x59/0x84)
[<c037974d>] (SyS_finit_module) from [<c030e981>] (ret_fast_syscall+0x1/0x18)
---[ end trace e1b64ced7a89adcc ]---
------------[ cut here ]------------
WARNING: CPU: 14 PID: 2265 at .../kernel/trace/ftrace.c:1979 ftrace_bug+0x1b1/0x234()
...
Hardware name: LSI Axxia AXM55XX
[<c0314a49>] (unwind_backtrace) from [<c03115e9>] (show_stack+0x11/0x14)
[<c03115e9>] (show_stack) from [<c0519f51>] (dump_stack+0x81/0xa8)
[<c0519f51>] (dump_stack) from [<c032185d>] (warn_slowpath_common+0x69/0x90)
[<c032185d>] (warn_slowpath_common) from [<c03218f3>] (warn_slowpath_null+0x17/0x1c)
[<c03218f3>] (warn_slowpath_null) from [<c038e87d>] (ftrace_bug+0x1b1/0x234)
[<c038e87d>] (ftrace_bug) from [<c038ebd5>] (ftrace_process_locs+0x285/0x3e8)
[<c038ebd5>] (ftrace_process_locs) from [<c0378d79>] (load_module+0x11e9/0x1a44)
[<c0378d79>] (load_module) from [<c037974d>] (SyS_finit_module+0x59/0x84)
[<c037974d>] (SyS_finit_module) from [<c030e981>] (ret_fast_syscall+0x1/0x18)
---[ end trace e1b64ced7a89adcd ]---
ftrace failed to modify [<e9ef7006>] 0xe9ef7006
actual: 02:f0:3b:fa
ftrace record flags: 0
(0) expected tramp: c0314265

Signed-off-by: Alexander Sverdlin <alexander.sverdlin@nokia.com>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/arm/include/asm/ftrace.h b/arch/arm/include/asm/ftrace.h
index 22b73112b75f2070e440068184f9655cff781afe..1c30be0f5dd023dd5ca101a6dd4f45d35b9901b9 100644 (file)
--- a/arch/arm/include/asm/ftrace.h
+++ b/arch/arm/include/asm/ftrace.h
@@ -14,6 +14,9 @@ struct dyn_arch_ftrace {
 #ifdef CONFIG_OLD_MCOUNT
        bool    old_mcount;
 #endif
+#ifdef CONFIG_ARM_MODULE_PLTS
+       struct module *mod;
+#endif
 };
 
 static inline unsigned long ftrace_call_adjust(unsigned long addr)

diff --git a/arch/arm/include/asm/module.h b/arch/arm/include/asm/module.h
index 2e9872a22359ce0020914ef4fbef2ef2f9d3d5d3..3cfbe8181224285e6f9bbe9de120338f408dd2c5 100644 (file)
--- a/arch/arm/include/asm/module.h
+++ b/arch/arm/include/asm/module.h
@@ -29,6 +29,7 @@ struct plt_entries {
 
 struct mod_plt_sec {
        struct elf32_shdr       *plt;
+       struct plt_entries      *plt_ent;
        int                     plt_count;
 };
 

diff --git a/arch/arm/kernel/ftrace.c b/arch/arm/kernel/ftrace.c
index a95bc0a02fd8046e848043a3cde4e12ec3d0f0ae..b1cf37fec354227232681ad89dc0c39544b6be8e 100644 (file)
--- a/arch/arm/kernel/ftrace.c
+++ b/arch/arm/kernel/ftrace.c
@@ -95,9 +95,10 @@ int ftrace_arch_code_modify_post_process(void)
        return 0;
 }
 
-static unsigned long ftrace_call_replace(unsigned long pc, unsigned long addr)
+static unsigned long ftrace_call_replace(unsigned long pc, unsigned long addr,
+                                        bool warn)
 {
-       return arm_gen_branch_link(pc, addr, true);
+       return arm_gen_branch_link(pc, addr, warn);
 }
 
 static int ftrace_modify_code(unsigned long pc, unsigned long old,
@@ -136,14 +137,14 @@ int ftrace_update_ftrace_func(ftrace_func_t func)
        int ret;
 
        pc = (unsigned long)&ftrace_call;
-       new = ftrace_call_replace(pc, (unsigned long)func);
+       new = ftrace_call_replace(pc, (unsigned long)func, true);
 
        ret = ftrace_modify_code(pc, 0, new, false);
 
 #ifdef CONFIG_OLD_MCOUNT
        if (!ret) {
                pc = (unsigned long)&ftrace_call_old;
-               new = ftrace_call_replace(pc, (unsigned long)func);
+               new = ftrace_call_replace(pc, (unsigned long)func, true);
 
                ret = ftrace_modify_code(pc, 0, new, false);
        }
@@ -156,9 +157,21 @@ int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
 {
        unsigned long new, old;
        unsigned long ip = rec->ip;
+       unsigned long aaddr = adjust_address(rec, addr);
+       struct module *mod = NULL;
+
+#ifdef CONFIG_ARM_MODULE_PLTS
+       mod = rec->arch.mod;
+#endif
 
        old = ftrace_nop_replace(rec);
-       new = ftrace_call_replace(ip, adjust_address(rec, addr));
+       new = ftrace_call_replace(ip, aaddr, !mod);
+#ifdef CONFIG_ARM_MODULE_PLTS
+       if (!new && mod) {
+               aaddr = get_module_plt(mod, ip, aaddr);
+               new = ftrace_call_replace(ip, aaddr, true);
+       }
+#endif
 
        return ftrace_modify_code(rec->ip, old, new, true);
 }
@@ -166,12 +179,29 @@ int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
 int ftrace_make_nop(struct module *mod,
                    struct dyn_ftrace *rec, unsigned long addr)
 {
+       unsigned long aaddr = adjust_address(rec, addr);
        unsigned long ip = rec->ip;
        unsigned long old;
        unsigned long new;
        int ret;
 
-       old = ftrace_call_replace(ip, adjust_address(rec, addr));
+#ifdef CONFIG_ARM_MODULE_PLTS
+       /* mod is only supplied during module loading */
+       if (!mod)
+               mod = rec->arch.mod;
+       else
+               rec->arch.mod = mod;
+#endif
+
+       old = ftrace_call_replace(ip, aaddr,
+                                 !IS_ENABLED(CONFIG_ARM_MODULE_PLTS) || !mod);
+#ifdef CONFIG_ARM_MODULE_PLTS
+       if (!old && mod) {
+               aaddr = get_module_plt(mod, ip, aaddr);
+               old = ftrace_call_replace(ip, aaddr, true);
+       }
+#endif
+
        new = ftrace_nop_replace(rec);
        ret = ftrace_modify_code(ip, old, new, true);
 
@@ -179,7 +209,8 @@ int ftrace_make_nop(struct module *mod,
        if (ret == -EINVAL && addr == MCOUNT_ADDR) {
                rec->arch.old_mcount = true;
 
-               old = ftrace_call_replace(ip, adjust_address(rec, addr));
+               old = ftrace_call_replace(ip, adjust_address(rec, addr),
+                                         !IS_ENABLED(CONFIG_ARM_MODULE_PLTS) || !mod);
                new = ftrace_nop_replace(rec);
                ret = ftrace_modify_code(ip, old, new, true);
        }

diff --git a/arch/arm/kernel/module-plts.c b/arch/arm/kernel/module-plts.c
index f272711c411f186411a263007b637162d76ebac9..6804a145be11f9215259c6d6db31af495432d732 100644 (file)
--- a/arch/arm/kernel/module-plts.c
+++ b/arch/arm/kernel/module-plts.c
@@ -7,6 +7,7 @@
  */
 
 #include <linux/elf.h>
+#include <linux/ftrace.h>
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/sort.h>
@@ -22,19 +23,52 @@
                                                    (PLT_ENT_STRIDE - 8))
 #endif
 
+static const u32 fixed_plts[] = {
+#ifdef CONFIG_FUNCTION_TRACER
+       FTRACE_ADDR,
+       MCOUNT_ADDR,
+#endif
+};
+
 static bool in_init(const struct module *mod, unsigned long loc)
 {
        return loc - (u32)mod->init_layout.base < mod->init_layout.size;
 }
 
+static void prealloc_fixed(struct mod_plt_sec *pltsec, struct plt_entries *plt)
+{
+       int i;
+
+       if (!ARRAY_SIZE(fixed_plts) || pltsec->plt_count)
+               return;
+       pltsec->plt_count = ARRAY_SIZE(fixed_plts);
+
+       for (i = 0; i < ARRAY_SIZE(plt->ldr); ++i)
+               plt->ldr[i] = PLT_ENT_LDR;
+
+       BUILD_BUG_ON(sizeof(fixed_plts) > sizeof(plt->lit));
+       memcpy(plt->lit, fixed_plts, sizeof(fixed_plts));
+}
+
 u32 get_module_plt(struct module *mod, unsigned long loc, Elf32_Addr val)
 {
        struct mod_plt_sec *pltsec = !in_init(mod, loc) ? &mod->arch.core :
                                                          &mod->arch.init;
+       struct plt_entries *plt;
+       int idx;
+
+       /* cache the address, ELF header is available only during module load */
+       if (!pltsec->plt_ent)
+               pltsec->plt_ent = (struct plt_entries *)pltsec->plt->sh_addr;
+       plt = pltsec->plt_ent;
 
-       struct plt_entries *plt = (struct plt_entries *)pltsec->plt->sh_addr;
-       int idx = 0;
+       prealloc_fixed(pltsec, plt);
+
+       for (idx = 0; idx < ARRAY_SIZE(fixed_plts); ++idx)
+               if (plt->lit[idx] == val)
+                       return (u32)&plt->ldr[idx];
 
+       idx = 0;
        /*
         * Look for an existing entry pointing to 'val'. Given that the
         * relocations are sorted, this will be the last entry we allocated.
@@ -182,8 +216,8 @@ static unsigned int count_plts(const Elf32_Sym *syms, Elf32_Addr base,
 int module_frob_arch_sections(Elf_Ehdr *ehdr, Elf_Shdr *sechdrs,
                              char *secstrings, struct module *mod)
 {
-       unsigned long core_plts = 0;
-       unsigned long init_plts = 0;
+       unsigned long core_plts = ARRAY_SIZE(fixed_plts);
+       unsigned long init_plts = ARRAY_SIZE(fixed_plts);
        Elf32_Shdr *s, *sechdrs_end = sechdrs + ehdr->e_shnum;
        Elf32_Sym *syms = NULL;
 
@@ -238,6 +272,7 @@ int module_frob_arch_sections(Elf_Ehdr *ehdr, Elf_Shdr *sechdrs,
        mod->arch.core.plt->sh_size = round_up(core_plts * PLT_ENT_SIZE,
                                               sizeof(struct plt_entries));
        mod->arch.core.plt_count = 0;
+       mod->arch.core.plt_ent = NULL;
 
        mod->arch.init.plt->sh_type = SHT_NOBITS;
        mod->arch.init.plt->sh_flags = SHF_EXECINSTR | SHF_ALLOC;
@@ -245,6 +280,7 @@ int module_frob_arch_sections(Elf_Ehdr *ehdr, Elf_Shdr *sechdrs,
        mod->arch.init.plt->sh_size = round_up(init_plts * PLT_ENT_SIZE,
                                               sizeof(struct plt_entries));
        mod->arch.init.plt_count = 0;
+       mod->arch.init.plt_ent = NULL;
 
        pr_debug("%s: plt=%x, init.plt=%x\n", __func__,
                 mod->arch.core.plt->sh_size, mod->arch.init.plt->sh_size);