Commit 4ab07fd3 authored by Alexander Sverdlin's avatar Alexander Sverdlin Committed by Russell King (Oracle)
Browse files

ARM: 9252/1: module: Teach unwinder about PLTs 

"unwind: Index not found eef26358" warnings keep popping up on
CONFIG_ARM_MODULE_PLTS-enabled systems if the PC points to a PLT veneer.
Teach the unwinder how to deal with them, taking into account they don't
change state of the stack or register file except loading PC.

Link: https://lore.kernel.org/linux-arm-kernel/20200402153845.30985-1-kursad.oney@broadcom.com/



Tested-by: default avatarKursad Oney <kursad.oney@broadcom.com>
Reviewed-by: default avatarLinus Walleij <linus.walleij@linaro.org>
Signed-off-by: default avatarAlexander Sverdlin <alexander.sverdlin@nokia.com>
Signed-off-by: default avatarRussell King (Oracle) <rmk+kernel@armlinux.org.uk>
parent e66372ec

arch/arm/include/asm/module.h

+5 −0
Original line number Diff line number Diff line
@@ -37,6 +37,11 @@ struct mod_arch_specific { 


struct module;

u32 get_module_plt(struct module *mod, unsigned long loc, Elf32_Addr val);

#ifdef CONFIG_ARM_MODULE_PLTS

bool in_module_plt(unsigned long loc);

#else

static inline bool in_module_plt(unsigned long loc) { return false; }

#endif



#ifdef CONFIG_THUMB2_KERNEL

#define HAVE_ARCH_KALLSYMS_SYMBOL_VALUE

arch/arm/kernel/module-plts.c

+14 −0
Original line number Diff line number Diff line
@@ -284,3 +284,17 @@ int module_frob_arch_sections(Elf_Ehdr *ehdr, Elf_Shdr *sechdrs, 
		 mod->arch.core.plt->sh_size, mod->arch.init.plt->sh_size);

	return 0;

}



bool in_module_plt(unsigned long loc)

{

	struct module *mod;

	bool ret;



	preempt_disable();

	mod = __module_text_address(loc);

	ret = mod && (loc - (u32)mod->arch.core.plt_ent < mod->arch.core.plt_count * PLT_ENT_SIZE ||

		      loc - (u32)mod->arch.init.plt_ent < mod->arch.init.plt_count * PLT_ENT_SIZE);

	preempt_enable();



	return ret;

}

arch/arm/kernel/unwind.c

+12 −1
Original line number Diff line number Diff line
@@ -28,6 +28,7 @@ 
#include <linux/slab.h>

#include <linux/spinlock.h>

#include <linux/list.h>

#include <linux/module.h>



#include <asm/stacktrace.h>

#include <asm/traps.h>
@@ -395,8 +396,18 @@ int unwind_frame(struct stackframe *frame) 


	idx = unwind_find_idx(frame->pc);

	if (!idx) {

		if (frame->pc && kernel_text_address(frame->pc))

		if (frame->pc && kernel_text_address(frame->pc)) {

			if (in_module_plt(frame->pc) && frame->pc != frame->lr) {

				/*

				 * Quoting Ard: Veneers only set PC using a

				 * PC+immediate LDR, and so they don't affect

				 * the state of the stack or the register file

				 */

				frame->pc = frame->lr;

				return URC_OK;

			}

			pr_warn("unwind: Index not found %08lx\n", frame->pc);

		}

		return -URC_FAILURE;

	}