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

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"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: Kursad Oney <kursad.oney@broadcom.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Alexander Sverdlin <alexander.sverdlin@nokia.com>
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
This commit is contained in:
Alex Sverdlin 2022-09-27 13:08:37 +01:00 committed by Russell King (Oracle)
parent e66372ecb8
commit 4ab07fd3fb
3 changed files with 31 additions and 1 deletions
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5
arch/arm/include/asm/module.h
View File

@ -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

14
arch/arm/kernel/module-plts.c
View File

@ -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;
}

13
arch/arm/kernel/unwind.c
View File

@ -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;
}