[PATCH v7 05/11] arm64/module, sframe: Add sframe support for modules
Dylan Hatch
dylanbhatch at google.com
Fri Sep 18 15:41:51 PDT 2026
Add sframe table to mod_arch_specific and support sframe PC lookups when
an .sframe section can be found on incoming modules. SFRAME_F_FDE_SORTED
is not set for module .sframe, so FDEs are sorted right after the sframe
header is read.
Co-developed-by: Weinan Liu <wnliu at google.com>
Signed-off-by: Weinan Liu <wnliu at google.com>
Suggested-by: Jens Remus <jremus at linux.ibm.com>
Reviewed-by: Jens Remus <jremus at linux.ibm.com>
Signed-off-by: Dylan Hatch <dylanbhatch at google.com>
---
Changes since v6:
- (sashiko) Check section flag SHF_ALLOC before reading in module
.sframe.
- (sashiko) Use READ_ONCE/WRITE_ONCE to enforce memory barrier when
checking mod->arch.sframe_init.
- Change IP range checks to strictly check text sections of
vmlinux/module (instead of is_ksym_addr(ip) / __module_address(ip)).
- (sashiko) Check kernel_sfsec.fdes_sorted during init, since
SFRAME_F_FDE_SORTED is no longer required (in order to support
modules).
- (sashiko) Drop WARN_ON to pr_warn() when module sframe header read
fails.
- Drop sec->sec_type check in sframe_sort_fdes(), return void.
---
arch/arm64/include/asm/module.h | 6 ++
arch/arm64/kernel/module.c | 5 ++
include/linux/sframe.h | 7 +++
kernel/unwind/sframe.c | 105 ++++++++++++++++++++++++++++++--
4 files changed, 119 insertions(+), 4 deletions(-)
diff --git a/arch/arm64/include/asm/module.h b/arch/arm64/include/asm/module.h
index fb9b88eebeb15..07f309c51eee6 100644
--- a/arch/arm64/include/asm/module.h
+++ b/arch/arm64/include/asm/module.h
@@ -6,6 +6,7 @@
#define __ASM_MODULE_H
#include <asm-generic/module.h>
+#include <linux/sframe.h>
struct mod_plt_sec {
int plt_shndx;
@@ -17,6 +18,11 @@ struct mod_arch_specific {
struct mod_plt_sec core;
struct mod_plt_sec init;
+#ifdef CONFIG_HAVE_UNWIND_KERNEL_SFRAME
+ struct sframe_section sframe_sec;
+ bool sframe_init;
+#endif
+
/* for CONFIG_DYNAMIC_FTRACE */
struct plt_entry *ftrace_trampolines;
struct plt_entry *init_ftrace_trampolines;
diff --git a/arch/arm64/kernel/module.c b/arch/arm64/kernel/module.c
index 24adb581af0eb..69334e22be34e 100644
--- a/arch/arm64/kernel/module.c
+++ b/arch/arm64/kernel/module.c
@@ -18,6 +18,7 @@
#include <linux/moduleloader.h>
#include <linux/random.h>
#include <linux/scs.h>
+#include <linux/sframe.h>
#include <asm/alternative.h>
#include <asm/insn.h>
@@ -515,5 +516,9 @@ int module_finalize(const Elf_Ehdr *hdr,
}
}
+ s = find_section(hdr, sechdrs, ".sframe");
+ if (s && (s->sh_flags & SHF_ALLOC))
+ sframe_module_init(me, (void *)s->sh_addr, s->sh_size);
+
return module_init_ftrace_plt(hdr, sechdrs, me);
}
diff --git a/include/linux/sframe.h b/include/linux/sframe.h
index c1fe8ac7df7b3..58a68de1396af 100644
--- a/include/linux/sframe.h
+++ b/include/linux/sframe.h
@@ -15,6 +15,7 @@ struct sframe_section {
unsigned long fres_start;
unsigned long fres_end;
unsigned int num_fdes;
+ bool fdes_sorted;
signed char ra_off;
signed char fp_off;
@@ -23,12 +24,18 @@ struct sframe_section {
extern struct sframe_section kernel_sfsec __ro_after_init;
void __init init_sframe_table(void);
+void sframe_module_init(struct module *mod, void *sframe, size_t sframe_size);
+
extern int sframe_find(unsigned long ip, struct unwind_frame *frame);
#else /* !CONFIG_UNWIND_SFRAME_LOOKUP */
static inline void __init init_sframe_table(void) {}
+static inline void sframe_module_init(struct module *mod, void *sframe,
+ size_t sframe_size) {}
+
static inline int sframe_find(unsigned long ip, struct unwind_frame *frame) { return -EINVAL; }
+
#endif /* CONFIG_UNWIND_SFRAME_LOOKUP */
#endif /* _LINUX_SFRAME_H */
diff --git a/kernel/unwind/sframe.c b/kernel/unwind/sframe.c
index 9aac703f7ce6e..503d4a2beb50e 100644
--- a/kernel/unwind/sframe.c
+++ b/kernel/unwind/sframe.c
@@ -8,6 +8,7 @@
#include <linux/mm.h>
#include <linux/string_helpers.h>
#include <linux/sframe.h>
+#include <linux/sort.h>
#include <linux/unaligned.h>
#include <linux/unwind_types.h>
#include <linux/kallsyms.h>
@@ -94,6 +95,9 @@ static __always_inline int __find_fde(struct sframe_section *sec,
struct sframe_fde_v3 *first, *low, *high, *found = NULL;
int ret;
+ if (!sec->fdes_sorted)
+ return -EINVAL;
+
first = (void *)sec->fdes_start;
low = first;
high = first + sec->num_fdes - 1;
@@ -405,12 +409,43 @@ static __always_inline int __sframe_find(struct sframe_section *sec,
return __find_fre(sec, &fde, ip, frame);
}
+#ifdef CONFIG_MODULES
+
+static __always_inline int __sframe_find_module(unsigned long ip,
+ struct unwind_frame *frame)
+{
+ struct module *mod;
+
+ mod = __module_text_address(ip);
+ if (!mod || !READ_ONCE(mod->arch.sframe_init))
+ return -EINVAL;
+
+ return __sframe_find(&mod->arch.sframe_sec, ip, frame);
+}
+
+#else
+
+static __always_inline int __sframe_find_module(unsigned long ip,
+ struct unwind_frame *frame)
+{
+ return -EINVAL;
+}
+
+#endif
+
int sframe_find(unsigned long ip, struct unwind_frame *frame)
{
- if (!frame || !sframe_init)
+ if (!frame)
return -EINVAL;
- return __sframe_find(&kernel_sfsec, ip, frame);
+ if (is_kernel_text(ip) || is_kernel_inittext(ip)) {
+ if (!sframe_init)
+ return -EINVAL;
+
+ return __sframe_find(&kernel_sfsec, ip, frame);
+ }
+
+ return __sframe_find_module(ip, frame);
}
static int sframe_read_header(struct sframe_section *sec)
@@ -429,7 +464,6 @@ static int sframe_read_header(struct sframe_section *sec)
if (shdr->preamble.magic != SFRAME_MAGIC ||
shdr->preamble.version != SFRAME_VERSION_3 ||
- !(shdr->preamble.flags & SFRAME_F_FDE_SORTED) ||
!(shdr->preamble.flags & SFRAME_F_FDE_FUNC_START_PCREL) ||
shdr->auxhdr_len) {
pr_debug("bad/unsupported sframe header\n");
@@ -453,6 +487,7 @@ static int sframe_read_header(struct sframe_section *sec)
return -EINVAL;
}
+ sec->fdes_sorted = shdr->preamble.flags & SFRAME_F_FDE_SORTED;
sec->num_fdes = num_fdes;
sec->fdes_start = fdes_start;
sec->fres_start = fres_start;
@@ -469,10 +504,72 @@ void __init init_sframe_table(void)
kernel_sfsec.sframe_start = (unsigned long)__start_sframe;
kernel_sfsec.sframe_end = (unsigned long)__end_sframe;
- if (sframe_read_header(&kernel_sfsec)) {
+ if (sframe_read_header(&kernel_sfsec) || !kernel_sfsec.fdes_sorted) {
pr_warn("invalid vmlinux SFrame header\n");
return;
}
sframe_init = true;
}
+
+#ifdef CONFIG_MODULES
+
+static int sframe_sort_cmp_fde(const void *a, const void *b)
+{
+ const struct sframe_fde_v3 *fde_a = a, *fde_b = b;
+ unsigned long func_start_a, func_start_b;
+
+ func_start_a = (unsigned long)fde_a + fde_a->func_start_off;
+ func_start_b = (unsigned long)fde_b + fde_b->func_start_off;
+
+ return cmp_int(func_start_a, func_start_b);
+}
+
+static void sframe_sort_swap_fde(void *a, void *b, int size)
+{
+ struct sframe_fde_v3 *fde_a = a, *fde_b = b;
+ struct sframe_fde_v3 temp;
+ long delta;
+
+ /* Swap potentially unaligned FDE */
+ memcpy(&temp, fde_a, sizeof(struct sframe_fde_v3));
+ memcpy(fde_a, fde_b, sizeof(struct sframe_fde_v3));
+ memcpy(fde_b, &temp, sizeof(struct sframe_fde_v3));
+
+ /* Adjust FDE function start offset from FDE */
+ delta = (long)((unsigned long)fde_b - (unsigned long)fde_a);
+ fde_a->func_start_off += delta;
+ fde_b->func_start_off -= delta;
+}
+
+static void sframe_sort_fdes(struct sframe_section *sec)
+{
+ void *fdes = (void *)sec->fdes_start;
+ size_t num_fdes = sec->num_fdes;
+
+ if (sec->fdes_sorted)
+ return;
+
+ sort(fdes, num_fdes, sizeof(struct sframe_fde_v3),
+ sframe_sort_cmp_fde, sframe_sort_swap_fde);
+ sec->fdes_sorted = true;
+}
+
+void sframe_module_init(struct module *mod, void *sframe, size_t sframe_size)
+{
+ struct sframe_section *sec = &mod->arch.sframe_sec;
+
+ sec->sframe_start = (unsigned long)sframe;
+ sec->sframe_end = (unsigned long)sframe + sframe_size;
+
+ if (sframe_read_header(sec)) {
+ pr_warn("invalid SFrame header in module %s\n", mod->name);
+ return;
+ }
+ sframe_sort_fdes(sec);
+
+ /* Ensure SFrame is initialized when sframe_find() happens */
+ WRITE_ONCE(mod->arch.sframe_init, true);
+}
+
+#endif
--
2.55.0.1082.g2b9226bbc0-goog
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