From: "Christopher M. Riedl" <cmr@bluescreens.de>
To: linuxppc-dev@lists.ozlabs.org
Cc: linux-hardening@vger.kernel.org
Subject: [PATCH v6 2/4] powerpc: Rework and improve STRICT_KERNEL_RWX patching
Date: Fri, 10 Sep 2021 21:29:02 -0500 [thread overview]
Message-ID: <20210911022904.30962-3-cmr@bluescreens.de> (raw)
In-Reply-To: <20210911022904.30962-1-cmr@bluescreens.de>
Rework code-patching with STRICT_KERNEL_RWX to prepare for a later patch
which uses a temporary mm for patching under the Book3s64 Radix MMU.
Make improvements by adding a WARN_ON when the patchsite doesn't match
after patching and return the error from __patch_instruction() properly.
Signed-off-by: Christopher M. Riedl <cmr@bluescreens.de>
---
v6: * Remove the pr_warn() message from unmap_patch_area().
v5: * New to series.
---
arch/powerpc/lib/code-patching.c | 35 ++++++++++++++++----------------
1 file changed, 17 insertions(+), 18 deletions(-)
diff --git a/arch/powerpc/lib/code-patching.c b/arch/powerpc/lib/code-patching.c
index 8d61a7d35b89..8d0bb86125d5 100644
--- a/arch/powerpc/lib/code-patching.c
+++ b/arch/powerpc/lib/code-patching.c
@@ -102,6 +102,7 @@ static inline void stop_using_temporary_mm(struct temp_mm *temp_mm)
}
static DEFINE_PER_CPU(struct vm_struct *, text_poke_area);
+static DEFINE_PER_CPU(unsigned long, cpu_patching_addr);
static int text_area_cpu_up(unsigned int cpu)
{
@@ -114,6 +115,7 @@ static int text_area_cpu_up(unsigned int cpu)
return -1;
}
this_cpu_write(text_poke_area, area);
+ this_cpu_write(cpu_patching_addr, (unsigned long)area->addr);
return 0;
}
@@ -139,7 +141,7 @@ void __init poking_init(void)
/*
* This can be called for kernel text or a module.
*/
-static int map_patch_area(void *addr, unsigned long text_poke_addr)
+static int map_patch_area(void *addr)
{
unsigned long pfn;
int err;
@@ -149,17 +151,20 @@ static int map_patch_area(void *addr, unsigned long text_poke_addr)
else
pfn = __pa_symbol(addr) >> PAGE_SHIFT;
- err = map_kernel_page(text_poke_addr, (pfn << PAGE_SHIFT), PAGE_KERNEL);
+ err = map_kernel_page(__this_cpu_read(cpu_patching_addr),
+ (pfn << PAGE_SHIFT), PAGE_KERNEL);
- pr_devel("Mapped addr %lx with pfn %lx:%d\n", text_poke_addr, pfn, err);
+ pr_devel("Mapped addr %lx with pfn %lx:%d\n",
+ __this_cpu_read(cpu_patching_addr), pfn, err);
if (err)
return -1;
return 0;
}
-static inline int unmap_patch_area(unsigned long addr)
+static inline int unmap_patch_area(void)
{
+ unsigned long addr = __this_cpu_read(cpu_patching_addr);
pte_t *ptep;
pmd_t *pmdp;
pud_t *pudp;
@@ -199,11 +204,9 @@ static inline int unmap_patch_area(unsigned long addr)
static int do_patch_instruction(u32 *addr, struct ppc_inst instr)
{
- int err;
+ int err, rc = 0;
u32 *patch_addr = NULL;
unsigned long flags;
- unsigned long text_poke_addr;
- unsigned long kaddr = (unsigned long)addr;
/*
* During early early boot patch_instruction is called
@@ -215,24 +218,20 @@ static int do_patch_instruction(u32 *addr, struct ppc_inst instr)
local_irq_save(flags);
- text_poke_addr = (unsigned long)__this_cpu_read(text_poke_area)->addr;
- if (map_patch_area(addr, text_poke_addr)) {
- err = -1;
+ err = map_patch_area(addr);
+ if (err)
goto out;
- }
- patch_addr = (u32 *)(text_poke_addr + (kaddr & ~PAGE_MASK));
+ patch_addr = (u32 *)(__this_cpu_read(cpu_patching_addr) | offset_in_page(addr));
+ rc = __patch_instruction(addr, instr, patch_addr);
- __patch_instruction(addr, instr, patch_addr);
-
- err = unmap_patch_area(text_poke_addr);
- if (err)
- pr_warn("failed to unmap %lx\n", text_poke_addr);
+ err = unmap_patch_area();
out:
local_irq_restore(flags);
+ WARN_ON(!ppc_inst_equal(ppc_inst_read(addr), instr));
- return err;
+ return rc ? rc : err;
}
#else /* !CONFIG_STRICT_KERNEL_RWX */
--
2.32.0
next prev parent reply other threads:[~2021-09-11 2:29 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-11 2:29 [PATCH v6 0/4] Use per-CPU temporary mappings for patching on Radix MMU Christopher M. Riedl
2021-09-11 2:29 ` [PATCH v6 1/4] powerpc/64s: Introduce temporary mm for " Christopher M. Riedl
2021-09-11 8:26 ` Jordan Niethe
2021-09-16 0:24 ` Christopher M. Riedl
2021-09-11 2:29 ` Christopher M. Riedl [this message]
2021-09-11 2:29 ` [PATCH v6 3/4] powerpc: Use WARN_ON and fix check in poking_init Christopher M. Riedl
2021-09-11 2:29 ` [PATCH v6 4/4] powerpc/64s: Initialize and use a temporary mm for patching on Radix Christopher M. Riedl
2021-09-11 9:14 ` Jordan Niethe
2021-09-16 0:29 ` Christopher M. Riedl
2021-09-16 1:52 ` Jordan Niethe
2021-09-15 4:24 ` Jordan Niethe
2021-09-16 0:45 ` Christopher M. Riedl
2021-09-16 2:04 ` Jordan Niethe
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